Hospital Physician: Hematology/Oncology

Introduction

Breast cancer is the second leading cause of cancer deaths among women in the United States, according to the SEER database. It is estimated that 1 in 8 women will be diagnosed with breast cancer at some point during their lifetime (12.4% lifetime risk).^1,2 Because breast tumors are clinically and histopathologically heterogeneous, different diagnostic and therapeutic approaches are required for each subtype. Among the subtypes, tumors that are positive for human epidermal growth factor receptor 2 (HER2) account for approximately 15% to 20% of all newly diagnosed localized and metastatic invasive breast tumors.^3,4 Historically, this subset of tumors has been considered the most aggressive due to a higher propensity to relapse and metastasize, translating into poorer prognosis compared with other subtypes.^5–7 However, with the advent of HER2-targeted therapy in the late 1990s, prognosis has significantly improved for both early- and late-stage HER2-positive tumors.⁸

Pathogenesis

The HER2 proto-oncogene belongs to a family of human epidermal growth factor receptors that includes 4 transmembrane tyrosine kinase receptors: HER1 (also commonly known as epidermal growth factor receptor, EGFR), HER2, HER3, and HER4. Another commonly used nomenclature for this family of receptors is ERBB1 to ERBB4. Each of the receptors has a similar structure consisting of a growth factor–binding extracellular domain, a single transmembrane segment, an intracellular protein-tyrosine kinase catalytic domain, and a tyrosine-containing cytoplasmic tail. Activation of the extracellular domain leads to conformational changes that initiate a cascade of reactions resulting in protein kinase activation. ERBB tyrosine receptor kinases subsequently activate several intracellular pathways that are critical for cellular function and survival, including the PI3K-AKT, RAS-MAPK, and mTOR pathways. Hyperactivation or overexpression of these receptors leads to uncontrolled cell growth and proliferation, and eventually cancerogenesis.^9,10

HER2 gene amplification can cause activation of the receptor’s extramembranous domain by way of either dimerization of two HER2 receptors or heterodimerization with other ERBB family receptors, leading to ligand-independent activation of cell signaling (ie, activation in the absence of external growth factors). Besides breast cancer, HER2 protein is overexpressed in several other tumor types, including esophageal and gastric adenocarcinomas, colon and gynecological malignancies, and to a lesser extent in other malignancies.

Biomarker Testing

All patients with newly diagnosed breast cancer should have their tumor tissue submitted for biomarker testing for estrogen receptors (ER), progesterone receptors (PR), and HER2 overexpression, as the result this testing dictates therapy choices. The purpose of HER2 testing is to investigate whether the HER2 gene, located on chromosome 17, is overexpressed or amplified. HER2 status provides the basis for treatment selection, which impacts long-term outcome measures such as recurrence and survival. Routine testing of carcinoma in situ for HER2 expression/amplification is not recommended and has no implication on choice of therapy at this time.

In 2013, the American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) updated their clinical guideline recommendations for HER2 testing in breast cancer to improve its accuracy and its utility as a predictive marker.¹¹ There are currently 2 approved modalities for HER2 testing: detection of HER2 protein overexpression by immunohistochemical staining (IHC), and detection of HER2 gene amplification using in-situ hybridization. The results of each type of testing are reported as positive, equivocal, or negative (Table 1).¹¹  IHC uses antibodies against HER2 protein to assess the level of protein expression at the membrane of invasive tumor cells; overexpression of HER2 is established based upon the intensity of cell membrane staining and the number of stained cells. Results are reported as positive for HER2 expression (3+ staining), negative for HER2 expression (0 or 1+ staining), or equivocal for HER2 expression (2+ staining).

Fluorescence in-situ hybridization (FISH) testing assesses for HER2 amplification by determining the number of HER2 signals and chromosome 17 centromere (CEP17) signals, respectively, in a tissue sample. HER2 status is based on the ratio of average HER2 signals to CEP17 signals and the average HER2 signal count per cell. FISH testing is considered positive when there are ≥ 6 copies of HER2 signals per cell or when the HER2/CEP17 ratio is ≥ 2. FISH testing is reported as negative when there are fewer than 4 copies of HER2 per cell and the HER2/CEP17 ratio is < 2. 

The test is considered equivocal if the number of HER2 copies is ≥ 4 but < 6 and the HER2/CEP17 ratio is < 2. In equivocal cases, repeat testing using an alternative probe or a different sample may be considered. Most institutions currently use IHC to determine HER2 status along with IHC staining for ER and PR. If HER2 status is 2+ or equivocal by IHC, then FISH testing is obtained as a confirmatory step (Figure 1).

 

Neoadjuvant and Adjuvant Therapy for Locoregional Disease

Case Patient 1

A 56-year-old woman undergoes ultrasound-guided biopsy of a self-palpated breast lump. Pathology shows invasive ductal carcinoma that is ER-positive, PR-negative, and HER2 equivocal by IHC (2+ staining). Follow-up FISH testing shows a HER2/CEP17 ratio of 2.5. The tumor is estimated to be 2 cm in diameter by imaging and exam with no clinically palpable axillary lymphadenopathy. The patient exhibits no constitutional or localized symptoms concerning for metastases.

• What is the recommended management approach for this patient?

According to the ASCO/CAP guidelines, this patient’s tumor qualifies as HER2-positive based upon testing results showing amplification of the gene. This result has important implications for management since nearly all patients with macroscopically invasive HER2-positive tumors should be considered for adjuvant chemotherapy in combination with anti-HER2 therapy. The patient should proceed with upfront tumor resection and sentinel lymph node biopsy. Systemic staging imaging (ie, computed tomography [CT] or bone scan) is not indicated in early stage breast cancer.^12,13 Systemic staging scans are indicated when (1) any anatomical stage III disease is suspected (eg, with involvement of the skin or chest wall, the presence of enlarged matted or fixed axillary lymph nodes, and involvement of nodal stations other than in the axilla), and (2) when symptoms or abnormal laboratory values raise suspicion for distant metastases (eg, unexplained bone pain, unintentional weight loss, elevated serum alkaline phosphatase, and transaminitis).

Case 1 Continued

The patient presents to discuss treatment options after undergoing a lumpectomy and sentinel node biopsy procedure. The pathology report notes a single focus of carcinoma measuring 2 cm with negative sentinel lymph nodes.

• What agents are used for adjuvant therapy in HER2-postive breast cancer?

Nearly all patients with macroscopically invasive (> 1 mm) breast carcinoma should be considered for adjuvant therapy using a regimen that contains a taxane and trastuzumab. However, the benefit may be small for patients with tumors ≤ 5 mm (T1a, N0), so it is important to carefully weigh the risk against the benefit. Among the agents that targeting HER2, only trastuzumab has been shown to improve overall survival (OS) in the adjuvant setting; long-term follow-up data are awaited for other agents.⁸ A trastuzumab biosimilar, trastuzumab-dkst, was recently approved by the US Food and Drug Administration (FDA) for the same indications as trastuzumab.¹⁴ The regimens most commonly used in the adjuvant and neoadjuvant settings for nonmetastatic breast cancer are summarized in Table 2.

Patients with small (≤ 3 cm), node-negative tumors can generally be considered for a reduced-intensity regimen that includes weekly paclitaxel plus trastuzumab. This combination proved efficacious in a single-group, multicenter study that enrolled 406 patients.¹⁵ Paclitaxel and trastuzumab were given once weekly for 12 weeks, followed by trastuzumab, either weekly or every 3 weeks, to complete 1 year of therapy.After a median follow-up of more than 6 years, the rates of distant and locoregional recurrence were 1% and 1.2%, respectively.¹⁶

A combination of docetaxel, carboplatin, and trastuzumab is a nonanthracycline regimen that is also appropriate in this setting, based on the results of the Breast Cancer International Research Group 006 (BCIRG-006) trial.¹⁷ This phase 3 randomized trial enrolled 3222 women with HER2-positive, invasive, high-risk adenocarcinoma. Eligible patients had a T1–3 tumor and either lymph node–negative or –positive disease and were randomly assigned to receive 1 of 3 regimens: group 1 received doxorubicin and cyclophosphamide every 3 weeks for 4 cycles followed by docetaxel every 3 weeks for 4 cycles (AC-T); group 2 received the AC-T regimen in combination with trastuzumab; and group 3 received docetaxel, carboplatin, and trastuzumab once every 3 weeks for 6 cycles (TCH). Groups 2 and 3 also received trastuzumab for an additional 34 weeks to complete 1 year of therapy. Trastuzumab-containing regimens were found to offer superior disease-free survival (DFS) and OS. When comparing the 2 trastuzumab arms after more than 10 years of follow-up, no statistically significant advantage of an anthracycline regimen over a nonanthracycline regimen was found.¹⁸ Furthermore, the anthracycline arm had a fivefold higher incidence of symptomatic congestive heart failure (grades 3 and 4), and the nonanthracycline regimen was associated with a lower incidence of treatment-related leukemia, a clinically significant finding despite not reaching statistical significance due to low overall numbers.

BCIRG-006, NSABP B-31, NCCTG N9831, and HERA are all large randomized trials with consistent results confirming trastuzumab’s role in reducing recurrence and improving survival in HER2-positive breast cancer in the adjuvant settings. The estimated overall benefit from addition of this agent was a 34% to 41% improvement in survival and a 33% to 52% improvement in DFS.^8,17–20

Dual anti-HER2 therapy containing both trastuzumab and pertuzumab should be strongly considered for patients with macroscopic lymph node involvement based on the results of the APHINITY trial.²¹ In this study, the addition of pertuzumab to standard trastuzumab-based therapy led to a significant improvement in invasive-disease-free survival at 3 years. In subgroup analysis, the benefit was restricted to the node-positive group (3-year invasive-disease-free survival rates of 92% in the pertuzumab group versus 90.2% in the placebo group, P = 0.02). Patients with hormone receptor–negative disease derived greater benefit from the addition of pertuzumab. Regimens used in the APHINITY trial included the anti-HER2 agents trastuzumab and pertuzumab in combination with 1 of the following chemotherapy regimens: sequential cyclophosphamide plus either doxorubicin or epirubicin, followed by either 4 cycles of docetaxel or 12 weekly doses of paclitaxel; sequential fluorouracil plus either epirubicin or doxorubicin plus cyclophosphamide (3 or 4 cycles), followed by 3 or 4 cycles of docetaxel or 12 weekly cycles of paclitaxel; or 6 cycles of concurrent docetaxel plus carboplatin.

One-year therapy with neratinib, an oral tyrosine kinase inhibitor of HER2, is now approved by the FDA after completion of trastuzumab in the adjuvant setting, based on the results of the ExteNET trial.²² In this study, patients who had completed trastuzumab within the preceding 12 months, without evidence of recurrence, were randomly assigned to receive either oral neratinib or placebo daily for 1 year. The 2-year DFS rate was 93.9% and 91.6% for the neratinib and placebo groups, respectively. The most common adverse effect of neratinib was diarrhea, with approximately 40% of patients experiencing grade 3 diarrhea. In subgroup analyses, hormone receptor–positive patients derived the most benefit, while hormone receptor–negative patients derived no or marginal benefit.²² OS benefit has not yet been established.²³

Trastuzumab therapy (with pertuzumab if indicated) should be offered for an optimal duration of 12 months (17 cycles, including those given with chemotherapy backbone). A shorter duration of therapy, 6 months, has been shown to be inferior,²⁴ while a longer duration, 24 months, has been shown to provide no additional benefit.²⁵

Finally, sequential addition of anti-estrogen endocrine therapy is indicated for hormone-positive tumors. Endocrine therapy is usually added after completion of the chemotherapy backbone of the regimen, but may be given concurrently with anti-HER2 therapy. If radiation is being administered, endocrine therapy can be given concurrently or started after radiation therapy is completed.

 

Case 1 Conclusion

The patient can be offered 1 of 2 adjuvant treatment regimens, either TH or TCH (Table 2). Since the patient had lumpectomy, she is an appropriate candidate for adjuvant radiation, which would be started after completion of the chemotherapy backbone (taxane/platinum). Endocrine therapy for at least 5 years should be offered sequentially or concurrently with radiation. Her long-term prognosis is very favorable.

Case Patient 2

A 43-year-old woman presents with a 4-cm breast mass, a separate skin nodule, and palpable matted axillary lymphadenopathy. Biopsies of the breast mass and subcutaneous nodule reveal invasive ductal carcinoma that is ER-negative, PR-negative, and HER2-positive by IHC (3+ staining). Based on clinical findings, the patient is staged as T4b (separate tumor nodule), N2 (matted axillary lymph nodes). Systemic staging with CT scan of the chest, abdomen, and pelvis shows no evidence of distant metastases.

• What is the recommended approach to management for this patient?

Recommendations for neoadjuvant therapy, given before definitive surgery, follow the same path as with other subtypes of breast cancer. Patients with suspected anatomical stage III disease are strongly encouraged to undergo upfront (neoadjuvant) chemotherapy in combination with HER2-targeted agents. In addition, all HER2-positive patients with clinically node-positive disease can be offered neoadjuvant therapy using chemotherapy plus dual anti-HER2 therapy (trastuzumab and pertuzumab), with complete pathological response expected in more than 60% of patients.^26,27 Because this patient has locally advanced disease, especially skin involvement and matted axillary nodes, she should undergo neoadjuvant therapy. Preferred regimens contain both trastuzumab and pertuzumab in combination with cytotoxic chemotherapy. The latter may be given concurrently (nonanthracycline regimens, such as docetaxel plus carboplatin) or sequentially (anthracycline-based regimens), as outlined in Table 2. Administration of anthracyclines and trastuzumab simultaneously is contraindicated due to increased risk of cardiomyopathy.²⁸

Endocrine therapy is not indicated for this patient per the current standard of care because the tumor was ER- and PR-negative. Had the tumor been hormone receptor–positive, endocrine therapy for a minimum of 5 years would have been indicated. Likewise, in the case of hormone receptor–positive disease, 12 months of neratinib therapy after completion of trastuzumab may add further benefit, as shown in the ExteNET trial.^22,23 Neratinib seems to have a propensity to prevent or delay trastuzumab-induced overexpression of estrogen receptors. This is mainly due to hormone receptor/HER2 crosstalk, a potential mechanism of resistance to trastuzumab.^29,30

In addition to the medical therapy options discussed here, this patient would be expected to benefit from adjuvant radiation to the breast and regional lymph nodes, given the presence of T4 disease and bulky adenopathy in the axilla.³¹

Case 2 Conclusion

The patient undergoes neoadjuvant treatment (docetaxel, carboplatin, trastuzumab, and pertuzumab every 21 days for a total of 6 cycles), followed by surgical resection (modified radical mastectomy) that reveals complete pathological response (no residual invasive carcinoma). Subsequently, she receives radiation therapy to the primary tumor site and regional lymph nodes while continuing trastuzumab and pertuzumab for 11 more cycles (17 total). Despite presenting with locally advanced disease, the patient has a favorable overall prognosis due to an excellent pathological response.

• What is the approach to follow-up after completion of primary therapy?

Patients may follow up every 3 to 6 months for clinical evaluation in the first 5 years after completing primary adjuvant therapy. An annual screening mammogram is recommended as well. Body imaging can be done if dictated by symptoms. However, routine CT, positron emission tomography, or bone scans are not recommended as part of follow-up in the absence of symptoms, mainly because of a lack of evidence that such surveillance improves survival.³²

 

Metastatic HER2-Positive Breast Cancer

Metastatic breast cancer most commonly presents as a distant recurrence of previously treated local disease. However, 6% to 18% of patients have no prior history of breast cancer and present with de novo metastatic disease.^33,34 The most commonly involved distant organs are the skeletal bones, liver, lung, distant lymph node stations, and brain. Compared to other subtypes, HER2-positive tumors have an increased tendency to involve the central nervous system.^35–38 Although metastatic HER2-positive breast cancer is not considered curable, significant improvement in survival has been achieved, and patients with metastatic disease have median survival approaching 5 years.³⁹

Case Presentation 3

A 69-year-old woman with a history of breast cancer 4 years ago presents with new-onset back pain and unintentional weight loss. On exam, she is found to have palpable axillary adenopathy on the same side as her previous cancer. Her initial disease was stage IIB ER-positive and HER2-positive and was treated with chemotherapy, mastectomy, and anastrozole, which the patient is still taking. She undergoes CT scan of the chest, abdomen, and pelvis and radionucleotide bone scan, which show multiple liver and bony lesions suspicious for metastatic disease. Axillary lymph node biopsy confirms recurrent invasive carcinoma that is ER-positive and HER2-positive by IHC (3+).

• What is the approach to management of a patient who presents with symptoms of recurrent HER2-positive disease?

This patient likely has metastatic breast cancer based on the imaging findings. In such cases, a biopsy of the recurrent disease should always be considered, if feasible, to confirm the diagnosis and rule out other etiologies such as different malignances and benign conditions. Hormone-receptor and HER2 testing should also be performed on recurrent disease, since a change in HER2 status can be seen in 15% to 33% of cases.^40–42

Based on data from the phase 3 CLEOPATRA trial, first-line systemic regimens for patients with metastatic breast cancer that is positive for HER2 should consist of a combination of docetaxel, trastuzumab, and pertuzumab.  Compared to placebo, adding pertuzumab yielded superior progression-free survival of 18.4 months (versus 12.4 months for placebo) and an unprecedented OS of 56.5 months (versus 40.8 for placebo).³⁹ Weekly paclitaxel can replace docetaxel with comparable efficacy (Table 3).⁴³

Patients can develop significant neuropathy as well as skin and nail changes after multiple cycles of taxane-based chemotherapy. Therefore, the taxane backbone may be dropped after 6 to 8 cycles, while patients continue the trastuzumab and pertuzumab combination until disease progression or unacceptable toxicity. Some patients may enjoy remarkable long-term survival on “maintenance” anti-HER2 therapy.⁴⁴ Despite lack of high-level evidence, such as from large randomized trials, some experts recommend the addition of a hormone blocker after discontinuation of the taxane in ER-positive tumors.⁴⁵

Premenopausal and perimenopausal women with hormone receptor–positive metastatic disease should be considered for simultaneous ovarian suppression. Ovarian suppression can be accomplished medically using a gonadotropin-releasing hormone agonist (goserelin) or surgically via salpingo-oophorectomy.^46–48

Case 3 Conclusion

The patient receives 6 cycles of docetaxel, trastuzumab, and pertuzumab, after which the docetaxel is discontinued due to neuropathy while she continues the other 2 agents. After 26 months of disease control, the patient is found to have new liver metastatic lesions, indicating progression of disease.

• What therapeutic options are available for this patient?

Patients whose disease progresses after receiving taxane- and trastuzumab-containing regimens are candidates to receive the novel antibody-drug conjugate ado-trastuzumab emtansine (T-DM1). Early progressors (ie, patients with early stage disease who have progression of disease while receiving adjuvant trastuzumab or within 6 months of completion of adjuvant trastuzumab) are also candidates for T-DM1. Treatment usually fits in the second line or beyond based on data from the EMILIA trial, which randomly assigned patients to receive either capecitabine plus lapatinib or T-DM1.^49,50 Progression-free survival in the T-DM1 group was 9.6 months versus 6.4 months for the comparator. Improvement of 4 months in OS persisted with longer follow-up despite a crossover rate of 27%. Furthermore, a significantly higher objective response rate and fewer adverse effects were reported in the T-DM1 patients. Most patients included in the EMILIA trial were pertuzumab-naive. However, the benefit of T-DM1 appears to persist, albeit to a lesser extent, for pertuzumab-pretreated patients.^51,52

Patients in whom treatment fails with 2 or more lines of therapy containing taxane-trastuzumab (with or without pertuzumab) and T-DM1 are candidates to receive a combination of capecitabine and lapatinib, a TKI, in the third line and beyond. Similarly, the combination of capecitabine with trastuzumab in the same settings appears to have equal efficacy.^53,54 Trastuzumab may be continued beyond progression while changing the single-agent chemotherapy drug for subsequent lines of therapy, per ASCO guidelines,⁵⁵ although improvement in OS has not been demonstrated beyond the third line in a large randomized trial (Table 3).

 

Approved HER2-Targeted Drugs

HER2-directed therapy is implemented in the management of nearly all stages of HER2-positive invasive breast cancer, including early and late stages (Table 4).

Trastuzumab

Trastuzumab was the first anti-HER2 agent to be approved by the FDA in 1998. It is a humanized monoclonal antibody directed against the extracellular domain of the HER2 receptor (domain IV).  Trastuzumab functions by interrupting HER2 signal transduction and by flagging tumor cells for immune destruction.⁵⁶ Cardiotoxicity, usually manifested as left ventricular systolic dysfunction, is the most noteworthy adverse effect of trastuzumab. The most prominent risk factors for cardiomyopathy in patients receiving trastuzumab are low baseline ejection fraction (< 55%), age > 50 years, co-administration and higher cumulative dose of anthracyclines, and increased body mass index and obesity.^57–59 Whether patients receive therapy in the neoadjuvant, adjuvant, or metastatic settings, baseline cardiac function assessment with echocardiogram or multiple-gated acquisition scan is required. While well-designed randomized trials validating the value and frequency of monitoring are lacking, repeated cardiac testing every 3 months is generally recommended for patients undergoing adjuvant therapy. Patients with metastatic disease who are receiving treatment with palliative intent may be monitored less frequently.^60,61

An asymptomatic drop in ejection fraction is the most common manifestation of cardiac toxicity. Other cardiac manifestations have also been reported with much less frequency, including arrhythmias, severe congestive heart failure, ventricular thrombus formation, and even cardiac death. Until monitoring and dose-adjustment guidelines are issued, the guidance provided in the FDA-approved prescribing information should be followed, which recommends holding trastuzumab when there is ≥ 16% absolute reduction in left ventricular ejection fraction (LVEF) from the baseline value; or if the LVEF value is below the institutional lower limit of normal and the drop is ≥ 10%. After holding the drug, cardiac function can be re-evaluated every 4 weeks. In most patients, trastuzumab-induced cardiotoxicity can be reversed by withholding trastuzumab and initiating cardioprotective therapy, although the latter remains controversial. Re-challenging after recovery of ejection fraction is possible and toxicity does not appear to be proportional to cumulative dose. Cardiomyopathy due to trastuzumab therapy is potentially reversible within 6 months in more than 80% of cases.^{28,57,60–63}

Other notable adverse effects of trastuzumab include pulmonary toxicity (such as interstitial lung disease) and infusion reactions (usually during or within 24 hours of first dose).

Pertuzumab

Pertuzumab is another humanized monoclonal antibody directed to a different extracellular domain of the HER2 receptor, the dimerization domain (domain II), which is responsible for heterodimerization of HER2 with other HER receptors, especially HER3. This agent should always be co-administered with trastuzumab as the 2 drugs produce synergistic anti-tumor effect, without competition for the receptor. Activation of HER3, via dimerization with HER2, produces an alternative mechanism of downstream signaling, even in the presence of trastuzumab and in the absence of growth factors (Figure 2). 

This dimerization is now a well-known mechanism of tumor resistance to trastuzumab; hence, co-administration of pertuzumab potentially prevents or delays such resistance.⁶⁴ The use of pertuzumab alone without trastuzumab is not currently recommended and does not confer significant clinical activity. The most notable adverse effects of this drug are infusion reactions and diarrhea. As pertuzumab is always given with trastuzumab, the same caution for cardiotoxicity must be exercised, and cardiac function evaluation and monitoring, as described for trastuzumab, is recommended. However, there is no evidence of increased cardiac dysfunction when pertuzumab is added to trastuzumab.⁶⁴

Ado-Trastuzumab Emtansine

Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate that combines the monoclonal antibody trastuzumab with the cytotoxic agent DM1 (emtansine), a potent microtubule inhibitor and a derivative of maytansine, in a single structure (Figure 3). 

In addition to the mechanisms of action of bare trastuzumab, T-DM1 adds significant cytotoxicity by way of releasing the maytansine moiety (DM1) intracellularly. It also exerts some bystander effect by disseminating locally to nearby cells that may express lower HER2 density (Figure 4).^65,66 

Aside from infusion reactions and cardiotoxicity that are mostly related to trastuzumab, this drug has adverse effects related to its cytotoxic component DM1. The most notable adverse effects include thrombocytopenia, which is attributable to uptake of the drug in the marrow by Fc-bearing megakaryocytes, and hepatotoxicity via drug binding to HER2 on hepatocytes and subsequent activation of cytokine-releasing Kupffer cells.^67,68 Neuropathy due to DM1 has also been reported, but the overall incidence of grade 3/4 adverse effects remains very low and the agent is generally very well tolerated.⁶⁶ Cardiac function monitoring follows the same principles described for trastuzumab.

Lapatinib

Lapatinib is an oral small-molecule tyrosine kinase inhibitor of EGFR (HER1) and HER2 receptors. It is approved in combination with capecitabine for patients with HER2-expressing metastatic breast cancer who previously received trastuzumab, an anthracycline, and a taxane chemotherapy or T-DM1. Lapatinib is also approved in combination with letrozole in postmenopausal women with HER2-positive, hormone receptor–positive metastatic disease, although it is unclear where this regimen would fit in the current schema. It may be considered for patients with hormone receptor–positive disease who are not candidates for therapy with taxane-trastuzumab and T-DM1 or who decline this therapy. Diarrhea is seen in most patients treated with lapatinib and may be severe in 20% of cases when lapatinib is combined with capecitabine. Decreases in LVEF have been reported and cardiac function monitoring at baseline and periodically may be considered.^69,70 Lapatinib is not approved for use in adjuvant settings.

Neratinib

Neratinib is an oral small-molecule irreversible tyrosine kinase inhibitor of HER1, HER2, and HER4. It is currently approved only for extended adjuvant therapy after completion of 1 year of standard trastuzumab therapy. It is given orally every day for 1 year. The main side effect, expected in nearly all patients, is diarrhea, which can be severe in up to 40% of patients and may lead to dehydration and electrolyte imbalance. Diarrhea usually starts early in the course of therapy and can be most intense during the first cycle. Therefore, prophylactic antidiarrheal therapy is recommended to reduce the intensity of diarrhea. Loperamide prophylaxis may be initiated simultaneously for all patients using a tapering schedule. Drug interruption or dose reduction may be required if diarrhea is severe or refractory.^21,71 Neratinib is not FDA-approved in the metastatic settings.

 

Conclusion

HER2-positive tumors represent a distinct subset(s) of breast tumors with unique pathological and clinical characteristics. Treatment with a combination of cytotoxic chemotherapy and HER2-targeted agents has led to a dramatic improvement in survival for patients with locoregional and advanced disease. Trastuzumab is an integral part of adjuvant therapy for HER2-positive invasive disease. Pertuzumab should be added to trastuzumab in node-positive disease. Neratinib may be considered after completion of trastuzumab therapy in patients with hormone receptor–positive disease. For metastatic HER2-positive breast cancer, a regimen consisting of docetaxel plus trastuzumab and pertuzumab is the standard first-line therapy. Ado-trastuzumab is an ideal next line option for patients whose disease progresses on trastuzumab and taxanes.

Introduction

Breast cancer is the second leading cause of cancer deaths among women in the United States, according to the SEER database. It is estimated that 1 in 8 women will be diagnosed with breast cancer at some point during their lifetime (12.4% lifetime risk).^1,2 Because breast tumors are clinically and histopathologically heterogeneous, different diagnostic and therapeutic approaches are required for each subtype. Among the subtypes, tumors that are positive for human epidermal growth factor receptor 2 (HER2) account for approximately 15% to 20% of all newly diagnosed localized and metastatic invasive breast tumors.^3,4 Historically, this subset of tumors has been considered the most aggressive due to a higher propensity to relapse and metastasize, translating into poorer prognosis compared with other subtypes.^5–7 However, with the advent of HER2-targeted therapy in the late 1990s, prognosis has significantly improved for both early- and late-stage HER2-positive tumors.⁸

Pathogenesis

The HER2 proto-oncogene belongs to a family of human epidermal growth factor receptors that includes 4 transmembrane tyrosine kinase receptors: HER1 (also commonly known as epidermal growth factor receptor, EGFR), HER2, HER3, and HER4. Another commonly used nomenclature for this family of receptors is ERBB1 to ERBB4. Each of the receptors has a similar structure consisting of a growth factor–binding extracellular domain, a single transmembrane segment, an intracellular protein-tyrosine kinase catalytic domain, and a tyrosine-containing cytoplasmic tail. Activation of the extracellular domain leads to conformational changes that initiate a cascade of reactions resulting in protein kinase activation. ERBB tyrosine receptor kinases subsequently activate several intracellular pathways that are critical for cellular function and survival, including the PI3K-AKT, RAS-MAPK, and mTOR pathways. Hyperactivation or overexpression of these receptors leads to uncontrolled cell growth and proliferation, and eventually cancerogenesis.^9,10

HER2 gene amplification can cause activation of the receptor’s extramembranous domain by way of either dimerization of two HER2 receptors or heterodimerization with other ERBB family receptors, leading to ligand-independent activation of cell signaling (ie, activation in the absence of external growth factors). Besides breast cancer, HER2 protein is overexpressed in several other tumor types, including esophageal and gastric adenocarcinomas, colon and gynecological malignancies, and to a lesser extent in other malignancies.

Biomarker Testing

All patients with newly diagnosed breast cancer should have their tumor tissue submitted for biomarker testing for estrogen receptors (ER), progesterone receptors (PR), and HER2 overexpression, as the result this testing dictates therapy choices. The purpose of HER2 testing is to investigate whether the HER2 gene, located on chromosome 17, is overexpressed or amplified. HER2 status provides the basis for treatment selection, which impacts long-term outcome measures such as recurrence and survival. Routine testing of carcinoma in situ for HER2 expression/amplification is not recommended and has no implication on choice of therapy at this time.

In 2013, the American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) updated their clinical guideline recommendations for HER2 testing in breast cancer to improve its accuracy and its utility as a predictive marker.¹¹ There are currently 2 approved modalities for HER2 testing: detection of HER2 protein overexpression by immunohistochemical staining (IHC), and detection of HER2 gene amplification using in-situ hybridization. The results of each type of testing are reported as positive, equivocal, or negative (Table 1).¹¹  IHC uses antibodies against HER2 protein to assess the level of protein expression at the membrane of invasive tumor cells; overexpression of HER2 is established based upon the intensity of cell membrane staining and the number of stained cells. Results are reported as positive for HER2 expression (3+ staining), negative for HER2 expression (0 or 1+ staining), or equivocal for HER2 expression (2+ staining).

Fluorescence in-situ hybridization (FISH) testing assesses for HER2 amplification by determining the number of HER2 signals and chromosome 17 centromere (CEP17) signals, respectively, in a tissue sample. HER2 status is based on the ratio of average HER2 signals to CEP17 signals and the average HER2 signal count per cell. FISH testing is considered positive when there are ≥ 6 copies of HER2 signals per cell or when the HER2/CEP17 ratio is ≥ 2. FISH testing is reported as negative when there are fewer than 4 copies of HER2 per cell and the HER2/CEP17 ratio is < 2. 

The test is considered equivocal if the number of HER2 copies is ≥ 4 but < 6 and the HER2/CEP17 ratio is < 2. In equivocal cases, repeat testing using an alternative probe or a different sample may be considered. Most institutions currently use IHC to determine HER2 status along with IHC staining for ER and PR. If HER2 status is 2+ or equivocal by IHC, then FISH testing is obtained as a confirmatory step (Figure 1).

 

Neoadjuvant and Adjuvant Therapy for Locoregional Disease

Case Patient 1

A 56-year-old woman undergoes ultrasound-guided biopsy of a self-palpated breast lump. Pathology shows invasive ductal carcinoma that is ER-positive, PR-negative, and HER2 equivocal by IHC (2+ staining). Follow-up FISH testing shows a HER2/CEP17 ratio of 2.5. The tumor is estimated to be 2 cm in diameter by imaging and exam with no clinically palpable axillary lymphadenopathy. The patient exhibits no constitutional or localized symptoms concerning for metastases.

• What is the recommended management approach for this patient?

According to the ASCO/CAP guidelines, this patient’s tumor qualifies as HER2-positive based upon testing results showing amplification of the gene. This result has important implications for management since nearly all patients with macroscopically invasive HER2-positive tumors should be considered for adjuvant chemotherapy in combination with anti-HER2 therapy. The patient should proceed with upfront tumor resection and sentinel lymph node biopsy. Systemic staging imaging (ie, computed tomography [CT] or bone scan) is not indicated in early stage breast cancer.^12,13 Systemic staging scans are indicated when (1) any anatomical stage III disease is suspected (eg, with involvement of the skin or chest wall, the presence of enlarged matted or fixed axillary lymph nodes, and involvement of nodal stations other than in the axilla), and (2) when symptoms or abnormal laboratory values raise suspicion for distant metastases (eg, unexplained bone pain, unintentional weight loss, elevated serum alkaline phosphatase, and transaminitis).

Case 1 Continued

The patient presents to discuss treatment options after undergoing a lumpectomy and sentinel node biopsy procedure. The pathology report notes a single focus of carcinoma measuring 2 cm with negative sentinel lymph nodes.

• What agents are used for adjuvant therapy in HER2-postive breast cancer?

Nearly all patients with macroscopically invasive (> 1 mm) breast carcinoma should be considered for adjuvant therapy using a regimen that contains a taxane and trastuzumab. However, the benefit may be small for patients with tumors ≤ 5 mm (T1a, N0), so it is important to carefully weigh the risk against the benefit. Among the agents that targeting HER2, only trastuzumab has been shown to improve overall survival (OS) in the adjuvant setting; long-term follow-up data are awaited for other agents.⁸ A trastuzumab biosimilar, trastuzumab-dkst, was recently approved by the US Food and Drug Administration (FDA) for the same indications as trastuzumab.¹⁴ The regimens most commonly used in the adjuvant and neoadjuvant settings for nonmetastatic breast cancer are summarized in Table 2.

Patients with small (≤ 3 cm), node-negative tumors can generally be considered for a reduced-intensity regimen that includes weekly paclitaxel plus trastuzumab. This combination proved efficacious in a single-group, multicenter study that enrolled 406 patients.¹⁵ Paclitaxel and trastuzumab were given once weekly for 12 weeks, followed by trastuzumab, either weekly or every 3 weeks, to complete 1 year of therapy.After a median follow-up of more than 6 years, the rates of distant and locoregional recurrence were 1% and 1.2%, respectively.¹⁶

A combination of docetaxel, carboplatin, and trastuzumab is a nonanthracycline regimen that is also appropriate in this setting, based on the results of the Breast Cancer International Research Group 006 (BCIRG-006) trial.¹⁷ This phase 3 randomized trial enrolled 3222 women with HER2-positive, invasive, high-risk adenocarcinoma. Eligible patients had a T1–3 tumor and either lymph node–negative or –positive disease and were randomly assigned to receive 1 of 3 regimens: group 1 received doxorubicin and cyclophosphamide every 3 weeks for 4 cycles followed by docetaxel every 3 weeks for 4 cycles (AC-T); group 2 received the AC-T regimen in combination with trastuzumab; and group 3 received docetaxel, carboplatin, and trastuzumab once every 3 weeks for 6 cycles (TCH). Groups 2 and 3 also received trastuzumab for an additional 34 weeks to complete 1 year of therapy. Trastuzumab-containing regimens were found to offer superior disease-free survival (DFS) and OS. When comparing the 2 trastuzumab arms after more than 10 years of follow-up, no statistically significant advantage of an anthracycline regimen over a nonanthracycline regimen was found.¹⁸ Furthermore, the anthracycline arm had a fivefold higher incidence of symptomatic congestive heart failure (grades 3 and 4), and the nonanthracycline regimen was associated with a lower incidence of treatment-related leukemia, a clinically significant finding despite not reaching statistical significance due to low overall numbers.

BCIRG-006, NSABP B-31, NCCTG N9831, and HERA are all large randomized trials with consistent results confirming trastuzumab’s role in reducing recurrence and improving survival in HER2-positive breast cancer in the adjuvant settings. The estimated overall benefit from addition of this agent was a 34% to 41% improvement in survival and a 33% to 52% improvement in DFS.^8,17–20

Dual anti-HER2 therapy containing both trastuzumab and pertuzumab should be strongly considered for patients with macroscopic lymph node involvement based on the results of the APHINITY trial.²¹ In this study, the addition of pertuzumab to standard trastuzumab-based therapy led to a significant improvement in invasive-disease-free survival at 3 years. In subgroup analysis, the benefit was restricted to the node-positive group (3-year invasive-disease-free survival rates of 92% in the pertuzumab group versus 90.2% in the placebo group, P = 0.02). Patients with hormone receptor–negative disease derived greater benefit from the addition of pertuzumab. Regimens used in the APHINITY trial included the anti-HER2 agents trastuzumab and pertuzumab in combination with 1 of the following chemotherapy regimens: sequential cyclophosphamide plus either doxorubicin or epirubicin, followed by either 4 cycles of docetaxel or 12 weekly doses of paclitaxel; sequential fluorouracil plus either epirubicin or doxorubicin plus cyclophosphamide (3 or 4 cycles), followed by 3 or 4 cycles of docetaxel or 12 weekly cycles of paclitaxel; or 6 cycles of concurrent docetaxel plus carboplatin.

One-year therapy with neratinib, an oral tyrosine kinase inhibitor of HER2, is now approved by the FDA after completion of trastuzumab in the adjuvant setting, based on the results of the ExteNET trial.²² In this study, patients who had completed trastuzumab within the preceding 12 months, without evidence of recurrence, were randomly assigned to receive either oral neratinib or placebo daily for 1 year. The 2-year DFS rate was 93.9% and 91.6% for the neratinib and placebo groups, respectively. The most common adverse effect of neratinib was diarrhea, with approximately 40% of patients experiencing grade 3 diarrhea. In subgroup analyses, hormone receptor–positive patients derived the most benefit, while hormone receptor–negative patients derived no or marginal benefit.²² OS benefit has not yet been established.²³

Trastuzumab therapy (with pertuzumab if indicated) should be offered for an optimal duration of 12 months (17 cycles, including those given with chemotherapy backbone). A shorter duration of therapy, 6 months, has been shown to be inferior,²⁴ while a longer duration, 24 months, has been shown to provide no additional benefit.²⁵

Finally, sequential addition of anti-estrogen endocrine therapy is indicated for hormone-positive tumors. Endocrine therapy is usually added after completion of the chemotherapy backbone of the regimen, but may be given concurrently with anti-HER2 therapy. If radiation is being administered, endocrine therapy can be given concurrently or started after radiation therapy is completed.

 

Case 1 Conclusion

The patient can be offered 1 of 2 adjuvant treatment regimens, either TH or TCH (Table 2). Since the patient had lumpectomy, she is an appropriate candidate for adjuvant radiation, which would be started after completion of the chemotherapy backbone (taxane/platinum). Endocrine therapy for at least 5 years should be offered sequentially or concurrently with radiation. Her long-term prognosis is very favorable.

Case Patient 2

A 43-year-old woman presents with a 4-cm breast mass, a separate skin nodule, and palpable matted axillary lymphadenopathy. Biopsies of the breast mass and subcutaneous nodule reveal invasive ductal carcinoma that is ER-negative, PR-negative, and HER2-positive by IHC (3+ staining). Based on clinical findings, the patient is staged as T4b (separate tumor nodule), N2 (matted axillary lymph nodes). Systemic staging with CT scan of the chest, abdomen, and pelvis shows no evidence of distant metastases.

• What is the recommended approach to management for this patient?

Recommendations for neoadjuvant therapy, given before definitive surgery, follow the same path as with other subtypes of breast cancer. Patients with suspected anatomical stage III disease are strongly encouraged to undergo upfront (neoadjuvant) chemotherapy in combination with HER2-targeted agents. In addition, all HER2-positive patients with clinically node-positive disease can be offered neoadjuvant therapy using chemotherapy plus dual anti-HER2 therapy (trastuzumab and pertuzumab), with complete pathological response expected in more than 60% of patients.^26,27 Because this patient has locally advanced disease, especially skin involvement and matted axillary nodes, she should undergo neoadjuvant therapy. Preferred regimens contain both trastuzumab and pertuzumab in combination with cytotoxic chemotherapy. The latter may be given concurrently (nonanthracycline regimens, such as docetaxel plus carboplatin) or sequentially (anthracycline-based regimens), as outlined in Table 2. Administration of anthracyclines and trastuzumab simultaneously is contraindicated due to increased risk of cardiomyopathy.²⁸

Endocrine therapy is not indicated for this patient per the current standard of care because the tumor was ER- and PR-negative. Had the tumor been hormone receptor–positive, endocrine therapy for a minimum of 5 years would have been indicated. Likewise, in the case of hormone receptor–positive disease, 12 months of neratinib therapy after completion of trastuzumab may add further benefit, as shown in the ExteNET trial.^22,23 Neratinib seems to have a propensity to prevent or delay trastuzumab-induced overexpression of estrogen receptors. This is mainly due to hormone receptor/HER2 crosstalk, a potential mechanism of resistance to trastuzumab.^29,30

In addition to the medical therapy options discussed here, this patient would be expected to benefit from adjuvant radiation to the breast and regional lymph nodes, given the presence of T4 disease and bulky adenopathy in the axilla.³¹

Case 2 Conclusion

The patient undergoes neoadjuvant treatment (docetaxel, carboplatin, trastuzumab, and pertuzumab every 21 days for a total of 6 cycles), followed by surgical resection (modified radical mastectomy) that reveals complete pathological response (no residual invasive carcinoma). Subsequently, she receives radiation therapy to the primary tumor site and regional lymph nodes while continuing trastuzumab and pertuzumab for 11 more cycles (17 total). Despite presenting with locally advanced disease, the patient has a favorable overall prognosis due to an excellent pathological response.

• What is the approach to follow-up after completion of primary therapy?

Patients may follow up every 3 to 6 months for clinical evaluation in the first 5 years after completing primary adjuvant therapy. An annual screening mammogram is recommended as well. Body imaging can be done if dictated by symptoms. However, routine CT, positron emission tomography, or bone scans are not recommended as part of follow-up in the absence of symptoms, mainly because of a lack of evidence that such surveillance improves survival.³²

 

Metastatic HER2-Positive Breast Cancer

Metastatic breast cancer most commonly presents as a distant recurrence of previously treated local disease. However, 6% to 18% of patients have no prior history of breast cancer and present with de novo metastatic disease.^33,34 The most commonly involved distant organs are the skeletal bones, liver, lung, distant lymph node stations, and brain. Compared to other subtypes, HER2-positive tumors have an increased tendency to involve the central nervous system.^35–38 Although metastatic HER2-positive breast cancer is not considered curable, significant improvement in survival has been achieved, and patients with metastatic disease have median survival approaching 5 years.³⁹

Case Presentation 3

A 69-year-old woman with a history of breast cancer 4 years ago presents with new-onset back pain and unintentional weight loss. On exam, she is found to have palpable axillary adenopathy on the same side as her previous cancer. Her initial disease was stage IIB ER-positive and HER2-positive and was treated with chemotherapy, mastectomy, and anastrozole, which the patient is still taking. She undergoes CT scan of the chest, abdomen, and pelvis and radionucleotide bone scan, which show multiple liver and bony lesions suspicious for metastatic disease. Axillary lymph node biopsy confirms recurrent invasive carcinoma that is ER-positive and HER2-positive by IHC (3+).

• What is the approach to management of a patient who presents with symptoms of recurrent HER2-positive disease?

This patient likely has metastatic breast cancer based on the imaging findings. In such cases, a biopsy of the recurrent disease should always be considered, if feasible, to confirm the diagnosis and rule out other etiologies such as different malignances and benign conditions. Hormone-receptor and HER2 testing should also be performed on recurrent disease, since a change in HER2 status can be seen in 15% to 33% of cases.^40–42

Based on data from the phase 3 CLEOPATRA trial, first-line systemic regimens for patients with metastatic breast cancer that is positive for HER2 should consist of a combination of docetaxel, trastuzumab, and pertuzumab.  Compared to placebo, adding pertuzumab yielded superior progression-free survival of 18.4 months (versus 12.4 months for placebo) and an unprecedented OS of 56.5 months (versus 40.8 for placebo).³⁹ Weekly paclitaxel can replace docetaxel with comparable efficacy (Table 3).⁴³

Patients can develop significant neuropathy as well as skin and nail changes after multiple cycles of taxane-based chemotherapy. Therefore, the taxane backbone may be dropped after 6 to 8 cycles, while patients continue the trastuzumab and pertuzumab combination until disease progression or unacceptable toxicity. Some patients may enjoy remarkable long-term survival on “maintenance” anti-HER2 therapy.⁴⁴ Despite lack of high-level evidence, such as from large randomized trials, some experts recommend the addition of a hormone blocker after discontinuation of the taxane in ER-positive tumors.⁴⁵

Premenopausal and perimenopausal women with hormone receptor–positive metastatic disease should be considered for simultaneous ovarian suppression. Ovarian suppression can be accomplished medically using a gonadotropin-releasing hormone agonist (goserelin) or surgically via salpingo-oophorectomy.^46–48

Case 3 Conclusion

The patient receives 6 cycles of docetaxel, trastuzumab, and pertuzumab, after which the docetaxel is discontinued due to neuropathy while she continues the other 2 agents. After 26 months of disease control, the patient is found to have new liver metastatic lesions, indicating progression of disease.

• What therapeutic options are available for this patient?

Patients whose disease progresses after receiving taxane- and trastuzumab-containing regimens are candidates to receive the novel antibody-drug conjugate ado-trastuzumab emtansine (T-DM1). Early progressors (ie, patients with early stage disease who have progression of disease while receiving adjuvant trastuzumab or within 6 months of completion of adjuvant trastuzumab) are also candidates for T-DM1. Treatment usually fits in the second line or beyond based on data from the EMILIA trial, which randomly assigned patients to receive either capecitabine plus lapatinib or T-DM1.^49,50 Progression-free survival in the T-DM1 group was 9.6 months versus 6.4 months for the comparator. Improvement of 4 months in OS persisted with longer follow-up despite a crossover rate of 27%. Furthermore, a significantly higher objective response rate and fewer adverse effects were reported in the T-DM1 patients. Most patients included in the EMILIA trial were pertuzumab-naive. However, the benefit of T-DM1 appears to persist, albeit to a lesser extent, for pertuzumab-pretreated patients.^51,52

Patients in whom treatment fails with 2 or more lines of therapy containing taxane-trastuzumab (with or without pertuzumab) and T-DM1 are candidates to receive a combination of capecitabine and lapatinib, a TKI, in the third line and beyond. Similarly, the combination of capecitabine with trastuzumab in the same settings appears to have equal efficacy.^53,54 Trastuzumab may be continued beyond progression while changing the single-agent chemotherapy drug for subsequent lines of therapy, per ASCO guidelines,⁵⁵ although improvement in OS has not been demonstrated beyond the third line in a large randomized trial (Table 3).

 

Approved HER2-Targeted Drugs

HER2-directed therapy is implemented in the management of nearly all stages of HER2-positive invasive breast cancer, including early and late stages (Table 4).

Trastuzumab

Trastuzumab was the first anti-HER2 agent to be approved by the FDA in 1998. It is a humanized monoclonal antibody directed against the extracellular domain of the HER2 receptor (domain IV).  Trastuzumab functions by interrupting HER2 signal transduction and by flagging tumor cells for immune destruction.⁵⁶ Cardiotoxicity, usually manifested as left ventricular systolic dysfunction, is the most noteworthy adverse effect of trastuzumab. The most prominent risk factors for cardiomyopathy in patients receiving trastuzumab are low baseline ejection fraction (< 55%), age > 50 years, co-administration and higher cumulative dose of anthracyclines, and increased body mass index and obesity.^57–59 Whether patients receive therapy in the neoadjuvant, adjuvant, or metastatic settings, baseline cardiac function assessment with echocardiogram or multiple-gated acquisition scan is required. While well-designed randomized trials validating the value and frequency of monitoring are lacking, repeated cardiac testing every 3 months is generally recommended for patients undergoing adjuvant therapy. Patients with metastatic disease who are receiving treatment with palliative intent may be monitored less frequently.^60,61

An asymptomatic drop in ejection fraction is the most common manifestation of cardiac toxicity. Other cardiac manifestations have also been reported with much less frequency, including arrhythmias, severe congestive heart failure, ventricular thrombus formation, and even cardiac death. Until monitoring and dose-adjustment guidelines are issued, the guidance provided in the FDA-approved prescribing information should be followed, which recommends holding trastuzumab when there is ≥ 16% absolute reduction in left ventricular ejection fraction (LVEF) from the baseline value; or if the LVEF value is below the institutional lower limit of normal and the drop is ≥ 10%. After holding the drug, cardiac function can be re-evaluated every 4 weeks. In most patients, trastuzumab-induced cardiotoxicity can be reversed by withholding trastuzumab and initiating cardioprotective therapy, although the latter remains controversial. Re-challenging after recovery of ejection fraction is possible and toxicity does not appear to be proportional to cumulative dose. Cardiomyopathy due to trastuzumab therapy is potentially reversible within 6 months in more than 80% of cases.^{28,57,60–63}

Other notable adverse effects of trastuzumab include pulmonary toxicity (such as interstitial lung disease) and infusion reactions (usually during or within 24 hours of first dose).

Pertuzumab

Pertuzumab is another humanized monoclonal antibody directed to a different extracellular domain of the HER2 receptor, the dimerization domain (domain II), which is responsible for heterodimerization of HER2 with other HER receptors, especially HER3. This agent should always be co-administered with trastuzumab as the 2 drugs produce synergistic anti-tumor effect, without competition for the receptor. Activation of HER3, via dimerization with HER2, produces an alternative mechanism of downstream signaling, even in the presence of trastuzumab and in the absence of growth factors (Figure 2). 

This dimerization is now a well-known mechanism of tumor resistance to trastuzumab; hence, co-administration of pertuzumab potentially prevents or delays such resistance.⁶⁴ The use of pertuzumab alone without trastuzumab is not currently recommended and does not confer significant clinical activity. The most notable adverse effects of this drug are infusion reactions and diarrhea. As pertuzumab is always given with trastuzumab, the same caution for cardiotoxicity must be exercised, and cardiac function evaluation and monitoring, as described for trastuzumab, is recommended. However, there is no evidence of increased cardiac dysfunction when pertuzumab is added to trastuzumab.⁶⁴

Ado-Trastuzumab Emtansine

Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate that combines the monoclonal antibody trastuzumab with the cytotoxic agent DM1 (emtansine), a potent microtubule inhibitor and a derivative of maytansine, in a single structure (Figure 3). 

In addition to the mechanisms of action of bare trastuzumab, T-DM1 adds significant cytotoxicity by way of releasing the maytansine moiety (DM1) intracellularly. It also exerts some bystander effect by disseminating locally to nearby cells that may express lower HER2 density (Figure 4).^65,66 

Aside from infusion reactions and cardiotoxicity that are mostly related to trastuzumab, this drug has adverse effects related to its cytotoxic component DM1. The most notable adverse effects include thrombocytopenia, which is attributable to uptake of the drug in the marrow by Fc-bearing megakaryocytes, and hepatotoxicity via drug binding to HER2 on hepatocytes and subsequent activation of cytokine-releasing Kupffer cells.^67,68 Neuropathy due to DM1 has also been reported, but the overall incidence of grade 3/4 adverse effects remains very low and the agent is generally very well tolerated.⁶⁶ Cardiac function monitoring follows the same principles described for trastuzumab.

Lapatinib

Lapatinib is an oral small-molecule tyrosine kinase inhibitor of EGFR (HER1) and HER2 receptors. It is approved in combination with capecitabine for patients with HER2-expressing metastatic breast cancer who previously received trastuzumab, an anthracycline, and a taxane chemotherapy or T-DM1. Lapatinib is also approved in combination with letrozole in postmenopausal women with HER2-positive, hormone receptor–positive metastatic disease, although it is unclear where this regimen would fit in the current schema. It may be considered for patients with hormone receptor–positive disease who are not candidates for therapy with taxane-trastuzumab and T-DM1 or who decline this therapy. Diarrhea is seen in most patients treated with lapatinib and may be severe in 20% of cases when lapatinib is combined with capecitabine. Decreases in LVEF have been reported and cardiac function monitoring at baseline and periodically may be considered.^69,70 Lapatinib is not approved for use in adjuvant settings.

Neratinib

Neratinib is an oral small-molecule irreversible tyrosine kinase inhibitor of HER1, HER2, and HER4. It is currently approved only for extended adjuvant therapy after completion of 1 year of standard trastuzumab therapy. It is given orally every day for 1 year. The main side effect, expected in nearly all patients, is diarrhea, which can be severe in up to 40% of patients and may lead to dehydration and electrolyte imbalance. Diarrhea usually starts early in the course of therapy and can be most intense during the first cycle. Therefore, prophylactic antidiarrheal therapy is recommended to reduce the intensity of diarrhea. Loperamide prophylaxis may be initiated simultaneously for all patients using a tapering schedule. Drug interruption or dose reduction may be required if diarrhea is severe or refractory.^21,71 Neratinib is not FDA-approved in the metastatic settings.

 

Conclusion

HER2-positive tumors represent a distinct subset(s) of breast tumors with unique pathological and clinical characteristics. Treatment with a combination of cytotoxic chemotherapy and HER2-targeted agents has led to a dramatic improvement in survival for patients with locoregional and advanced disease. Trastuzumab is an integral part of adjuvant therapy for HER2-positive invasive disease. Pertuzumab should be added to trastuzumab in node-positive disease. Neratinib may be considered after completion of trastuzumab therapy in patients with hormone receptor–positive disease. For metastatic HER2-positive breast cancer, a regimen consisting of docetaxel plus trastuzumab and pertuzumab is the standard first-line therapy. Ado-trastuzumab is an ideal next line option for patients whose disease progresses on trastuzumab and taxanes.

Introduction

Breast cancer is the second leading cause of cancer deaths among women in the United States, according to the SEER database. It is estimated that 1 in 8 women will be diagnosed with breast cancer at some point during their lifetime (12.4% lifetime risk).^1,2 Because breast tumors are clinically and histopathologically heterogeneous, different diagnostic and therapeutic approaches are required for each subtype. Among the subtypes, tumors that are positive for human epidermal growth factor receptor 2 (HER2) account for approximately 15% to 20% of all newly diagnosed localized and metastatic invasive breast tumors.^3,4 Historically, this subset of tumors has been considered the most aggressive due to a higher propensity to relapse and metastasize, translating into poorer prognosis compared with other subtypes.^5–7 However, with the advent of HER2-targeted therapy in the late 1990s, prognosis has significantly improved for both early- and late-stage HER2-positive tumors.⁸

Pathogenesis

The HER2 proto-oncogene belongs to a family of human epidermal growth factor receptors that includes 4 transmembrane tyrosine kinase receptors: HER1 (also commonly known as epidermal growth factor receptor, EGFR), HER2, HER3, and HER4. Another commonly used nomenclature for this family of receptors is ERBB1 to ERBB4. Each of the receptors has a similar structure consisting of a growth factor–binding extracellular domain, a single transmembrane segment, an intracellular protein-tyrosine kinase catalytic domain, and a tyrosine-containing cytoplasmic tail. Activation of the extracellular domain leads to conformational changes that initiate a cascade of reactions resulting in protein kinase activation. ERBB tyrosine receptor kinases subsequently activate several intracellular pathways that are critical for cellular function and survival, including the PI3K-AKT, RAS-MAPK, and mTOR pathways. Hyperactivation or overexpression of these receptors leads to uncontrolled cell growth and proliferation, and eventually cancerogenesis.^9,10

HER2 gene amplification can cause activation of the receptor’s extramembranous domain by way of either dimerization of two HER2 receptors or heterodimerization with other ERBB family receptors, leading to ligand-independent activation of cell signaling (ie, activation in the absence of external growth factors). Besides breast cancer, HER2 protein is overexpressed in several other tumor types, including esophageal and gastric adenocarcinomas, colon and gynecological malignancies, and to a lesser extent in other malignancies.

Biomarker Testing

All patients with newly diagnosed breast cancer should have their tumor tissue submitted for biomarker testing for estrogen receptors (ER), progesterone receptors (PR), and HER2 overexpression, as the result this testing dictates therapy choices. The purpose of HER2 testing is to investigate whether the HER2 gene, located on chromosome 17, is overexpressed or amplified. HER2 status provides the basis for treatment selection, which impacts long-term outcome measures such as recurrence and survival. Routine testing of carcinoma in situ for HER2 expression/amplification is not recommended and has no implication on choice of therapy at this time.

In 2013, the American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) updated their clinical guideline recommendations for HER2 testing in breast cancer to improve its accuracy and its utility as a predictive marker.¹¹ There are currently 2 approved modalities for HER2 testing: detection of HER2 protein overexpression by immunohistochemical staining (IHC), and detection of HER2 gene amplification using in-situ hybridization. The results of each type of testing are reported as positive, equivocal, or negative (Table 1).¹¹  IHC uses antibodies against HER2 protein to assess the level of protein expression at the membrane of invasive tumor cells; overexpression of HER2 is established based upon the intensity of cell membrane staining and the number of stained cells. Results are reported as positive for HER2 expression (3+ staining), negative for HER2 expression (0 or 1+ staining), or equivocal for HER2 expression (2+ staining).

Fluorescence in-situ hybridization (FISH) testing assesses for HER2 amplification by determining the number of HER2 signals and chromosome 17 centromere (CEP17) signals, respectively, in a tissue sample. HER2 status is based on the ratio of average HER2 signals to CEP17 signals and the average HER2 signal count per cell. FISH testing is considered positive when there are ≥ 6 copies of HER2 signals per cell or when the HER2/CEP17 ratio is ≥ 2. FISH testing is reported as negative when there are fewer than 4 copies of HER2 per cell and the HER2/CEP17 ratio is < 2. 

The test is considered equivocal if the number of HER2 copies is ≥ 4 but < 6 and the HER2/CEP17 ratio is < 2. In equivocal cases, repeat testing using an alternative probe or a different sample may be considered. Most institutions currently use IHC to determine HER2 status along with IHC staining for ER and PR. If HER2 status is 2+ or equivocal by IHC, then FISH testing is obtained as a confirmatory step (Figure 1).

 

Neoadjuvant and Adjuvant Therapy for Locoregional Disease

Case Patient 1

A 56-year-old woman undergoes ultrasound-guided biopsy of a self-palpated breast lump. Pathology shows invasive ductal carcinoma that is ER-positive, PR-negative, and HER2 equivocal by IHC (2+ staining). Follow-up FISH testing shows a HER2/CEP17 ratio of 2.5. The tumor is estimated to be 2 cm in diameter by imaging and exam with no clinically palpable axillary lymphadenopathy. The patient exhibits no constitutional or localized symptoms concerning for metastases.

• What is the recommended management approach for this patient?

According to the ASCO/CAP guidelines, this patient’s tumor qualifies as HER2-positive based upon testing results showing amplification of the gene. This result has important implications for management since nearly all patients with macroscopically invasive HER2-positive tumors should be considered for adjuvant chemotherapy in combination with anti-HER2 therapy. The patient should proceed with upfront tumor resection and sentinel lymph node biopsy. Systemic staging imaging (ie, computed tomography [CT] or bone scan) is not indicated in early stage breast cancer.^12,13 Systemic staging scans are indicated when (1) any anatomical stage III disease is suspected (eg, with involvement of the skin or chest wall, the presence of enlarged matted or fixed axillary lymph nodes, and involvement of nodal stations other than in the axilla), and (2) when symptoms or abnormal laboratory values raise suspicion for distant metastases (eg, unexplained bone pain, unintentional weight loss, elevated serum alkaline phosphatase, and transaminitis).

Case 1 Continued

The patient presents to discuss treatment options after undergoing a lumpectomy and sentinel node biopsy procedure. The pathology report notes a single focus of carcinoma measuring 2 cm with negative sentinel lymph nodes.

• What agents are used for adjuvant therapy in HER2-postive breast cancer?

Nearly all patients with macroscopically invasive (> 1 mm) breast carcinoma should be considered for adjuvant therapy using a regimen that contains a taxane and trastuzumab. However, the benefit may be small for patients with tumors ≤ 5 mm (T1a, N0), so it is important to carefully weigh the risk against the benefit. Among the agents that targeting HER2, only trastuzumab has been shown to improve overall survival (OS) in the adjuvant setting; long-term follow-up data are awaited for other agents.⁸ A trastuzumab biosimilar, trastuzumab-dkst, was recently approved by the US Food and Drug Administration (FDA) for the same indications as trastuzumab.¹⁴ The regimens most commonly used in the adjuvant and neoadjuvant settings for nonmetastatic breast cancer are summarized in Table 2.

Patients with small (≤ 3 cm), node-negative tumors can generally be considered for a reduced-intensity regimen that includes weekly paclitaxel plus trastuzumab. This combination proved efficacious in a single-group, multicenter study that enrolled 406 patients.¹⁵ Paclitaxel and trastuzumab were given once weekly for 12 weeks, followed by trastuzumab, either weekly or every 3 weeks, to complete 1 year of therapy.After a median follow-up of more than 6 years, the rates of distant and locoregional recurrence were 1% and 1.2%, respectively.¹⁶

A combination of docetaxel, carboplatin, and trastuzumab is a nonanthracycline regimen that is also appropriate in this setting, based on the results of the Breast Cancer International Research Group 006 (BCIRG-006) trial.¹⁷ This phase 3 randomized trial enrolled 3222 women with HER2-positive, invasive, high-risk adenocarcinoma. Eligible patients had a T1–3 tumor and either lymph node–negative or –positive disease and were randomly assigned to receive 1 of 3 regimens: group 1 received doxorubicin and cyclophosphamide every 3 weeks for 4 cycles followed by docetaxel every 3 weeks for 4 cycles (AC-T); group 2 received the AC-T regimen in combination with trastuzumab; and group 3 received docetaxel, carboplatin, and trastuzumab once every 3 weeks for 6 cycles (TCH). Groups 2 and 3 also received trastuzumab for an additional 34 weeks to complete 1 year of therapy. Trastuzumab-containing regimens were found to offer superior disease-free survival (DFS) and OS. When comparing the 2 trastuzumab arms after more than 10 years of follow-up, no statistically significant advantage of an anthracycline regimen over a nonanthracycline regimen was found.¹⁸ Furthermore, the anthracycline arm had a fivefold higher incidence of symptomatic congestive heart failure (grades 3 and 4), and the nonanthracycline regimen was associated with a lower incidence of treatment-related leukemia, a clinically significant finding despite not reaching statistical significance due to low overall numbers.

BCIRG-006, NSABP B-31, NCCTG N9831, and HERA are all large randomized trials with consistent results confirming trastuzumab’s role in reducing recurrence and improving survival in HER2-positive breast cancer in the adjuvant settings. The estimated overall benefit from addition of this agent was a 34% to 41% improvement in survival and a 33% to 52% improvement in DFS.^8,17–20

Dual anti-HER2 therapy containing both trastuzumab and pertuzumab should be strongly considered for patients with macroscopic lymph node involvement based on the results of the APHINITY trial.²¹ In this study, the addition of pertuzumab to standard trastuzumab-based therapy led to a significant improvement in invasive-disease-free survival at 3 years. In subgroup analysis, the benefit was restricted to the node-positive group (3-year invasive-disease-free survival rates of 92% in the pertuzumab group versus 90.2% in the placebo group, P = 0.02). Patients with hormone receptor–negative disease derived greater benefit from the addition of pertuzumab. Regimens used in the APHINITY trial included the anti-HER2 agents trastuzumab and pertuzumab in combination with 1 of the following chemotherapy regimens: sequential cyclophosphamide plus either doxorubicin or epirubicin, followed by either 4 cycles of docetaxel or 12 weekly doses of paclitaxel; sequential fluorouracil plus either epirubicin or doxorubicin plus cyclophosphamide (3 or 4 cycles), followed by 3 or 4 cycles of docetaxel or 12 weekly cycles of paclitaxel; or 6 cycles of concurrent docetaxel plus carboplatin.

One-year therapy with neratinib, an oral tyrosine kinase inhibitor of HER2, is now approved by the FDA after completion of trastuzumab in the adjuvant setting, based on the results of the ExteNET trial.²² In this study, patients who had completed trastuzumab within the preceding 12 months, without evidence of recurrence, were randomly assigned to receive either oral neratinib or placebo daily for 1 year. The 2-year DFS rate was 93.9% and 91.6% for the neratinib and placebo groups, respectively. The most common adverse effect of neratinib was diarrhea, with approximately 40% of patients experiencing grade 3 diarrhea. In subgroup analyses, hormone receptor–positive patients derived the most benefit, while hormone receptor–negative patients derived no or marginal benefit.²² OS benefit has not yet been established.²³

Trastuzumab therapy (with pertuzumab if indicated) should be offered for an optimal duration of 12 months (17 cycles, including those given with chemotherapy backbone). A shorter duration of therapy, 6 months, has been shown to be inferior,²⁴ while a longer duration, 24 months, has been shown to provide no additional benefit.²⁵

Finally, sequential addition of anti-estrogen endocrine therapy is indicated for hormone-positive tumors. Endocrine therapy is usually added after completion of the chemotherapy backbone of the regimen, but may be given concurrently with anti-HER2 therapy. If radiation is being administered, endocrine therapy can be given concurrently or started after radiation therapy is completed.

 

Case 1 Conclusion

The patient can be offered 1 of 2 adjuvant treatment regimens, either TH or TCH (Table 2). Since the patient had lumpectomy, she is an appropriate candidate for adjuvant radiation, which would be started after completion of the chemotherapy backbone (taxane/platinum). Endocrine therapy for at least 5 years should be offered sequentially or concurrently with radiation. Her long-term prognosis is very favorable.

Case Patient 2

A 43-year-old woman presents with a 4-cm breast mass, a separate skin nodule, and palpable matted axillary lymphadenopathy. Biopsies of the breast mass and subcutaneous nodule reveal invasive ductal carcinoma that is ER-negative, PR-negative, and HER2-positive by IHC (3+ staining). Based on clinical findings, the patient is staged as T4b (separate tumor nodule), N2 (matted axillary lymph nodes). Systemic staging with CT scan of the chest, abdomen, and pelvis shows no evidence of distant metastases.

• What is the recommended approach to management for this patient?

Recommendations for neoadjuvant therapy, given before definitive surgery, follow the same path as with other subtypes of breast cancer. Patients with suspected anatomical stage III disease are strongly encouraged to undergo upfront (neoadjuvant) chemotherapy in combination with HER2-targeted agents. In addition, all HER2-positive patients with clinically node-positive disease can be offered neoadjuvant therapy using chemotherapy plus dual anti-HER2 therapy (trastuzumab and pertuzumab), with complete pathological response expected in more than 60% of patients.^26,27 Because this patient has locally advanced disease, especially skin involvement and matted axillary nodes, she should undergo neoadjuvant therapy. Preferred regimens contain both trastuzumab and pertuzumab in combination with cytotoxic chemotherapy. The latter may be given concurrently (nonanthracycline regimens, such as docetaxel plus carboplatin) or sequentially (anthracycline-based regimens), as outlined in Table 2. Administration of anthracyclines and trastuzumab simultaneously is contraindicated due to increased risk of cardiomyopathy.²⁸

Endocrine therapy is not indicated for this patient per the current standard of care because the tumor was ER- and PR-negative. Had the tumor been hormone receptor–positive, endocrine therapy for a minimum of 5 years would have been indicated. Likewise, in the case of hormone receptor–positive disease, 12 months of neratinib therapy after completion of trastuzumab may add further benefit, as shown in the ExteNET trial.^22,23 Neratinib seems to have a propensity to prevent or delay trastuzumab-induced overexpression of estrogen receptors. This is mainly due to hormone receptor/HER2 crosstalk, a potential mechanism of resistance to trastuzumab.^29,30

In addition to the medical therapy options discussed here, this patient would be expected to benefit from adjuvant radiation to the breast and regional lymph nodes, given the presence of T4 disease and bulky adenopathy in the axilla.³¹

Case 2 Conclusion

The patient undergoes neoadjuvant treatment (docetaxel, carboplatin, trastuzumab, and pertuzumab every 21 days for a total of 6 cycles), followed by surgical resection (modified radical mastectomy) that reveals complete pathological response (no residual invasive carcinoma). Subsequently, she receives radiation therapy to the primary tumor site and regional lymph nodes while continuing trastuzumab and pertuzumab for 11 more cycles (17 total). Despite presenting with locally advanced disease, the patient has a favorable overall prognosis due to an excellent pathological response.

• What is the approach to follow-up after completion of primary therapy?

Patients may follow up every 3 to 6 months for clinical evaluation in the first 5 years after completing primary adjuvant therapy. An annual screening mammogram is recommended as well. Body imaging can be done if dictated by symptoms. However, routine CT, positron emission tomography, or bone scans are not recommended as part of follow-up in the absence of symptoms, mainly because of a lack of evidence that such surveillance improves survival.³²

 

Metastatic HER2-Positive Breast Cancer

Metastatic breast cancer most commonly presents as a distant recurrence of previously treated local disease. However, 6% to 18% of patients have no prior history of breast cancer and present with de novo metastatic disease.^33,34 The most commonly involved distant organs are the skeletal bones, liver, lung, distant lymph node stations, and brain. Compared to other subtypes, HER2-positive tumors have an increased tendency to involve the central nervous system.^35–38 Although metastatic HER2-positive breast cancer is not considered curable, significant improvement in survival has been achieved, and patients with metastatic disease have median survival approaching 5 years.³⁹

Case Presentation 3

A 69-year-old woman with a history of breast cancer 4 years ago presents with new-onset back pain and unintentional weight loss. On exam, she is found to have palpable axillary adenopathy on the same side as her previous cancer. Her initial disease was stage IIB ER-positive and HER2-positive and was treated with chemotherapy, mastectomy, and anastrozole, which the patient is still taking. She undergoes CT scan of the chest, abdomen, and pelvis and radionucleotide bone scan, which show multiple liver and bony lesions suspicious for metastatic disease. Axillary lymph node biopsy confirms recurrent invasive carcinoma that is ER-positive and HER2-positive by IHC (3+).

• What is the approach to management of a patient who presents with symptoms of recurrent HER2-positive disease?

This patient likely has metastatic breast cancer based on the imaging findings. In such cases, a biopsy of the recurrent disease should always be considered, if feasible, to confirm the diagnosis and rule out other etiologies such as different malignances and benign conditions. Hormone-receptor and HER2 testing should also be performed on recurrent disease, since a change in HER2 status can be seen in 15% to 33% of cases.^40–42

Based on data from the phase 3 CLEOPATRA trial, first-line systemic regimens for patients with metastatic breast cancer that is positive for HER2 should consist of a combination of docetaxel, trastuzumab, and pertuzumab.  Compared to placebo, adding pertuzumab yielded superior progression-free survival of 18.4 months (versus 12.4 months for placebo) and an unprecedented OS of 56.5 months (versus 40.8 for placebo).³⁹ Weekly paclitaxel can replace docetaxel with comparable efficacy (Table 3).⁴³

Patients can develop significant neuropathy as well as skin and nail changes after multiple cycles of taxane-based chemotherapy. Therefore, the taxane backbone may be dropped after 6 to 8 cycles, while patients continue the trastuzumab and pertuzumab combination until disease progression or unacceptable toxicity. Some patients may enjoy remarkable long-term survival on “maintenance” anti-HER2 therapy.⁴⁴ Despite lack of high-level evidence, such as from large randomized trials, some experts recommend the addition of a hormone blocker after discontinuation of the taxane in ER-positive tumors.⁴⁵

Premenopausal and perimenopausal women with hormone receptor–positive metastatic disease should be considered for simultaneous ovarian suppression. Ovarian suppression can be accomplished medically using a gonadotropin-releasing hormone agonist (goserelin) or surgically via salpingo-oophorectomy.^46–48

Case 3 Conclusion

The patient receives 6 cycles of docetaxel, trastuzumab, and pertuzumab, after which the docetaxel is discontinued due to neuropathy while she continues the other 2 agents. After 26 months of disease control, the patient is found to have new liver metastatic lesions, indicating progression of disease.

• What therapeutic options are available for this patient?

Patients whose disease progresses after receiving taxane- and trastuzumab-containing regimens are candidates to receive the novel antibody-drug conjugate ado-trastuzumab emtansine (T-DM1). Early progressors (ie, patients with early stage disease who have progression of disease while receiving adjuvant trastuzumab or within 6 months of completion of adjuvant trastuzumab) are also candidates for T-DM1. Treatment usually fits in the second line or beyond based on data from the EMILIA trial, which randomly assigned patients to receive either capecitabine plus lapatinib or T-DM1.^49,50 Progression-free survival in the T-DM1 group was 9.6 months versus 6.4 months for the comparator. Improvement of 4 months in OS persisted with longer follow-up despite a crossover rate of 27%. Furthermore, a significantly higher objective response rate and fewer adverse effects were reported in the T-DM1 patients. Most patients included in the EMILIA trial were pertuzumab-naive. However, the benefit of T-DM1 appears to persist, albeit to a lesser extent, for pertuzumab-pretreated patients.^51,52

Patients in whom treatment fails with 2 or more lines of therapy containing taxane-trastuzumab (with or without pertuzumab) and T-DM1 are candidates to receive a combination of capecitabine and lapatinib, a TKI, in the third line and beyond. Similarly, the combination of capecitabine with trastuzumab in the same settings appears to have equal efficacy.^53,54 Trastuzumab may be continued beyond progression while changing the single-agent chemotherapy drug for subsequent lines of therapy, per ASCO guidelines,⁵⁵ although improvement in OS has not been demonstrated beyond the third line in a large randomized trial (Table 3).

 

Approved HER2-Targeted Drugs

HER2-directed therapy is implemented in the management of nearly all stages of HER2-positive invasive breast cancer, including early and late stages (Table 4).

Trastuzumab

Trastuzumab was the first anti-HER2 agent to be approved by the FDA in 1998. It is a humanized monoclonal antibody directed against the extracellular domain of the HER2 receptor (domain IV).  Trastuzumab functions by interrupting HER2 signal transduction and by flagging tumor cells for immune destruction.⁵⁶ Cardiotoxicity, usually manifested as left ventricular systolic dysfunction, is the most noteworthy adverse effect of trastuzumab. The most prominent risk factors for cardiomyopathy in patients receiving trastuzumab are low baseline ejection fraction (< 55%), age > 50 years, co-administration and higher cumulative dose of anthracyclines, and increased body mass index and obesity.^57–59 Whether patients receive therapy in the neoadjuvant, adjuvant, or metastatic settings, baseline cardiac function assessment with echocardiogram or multiple-gated acquisition scan is required. While well-designed randomized trials validating the value and frequency of monitoring are lacking, repeated cardiac testing every 3 months is generally recommended for patients undergoing adjuvant therapy. Patients with metastatic disease who are receiving treatment with palliative intent may be monitored less frequently.^60,61

An asymptomatic drop in ejection fraction is the most common manifestation of cardiac toxicity. Other cardiac manifestations have also been reported with much less frequency, including arrhythmias, severe congestive heart failure, ventricular thrombus formation, and even cardiac death. Until monitoring and dose-adjustment guidelines are issued, the guidance provided in the FDA-approved prescribing information should be followed, which recommends holding trastuzumab when there is ≥ 16% absolute reduction in left ventricular ejection fraction (LVEF) from the baseline value; or if the LVEF value is below the institutional lower limit of normal and the drop is ≥ 10%. After holding the drug, cardiac function can be re-evaluated every 4 weeks. In most patients, trastuzumab-induced cardiotoxicity can be reversed by withholding trastuzumab and initiating cardioprotective therapy, although the latter remains controversial. Re-challenging after recovery of ejection fraction is possible and toxicity does not appear to be proportional to cumulative dose. Cardiomyopathy due to trastuzumab therapy is potentially reversible within 6 months in more than 80% of cases.^{28,57,60–63}

Other notable adverse effects of trastuzumab include pulmonary toxicity (such as interstitial lung disease) and infusion reactions (usually during or within 24 hours of first dose).

Pertuzumab

Pertuzumab is another humanized monoclonal antibody directed to a different extracellular domain of the HER2 receptor, the dimerization domain (domain II), which is responsible for heterodimerization of HER2 with other HER receptors, especially HER3. This agent should always be co-administered with trastuzumab as the 2 drugs produce synergistic anti-tumor effect, without competition for the receptor. Activation of HER3, via dimerization with HER2, produces an alternative mechanism of downstream signaling, even in the presence of trastuzumab and in the absence of growth factors (Figure 2). 

This dimerization is now a well-known mechanism of tumor resistance to trastuzumab; hence, co-administration of pertuzumab potentially prevents or delays such resistance.⁶⁴ The use of pertuzumab alone without trastuzumab is not currently recommended and does not confer significant clinical activity. The most notable adverse effects of this drug are infusion reactions and diarrhea. As pertuzumab is always given with trastuzumab, the same caution for cardiotoxicity must be exercised, and cardiac function evaluation and monitoring, as described for trastuzumab, is recommended. However, there is no evidence of increased cardiac dysfunction when pertuzumab is added to trastuzumab.⁶⁴

Ado-Trastuzumab Emtansine

Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate that combines the monoclonal antibody trastuzumab with the cytotoxic agent DM1 (emtansine), a potent microtubule inhibitor and a derivative of maytansine, in a single structure (Figure 3). 

In addition to the mechanisms of action of bare trastuzumab, T-DM1 adds significant cytotoxicity by way of releasing the maytansine moiety (DM1) intracellularly. It also exerts some bystander effect by disseminating locally to nearby cells that may express lower HER2 density (Figure 4).^65,66 

Aside from infusion reactions and cardiotoxicity that are mostly related to trastuzumab, this drug has adverse effects related to its cytotoxic component DM1. The most notable adverse effects include thrombocytopenia, which is attributable to uptake of the drug in the marrow by Fc-bearing megakaryocytes, and hepatotoxicity via drug binding to HER2 on hepatocytes and subsequent activation of cytokine-releasing Kupffer cells.^67,68 Neuropathy due to DM1 has also been reported, but the overall incidence of grade 3/4 adverse effects remains very low and the agent is generally very well tolerated.⁶⁶ Cardiac function monitoring follows the same principles described for trastuzumab.

Lapatinib

Lapatinib is an oral small-molecule tyrosine kinase inhibitor of EGFR (HER1) and HER2 receptors. It is approved in combination with capecitabine for patients with HER2-expressing metastatic breast cancer who previously received trastuzumab, an anthracycline, and a taxane chemotherapy or T-DM1. Lapatinib is also approved in combination with letrozole in postmenopausal women with HER2-positive, hormone receptor–positive metastatic disease, although it is unclear where this regimen would fit in the current schema. It may be considered for patients with hormone receptor–positive disease who are not candidates for therapy with taxane-trastuzumab and T-DM1 or who decline this therapy. Diarrhea is seen in most patients treated with lapatinib and may be severe in 20% of cases when lapatinib is combined with capecitabine. Decreases in LVEF have been reported and cardiac function monitoring at baseline and periodically may be considered.^69,70 Lapatinib is not approved for use in adjuvant settings.

Neratinib

Neratinib is an oral small-molecule irreversible tyrosine kinase inhibitor of HER1, HER2, and HER4. It is currently approved only for extended adjuvant therapy after completion of 1 year of standard trastuzumab therapy. It is given orally every day for 1 year. The main side effect, expected in nearly all patients, is diarrhea, which can be severe in up to 40% of patients and may lead to dehydration and electrolyte imbalance. Diarrhea usually starts early in the course of therapy and can be most intense during the first cycle. Therefore, prophylactic antidiarrheal therapy is recommended to reduce the intensity of diarrhea. Loperamide prophylaxis may be initiated simultaneously for all patients using a tapering schedule. Drug interruption or dose reduction may be required if diarrhea is severe or refractory.^21,71 Neratinib is not FDA-approved in the metastatic settings.

 

Conclusion

HER2-positive tumors represent a distinct subset(s) of breast tumors with unique pathological and clinical characteristics. Treatment with a combination of cytotoxic chemotherapy and HER2-targeted agents has led to a dramatic improvement in survival for patients with locoregional and advanced disease. Trastuzumab is an integral part of adjuvant therapy for HER2-positive invasive disease. Pertuzumab should be added to trastuzumab in node-positive disease. Neratinib may be considered after completion of trastuzumab therapy in patients with hormone receptor–positive disease. For metastatic HER2-positive breast cancer, a regimen consisting of docetaxel plus trastuzumab and pertuzumab is the standard first-line therapy. Ado-trastuzumab is an ideal next line option for patients whose disease progresses on trastuzumab and taxanes.

Introduction

von Willebrand disease (VWD) is an inherited bleeding disorder caused by deficient or defective plasma von Willebrand factor (VWF). VWF is an adhesive multimeric plasma glycoprotein that performs 2 major functions in hemostasis: it mediates platelet adhesion to injured subendothelium via glycoprotein 1bα (GPIbα), and it binds and stabilizes factor VIII (FVIII) in circulation, protecting it from proteolytic degradation by enzymes. The current VWD classification recognizes 3 types (Table 1).¹ 

In order to understand the role of the numerous laboratory investigations as well as the classification of VWD, it is important to review the structure and function of the VWF subunit. Bleeding symptoms, including mucocutaneous bleeding and excessive bleeding after surgery or trauma, reflect the defect in primary hemostasis. Treatment focuses on increasing VWF levels with desmopressin (1-deamino-8-D-arginine vasopressin, DDAVP) or clotting factor concentrates containing both VWF and FVIII (VWF/FVIII concentrate). Nonspecific treatment options include antifibrinolytic agents (tranexamic acid) and hormone therapy (oral contraceptive pill).

Prevalence

VWD is the most common inherited bleeding disorder. However, because VWF levels are highly variable and disease severity ranges from mild bleeding symptoms to severe or life-threatening bleeds, the reported prevalence of VWD depends on the diagnostic definition used. Two large epidemiologic studies have reported prevalence rates of approximately 1%.^2,3 In these studies, healthy school-aged children were screened and diagnosed with VWD based on low VWF activity, measured as ristocetin cofactor, and a personal and family history of bleeding symptoms. At the other extreme, when considering patients whose bleeding symptoms are sufficiently severe to warrant referral to specialized centers, the reported prevalence of VWD ranges from 20 to 113 per million.⁴ These studies likely over- and underestimate clinically significant VWD. More recent studies suggest that the prevalence of VWD in individuals whose bleeding symptoms are significant enough to present to a primary care physician is approximately 0.1%.⁵ This figure is likely a more accurate estimate of the true prevalence of symptomatic VWD.

Although VWD is autosomally inherited, females are more likely to present with bleeding symptoms and be diagnosed because of increased exposure to bleeding challenges, such as menorrhagia and childbirth. VWD does not show any geographic or ethnic predilection, but there is an increased prevalence of the recessive forms, such as type 2N and type 3 VWD, in areas with high rates of consanguinity.

VWF Protein Structure and Function

The VWF gene is located on chromosome 12 at p13.3 and spans 178 kb comprising 52 exons.⁶ The expression of the VWF gene is tightly restricted to endothelial cells, platelets, and megakaryocytes, where VWF is stored in Weibel-Palade bodies and α-granules. VWF is a large multimeric glycoprotein with several important functional domains (Figure).

Extensive post-translational modifications, mediated by domains D3 and CK as well as the VWF propeptide, result in disulfide-linked multimers that can be greater than 20,000 kDa, while the VWF subunit is approximately 250 kDa. The high-molecular-weight (HMW) multimers are most effective in mediating platelet adhesion to the site of vascular injury; therefore, appropriate multimer formation is integral to VWF’s function. VWF is either secreted from local endothelial cells or recruited from the circulation to the site of endothelial injury, where it adheres to exposed collagen, predominately via the collagen-binding site in the A3 domain. Once immobilized, VWF is subjected to the high shear rates of the arterial circulation and undergoes a conformational change that exposes the platelet GPIbα binding site within the A1 domain.⁷ The high-affinity, rapid and reversible interaction between VWF and GPIbα tethers platelets to the endothelium where they roll until they are immobilized by integrin-mediated binding, which has slower binding kinetics. The RGD (Arg-Gly-Asp) sequence within the C4 domain also contributes to platelet adhesion by interacting with GPIIb-IIIa of activated platelets.⁸ ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) is a plasma protease that cleaves circulating VWF in the A2 domain when VWF multimers unfold in response to sufficient shear, exposing the cleavage site within the A2 domain.⁹ VWF’s second role in hemostasis is fulfilled by the D’ and D3 domains, which bind and protect FVIII from proteolytic degradation, thereby prolonging its half-life. In the absence of VWF, FVIII has a half-life of approximately 2 hours, in contrast to a normal half-life of 12 to 20 hours when bound to VWF.⁴

Classification, Pathophysiology, and Genetics

The International Society of Thrombosis and Hemostasis (ISTH) classification of VWD was updated in 2006 (Table 1).¹ It incorporates important aspects of clinical phenotype, pathophysiological mechanisms, and treatment considerations. The 3 categories are: type 1, which is a partial quantitative deficiency; type 2 with 4 subtypes (2A, 2B, 2M, and 2N), which is a qualitative defect; and type 3, which is a virtual absence of VWF. Although the diagnosis and categorization of VWD can be achieved with widely available laboratory testing, further subcategorization among type 2 VWD subtypes may require referral to a specialized laboratory. The current ISTH classification intentionally does not incorporate genotypic data. In type 2 or type 3 VWD disease, VWF mutations are identified in more than 90% of cases and are completely penetrant, whereas mutations are identified in only approximately 65% of type 1 VWD cases and have been associated with incomplete penetrance and variable expressivity.¹⁰ These studies suggest that type 1 VWD is an oligogenic disease with mutations in genes regulating secretion or clearance contributing to a VWD phenotype.

 

VWD Types

Type 1

Type 1 VWD is caused by a partial quantitative deficiency of VWF and represents approximately 75% of VWD cases. It is the most clinically heterogeneous type, with patients having a mild to moderate bleeding phenotype.¹¹ Bleeding in type 1 VWD results from a decrease in the concentration of VWF. The VWF function is normal without a significant abnormality in the platelet, collagen, or FVIII binding sites or a significant decrease in HMW multimers. Functional assays of VWF, such as VWF ristocetin cofactor (VWF:RCo) or VWF activity (VWF:Act) (see section on Laboratory Testing for further details), are proportionally decreased relative to the VWF antigen level (VWF:Ag), and the ratio of functional activity as compared with the VWF level is normal (ie, VWF:RCo/VWF:Ag ratio is > 0.6). As noted, VWF mutations are identified in only 65% of type 1 VWD cases and have incomplete penetrance and variable expressivity.¹⁰ Approximately 70% of mutations identified are missense mutations. Missense mutations may affect VWF levels by affecting any part of the biosynthetic pathway, including trafficking, storage, secretion, and/or clearance of VWF.

Increased VWF clearance is a well-described mechanism for type 1 VWD, known as type 1C. These patients will typically have very low VWF levels, an increased VWF propeptide to antigen ratio (VWFpp/VWF:Ag), and a marked but short-lived response to DDAVP, limiting DDAVP’s clinical applicability.¹² On the other hand, the half-life of VWF/FVIII concentrates is normal in these individuals. Type 1C VWD is caused by missense mutations which occur mainly in the D3 domain and reduce the half-life of VWF up to 15-fold. R1205H, known as the “Vicenza” variant, is the most common and severe as well as the best characterized of these mutations.¹³

Type 2

Accounting for approximately 25% of VWD cases, type 2 VWD is characterized by a qualitative deficiency of VWF activity and is further subcategorized based on the mechanism of VWF dysfunction. Type 2A, 2B, and 2M affect VWF–platelet interactions by way of loss of HMW multimers, a gain of function of the GPIbα binding site, or a loss of function of the same site, respectively. On the other hand, type 2N is caused by defective VWF binding to FVIII. Type 2 VWD is often suspected when investigations demonstrate a function-antigen discordance: the VWF:RCo or VWF:Act is decreased disproportionately to the decrease in VWF:Ag, and the VWF:RCo/VWF:Ag ratio is less than 0.6.

Type 2A VWD is the most common type 2 variant. It is characterized by disproportionately low functional activity compared to antigen level (ie, VWF:RCo/VWF:ag ratio is < 0.6) and a loss of HMW and sometimes intermediate molecular weight (IMW) multimers. Ristocetin-induced platelet agglutination (RIPA) will be decreased with standard doses of ristocetin and absent with low doses. Type 2A VWD is usually inherited as an autosomal dominant trait. This subtype encompasses missense mutations that impair dimerization or multimerization of VWF subunits (CK, D1, and D2 domains); disrupt intersubunit disulphide bonds (D3 and D2 domains); enhance susceptibility to ADAMTS13-mediated proteolysis (A2 and A1 domains); or result in intracellular retention of the HMW multimers (D3, A1, and A2 domains).¹⁰ The result is VWF that lacks HMW multimers, thereby possessing fewer GPIbα binding sites, and that is less effective in binding platelets.

Type 2B VWD is the result of gain-of-function mutations within the GPIbα binding site of VWF. Generally, the platelet-binding site of VWF within the A1 domain is only exposed once VWF is immobilized on injured collagen and subjected to shear forces, resulting in a conformational change.⁷ In type 2B VWD, the gain-of-function mutation results in spontaneous binding of VWF to platelets without the need for a VWF-collagen interaction and unfolding of VWF by shear forces. The VWF–platelet interaction selectively depletes the HMW multimers by the unfolding of the A2 domain and increasing ADAMTS13 proteolysis. The increased binding of mutant VWF to platelets also triggers the formation of platelet aggregates, which are removed from circulation resulting in thrombocytopenia. Increases in endogenous VWF seen with acute stressors or pregnancy can worsen thrombocytopenia and increase the risk of bleeding.¹⁴ Certain mutations, such as V1316M, alter megakaryocytopoiesis and are characterized by giant platelets with abnormal ultrastructure and further exacerbate the thrombocytopenia.¹⁵ The laboratory profile reveals a VWF:RCo/VWF:Ag ratio of < 0.6 and absence of HMW multimers. In contrast to type 2A, platelets will agglutinate with low-dose ristocetin. Missense mutations are highly penetrant dominant and occur in or close to the A1 domain.¹⁶

Type 2M VWD is characterized by loss-of-function mutations within the GPIbα binding site of VWF. Phenotypic characteristics include a reduced ratio of VWF:RCo/VWF:Ag of < 0.6 but a normal multimer pattern.¹⁷ Missense mutations are reported in the A1 domain affecting the GPIbα-binding site. In very rare instances, mutations in the A3 domain that impair the VWF/collagen interaction have been described.¹⁸ These collagen-binding mutations are not included in the last iteration of the ISTH classification in 2006,¹ but fit best in the type 2M category. In these cases, VWF:RCo or VWF:Act, which reflect activity at the GPIbα-binding site, may be normal and the diagnosis requires VWF/collagen binding assays (VWF:CB).

Type 2N VWD results from mutations of the FVIII binding site or conformational changes that impair the VWF–FVIII interaction. Most (~80%) missense mutations are located in domains D’ and D3.¹⁹ These mutations are autosomal recessive, and affected individuals are either homozygous or compound heterozygous for type 2N/2N or type 1/2N mutations, or compound heterozygous for a missense mutation and a mutation resulting in a null allele (type 2N/3 mutations). The laboratory phenotype is a disproportionate reduction in the FVIII level relative to the VWF level, which may be low or normal. Most cases of type 2N VWD have a normal multimeric profile, but rare cases will demonstrate loss of HMW multimers. Definitive diagnosis requires evidence of reduced FVIII binding to VWF (VWF:FVIIIB) or the identification of causative mutations in the FVIII binding region of the VWF gene.²⁰

 

Type 3

Type 3 VWD is defined by a virtual absence of VWF. The inheritance of type 3 VWD has often been reported as autosomal recessive. However, there is emerging evidence that it can also be inherited in a co-dominant pattern: obligate carriers of type 3 VWD mutations have more mucocutaneous bleeding symptoms than normal individuals, and in approximately 50% of cases may carry a diagnosis of type 1 VWD.²¹ This condition is characterized by prolongation of the activated partial thromboplastin time (aPTT), undetectable levels of VWF:Ag, and VWF:RCo and FVIII levels less than 10 IU/dL (10%). The majority (~80%) of type 3 VWD patients have 2 null alleles as a result of a variety of mutations, with nonsense mutations accounting for about one-third.¹⁰ The remainder of the mutational spectrum is made up of missense mutations predominantly located in the D1-D2 (exons 3–11) and D4-CK (exons 37–52) domains that result in intracellular VWF retention, or large deletions, resulting in frameshift mutations affecting 1 or more exons. Because there is little or no circulating VWF, patients with type 3 VWD may develop alloantibodies to VWF, which can complicate treatment.²²

Diagnosis

Clinical Manifestations

VWD is a congenital bleeding disorder. The increased risk of bleeding is present from birth, but symptoms may only manifest when there is a hemostatic challenge. Bleeding symptoms become more apparent with increasing age and exposure to hemostatic challenges. As a result, the diagnosis is often delayed into adulthood in mild to moderate forms of VWD. On the other hand, with more severe bleeding phenotypes such as type 3 VWD, the diagnosis is often made in childhood. Individuals with VWD primarily complain of excessive mucocutaneous bleeding, which includes spontaneous bruising, recurrent epistaxis, and bleeding from the gums after brushing, dental cleaning, and extractions. In addition, prolonged or excessive bleeding after surgery or trauma is often reported. Females frequently experience menorrhagia, usually beginning at menarche, and can have prolonged or excessive bleeding after childbirth.²³ Musculoskeletal bleeding is unusual, except in type 2N or type 3 VWD when the FVIII:C level may be less than 10 IU/dL.

Mucocutaneous bleeding symptoms such as epistaxis, gum bleeding, ecchymosis, and menorrhagia overlap with those experienced by a normal population, and therefore can be easily overlooked by both patients and physicians.¹¹ The use of bleeding assessment tools (BATs) to standardize the bleeding history and interpretation of the severity of the bleeding phenotype is becoming part of routine clinical practice. Three different BATs, each an adaptation of its predecessor, have been created and validated.²⁴ Each of the scores performs well in an undiagnosed population presenting with bleeding symptoms. The negative predictive value is typically greater than 0.99, meaning that a negative bleeding score nearly excludes a clinically significant bleeding disorder. Thus, the main utility of the current BATs is at the time of new patient assessments: a negative bleeding score will help avoid unnecessary laboratory testing and prevent false-positive diagnoses of VWD (borderline low VWF:Ag without a significant bleeding history). However, the currently available BATs have some limitations. When scoring severe bleeding disorders, BATs become saturated as they take into account the worst episode of bleeding within each category but not the frequency of bleeding. BATs need to be administered by an expert and are time consuming to complete. Finally, they are not useful for monitoring bleeding symptoms or response to therapy because of the cumulative nature of the scores. In an attempt to standardize the BAT and bleeding score, the ISTH/Scientific and Standardization Committee (SSC) Joint VWF and Perinatal/Pediatric Hemostasis Sub­committees Working Group has established a revised BAT, known as the ISTH-BAT, specifically designed to extend the utility of the earlier BATS by incorporating information on both symptom frequency and severity.^25,26 The ISTH-BAT has been further modified to a patient- or self-administered BAT (SELF-BAT). The SELF-BAT has been shown to be a reliable and effective tool in the assessment of patients who are being evaluated for VWD.²⁷

Laboratory Testing

Screening tests include a complete blood count (CBC), prothrombin time, aPTT, thrombin time, and fibrinogen concentration to exclude the presence of other hemostatic disorders. The CBC may show thrombocytopenia in type 2B VWD. The aPTT is often normal, but will be prolonged if the FVIII level is below 30 IU/dL, as can be seen in severe type 1, type 2N, or type 3 VWD. The platelet function analyzer (PFA-100) is a system for analyzing primary hemostasis under high shear rates, but its role in the diagnosis of VWD is controversial.¹¹

The evaluation of VWD involves quantitative (VWF:Ag) and qualitative measurements of VWF (VWF:RCo, or one of the novel assays: VWF:Act or VWF:GPIbM) and FVIII activity (FVIII:C). Type 2 VWD is suspected when the VWF activity to VWF:Ag ratio is < 0.6, the FVIII:C is more significantly decreased as compared to VWF:Ag, or with the presence of thrombocytopenia. In these cases, further testing (multimer gel electrophoresis, VWF:CB, RIPA, VWF:FVIIIB, and genotyping) is required to discriminate the type 2 VWD subtype, but such testing may be available only in  specialized laboratories. If type 1C VWD is suspected, the VWFpp/VWF:ag ratio may confirm the diagnosis. Table 2 summarizes the results seen with each subtype. These assays are described in detail below.

 

VWD Assays

VWF:Ag represents the quantity of VWF protein (antigen) in the plasma measured using an enzyme-linked immunosorbent assay (ELISA) or latex immunoassay. The normal range is approximately 50 to 200 IU/dL.

VWF:RCo is a functional assay that determines the capacity of VWF to agglutinate platelets via the platelet receptor GPIbα in the presence of ristocetin. The normal range is approximately 50 to 200 IU/dL. Novel methods of measuring VWF’s platelet-binding activity are increasingly being adopted by clinical laboratories and are associated with greater precision and improved lower limits of detection and coefficients of variation.^28,29 The first is the VWF:Act, a rapid automated assay that measures VWF activity using an antibody directed to the GPIbα binding site of VWF.²⁸ The second novel assay is VWF:GPIbM, which involves a gain-of-function GPIB construct that binds VWF without ristocetin.^30,31 For simplicity, VWF:RCo will be used to refer to VWF platelet-binding activity in the ensuing text. Factor VIII:C is a functional FVIII assay that determines the activity of FVIII in aPTT-based assays. The normal range is approximately 50 to 150 IU/dL.

VWF multimer analysis by SDS-agarose electrophoresis assesses VWF oligomers in plasma.³² Normal plasma contains multimers composed of over 40 VWF dimers, and these multimers are classified as high (HMW), intermediate (IMW), or low molecular weight (LMW). HMW multimers are decreased or missing in types 2A and 2B VWD, and IMW multimers may also be absent in type 2A VWD.

Low-dose RIPA tests the capacity of the patient’s platelets to agglutinate at low concentrations of ristocetin (~0.5 mg/mL). This is in contrast to the VWF:RCo, in which formalin-fixed control platelets are used. With type 2B, the platelet membrane is “overloaded” with high-affinity mutant VWF, resulting in abnormal platelet agglutination at low ristocetin concentrations. In some cases of type 2B VWD, all variables except RIPA may be normal.²⁹

VWF:FVIIIB is an ELISA-based assay that determines the ability of VWF to bind FVIII and is used to make the diagnosis of type 2N VWD.¹⁹

VWF:CB is an ELISA-based assay that measures the ability of VWF to bind to collagen, a function of VWF that is dependent on the collagen-binding domain (A3) and on the presence of HMW multimers. VWF:CB helps to distinguish between types 1 and 2 VWD by reflecting the loss of HMW multimer forms (type 2A VWD) or can reflect a specific collagen-binding deficiency (type 2M VWD).³³ The normal range is approximately 50 to 200 IU/dL. This assay is not available in most clinical laboratories.

VWFpp/VWF:Ag takes advantage of 2 facts: the VWF propeptide is secreted in a one-to-one ratio to VWF subunits and has a stable half-life in plasma. Thus, an increased ratio identifies patients with mutations that increase VWF clearance, such as type 1C VWD.³⁴ The mean ratio in normal individuals is 1.3, with a normal range of 0.54 to 1.98.

Genotyping should be considered when specialized testing with the VWF:FVIIIB, RIPA, or VWF:CB assays is unavailable and a diagnosis of type 2 VWD is suspected. A guideline on VWD genetic testing has been published by the UK Haemophilia Centre Doctors Organisation.³⁵

Interpretation of Clinical History and Laboratory Investigations

Normal plasma levels of VWF are approximately 100 IU/dL (100%, corresponds to ~10 μg/mL) with a population range of 50 to 200 IU/dL (50%–200%). There are a number of preanalytical variables (patient specific or laboratory specific) that affect the results of VWF laboratory testing. Patient-specific variables that are associated with increased VWF levels include increasing age, African ethnicity, exercise, inflammatory disease states, blood group A or B, increased levels of epinephrine, cocaine use, and neuroendocrine hormone levels. Decreased VWF levels are associated with medications such as valproic acid, hypothyroidism, autoantibodies, and blood group O. Individuals with blood group O have VWF levels that are 25% lower than levels in other blood groups.³⁶ Several analytical variables also can complicate the diagnosis of VWD: methods for established reference ranges, limitations to the sensitivity of assays, and sample handling issues.¹¹ These factors (summarized in Table 3)  must be considered when interpreting VWF laboratory results, and at least 2 sets of tests using fresh samples are needed to confirm the diagnosis of VWD. Testing should be avoided in stressed, ill, or pregnant patients.

Mild type 1 VWD can be a difficult diagnosis to make because of the overlap of bleeding symptoms among normal individuals and those with mild type 1 VWD, as well as the variability of VWF levels. There is no consensus on the exact VWF levels required to confirm the diagnosis: the NHLBI Expert Panel recommends VWF:Ag and VWF:RCo levels less than 0.30 IU/mL to diagnose type 1 VWD,¹¹ whereas the ISTH-SSC Subcommittee on von Willebrand factor recommends using VWF:RCo and VWF:Ag levels greater than 2 standard deviations below the population mean.³⁷ In the absence of a bleeding history, slightly reduced VWF levels do not predict future significant bleeding events.³⁸ Therefore, regardless of the laboratory cut-off used, the cornerstone of a VWD diagnosis should be a history of excessive mucocutaneous bleeding.

 

Differential Diagnosis

When considering a diagnosis of VWD, the differential diagnosis must be considered and includes acquired von Willebrand syndrome (AVWS), platelet-type VWD (PT-VWD), and hemophilia A. AVWS is the result of an acquired deficiency or defect of VWF and manifests with a mild to moderate bleeding disorder without a lifelong personal and family history of bleeding. AVWS has diverse pathology. The most common mechanism is proteolytic cleavage of VWF after shear stress–induced unfolding, as seen with aortic stenosis and ventricular assist devices, where as many as 79% of persons with aortic stenosis³⁹ and up to 100% with left ventricular assist devices are affected.⁴⁰ Other disease mechanisms include autoantibody formation that impairs VWF function or increases its clearance (autoimmune disease or lymphoproliferative disease), adsorption of HMW VWF multimers to malignant cells or platelets (myeloproliferative neoplasms and Wilm’s tumor), or decreased synthesis (hypothyroidism, valproic acid). The median age of diagnosis is 62 years, but the disorder may occur in any age-group (range 2–96 years).⁴¹ The approach to management of AVWS should focus on treatment of bleeding and induction of long-term remission. Treatment of bleeding will depend on the underlying mechanism of AVWS and may include a combination of DDAVP or VWF/FVIII concentrates, recombinant factor VIIa, antifibrinolytic agents, intravenous immunoglobulin, or plasmapheresis for AVWS associated with autoantibodies. Treatment of the underlying disorder (eg, aortic valve repair or treatment of a lymphoproliferative disorder) may result in remission of the AVWS.

Mild hemophilia A (caused by mutations in the F8 gene) and type 2N VWD can be difficult to differentiate clinically. Both present with reduced FVIII:C, and type 2N VWD may have normal or borderline low levels of VWF. Although the VWF:FVIIIB assay will distinguish between the 2 disorders, the test is not available in many centers. The pattern of inheritance may be helpful: hemophilia A is an X-linked disorder, whereas type 2N is autosomal recessive. Often, the diagnosis of type 2N VWD is suspected when genotyping of F8 does not identify a mutation in mild hemophilia A, when infused FVIII concentrates have a decreased half-life, or when DDAVP is associated with a brisk but short-lived response. In the absence of VWF:FVIIIB assay availability, genotyping of VWF will confirm the diagnosis, with missense mutations being located in exons 17–20 or 24–27.¹⁹

PT-VWD represents the phenocopy of type 2B VWD. The mutation is in the platelet receptor gene GPIBA and causes enhanced VWF-platelet binding. The disorders can be differentiated by RIPA plasma/platelet mixing studies or flow cytometry.^42,43 However, these assays are technically challenging. In the absence of mutations in exon 28 of VWF, mutations in exon 2 of GPIBA may be identified in approximately 10% of persons misdiagnosed with type 2B VWD.

Management

Patients with VWD present to medical attention in a number of ways: excessive post-trauma or surgical bleeding, recurrent mucocutaneous bleeding such as epistaxis, menorrhagia, gastrointestinal bleeding, or, in severe cases, recurrent hemarthroses and muscle hematomas. Irrespective of the presentation, the goal is to minimize and control bleeding. Therapeutic options can be divided into 3 main categories: (1) localized measures to stop bleeding; (2) pharmacologic agents with indirect hemostatic benefit; and (3) treatments that directly increase plasma VWF and FVIII levels. A combination of all 3 of these modalities can be used depending on the bleeding location and severity.

Localized Measures

Localized measures to control bleeding in VWD will depend on the site of bleeding. Epistaxis can be particularly problematic for affected children, and patients should be armed with a step-wise action plan that escalates from pressure to packing and includes guidelines regarding how long to wait before seeking medical attention. In selected cases, nasal cautery may be required for prolonged or excessive epistaxis. Topical hemostatic agents such as gelatin foam/matrix, topical thrombin, and fibrin sealants are predominately used to achieve surgical hemostasis and may have a limited role in the treatment of VWD-associated bleeding. In the case of menorrhagia, hormonal treatments (ie, the combined oral contraceptive pill, OCP), levonorgestrel-releasing intrauterine systems, or endometrial ablation all effectively reduce menstrual blood loss through their local effects on the endometrial lining.⁴⁴ In addition, older generations of OCP are associated with increases in VWF levels. This effect is mediated by the estrogen component and is evident with ethynylestradiol doses of 0.5 μg or higher. Lower estrogen doses, seen in currently used OCP, have little or no effect on VWF levels.^11,45

Pharmacologic Therapy

Indirect therapies include the antifibrinolytic agents (eg, tranexamic acid and aminocaproic acid). These agents are used either as the sole therapy at the time of minor surgical and dental procedures, or as an adjunct in combination with DDAVP or VWF/FVIII concentrates. Antifibrinolytics are thought to be particularly useful for controlling mucosal bleeding in areas of high fibrinolytic activity: the oral cavity, gastrointestinal tract, or uterus. Tranexamic acid inhibits the conversion of plasminogen to plasmin, and is the more commonly used antifibrinolytic.¹¹ Tranexamic acid can be administered either intravenously or orally at doses of 10 to 25 mg/kg, respectively. It is usually continued until bleeding is controlled or up to 7 to 10 days postoperatively. The most common adverse events associated with tranexamic acid are headache, back pain, and gastrointestinal side effects.⁴⁶ Tranexamic acid is contraindicated in disseminated intravascular coagulation and bleeding from the upper urinary tract, where it can lead to urinary tract obstruction by clots.

 

DDAVP, a synthetic derivative of vasopressin, promotes release of stored VWF from endothelial cells. Most individuals with type 1 VWD and some with type 2A VWD respond to treatment with DDAVP: a therapeutic trial to confirm adequate DDAVP response should be performed prior to its clinical use. Assessment of VWF:Ag, VWF:RCo, and FVIII levels should be performed before and at several time points after the DDAVP administration up to and including 4 hours. Peak VWF levels are achieved 30 and 90 minutes after intravenous and intranasal delivery, respectively. An increase in VWF:Ag/VWF:RCo and FVIII levels to at least 30 IU/dL is adequate for most dental procedures, minor surgery, or the treatment of epistaxis or menorrhagia. DDAVP may be adequate to treat major bleeds or for major surgery when VWF levels increase well above 50 IU/dL. Decisions surrounding the use of DDAVP versus a VWF/FVIII concentrate will depend on the expected DDAVP response, the type of surgery, and the anticipated duration of therapy required to achieve hemostasis. If treatment is required for more than 3 days, concerns regarding tachyphylaxis and side effects may limit its use. Significantly decreased VWF:Ag/VWF:RCo or FVIII at the 4-hour time point of a DDAVP trial may indicate type 1C or type 2N VWD, which are associated with increased clearance of endogenous VWF or FVIII, respectively. Despite the transient response in these patients, DDAVP remains a therapeutic option and its use should be assessed on a case-by-case basis.⁴⁷

The parenteral dose of DDAVP is 0.3 μg/kg infused in 30 to 50 mL of normal saline over approximately 30 minutes every 12 to 24 hours. The dose of the highly concentrated intranasal preparation is 150 μg for children under 50 kg and 300 μg for larger children and adults (1 spray per naris). It is important to note that the products used to treat VWD (eg, Stimate) deliver 150 μg per spray, a much higher concentration than that used to treat enuresis. Repeated DDAVP dosing is associated with the development of tachyphylaxis: with subsequent dosing, the magnitude of the VWF and FVIII increments can fall to approximately 70% of that obtained with the initial dose.⁴⁸ DDAVP is safe and generally well tolerated. Side effects include facial flushing, headache, tachycardia, light-headedness, and mild hypotension. The most serious side effects, severe hyponatremia and seizures,⁴⁹ can be avoided by fluid restriction for 24 hours after DDAVP administration. Serum sodium levels should be monitored with repeated doses. DDAVP is generally avoided in those younger than 2 years of age because of a higher risk of hyponatremia. Patients who are intolerant of DDAVP or have a poor VWF response need to be treated with a VWF/FVIII concentrate.

VWF/FVIII Concentrate

VWF/FVIII concentrates are required for patients who do not have an adequate response to DDAVP, who have side effects from or contraindications to DDAVP, or who require a long duration of treatment, rendering the use of DDAVP impractical. Purified, viral-inactivated, plasma-derived VWF/FVIII concentrates are the products most frequently used (eg, Humate-P, Wilate, Alphanate SD/HT). The quantity of VWF:RCo activity relative to FVIII:C varies by product; Humate-P contains 2.4 VWF:RCo units for each unit of FVIII:C; Wilate contains a 1:1 ratio; and Alphanate contains a 0.5:1 ratio. Both Humate-P and Wilate are reported to contain a full spectrum of VWF multimers, including HMW multimers, and closely resemble normal plasma, but Alphanate SD/HT lacks HMW mutimers.^11,50 Thus, the available VWF/FVIII vary in terms of VWF:RCo to FVIII concentrate, HMW multimer composition, reported VWF:RCo, and FVIII half-lives and even approved indications. They should not be considered interchangeable, and further information should be sought from the respective product inserts.

Dosing recommendations are provided either in VWF:RCo (North America) or FVIII:C units (Europe) and are weight-based (Table 4); repeat infusions can be given every 8 to 24 hours depending on the type of surgery/injury and the product used. 

For surgeries, the goal is to maintain VWF:RCo and FVIII:C greater than 100 IU/dL at peak and greater than 50 IU/dL at trough until hemostasis is achieved during the acute bleed or at the time of surgical intervention. The duration of factor replacement is 5 to 10 days for major surgeries and 1 to 4 days for minor surgeries. With VWF/FVIII concentrates, the FVIII:C response is higher and more sustained than predicted from the dose because of the stabilizing effect of exogenous VWF on endogenous FVIII.⁵¹ VWF:RCo and FVIII:C levels should be measured in patients receiving repeat infusions to ensure appropriate hemostatic levels and to avoid supratherapeutic levels because thromboembolic events have been associated with high FVIII levels. Thromboembolic events are rare, and most cases have been described in surgical patients with other risk factors.⁵² Adverse reactions to VWF/FVIII concentrates are rare but include allergic and anaphylactic symptoms.⁵³ A rare complication is the development of alloantibodies to VWF, which occurs in 5% to 10% of type 3 patients and manifests as a loss of hemostatic response to infused concentrates or anaphylactic reactions.²²

 

Long-term continuous use of concentrates to prevent bleeds, known as prophylaxis, is the standard of care in severe hemophilia A and B and is now being adopted in severe VWD. Patients with type 3 VWD or severe type 1 or type 2 VWD may experience recurrent bleeds into joints, nasal/oropharynx, or gastrointestinal tract or excessive menstrual bleeding. Retrospective cohort and case series suggest that prophylaxis improves quality of life; reduces the frequency of bleeding, need for transfusions, and hospitalizations; and prevents chronic joint disease.^54,55 More recently, a prospective study confirmed that prophylaxis with VWF concentrates at doses ranging from 50 IU VWF RCo/kg 1 to 3 times per week was highly effective at reducing bleeding rates, with annualized bleeding rates decreasing from 25 to 6.1 in 11 participants with either type 2A or type 3 VWD.⁵⁶

VWF/FVIII concentrates are effective in more than 97% of events.⁵⁷ Rarely, when infusion of a VWF/FVIII concentrate is ineffective at stopping bleeding, transfusion of platelet concentrates may be beneficial, presumably because they facilitate the delivery of small amounts of platelet VWF to the site of vascular injury. Highly purified FVIII concentrates (monoclonal antibody purified and recombinant) should not be used to treat VWD because they lack VWF.

A recombinant VWF concentrate (Vonvendi) combined initially with recombinant FVIII concentrate in a 1.3:1 ratio of VWF:RCo to FVIII:C has been shown to be safe and efficacious for the on-demand treatment of bleeds.^58,59 After the initial FVIII dose, the patients’ endogenous FVIII levels are stabilized within 6 hours and further FVIII administration may not required. A prospective phase 3 trial investigating the efficacy of recombinant VWF in the prophylaxis of severe VWD is ongoing. Vonvendi has been licensed for on-demand treatment in the United States since 2015. For further dosing information, please refer to the product insert.

Conclusion

VWF is a complex protein with several important and distinct functional domains: binding sites to collagen, FVIII, and platelet GPIbα; an ADAMTS13 cleavage site; and domains important for multimer formation. Mutations in any of these sites can result in a dysfunctional protein and as a result, VWD is a heterogeneous disorder with many specific assays available to determine the subtype. Despite this, the treatment of VWD is straightforward with only a small number of therapeutic options: indirect therapies such as antifibrinolytic agents, or direct therapies that increase VWF levels, DDAVP, or VWF/FVIII concentrates. Management focuses on preventing bleeding complications associated with invasive procedures or promptly treating bleeding episodes.

Introduction

von Willebrand disease (VWD) is an inherited bleeding disorder caused by deficient or defective plasma von Willebrand factor (VWF). VWF is an adhesive multimeric plasma glycoprotein that performs 2 major functions in hemostasis: it mediates platelet adhesion to injured subendothelium via glycoprotein 1bα (GPIbα), and it binds and stabilizes factor VIII (FVIII) in circulation, protecting it from proteolytic degradation by enzymes. The current VWD classification recognizes 3 types (Table 1).¹ 

In order to understand the role of the numerous laboratory investigations as well as the classification of VWD, it is important to review the structure and function of the VWF subunit. Bleeding symptoms, including mucocutaneous bleeding and excessive bleeding after surgery or trauma, reflect the defect in primary hemostasis. Treatment focuses on increasing VWF levels with desmopressin (1-deamino-8-D-arginine vasopressin, DDAVP) or clotting factor concentrates containing both VWF and FVIII (VWF/FVIII concentrate). Nonspecific treatment options include antifibrinolytic agents (tranexamic acid) and hormone therapy (oral contraceptive pill).

Prevalence

VWD is the most common inherited bleeding disorder. However, because VWF levels are highly variable and disease severity ranges from mild bleeding symptoms to severe or life-threatening bleeds, the reported prevalence of VWD depends on the diagnostic definition used. Two large epidemiologic studies have reported prevalence rates of approximately 1%.^2,3 In these studies, healthy school-aged children were screened and diagnosed with VWD based on low VWF activity, measured as ristocetin cofactor, and a personal and family history of bleeding symptoms. At the other extreme, when considering patients whose bleeding symptoms are sufficiently severe to warrant referral to specialized centers, the reported prevalence of VWD ranges from 20 to 113 per million.⁴ These studies likely over- and underestimate clinically significant VWD. More recent studies suggest that the prevalence of VWD in individuals whose bleeding symptoms are significant enough to present to a primary care physician is approximately 0.1%.⁵ This figure is likely a more accurate estimate of the true prevalence of symptomatic VWD.

Although VWD is autosomally inherited, females are more likely to present with bleeding symptoms and be diagnosed because of increased exposure to bleeding challenges, such as menorrhagia and childbirth. VWD does not show any geographic or ethnic predilection, but there is an increased prevalence of the recessive forms, such as type 2N and type 3 VWD, in areas with high rates of consanguinity.

VWF Protein Structure and Function

The VWF gene is located on chromosome 12 at p13.3 and spans 178 kb comprising 52 exons.⁶ The expression of the VWF gene is tightly restricted to endothelial cells, platelets, and megakaryocytes, where VWF is stored in Weibel-Palade bodies and α-granules. VWF is a large multimeric glycoprotein with several important functional domains (Figure).

Extensive post-translational modifications, mediated by domains D3 and CK as well as the VWF propeptide, result in disulfide-linked multimers that can be greater than 20,000 kDa, while the VWF subunit is approximately 250 kDa. The high-molecular-weight (HMW) multimers are most effective in mediating platelet adhesion to the site of vascular injury; therefore, appropriate multimer formation is integral to VWF’s function. VWF is either secreted from local endothelial cells or recruited from the circulation to the site of endothelial injury, where it adheres to exposed collagen, predominately via the collagen-binding site in the A3 domain. Once immobilized, VWF is subjected to the high shear rates of the arterial circulation and undergoes a conformational change that exposes the platelet GPIbα binding site within the A1 domain.⁷ The high-affinity, rapid and reversible interaction between VWF and GPIbα tethers platelets to the endothelium where they roll until they are immobilized by integrin-mediated binding, which has slower binding kinetics. The RGD (Arg-Gly-Asp) sequence within the C4 domain also contributes to platelet adhesion by interacting with GPIIb-IIIa of activated platelets.⁸ ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) is a plasma protease that cleaves circulating VWF in the A2 domain when VWF multimers unfold in response to sufficient shear, exposing the cleavage site within the A2 domain.⁹ VWF’s second role in hemostasis is fulfilled by the D’ and D3 domains, which bind and protect FVIII from proteolytic degradation, thereby prolonging its half-life. In the absence of VWF, FVIII has a half-life of approximately 2 hours, in contrast to a normal half-life of 12 to 20 hours when bound to VWF.⁴

Classification, Pathophysiology, and Genetics

The International Society of Thrombosis and Hemostasis (ISTH) classification of VWD was updated in 2006 (Table 1).¹ It incorporates important aspects of clinical phenotype, pathophysiological mechanisms, and treatment considerations. The 3 categories are: type 1, which is a partial quantitative deficiency; type 2 with 4 subtypes (2A, 2B, 2M, and 2N), which is a qualitative defect; and type 3, which is a virtual absence of VWF. Although the diagnosis and categorization of VWD can be achieved with widely available laboratory testing, further subcategorization among type 2 VWD subtypes may require referral to a specialized laboratory. The current ISTH classification intentionally does not incorporate genotypic data. In type 2 or type 3 VWD disease, VWF mutations are identified in more than 90% of cases and are completely penetrant, whereas mutations are identified in only approximately 65% of type 1 VWD cases and have been associated with incomplete penetrance and variable expressivity.¹⁰ These studies suggest that type 1 VWD is an oligogenic disease with mutations in genes regulating secretion or clearance contributing to a VWD phenotype.

 

VWD Types

Type 1

Type 1 VWD is caused by a partial quantitative deficiency of VWF and represents approximately 75% of VWD cases. It is the most clinically heterogeneous type, with patients having a mild to moderate bleeding phenotype.¹¹ Bleeding in type 1 VWD results from a decrease in the concentration of VWF. The VWF function is normal without a significant abnormality in the platelet, collagen, or FVIII binding sites or a significant decrease in HMW multimers. Functional assays of VWF, such as VWF ristocetin cofactor (VWF:RCo) or VWF activity (VWF:Act) (see section on Laboratory Testing for further details), are proportionally decreased relative to the VWF antigen level (VWF:Ag), and the ratio of functional activity as compared with the VWF level is normal (ie, VWF:RCo/VWF:Ag ratio is > 0.6). As noted, VWF mutations are identified in only 65% of type 1 VWD cases and have incomplete penetrance and variable expressivity.¹⁰ Approximately 70% of mutations identified are missense mutations. Missense mutations may affect VWF levels by affecting any part of the biosynthetic pathway, including trafficking, storage, secretion, and/or clearance of VWF.

Increased VWF clearance is a well-described mechanism for type 1 VWD, known as type 1C. These patients will typically have very low VWF levels, an increased VWF propeptide to antigen ratio (VWFpp/VWF:Ag), and a marked but short-lived response to DDAVP, limiting DDAVP’s clinical applicability.¹² On the other hand, the half-life of VWF/FVIII concentrates is normal in these individuals. Type 1C VWD is caused by missense mutations which occur mainly in the D3 domain and reduce the half-life of VWF up to 15-fold. R1205H, known as the “Vicenza” variant, is the most common and severe as well as the best characterized of these mutations.¹³

Type 2

Accounting for approximately 25% of VWD cases, type 2 VWD is characterized by a qualitative deficiency of VWF activity and is further subcategorized based on the mechanism of VWF dysfunction. Type 2A, 2B, and 2M affect VWF–platelet interactions by way of loss of HMW multimers, a gain of function of the GPIbα binding site, or a loss of function of the same site, respectively. On the other hand, type 2N is caused by defective VWF binding to FVIII. Type 2 VWD is often suspected when investigations demonstrate a function-antigen discordance: the VWF:RCo or VWF:Act is decreased disproportionately to the decrease in VWF:Ag, and the VWF:RCo/VWF:Ag ratio is less than 0.6.

Type 2A VWD is the most common type 2 variant. It is characterized by disproportionately low functional activity compared to antigen level (ie, VWF:RCo/VWF:ag ratio is < 0.6) and a loss of HMW and sometimes intermediate molecular weight (IMW) multimers. Ristocetin-induced platelet agglutination (RIPA) will be decreased with standard doses of ristocetin and absent with low doses. Type 2A VWD is usually inherited as an autosomal dominant trait. This subtype encompasses missense mutations that impair dimerization or multimerization of VWF subunits (CK, D1, and D2 domains); disrupt intersubunit disulphide bonds (D3 and D2 domains); enhance susceptibility to ADAMTS13-mediated proteolysis (A2 and A1 domains); or result in intracellular retention of the HMW multimers (D3, A1, and A2 domains).¹⁰ The result is VWF that lacks HMW multimers, thereby possessing fewer GPIbα binding sites, and that is less effective in binding platelets.

Type 2B VWD is the result of gain-of-function mutations within the GPIbα binding site of VWF. Generally, the platelet-binding site of VWF within the A1 domain is only exposed once VWF is immobilized on injured collagen and subjected to shear forces, resulting in a conformational change.⁷ In type 2B VWD, the gain-of-function mutation results in spontaneous binding of VWF to platelets without the need for a VWF-collagen interaction and unfolding of VWF by shear forces. The VWF–platelet interaction selectively depletes the HMW multimers by the unfolding of the A2 domain and increasing ADAMTS13 proteolysis. The increased binding of mutant VWF to platelets also triggers the formation of platelet aggregates, which are removed from circulation resulting in thrombocytopenia. Increases in endogenous VWF seen with acute stressors or pregnancy can worsen thrombocytopenia and increase the risk of bleeding.¹⁴ Certain mutations, such as V1316M, alter megakaryocytopoiesis and are characterized by giant platelets with abnormal ultrastructure and further exacerbate the thrombocytopenia.¹⁵ The laboratory profile reveals a VWF:RCo/VWF:Ag ratio of < 0.6 and absence of HMW multimers. In contrast to type 2A, platelets will agglutinate with low-dose ristocetin. Missense mutations are highly penetrant dominant and occur in or close to the A1 domain.¹⁶

Type 2M VWD is characterized by loss-of-function mutations within the GPIbα binding site of VWF. Phenotypic characteristics include a reduced ratio of VWF:RCo/VWF:Ag of < 0.6 but a normal multimer pattern.¹⁷ Missense mutations are reported in the A1 domain affecting the GPIbα-binding site. In very rare instances, mutations in the A3 domain that impair the VWF/collagen interaction have been described.¹⁸ These collagen-binding mutations are not included in the last iteration of the ISTH classification in 2006,¹ but fit best in the type 2M category. In these cases, VWF:RCo or VWF:Act, which reflect activity at the GPIbα-binding site, may be normal and the diagnosis requires VWF/collagen binding assays (VWF:CB).

Type 2N VWD results from mutations of the FVIII binding site or conformational changes that impair the VWF–FVIII interaction. Most (~80%) missense mutations are located in domains D’ and D3.¹⁹ These mutations are autosomal recessive, and affected individuals are either homozygous or compound heterozygous for type 2N/2N or type 1/2N mutations, or compound heterozygous for a missense mutation and a mutation resulting in a null allele (type 2N/3 mutations). The laboratory phenotype is a disproportionate reduction in the FVIII level relative to the VWF level, which may be low or normal. Most cases of type 2N VWD have a normal multimeric profile, but rare cases will demonstrate loss of HMW multimers. Definitive diagnosis requires evidence of reduced FVIII binding to VWF (VWF:FVIIIB) or the identification of causative mutations in the FVIII binding region of the VWF gene.²⁰

 

Type 3

Type 3 VWD is defined by a virtual absence of VWF. The inheritance of type 3 VWD has often been reported as autosomal recessive. However, there is emerging evidence that it can also be inherited in a co-dominant pattern: obligate carriers of type 3 VWD mutations have more mucocutaneous bleeding symptoms than normal individuals, and in approximately 50% of cases may carry a diagnosis of type 1 VWD.²¹ This condition is characterized by prolongation of the activated partial thromboplastin time (aPTT), undetectable levels of VWF:Ag, and VWF:RCo and FVIII levels less than 10 IU/dL (10%). The majority (~80%) of type 3 VWD patients have 2 null alleles as a result of a variety of mutations, with nonsense mutations accounting for about one-third.¹⁰ The remainder of the mutational spectrum is made up of missense mutations predominantly located in the D1-D2 (exons 3–11) and D4-CK (exons 37–52) domains that result in intracellular VWF retention, or large deletions, resulting in frameshift mutations affecting 1 or more exons. Because there is little or no circulating VWF, patients with type 3 VWD may develop alloantibodies to VWF, which can complicate treatment.²²

Diagnosis

Clinical Manifestations

VWD is a congenital bleeding disorder. The increased risk of bleeding is present from birth, but symptoms may only manifest when there is a hemostatic challenge. Bleeding symptoms become more apparent with increasing age and exposure to hemostatic challenges. As a result, the diagnosis is often delayed into adulthood in mild to moderate forms of VWD. On the other hand, with more severe bleeding phenotypes such as type 3 VWD, the diagnosis is often made in childhood. Individuals with VWD primarily complain of excessive mucocutaneous bleeding, which includes spontaneous bruising, recurrent epistaxis, and bleeding from the gums after brushing, dental cleaning, and extractions. In addition, prolonged or excessive bleeding after surgery or trauma is often reported. Females frequently experience menorrhagia, usually beginning at menarche, and can have prolonged or excessive bleeding after childbirth.²³ Musculoskeletal bleeding is unusual, except in type 2N or type 3 VWD when the FVIII:C level may be less than 10 IU/dL.

Mucocutaneous bleeding symptoms such as epistaxis, gum bleeding, ecchymosis, and menorrhagia overlap with those experienced by a normal population, and therefore can be easily overlooked by both patients and physicians.¹¹ The use of bleeding assessment tools (BATs) to standardize the bleeding history and interpretation of the severity of the bleeding phenotype is becoming part of routine clinical practice. Three different BATs, each an adaptation of its predecessor, have been created and validated.²⁴ Each of the scores performs well in an undiagnosed population presenting with bleeding symptoms. The negative predictive value is typically greater than 0.99, meaning that a negative bleeding score nearly excludes a clinically significant bleeding disorder. Thus, the main utility of the current BATs is at the time of new patient assessments: a negative bleeding score will help avoid unnecessary laboratory testing and prevent false-positive diagnoses of VWD (borderline low VWF:Ag without a significant bleeding history). However, the currently available BATs have some limitations. When scoring severe bleeding disorders, BATs become saturated as they take into account the worst episode of bleeding within each category but not the frequency of bleeding. BATs need to be administered by an expert and are time consuming to complete. Finally, they are not useful for monitoring bleeding symptoms or response to therapy because of the cumulative nature of the scores. In an attempt to standardize the BAT and bleeding score, the ISTH/Scientific and Standardization Committee (SSC) Joint VWF and Perinatal/Pediatric Hemostasis Sub­committees Working Group has established a revised BAT, known as the ISTH-BAT, specifically designed to extend the utility of the earlier BATS by incorporating information on both symptom frequency and severity.^25,26 The ISTH-BAT has been further modified to a patient- or self-administered BAT (SELF-BAT). The SELF-BAT has been shown to be a reliable and effective tool in the assessment of patients who are being evaluated for VWD.²⁷

Laboratory Testing

Screening tests include a complete blood count (CBC), prothrombin time, aPTT, thrombin time, and fibrinogen concentration to exclude the presence of other hemostatic disorders. The CBC may show thrombocytopenia in type 2B VWD. The aPTT is often normal, but will be prolonged if the FVIII level is below 30 IU/dL, as can be seen in severe type 1, type 2N, or type 3 VWD. The platelet function analyzer (PFA-100) is a system for analyzing primary hemostasis under high shear rates, but its role in the diagnosis of VWD is controversial.¹¹

The evaluation of VWD involves quantitative (VWF:Ag) and qualitative measurements of VWF (VWF:RCo, or one of the novel assays: VWF:Act or VWF:GPIbM) and FVIII activity (FVIII:C). Type 2 VWD is suspected when the VWF activity to VWF:Ag ratio is < 0.6, the FVIII:C is more significantly decreased as compared to VWF:Ag, or with the presence of thrombocytopenia. In these cases, further testing (multimer gel electrophoresis, VWF:CB, RIPA, VWF:FVIIIB, and genotyping) is required to discriminate the type 2 VWD subtype, but such testing may be available only in  specialized laboratories. If type 1C VWD is suspected, the VWFpp/VWF:ag ratio may confirm the diagnosis. Table 2 summarizes the results seen with each subtype. These assays are described in detail below.

 

VWD Assays

VWF:Ag represents the quantity of VWF protein (antigen) in the plasma measured using an enzyme-linked immunosorbent assay (ELISA) or latex immunoassay. The normal range is approximately 50 to 200 IU/dL.

VWF:RCo is a functional assay that determines the capacity of VWF to agglutinate platelets via the platelet receptor GPIbα in the presence of ristocetin. The normal range is approximately 50 to 200 IU/dL. Novel methods of measuring VWF’s platelet-binding activity are increasingly being adopted by clinical laboratories and are associated with greater precision and improved lower limits of detection and coefficients of variation.^28,29 The first is the VWF:Act, a rapid automated assay that measures VWF activity using an antibody directed to the GPIbα binding site of VWF.²⁸ The second novel assay is VWF:GPIbM, which involves a gain-of-function GPIB construct that binds VWF without ristocetin.^30,31 For simplicity, VWF:RCo will be used to refer to VWF platelet-binding activity in the ensuing text. Factor VIII:C is a functional FVIII assay that determines the activity of FVIII in aPTT-based assays. The normal range is approximately 50 to 150 IU/dL.

VWF multimer analysis by SDS-agarose electrophoresis assesses VWF oligomers in plasma.³² Normal plasma contains multimers composed of over 40 VWF dimers, and these multimers are classified as high (HMW), intermediate (IMW), or low molecular weight (LMW). HMW multimers are decreased or missing in types 2A and 2B VWD, and IMW multimers may also be absent in type 2A VWD.

Low-dose RIPA tests the capacity of the patient’s platelets to agglutinate at low concentrations of ristocetin (~0.5 mg/mL). This is in contrast to the VWF:RCo, in which formalin-fixed control platelets are used. With type 2B, the platelet membrane is “overloaded” with high-affinity mutant VWF, resulting in abnormal platelet agglutination at low ristocetin concentrations. In some cases of type 2B VWD, all variables except RIPA may be normal.²⁹

VWF:FVIIIB is an ELISA-based assay that determines the ability of VWF to bind FVIII and is used to make the diagnosis of type 2N VWD.¹⁹

VWF:CB is an ELISA-based assay that measures the ability of VWF to bind to collagen, a function of VWF that is dependent on the collagen-binding domain (A3) and on the presence of HMW multimers. VWF:CB helps to distinguish between types 1 and 2 VWD by reflecting the loss of HMW multimer forms (type 2A VWD) or can reflect a specific collagen-binding deficiency (type 2M VWD).³³ The normal range is approximately 50 to 200 IU/dL. This assay is not available in most clinical laboratories.

VWFpp/VWF:Ag takes advantage of 2 facts: the VWF propeptide is secreted in a one-to-one ratio to VWF subunits and has a stable half-life in plasma. Thus, an increased ratio identifies patients with mutations that increase VWF clearance, such as type 1C VWD.³⁴ The mean ratio in normal individuals is 1.3, with a normal range of 0.54 to 1.98.

Genotyping should be considered when specialized testing with the VWF:FVIIIB, RIPA, or VWF:CB assays is unavailable and a diagnosis of type 2 VWD is suspected. A guideline on VWD genetic testing has been published by the UK Haemophilia Centre Doctors Organisation.³⁵

Interpretation of Clinical History and Laboratory Investigations

Normal plasma levels of VWF are approximately 100 IU/dL (100%, corresponds to ~10 μg/mL) with a population range of 50 to 200 IU/dL (50%–200%). There are a number of preanalytical variables (patient specific or laboratory specific) that affect the results of VWF laboratory testing. Patient-specific variables that are associated with increased VWF levels include increasing age, African ethnicity, exercise, inflammatory disease states, blood group A or B, increased levels of epinephrine, cocaine use, and neuroendocrine hormone levels. Decreased VWF levels are associated with medications such as valproic acid, hypothyroidism, autoantibodies, and blood group O. Individuals with blood group O have VWF levels that are 25% lower than levels in other blood groups.³⁶ Several analytical variables also can complicate the diagnosis of VWD: methods for established reference ranges, limitations to the sensitivity of assays, and sample handling issues.¹¹ These factors (summarized in Table 3)  must be considered when interpreting VWF laboratory results, and at least 2 sets of tests using fresh samples are needed to confirm the diagnosis of VWD. Testing should be avoided in stressed, ill, or pregnant patients.

Mild type 1 VWD can be a difficult diagnosis to make because of the overlap of bleeding symptoms among normal individuals and those with mild type 1 VWD, as well as the variability of VWF levels. There is no consensus on the exact VWF levels required to confirm the diagnosis: the NHLBI Expert Panel recommends VWF:Ag and VWF:RCo levels less than 0.30 IU/mL to diagnose type 1 VWD,¹¹ whereas the ISTH-SSC Subcommittee on von Willebrand factor recommends using VWF:RCo and VWF:Ag levels greater than 2 standard deviations below the population mean.³⁷ In the absence of a bleeding history, slightly reduced VWF levels do not predict future significant bleeding events.³⁸ Therefore, regardless of the laboratory cut-off used, the cornerstone of a VWD diagnosis should be a history of excessive mucocutaneous bleeding.

 

Differential Diagnosis

When considering a diagnosis of VWD, the differential diagnosis must be considered and includes acquired von Willebrand syndrome (AVWS), platelet-type VWD (PT-VWD), and hemophilia A. AVWS is the result of an acquired deficiency or defect of VWF and manifests with a mild to moderate bleeding disorder without a lifelong personal and family history of bleeding. AVWS has diverse pathology. The most common mechanism is proteolytic cleavage of VWF after shear stress–induced unfolding, as seen with aortic stenosis and ventricular assist devices, where as many as 79% of persons with aortic stenosis³⁹ and up to 100% with left ventricular assist devices are affected.⁴⁰ Other disease mechanisms include autoantibody formation that impairs VWF function or increases its clearance (autoimmune disease or lymphoproliferative disease), adsorption of HMW VWF multimers to malignant cells or platelets (myeloproliferative neoplasms and Wilm’s tumor), or decreased synthesis (hypothyroidism, valproic acid). The median age of diagnosis is 62 years, but the disorder may occur in any age-group (range 2–96 years).⁴¹ The approach to management of AVWS should focus on treatment of bleeding and induction of long-term remission. Treatment of bleeding will depend on the underlying mechanism of AVWS and may include a combination of DDAVP or VWF/FVIII concentrates, recombinant factor VIIa, antifibrinolytic agents, intravenous immunoglobulin, or plasmapheresis for AVWS associated with autoantibodies. Treatment of the underlying disorder (eg, aortic valve repair or treatment of a lymphoproliferative disorder) may result in remission of the AVWS.

Mild hemophilia A (caused by mutations in the F8 gene) and type 2N VWD can be difficult to differentiate clinically. Both present with reduced FVIII:C, and type 2N VWD may have normal or borderline low levels of VWF. Although the VWF:FVIIIB assay will distinguish between the 2 disorders, the test is not available in many centers. The pattern of inheritance may be helpful: hemophilia A is an X-linked disorder, whereas type 2N is autosomal recessive. Often, the diagnosis of type 2N VWD is suspected when genotyping of F8 does not identify a mutation in mild hemophilia A, when infused FVIII concentrates have a decreased half-life, or when DDAVP is associated with a brisk but short-lived response. In the absence of VWF:FVIIIB assay availability, genotyping of VWF will confirm the diagnosis, with missense mutations being located in exons 17–20 or 24–27.¹⁹

PT-VWD represents the phenocopy of type 2B VWD. The mutation is in the platelet receptor gene GPIBA and causes enhanced VWF-platelet binding. The disorders can be differentiated by RIPA plasma/platelet mixing studies or flow cytometry.^42,43 However, these assays are technically challenging. In the absence of mutations in exon 28 of VWF, mutations in exon 2 of GPIBA may be identified in approximately 10% of persons misdiagnosed with type 2B VWD.

Management

Patients with VWD present to medical attention in a number of ways: excessive post-trauma or surgical bleeding, recurrent mucocutaneous bleeding such as epistaxis, menorrhagia, gastrointestinal bleeding, or, in severe cases, recurrent hemarthroses and muscle hematomas. Irrespective of the presentation, the goal is to minimize and control bleeding. Therapeutic options can be divided into 3 main categories: (1) localized measures to stop bleeding; (2) pharmacologic agents with indirect hemostatic benefit; and (3) treatments that directly increase plasma VWF and FVIII levels. A combination of all 3 of these modalities can be used depending on the bleeding location and severity.

Localized Measures

Localized measures to control bleeding in VWD will depend on the site of bleeding. Epistaxis can be particularly problematic for affected children, and patients should be armed with a step-wise action plan that escalates from pressure to packing and includes guidelines regarding how long to wait before seeking medical attention. In selected cases, nasal cautery may be required for prolonged or excessive epistaxis. Topical hemostatic agents such as gelatin foam/matrix, topical thrombin, and fibrin sealants are predominately used to achieve surgical hemostasis and may have a limited role in the treatment of VWD-associated bleeding. In the case of menorrhagia, hormonal treatments (ie, the combined oral contraceptive pill, OCP), levonorgestrel-releasing intrauterine systems, or endometrial ablation all effectively reduce menstrual blood loss through their local effects on the endometrial lining.⁴⁴ In addition, older generations of OCP are associated with increases in VWF levels. This effect is mediated by the estrogen component and is evident with ethynylestradiol doses of 0.5 μg or higher. Lower estrogen doses, seen in currently used OCP, have little or no effect on VWF levels.^11,45

Pharmacologic Therapy

Indirect therapies include the antifibrinolytic agents (eg, tranexamic acid and aminocaproic acid). These agents are used either as the sole therapy at the time of minor surgical and dental procedures, or as an adjunct in combination with DDAVP or VWF/FVIII concentrates. Antifibrinolytics are thought to be particularly useful for controlling mucosal bleeding in areas of high fibrinolytic activity: the oral cavity, gastrointestinal tract, or uterus. Tranexamic acid inhibits the conversion of plasminogen to plasmin, and is the more commonly used antifibrinolytic.¹¹ Tranexamic acid can be administered either intravenously or orally at doses of 10 to 25 mg/kg, respectively. It is usually continued until bleeding is controlled or up to 7 to 10 days postoperatively. The most common adverse events associated with tranexamic acid are headache, back pain, and gastrointestinal side effects.⁴⁶ Tranexamic acid is contraindicated in disseminated intravascular coagulation and bleeding from the upper urinary tract, where it can lead to urinary tract obstruction by clots.

 

DDAVP, a synthetic derivative of vasopressin, promotes release of stored VWF from endothelial cells. Most individuals with type 1 VWD and some with type 2A VWD respond to treatment with DDAVP: a therapeutic trial to confirm adequate DDAVP response should be performed prior to its clinical use. Assessment of VWF:Ag, VWF:RCo, and FVIII levels should be performed before and at several time points after the DDAVP administration up to and including 4 hours. Peak VWF levels are achieved 30 and 90 minutes after intravenous and intranasal delivery, respectively. An increase in VWF:Ag/VWF:RCo and FVIII levels to at least 30 IU/dL is adequate for most dental procedures, minor surgery, or the treatment of epistaxis or menorrhagia. DDAVP may be adequate to treat major bleeds or for major surgery when VWF levels increase well above 50 IU/dL. Decisions surrounding the use of DDAVP versus a VWF/FVIII concentrate will depend on the expected DDAVP response, the type of surgery, and the anticipated duration of therapy required to achieve hemostasis. If treatment is required for more than 3 days, concerns regarding tachyphylaxis and side effects may limit its use. Significantly decreased VWF:Ag/VWF:RCo or FVIII at the 4-hour time point of a DDAVP trial may indicate type 1C or type 2N VWD, which are associated with increased clearance of endogenous VWF or FVIII, respectively. Despite the transient response in these patients, DDAVP remains a therapeutic option and its use should be assessed on a case-by-case basis.⁴⁷

The parenteral dose of DDAVP is 0.3 μg/kg infused in 30 to 50 mL of normal saline over approximately 30 minutes every 12 to 24 hours. The dose of the highly concentrated intranasal preparation is 150 μg for children under 50 kg and 300 μg for larger children and adults (1 spray per naris). It is important to note that the products used to treat VWD (eg, Stimate) deliver 150 μg per spray, a much higher concentration than that used to treat enuresis. Repeated DDAVP dosing is associated with the development of tachyphylaxis: with subsequent dosing, the magnitude of the VWF and FVIII increments can fall to approximately 70% of that obtained with the initial dose.⁴⁸ DDAVP is safe and generally well tolerated. Side effects include facial flushing, headache, tachycardia, light-headedness, and mild hypotension. The most serious side effects, severe hyponatremia and seizures,⁴⁹ can be avoided by fluid restriction for 24 hours after DDAVP administration. Serum sodium levels should be monitored with repeated doses. DDAVP is generally avoided in those younger than 2 years of age because of a higher risk of hyponatremia. Patients who are intolerant of DDAVP or have a poor VWF response need to be treated with a VWF/FVIII concentrate.

VWF/FVIII Concentrate

VWF/FVIII concentrates are required for patients who do not have an adequate response to DDAVP, who have side effects from or contraindications to DDAVP, or who require a long duration of treatment, rendering the use of DDAVP impractical. Purified, viral-inactivated, plasma-derived VWF/FVIII concentrates are the products most frequently used (eg, Humate-P, Wilate, Alphanate SD/HT). The quantity of VWF:RCo activity relative to FVIII:C varies by product; Humate-P contains 2.4 VWF:RCo units for each unit of FVIII:C; Wilate contains a 1:1 ratio; and Alphanate contains a 0.5:1 ratio. Both Humate-P and Wilate are reported to contain a full spectrum of VWF multimers, including HMW multimers, and closely resemble normal plasma, but Alphanate SD/HT lacks HMW mutimers.^11,50 Thus, the available VWF/FVIII vary in terms of VWF:RCo to FVIII concentrate, HMW multimer composition, reported VWF:RCo, and FVIII half-lives and even approved indications. They should not be considered interchangeable, and further information should be sought from the respective product inserts.

Dosing recommendations are provided either in VWF:RCo (North America) or FVIII:C units (Europe) and are weight-based (Table 4); repeat infusions can be given every 8 to 24 hours depending on the type of surgery/injury and the product used. 

For surgeries, the goal is to maintain VWF:RCo and FVIII:C greater than 100 IU/dL at peak and greater than 50 IU/dL at trough until hemostasis is achieved during the acute bleed or at the time of surgical intervention. The duration of factor replacement is 5 to 10 days for major surgeries and 1 to 4 days for minor surgeries. With VWF/FVIII concentrates, the FVIII:C response is higher and more sustained than predicted from the dose because of the stabilizing effect of exogenous VWF on endogenous FVIII.⁵¹ VWF:RCo and FVIII:C levels should be measured in patients receiving repeat infusions to ensure appropriate hemostatic levels and to avoid supratherapeutic levels because thromboembolic events have been associated with high FVIII levels. Thromboembolic events are rare, and most cases have been described in surgical patients with other risk factors.⁵² Adverse reactions to VWF/FVIII concentrates are rare but include allergic and anaphylactic symptoms.⁵³ A rare complication is the development of alloantibodies to VWF, which occurs in 5% to 10% of type 3 patients and manifests as a loss of hemostatic response to infused concentrates or anaphylactic reactions.²²

 

Long-term continuous use of concentrates to prevent bleeds, known as prophylaxis, is the standard of care in severe hemophilia A and B and is now being adopted in severe VWD. Patients with type 3 VWD or severe type 1 or type 2 VWD may experience recurrent bleeds into joints, nasal/oropharynx, or gastrointestinal tract or excessive menstrual bleeding. Retrospective cohort and case series suggest that prophylaxis improves quality of life; reduces the frequency of bleeding, need for transfusions, and hospitalizations; and prevents chronic joint disease.^54,55 More recently, a prospective study confirmed that prophylaxis with VWF concentrates at doses ranging from 50 IU VWF RCo/kg 1 to 3 times per week was highly effective at reducing bleeding rates, with annualized bleeding rates decreasing from 25 to 6.1 in 11 participants with either type 2A or type 3 VWD.⁵⁶

VWF/FVIII concentrates are effective in more than 97% of events.⁵⁷ Rarely, when infusion of a VWF/FVIII concentrate is ineffective at stopping bleeding, transfusion of platelet concentrates may be beneficial, presumably because they facilitate the delivery of small amounts of platelet VWF to the site of vascular injury. Highly purified FVIII concentrates (monoclonal antibody purified and recombinant) should not be used to treat VWD because they lack VWF.

A recombinant VWF concentrate (Vonvendi) combined initially with recombinant FVIII concentrate in a 1.3:1 ratio of VWF:RCo to FVIII:C has been shown to be safe and efficacious for the on-demand treatment of bleeds.^58,59 After the initial FVIII dose, the patients’ endogenous FVIII levels are stabilized within 6 hours and further FVIII administration may not required. A prospective phase 3 trial investigating the efficacy of recombinant VWF in the prophylaxis of severe VWD is ongoing. Vonvendi has been licensed for on-demand treatment in the United States since 2015. For further dosing information, please refer to the product insert.

Conclusion

VWF is a complex protein with several important and distinct functional domains: binding sites to collagen, FVIII, and platelet GPIbα; an ADAMTS13 cleavage site; and domains important for multimer formation. Mutations in any of these sites can result in a dysfunctional protein and as a result, VWD is a heterogeneous disorder with many specific assays available to determine the subtype. Despite this, the treatment of VWD is straightforward with only a small number of therapeutic options: indirect therapies such as antifibrinolytic agents, or direct therapies that increase VWF levels, DDAVP, or VWF/FVIII concentrates. Management focuses on preventing bleeding complications associated with invasive procedures or promptly treating bleeding episodes.

Introduction

von Willebrand disease (VWD) is an inherited bleeding disorder caused by deficient or defective plasma von Willebrand factor (VWF). VWF is an adhesive multimeric plasma glycoprotein that performs 2 major functions in hemostasis: it mediates platelet adhesion to injured subendothelium via glycoprotein 1bα (GPIbα), and it binds and stabilizes factor VIII (FVIII) in circulation, protecting it from proteolytic degradation by enzymes. The current VWD classification recognizes 3 types (Table 1).¹ 

In order to understand the role of the numerous laboratory investigations as well as the classification of VWD, it is important to review the structure and function of the VWF subunit. Bleeding symptoms, including mucocutaneous bleeding and excessive bleeding after surgery or trauma, reflect the defect in primary hemostasis. Treatment focuses on increasing VWF levels with desmopressin (1-deamino-8-D-arginine vasopressin, DDAVP) or clotting factor concentrates containing both VWF and FVIII (VWF/FVIII concentrate). Nonspecific treatment options include antifibrinolytic agents (tranexamic acid) and hormone therapy (oral contraceptive pill).

Prevalence

VWD is the most common inherited bleeding disorder. However, because VWF levels are highly variable and disease severity ranges from mild bleeding symptoms to severe or life-threatening bleeds, the reported prevalence of VWD depends on the diagnostic definition used. Two large epidemiologic studies have reported prevalence rates of approximately 1%.^2,3 In these studies, healthy school-aged children were screened and diagnosed with VWD based on low VWF activity, measured as ristocetin cofactor, and a personal and family history of bleeding symptoms. At the other extreme, when considering patients whose bleeding symptoms are sufficiently severe to warrant referral to specialized centers, the reported prevalence of VWD ranges from 20 to 113 per million.⁴ These studies likely over- and underestimate clinically significant VWD. More recent studies suggest that the prevalence of VWD in individuals whose bleeding symptoms are significant enough to present to a primary care physician is approximately 0.1%.⁵ This figure is likely a more accurate estimate of the true prevalence of symptomatic VWD.

Although VWD is autosomally inherited, females are more likely to present with bleeding symptoms and be diagnosed because of increased exposure to bleeding challenges, such as menorrhagia and childbirth. VWD does not show any geographic or ethnic predilection, but there is an increased prevalence of the recessive forms, such as type 2N and type 3 VWD, in areas with high rates of consanguinity.

VWF Protein Structure and Function

The VWF gene is located on chromosome 12 at p13.3 and spans 178 kb comprising 52 exons.⁶ The expression of the VWF gene is tightly restricted to endothelial cells, platelets, and megakaryocytes, where VWF is stored in Weibel-Palade bodies and α-granules. VWF is a large multimeric glycoprotein with several important functional domains (Figure).

Extensive post-translational modifications, mediated by domains D3 and CK as well as the VWF propeptide, result in disulfide-linked multimers that can be greater than 20,000 kDa, while the VWF subunit is approximately 250 kDa. The high-molecular-weight (HMW) multimers are most effective in mediating platelet adhesion to the site of vascular injury; therefore, appropriate multimer formation is integral to VWF’s function. VWF is either secreted from local endothelial cells or recruited from the circulation to the site of endothelial injury, where it adheres to exposed collagen, predominately via the collagen-binding site in the A3 domain. Once immobilized, VWF is subjected to the high shear rates of the arterial circulation and undergoes a conformational change that exposes the platelet GPIbα binding site within the A1 domain.⁷ The high-affinity, rapid and reversible interaction between VWF and GPIbα tethers platelets to the endothelium where they roll until they are immobilized by integrin-mediated binding, which has slower binding kinetics. The RGD (Arg-Gly-Asp) sequence within the C4 domain also contributes to platelet adhesion by interacting with GPIIb-IIIa of activated platelets.⁸ ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) is a plasma protease that cleaves circulating VWF in the A2 domain when VWF multimers unfold in response to sufficient shear, exposing the cleavage site within the A2 domain.⁹ VWF’s second role in hemostasis is fulfilled by the D’ and D3 domains, which bind and protect FVIII from proteolytic degradation, thereby prolonging its half-life. In the absence of VWF, FVIII has a half-life of approximately 2 hours, in contrast to a normal half-life of 12 to 20 hours when bound to VWF.⁴

Classification, Pathophysiology, and Genetics

The International Society of Thrombosis and Hemostasis (ISTH) classification of VWD was updated in 2006 (Table 1).¹ It incorporates important aspects of clinical phenotype, pathophysiological mechanisms, and treatment considerations. The 3 categories are: type 1, which is a partial quantitative deficiency; type 2 with 4 subtypes (2A, 2B, 2M, and 2N), which is a qualitative defect; and type 3, which is a virtual absence of VWF. Although the diagnosis and categorization of VWD can be achieved with widely available laboratory testing, further subcategorization among type 2 VWD subtypes may require referral to a specialized laboratory. The current ISTH classification intentionally does not incorporate genotypic data. In type 2 or type 3 VWD disease, VWF mutations are identified in more than 90% of cases and are completely penetrant, whereas mutations are identified in only approximately 65% of type 1 VWD cases and have been associated with incomplete penetrance and variable expressivity.¹⁰ These studies suggest that type 1 VWD is an oligogenic disease with mutations in genes regulating secretion or clearance contributing to a VWD phenotype.

 

VWD Types

Type 1

Type 1 VWD is caused by a partial quantitative deficiency of VWF and represents approximately 75% of VWD cases. It is the most clinically heterogeneous type, with patients having a mild to moderate bleeding phenotype.¹¹ Bleeding in type 1 VWD results from a decrease in the concentration of VWF. The VWF function is normal without a significant abnormality in the platelet, collagen, or FVIII binding sites or a significant decrease in HMW multimers. Functional assays of VWF, such as VWF ristocetin cofactor (VWF:RCo) or VWF activity (VWF:Act) (see section on Laboratory Testing for further details), are proportionally decreased relative to the VWF antigen level (VWF:Ag), and the ratio of functional activity as compared with the VWF level is normal (ie, VWF:RCo/VWF:Ag ratio is > 0.6). As noted, VWF mutations are identified in only 65% of type 1 VWD cases and have incomplete penetrance and variable expressivity.¹⁰ Approximately 70% of mutations identified are missense mutations. Missense mutations may affect VWF levels by affecting any part of the biosynthetic pathway, including trafficking, storage, secretion, and/or clearance of VWF.

Increased VWF clearance is a well-described mechanism for type 1 VWD, known as type 1C. These patients will typically have very low VWF levels, an increased VWF propeptide to antigen ratio (VWFpp/VWF:Ag), and a marked but short-lived response to DDAVP, limiting DDAVP’s clinical applicability.¹² On the other hand, the half-life of VWF/FVIII concentrates is normal in these individuals. Type 1C VWD is caused by missense mutations which occur mainly in the D3 domain and reduce the half-life of VWF up to 15-fold. R1205H, known as the “Vicenza” variant, is the most common and severe as well as the best characterized of these mutations.¹³

Type 2

Accounting for approximately 25% of VWD cases, type 2 VWD is characterized by a qualitative deficiency of VWF activity and is further subcategorized based on the mechanism of VWF dysfunction. Type 2A, 2B, and 2M affect VWF–platelet interactions by way of loss of HMW multimers, a gain of function of the GPIbα binding site, or a loss of function of the same site, respectively. On the other hand, type 2N is caused by defective VWF binding to FVIII. Type 2 VWD is often suspected when investigations demonstrate a function-antigen discordance: the VWF:RCo or VWF:Act is decreased disproportionately to the decrease in VWF:Ag, and the VWF:RCo/VWF:Ag ratio is less than 0.6.

Type 2A VWD is the most common type 2 variant. It is characterized by disproportionately low functional activity compared to antigen level (ie, VWF:RCo/VWF:ag ratio is < 0.6) and a loss of HMW and sometimes intermediate molecular weight (IMW) multimers. Ristocetin-induced platelet agglutination (RIPA) will be decreased with standard doses of ristocetin and absent with low doses. Type 2A VWD is usually inherited as an autosomal dominant trait. This subtype encompasses missense mutations that impair dimerization or multimerization of VWF subunits (CK, D1, and D2 domains); disrupt intersubunit disulphide bonds (D3 and D2 domains); enhance susceptibility to ADAMTS13-mediated proteolysis (A2 and A1 domains); or result in intracellular retention of the HMW multimers (D3, A1, and A2 domains).¹⁰ The result is VWF that lacks HMW multimers, thereby possessing fewer GPIbα binding sites, and that is less effective in binding platelets.

Type 2B VWD is the result of gain-of-function mutations within the GPIbα binding site of VWF. Generally, the platelet-binding site of VWF within the A1 domain is only exposed once VWF is immobilized on injured collagen and subjected to shear forces, resulting in a conformational change.⁷ In type 2B VWD, the gain-of-function mutation results in spontaneous binding of VWF to platelets without the need for a VWF-collagen interaction and unfolding of VWF by shear forces. The VWF–platelet interaction selectively depletes the HMW multimers by the unfolding of the A2 domain and increasing ADAMTS13 proteolysis. The increased binding of mutant VWF to platelets also triggers the formation of platelet aggregates, which are removed from circulation resulting in thrombocytopenia. Increases in endogenous VWF seen with acute stressors or pregnancy can worsen thrombocytopenia and increase the risk of bleeding.¹⁴ Certain mutations, such as V1316M, alter megakaryocytopoiesis and are characterized by giant platelets with abnormal ultrastructure and further exacerbate the thrombocytopenia.¹⁵ The laboratory profile reveals a VWF:RCo/VWF:Ag ratio of < 0.6 and absence of HMW multimers. In contrast to type 2A, platelets will agglutinate with low-dose ristocetin. Missense mutations are highly penetrant dominant and occur in or close to the A1 domain.¹⁶

Type 2M VWD is characterized by loss-of-function mutations within the GPIbα binding site of VWF. Phenotypic characteristics include a reduced ratio of VWF:RCo/VWF:Ag of < 0.6 but a normal multimer pattern.¹⁷ Missense mutations are reported in the A1 domain affecting the GPIbα-binding site. In very rare instances, mutations in the A3 domain that impair the VWF/collagen interaction have been described.¹⁸ These collagen-binding mutations are not included in the last iteration of the ISTH classification in 2006,¹ but fit best in the type 2M category. In these cases, VWF:RCo or VWF:Act, which reflect activity at the GPIbα-binding site, may be normal and the diagnosis requires VWF/collagen binding assays (VWF:CB).

Type 2N VWD results from mutations of the FVIII binding site or conformational changes that impair the VWF–FVIII interaction. Most (~80%) missense mutations are located in domains D’ and D3.¹⁹ These mutations are autosomal recessive, and affected individuals are either homozygous or compound heterozygous for type 2N/2N or type 1/2N mutations, or compound heterozygous for a missense mutation and a mutation resulting in a null allele (type 2N/3 mutations). The laboratory phenotype is a disproportionate reduction in the FVIII level relative to the VWF level, which may be low or normal. Most cases of type 2N VWD have a normal multimeric profile, but rare cases will demonstrate loss of HMW multimers. Definitive diagnosis requires evidence of reduced FVIII binding to VWF (VWF:FVIIIB) or the identification of causative mutations in the FVIII binding region of the VWF gene.²⁰

 

Type 3

Type 3 VWD is defined by a virtual absence of VWF. The inheritance of type 3 VWD has often been reported as autosomal recessive. However, there is emerging evidence that it can also be inherited in a co-dominant pattern: obligate carriers of type 3 VWD mutations have more mucocutaneous bleeding symptoms than normal individuals, and in approximately 50% of cases may carry a diagnosis of type 1 VWD.²¹ This condition is characterized by prolongation of the activated partial thromboplastin time (aPTT), undetectable levels of VWF:Ag, and VWF:RCo and FVIII levels less than 10 IU/dL (10%). The majority (~80%) of type 3 VWD patients have 2 null alleles as a result of a variety of mutations, with nonsense mutations accounting for about one-third.¹⁰ The remainder of the mutational spectrum is made up of missense mutations predominantly located in the D1-D2 (exons 3–11) and D4-CK (exons 37–52) domains that result in intracellular VWF retention, or large deletions, resulting in frameshift mutations affecting 1 or more exons. Because there is little or no circulating VWF, patients with type 3 VWD may develop alloantibodies to VWF, which can complicate treatment.²²

Diagnosis

Clinical Manifestations

VWD is a congenital bleeding disorder. The increased risk of bleeding is present from birth, but symptoms may only manifest when there is a hemostatic challenge. Bleeding symptoms become more apparent with increasing age and exposure to hemostatic challenges. As a result, the diagnosis is often delayed into adulthood in mild to moderate forms of VWD. On the other hand, with more severe bleeding phenotypes such as type 3 VWD, the diagnosis is often made in childhood. Individuals with VWD primarily complain of excessive mucocutaneous bleeding, which includes spontaneous bruising, recurrent epistaxis, and bleeding from the gums after brushing, dental cleaning, and extractions. In addition, prolonged or excessive bleeding after surgery or trauma is often reported. Females frequently experience menorrhagia, usually beginning at menarche, and can have prolonged or excessive bleeding after childbirth.²³ Musculoskeletal bleeding is unusual, except in type 2N or type 3 VWD when the FVIII:C level may be less than 10 IU/dL.

Mucocutaneous bleeding symptoms such as epistaxis, gum bleeding, ecchymosis, and menorrhagia overlap with those experienced by a normal population, and therefore can be easily overlooked by both patients and physicians.¹¹ The use of bleeding assessment tools (BATs) to standardize the bleeding history and interpretation of the severity of the bleeding phenotype is becoming part of routine clinical practice. Three different BATs, each an adaptation of its predecessor, have been created and validated.²⁴ Each of the scores performs well in an undiagnosed population presenting with bleeding symptoms. The negative predictive value is typically greater than 0.99, meaning that a negative bleeding score nearly excludes a clinically significant bleeding disorder. Thus, the main utility of the current BATs is at the time of new patient assessments: a negative bleeding score will help avoid unnecessary laboratory testing and prevent false-positive diagnoses of VWD (borderline low VWF:Ag without a significant bleeding history). However, the currently available BATs have some limitations. When scoring severe bleeding disorders, BATs become saturated as they take into account the worst episode of bleeding within each category but not the frequency of bleeding. BATs need to be administered by an expert and are time consuming to complete. Finally, they are not useful for monitoring bleeding symptoms or response to therapy because of the cumulative nature of the scores. In an attempt to standardize the BAT and bleeding score, the ISTH/Scientific and Standardization Committee (SSC) Joint VWF and Perinatal/Pediatric Hemostasis Sub­committees Working Group has established a revised BAT, known as the ISTH-BAT, specifically designed to extend the utility of the earlier BATS by incorporating information on both symptom frequency and severity.^25,26 The ISTH-BAT has been further modified to a patient- or self-administered BAT (SELF-BAT). The SELF-BAT has been shown to be a reliable and effective tool in the assessment of patients who are being evaluated for VWD.²⁷

Laboratory Testing

Screening tests include a complete blood count (CBC), prothrombin time, aPTT, thrombin time, and fibrinogen concentration to exclude the presence of other hemostatic disorders. The CBC may show thrombocytopenia in type 2B VWD. The aPTT is often normal, but will be prolonged if the FVIII level is below 30 IU/dL, as can be seen in severe type 1, type 2N, or type 3 VWD. The platelet function analyzer (PFA-100) is a system for analyzing primary hemostasis under high shear rates, but its role in the diagnosis of VWD is controversial.¹¹

The evaluation of VWD involves quantitative (VWF:Ag) and qualitative measurements of VWF (VWF:RCo, or one of the novel assays: VWF:Act or VWF:GPIbM) and FVIII activity (FVIII:C). Type 2 VWD is suspected when the VWF activity to VWF:Ag ratio is < 0.6, the FVIII:C is more significantly decreased as compared to VWF:Ag, or with the presence of thrombocytopenia. In these cases, further testing (multimer gel electrophoresis, VWF:CB, RIPA, VWF:FVIIIB, and genotyping) is required to discriminate the type 2 VWD subtype, but such testing may be available only in  specialized laboratories. If type 1C VWD is suspected, the VWFpp/VWF:ag ratio may confirm the diagnosis. Table 2 summarizes the results seen with each subtype. These assays are described in detail below.

 

VWD Assays

VWF:Ag represents the quantity of VWF protein (antigen) in the plasma measured using an enzyme-linked immunosorbent assay (ELISA) or latex immunoassay. The normal range is approximately 50 to 200 IU/dL.

VWF:RCo is a functional assay that determines the capacity of VWF to agglutinate platelets via the platelet receptor GPIbα in the presence of ristocetin. The normal range is approximately 50 to 200 IU/dL. Novel methods of measuring VWF’s platelet-binding activity are increasingly being adopted by clinical laboratories and are associated with greater precision and improved lower limits of detection and coefficients of variation.^28,29 The first is the VWF:Act, a rapid automated assay that measures VWF activity using an antibody directed to the GPIbα binding site of VWF.²⁸ The second novel assay is VWF:GPIbM, which involves a gain-of-function GPIB construct that binds VWF without ristocetin.^30,31 For simplicity, VWF:RCo will be used to refer to VWF platelet-binding activity in the ensuing text. Factor VIII:C is a functional FVIII assay that determines the activity of FVIII in aPTT-based assays. The normal range is approximately 50 to 150 IU/dL.

VWF multimer analysis by SDS-agarose electrophoresis assesses VWF oligomers in plasma.³² Normal plasma contains multimers composed of over 40 VWF dimers, and these multimers are classified as high (HMW), intermediate (IMW), or low molecular weight (LMW). HMW multimers are decreased or missing in types 2A and 2B VWD, and IMW multimers may also be absent in type 2A VWD.

Low-dose RIPA tests the capacity of the patient’s platelets to agglutinate at low concentrations of ristocetin (~0.5 mg/mL). This is in contrast to the VWF:RCo, in which formalin-fixed control platelets are used. With type 2B, the platelet membrane is “overloaded” with high-affinity mutant VWF, resulting in abnormal platelet agglutination at low ristocetin concentrations. In some cases of type 2B VWD, all variables except RIPA may be normal.²⁹

VWF:FVIIIB is an ELISA-based assay that determines the ability of VWF to bind FVIII and is used to make the diagnosis of type 2N VWD.¹⁹

VWF:CB is an ELISA-based assay that measures the ability of VWF to bind to collagen, a function of VWF that is dependent on the collagen-binding domain (A3) and on the presence of HMW multimers. VWF:CB helps to distinguish between types 1 and 2 VWD by reflecting the loss of HMW multimer forms (type 2A VWD) or can reflect a specific collagen-binding deficiency (type 2M VWD).³³ The normal range is approximately 50 to 200 IU/dL. This assay is not available in most clinical laboratories.

VWFpp/VWF:Ag takes advantage of 2 facts: the VWF propeptide is secreted in a one-to-one ratio to VWF subunits and has a stable half-life in plasma. Thus, an increased ratio identifies patients with mutations that increase VWF clearance, such as type 1C VWD.³⁴ The mean ratio in normal individuals is 1.3, with a normal range of 0.54 to 1.98.

Genotyping should be considered when specialized testing with the VWF:FVIIIB, RIPA, or VWF:CB assays is unavailable and a diagnosis of type 2 VWD is suspected. A guideline on VWD genetic testing has been published by the UK Haemophilia Centre Doctors Organisation.³⁵

Interpretation of Clinical History and Laboratory Investigations

Normal plasma levels of VWF are approximately 100 IU/dL (100%, corresponds to ~10 μg/mL) with a population range of 50 to 200 IU/dL (50%–200%). There are a number of preanalytical variables (patient specific or laboratory specific) that affect the results of VWF laboratory testing. Patient-specific variables that are associated with increased VWF levels include increasing age, African ethnicity, exercise, inflammatory disease states, blood group A or B, increased levels of epinephrine, cocaine use, and neuroendocrine hormone levels. Decreased VWF levels are associated with medications such as valproic acid, hypothyroidism, autoantibodies, and blood group O. Individuals with blood group O have VWF levels that are 25% lower than levels in other blood groups.³⁶ Several analytical variables also can complicate the diagnosis of VWD: methods for established reference ranges, limitations to the sensitivity of assays, and sample handling issues.¹¹ These factors (summarized in Table 3)  must be considered when interpreting VWF laboratory results, and at least 2 sets of tests using fresh samples are needed to confirm the diagnosis of VWD. Testing should be avoided in stressed, ill, or pregnant patients.

Mild type 1 VWD can be a difficult diagnosis to make because of the overlap of bleeding symptoms among normal individuals and those with mild type 1 VWD, as well as the variability of VWF levels. There is no consensus on the exact VWF levels required to confirm the diagnosis: the NHLBI Expert Panel recommends VWF:Ag and VWF:RCo levels less than 0.30 IU/mL to diagnose type 1 VWD,¹¹ whereas the ISTH-SSC Subcommittee on von Willebrand factor recommends using VWF:RCo and VWF:Ag levels greater than 2 standard deviations below the population mean.³⁷ In the absence of a bleeding history, slightly reduced VWF levels do not predict future significant bleeding events.³⁸ Therefore, regardless of the laboratory cut-off used, the cornerstone of a VWD diagnosis should be a history of excessive mucocutaneous bleeding.

 

Differential Diagnosis

When considering a diagnosis of VWD, the differential diagnosis must be considered and includes acquired von Willebrand syndrome (AVWS), platelet-type VWD (PT-VWD), and hemophilia A. AVWS is the result of an acquired deficiency or defect of VWF and manifests with a mild to moderate bleeding disorder without a lifelong personal and family history of bleeding. AVWS has diverse pathology. The most common mechanism is proteolytic cleavage of VWF after shear stress–induced unfolding, as seen with aortic stenosis and ventricular assist devices, where as many as 79% of persons with aortic stenosis³⁹ and up to 100% with left ventricular assist devices are affected.⁴⁰ Other disease mechanisms include autoantibody formation that impairs VWF function or increases its clearance (autoimmune disease or lymphoproliferative disease), adsorption of HMW VWF multimers to malignant cells or platelets (myeloproliferative neoplasms and Wilm’s tumor), or decreased synthesis (hypothyroidism, valproic acid). The median age of diagnosis is 62 years, but the disorder may occur in any age-group (range 2–96 years).⁴¹ The approach to management of AVWS should focus on treatment of bleeding and induction of long-term remission. Treatment of bleeding will depend on the underlying mechanism of AVWS and may include a combination of DDAVP or VWF/FVIII concentrates, recombinant factor VIIa, antifibrinolytic agents, intravenous immunoglobulin, or plasmapheresis for AVWS associated with autoantibodies. Treatment of the underlying disorder (eg, aortic valve repair or treatment of a lymphoproliferative disorder) may result in remission of the AVWS.

Mild hemophilia A (caused by mutations in the F8 gene) and type 2N VWD can be difficult to differentiate clinically. Both present with reduced FVIII:C, and type 2N VWD may have normal or borderline low levels of VWF. Although the VWF:FVIIIB assay will distinguish between the 2 disorders, the test is not available in many centers. The pattern of inheritance may be helpful: hemophilia A is an X-linked disorder, whereas type 2N is autosomal recessive. Often, the diagnosis of type 2N VWD is suspected when genotyping of F8 does not identify a mutation in mild hemophilia A, when infused FVIII concentrates have a decreased half-life, or when DDAVP is associated with a brisk but short-lived response. In the absence of VWF:FVIIIB assay availability, genotyping of VWF will confirm the diagnosis, with missense mutations being located in exons 17–20 or 24–27.¹⁹

PT-VWD represents the phenocopy of type 2B VWD. The mutation is in the platelet receptor gene GPIBA and causes enhanced VWF-platelet binding. The disorders can be differentiated by RIPA plasma/platelet mixing studies or flow cytometry.^42,43 However, these assays are technically challenging. In the absence of mutations in exon 28 of VWF, mutations in exon 2 of GPIBA may be identified in approximately 10% of persons misdiagnosed with type 2B VWD.

Management

Patients with VWD present to medical attention in a number of ways: excessive post-trauma or surgical bleeding, recurrent mucocutaneous bleeding such as epistaxis, menorrhagia, gastrointestinal bleeding, or, in severe cases, recurrent hemarthroses and muscle hematomas. Irrespective of the presentation, the goal is to minimize and control bleeding. Therapeutic options can be divided into 3 main categories: (1) localized measures to stop bleeding; (2) pharmacologic agents with indirect hemostatic benefit; and (3) treatments that directly increase plasma VWF and FVIII levels. A combination of all 3 of these modalities can be used depending on the bleeding location and severity.

Localized Measures

Localized measures to control bleeding in VWD will depend on the site of bleeding. Epistaxis can be particularly problematic for affected children, and patients should be armed with a step-wise action plan that escalates from pressure to packing and includes guidelines regarding how long to wait before seeking medical attention. In selected cases, nasal cautery may be required for prolonged or excessive epistaxis. Topical hemostatic agents such as gelatin foam/matrix, topical thrombin, and fibrin sealants are predominately used to achieve surgical hemostasis and may have a limited role in the treatment of VWD-associated bleeding. In the case of menorrhagia, hormonal treatments (ie, the combined oral contraceptive pill, OCP), levonorgestrel-releasing intrauterine systems, or endometrial ablation all effectively reduce menstrual blood loss through their local effects on the endometrial lining.⁴⁴ In addition, older generations of OCP are associated with increases in VWF levels. This effect is mediated by the estrogen component and is evident with ethynylestradiol doses of 0.5 μg or higher. Lower estrogen doses, seen in currently used OCP, have little or no effect on VWF levels.^11,45

Pharmacologic Therapy

Indirect therapies include the antifibrinolytic agents (eg, tranexamic acid and aminocaproic acid). These agents are used either as the sole therapy at the time of minor surgical and dental procedures, or as an adjunct in combination with DDAVP or VWF/FVIII concentrates. Antifibrinolytics are thought to be particularly useful for controlling mucosal bleeding in areas of high fibrinolytic activity: the oral cavity, gastrointestinal tract, or uterus. Tranexamic acid inhibits the conversion of plasminogen to plasmin, and is the more commonly used antifibrinolytic.¹¹ Tranexamic acid can be administered either intravenously or orally at doses of 10 to 25 mg/kg, respectively. It is usually continued until bleeding is controlled or up to 7 to 10 days postoperatively. The most common adverse events associated with tranexamic acid are headache, back pain, and gastrointestinal side effects.⁴⁶ Tranexamic acid is contraindicated in disseminated intravascular coagulation and bleeding from the upper urinary tract, where it can lead to urinary tract obstruction by clots.

 

DDAVP, a synthetic derivative of vasopressin, promotes release of stored VWF from endothelial cells. Most individuals with type 1 VWD and some with type 2A VWD respond to treatment with DDAVP: a therapeutic trial to confirm adequate DDAVP response should be performed prior to its clinical use. Assessment of VWF:Ag, VWF:RCo, and FVIII levels should be performed before and at several time points after the DDAVP administration up to and including 4 hours. Peak VWF levels are achieved 30 and 90 minutes after intravenous and intranasal delivery, respectively. An increase in VWF:Ag/VWF:RCo and FVIII levels to at least 30 IU/dL is adequate for most dental procedures, minor surgery, or the treatment of epistaxis or menorrhagia. DDAVP may be adequate to treat major bleeds or for major surgery when VWF levels increase well above 50 IU/dL. Decisions surrounding the use of DDAVP versus a VWF/FVIII concentrate will depend on the expected DDAVP response, the type of surgery, and the anticipated duration of therapy required to achieve hemostasis. If treatment is required for more than 3 days, concerns regarding tachyphylaxis and side effects may limit its use. Significantly decreased VWF:Ag/VWF:RCo or FVIII at the 4-hour time point of a DDAVP trial may indicate type 1C or type 2N VWD, which are associated with increased clearance of endogenous VWF or FVIII, respectively. Despite the transient response in these patients, DDAVP remains a therapeutic option and its use should be assessed on a case-by-case basis.⁴⁷

The parenteral dose of DDAVP is 0.3 μg/kg infused in 30 to 50 mL of normal saline over approximately 30 minutes every 12 to 24 hours. The dose of the highly concentrated intranasal preparation is 150 μg for children under 50 kg and 300 μg for larger children and adults (1 spray per naris). It is important to note that the products used to treat VWD (eg, Stimate) deliver 150 μg per spray, a much higher concentration than that used to treat enuresis. Repeated DDAVP dosing is associated with the development of tachyphylaxis: with subsequent dosing, the magnitude of the VWF and FVIII increments can fall to approximately 70% of that obtained with the initial dose.⁴⁸ DDAVP is safe and generally well tolerated. Side effects include facial flushing, headache, tachycardia, light-headedness, and mild hypotension. The most serious side effects, severe hyponatremia and seizures,⁴⁹ can be avoided by fluid restriction for 24 hours after DDAVP administration. Serum sodium levels should be monitored with repeated doses. DDAVP is generally avoided in those younger than 2 years of age because of a higher risk of hyponatremia. Patients who are intolerant of DDAVP or have a poor VWF response need to be treated with a VWF/FVIII concentrate.

VWF/FVIII Concentrate

VWF/FVIII concentrates are required for patients who do not have an adequate response to DDAVP, who have side effects from or contraindications to DDAVP, or who require a long duration of treatment, rendering the use of DDAVP impractical. Purified, viral-inactivated, plasma-derived VWF/FVIII concentrates are the products most frequently used (eg, Humate-P, Wilate, Alphanate SD/HT). The quantity of VWF:RCo activity relative to FVIII:C varies by product; Humate-P contains 2.4 VWF:RCo units for each unit of FVIII:C; Wilate contains a 1:1 ratio; and Alphanate contains a 0.5:1 ratio. Both Humate-P and Wilate are reported to contain a full spectrum of VWF multimers, including HMW multimers, and closely resemble normal plasma, but Alphanate SD/HT lacks HMW mutimers.^11,50 Thus, the available VWF/FVIII vary in terms of VWF:RCo to FVIII concentrate, HMW multimer composition, reported VWF:RCo, and FVIII half-lives and even approved indications. They should not be considered interchangeable, and further information should be sought from the respective product inserts.

Dosing recommendations are provided either in VWF:RCo (North America) or FVIII:C units (Europe) and are weight-based (Table 4); repeat infusions can be given every 8 to 24 hours depending on the type of surgery/injury and the product used. 

For surgeries, the goal is to maintain VWF:RCo and FVIII:C greater than 100 IU/dL at peak and greater than 50 IU/dL at trough until hemostasis is achieved during the acute bleed or at the time of surgical intervention. The duration of factor replacement is 5 to 10 days for major surgeries and 1 to 4 days for minor surgeries. With VWF/FVIII concentrates, the FVIII:C response is higher and more sustained than predicted from the dose because of the stabilizing effect of exogenous VWF on endogenous FVIII.⁵¹ VWF:RCo and FVIII:C levels should be measured in patients receiving repeat infusions to ensure appropriate hemostatic levels and to avoid supratherapeutic levels because thromboembolic events have been associated with high FVIII levels. Thromboembolic events are rare, and most cases have been described in surgical patients with other risk factors.⁵² Adverse reactions to VWF/FVIII concentrates are rare but include allergic and anaphylactic symptoms.⁵³ A rare complication is the development of alloantibodies to VWF, which occurs in 5% to 10% of type 3 patients and manifests as a loss of hemostatic response to infused concentrates or anaphylactic reactions.²²

 

Long-term continuous use of concentrates to prevent bleeds, known as prophylaxis, is the standard of care in severe hemophilia A and B and is now being adopted in severe VWD. Patients with type 3 VWD or severe type 1 or type 2 VWD may experience recurrent bleeds into joints, nasal/oropharynx, or gastrointestinal tract or excessive menstrual bleeding. Retrospective cohort and case series suggest that prophylaxis improves quality of life; reduces the frequency of bleeding, need for transfusions, and hospitalizations; and prevents chronic joint disease.^54,55 More recently, a prospective study confirmed that prophylaxis with VWF concentrates at doses ranging from 50 IU VWF RCo/kg 1 to 3 times per week was highly effective at reducing bleeding rates, with annualized bleeding rates decreasing from 25 to 6.1 in 11 participants with either type 2A or type 3 VWD.⁵⁶

VWF/FVIII concentrates are effective in more than 97% of events.⁵⁷ Rarely, when infusion of a VWF/FVIII concentrate is ineffective at stopping bleeding, transfusion of platelet concentrates may be beneficial, presumably because they facilitate the delivery of small amounts of platelet VWF to the site of vascular injury. Highly purified FVIII concentrates (monoclonal antibody purified and recombinant) should not be used to treat VWD because they lack VWF.

A recombinant VWF concentrate (Vonvendi) combined initially with recombinant FVIII concentrate in a 1.3:1 ratio of VWF:RCo to FVIII:C has been shown to be safe and efficacious for the on-demand treatment of bleeds.^58,59 After the initial FVIII dose, the patients’ endogenous FVIII levels are stabilized within 6 hours and further FVIII administration may not required. A prospective phase 3 trial investigating the efficacy of recombinant VWF in the prophylaxis of severe VWD is ongoing. Vonvendi has been licensed for on-demand treatment in the United States since 2015. For further dosing information, please refer to the product insert.

Conclusion

VWF is a complex protein with several important and distinct functional domains: binding sites to collagen, FVIII, and platelet GPIbα; an ADAMTS13 cleavage site; and domains important for multimer formation. Mutations in any of these sites can result in a dysfunctional protein and as a result, VWD is a heterogeneous disorder with many specific assays available to determine the subtype. Despite this, the treatment of VWD is straightforward with only a small number of therapeutic options: indirect therapies such as antifibrinolytic agents, or direct therapies that increase VWF levels, DDAVP, or VWF/FVIII concentrates. Management focuses on preventing bleeding complications associated with invasive procedures or promptly treating bleeding episodes.

Introduction

Exocrine pancreatic cancer refers to pancreatic adenocarcinomas that arise from ductal epithelial cells. Pancreatic ductal adenocarcinoma is a highly lethal malignancy, ranking as the fourth most common cause of cancer-related death in the United States¹ and the eighth most common worldwide.² In the United States, the pancreas is the second most common site of gastrointestinal malignancy after the colon.¹ The only potentially curative modality for pancreatic adenocarcinomas is complete resection, followed by adjuvant therapy; unfortunately, only around 20% of patients are surgical candidates at the time of presentation due to delayed development of symptoms and consequently diagnosis.³ Most symptomatic patients with pancreatic cancer have locally advanced disease at diagnosis, and only a select group of patients with good performance status and borderline resectable disease can be offered neoadjuvant therapy. Adjuvant chemotherapy is typically recommended for patients who undergo potentially curative resection for pancreatic cancer.

Epidemiology

In the United States, pancreatic cancer has an annual estimated incidence of 55,440 new cases.¹ It causes an estimated 44,330 deaths per year, with a 5-year overall survival (OS) rate of 8.2%.¹ Worldwide an estimated 138,100 men and 127,900 women die of pancreatic cancer each year.² In general, pancreatic cancers occur more commonly in persons living in Western/industrialized countries, older persons (age > 60 years), males (ratio 1.3:1 female), and African-Americans and native Hawaiians.⁴

Etiology

The major preventable environmental risk factor for pancreatic cancer is cigarette smoking, which accounts for 25% of all cases.⁵ A prospective study that estimated the excess incidence of pancreatic cancer among cigarette smokers and assessed the influence of smoking cessation on the risk for pancreatic cancer showed that persons who quit smoking reduced their risk of pancreatic cancer by 48% after 2 years of cessation, compared with smokers who did not quit, and reduced their risk to near the level of a never smoker after 10 years of cessation.⁵ Risk is higher for heavy smokers and those with homozygous deletions of the glutathione S-transferase theta 1 gene (GSTT1), which results in the absence of the carcinogen-metabolizing function of the glutathione S-transferase enzyme. High body mass index and sedentary lifestyle have been linked to pancreatic cancer.⁶ Data regarding aspirin, diet, coffee, and excess alcohol consumption are insufficient, inconclusive, and even conflicting, and thus the effect of these factors on risk for pancreatic cancer remains unclear. Infectious risk factors such as Helicobacter pylori and hepatitis B and C virus have weak associations with pancreatic cancer. Chronic pancreatitis and pancreatic cysts (eg, intraductal papillary mucinous neoplasm [IPMN] of the pancreas) carry a risk for malignant transformation, and hence may require surveillance. Multiple epidemiologic studies have shown a strong association between pancreatic cancer and recently diagnosed diabetes mellitus (relative risk [RR] 1.97 [95% confidence interval {CI} 1.78 to 2.18]); the presence of diabetes also may be a long-term predisposing factor for pancreatic cancer, and cancer screening needs to be considered for selected patients.⁷

A predisposing genetic anomaly accounts for 15% of all cases of pancreatic cancer.⁸ Hereditary risk factors are divided into 2 broad categories: defined genetic syndromes and familial pancreatic cancer. Familial predispositions that do not meet genetic syndrome criteria account for approximately 5% to 10% of all cases associated with hereditary factors; in one study, 29% of tested kindreds with an incident pancreatic cancer had a germline BRCA2 mutation.⁹ Other predisposing genetic syndromes that have been linked to pancreatic cancer include:

• Peutz-Jeghers syndrome with germline STK11 mutations (RR 132);
• Hereditary pancreatitis with germline PRSS1, SPINK1, and CFTR mutations (RR 26–87);
• Familial atypical multiple mole melanoma syndrome with CDKN2A mutations (RR 20–40);
• Familial breast and ovarian cancer with BRCA2 (RR 10) and BRCA1 (RR 2.8) mutations;
• Hereditary nonpolyposis colorectal cancer (HNPCC, Lynch II syndrome) with MLH1, MSH2, MSH6, and PMS2 mutations (RR 9–11); and
• Familial adenomatous polyposis with APC mutations (RR 5).¹⁰

Other gene mutations with unknown relative risk for pancreatic cancer include mutations affecting PALB2, ATM, and TP53.

The International Cancer of the Pancreas Screening consortium consensus on screening for pancreatic cancer in patients with increased risk for familial pancreatic cancer recommends screening those at high risk: first-degree relatives (FDRs) of patients with pancreatic cancer from a familial pancreatic kindred with at least 2 affected FDRs; patients with Peutz-Jeghers syndrome; and p16, BRCA2, and HNPCC mutation carriers with 1 or more affected FDRs and hereditary pancreatitis. The guidelines emphasize that screening should be done only in those who are surgical candidates and are evaluated at an experienced multidisciplinary center.⁸

Deleterious germline mutations in pancreatic cancer can account for 33% of patients with apparent sporadic cancers and no hereditary risk. These include germline mutations affecting BRCA1/2, PALB2, ATM, MLH1, CHK-2, CDKN2A, and TP53.¹¹

 

Pathogenesis

Pancreatic neoplasms can be benign or malignant and thus a tissue histologic diagnosis is paramount. Pancreatic adenocarcinomas with exocrine features represent more than 95% of all pancreatic neoplasms, with only 5% arising from the endocrine pancreas (ie, neuroendocrine tumors). Pancreatic neuroendocrine tumors and pancreatic adenocarcinoma must be distinguished histologically because treatment of the 2 neoplasms is completely different. Other malignant pancreatic tumors are signet ring cell carcinoma, adenosquamous carcinoma, undifferentiated (anaplastic) carcinoma, and mucinous noncystic (colloid) carcinoma; the latter tumor has a better prognosis.¹² It is essential to characterize and distinguish among benign cystic neoplasms, as some require surgical resection due to the risk of malignant transformation. IPMN, pancreatic intraepithelial neoplasia, and mucinous cystic neoplasms are thought to be premalignant lesions of invasive ductal adenocarcinomas, and the pathological report should highlight the degree of dysplasia for adequate risk stratification.¹³ This information could be the deciding factor in whether a pancreatectomy is recommended by a multidisciplinary team.

Most pancreatic cancers harbor activating or silencing genetic mutations, and multiple combinations of altered genes can be detected by next-generation sequencing (average of 63 genetic alterations per cancer).¹⁴ Mutational activated KRAS is the most frequent (> 90%) genetic alteration in pancreatic cancer, even in early neoplastic precursors (IPMN > 75%). KRAS is a highly complex, dynamic proto-oncogene involved in signaling of various receptor kinases such as the epidermal growth factor receptor and the insulin-like growth factor receptor-I. It also engages in canonical downstream effector pathways, mainly Raf/MEK/ERK, PI3K/PDK1/Akt, and the Ral guanine nucleotide exchange factor pathway, which drive much of the pathogenesis of malignancy. These pathways lead to sustained proliferation, metabolic reprogramming, anti-apoptosis, remodeling of the tumor microenvironment, evasion of the immune response, cell migration, and metastasis. An activating point mutation in codon G12 is the most common (98%) locus of KRAS mutation in pancreatic adenocarcinoma, but all drugs targeting this mutation have failed in clinical practice.¹⁵ Additionally, inactivation of tumor suppressor genes such as p53, DPC4 (SMAD4/MADH4), CDKN2A (p16/MTS1), and BRCA2 can be found in 75%, 30%, 35%, and 4% of pancreatic adenocarcinoma cases, respectively.¹⁴ Another pancreatic cancer hallmark is inactivation of DNA damage repair genes, which include MLH1 and MSH2.¹⁶

Diagnosis and Staging

Case Presentation

A 71-year-old male veteran with no significant past medical history other than hypertension and hyperlipidemia and an excellent performance status presents to the emergency department after noticing a yellowish skin and sclera color. He denies weight loss, abdominal pain, or any other pertinent symptom or sign. Physical examination reveals a healthy developed man with yellowish discoloration of the skin and sclera and a soft, nontender benign abdomen; physical examination is otherwise unremarkable. Laboratory evaluation reveals a direct bilirubin level of 4.5 mg/dL and normal values for complete blood count and renal, liver, and coagulation panels. Abdominal and pelvis computed tomography (CT) with intravenous contrast shows a pancreatic head mass measuring 2.6 × 2.3 cm minimally abutting the anterior surface of the superior mesenteric vein, which remains patent. Follow-up endoscopic ultrasound (EUS) confirms an irregular mass at the head of the pancreas measuring 3.2 × 2.6 cm with sonographic evidence suggesting invasion into the portal vein. During the procedure, the bile duct is successfully stented, the mass is biopsied, and bile duct brushing is performed. Pathology report is consistent with pancreatic adenocarcinoma.

• What is the typical presentation of pancreatic cancer?

The most common symptoms of pancreatic cancer at the time of presentation include weight loss (85%), asthenia/anorexia (86%), and/or abdominal pain (79%).¹⁷ The most frequent signs are jaundice (55%), hepatomegaly (39%), and cachexia (13%). Courvoisier sign, a nontender but palpable distended gallbladder at the right costal margin, is neither sensitive nor specific for pancreatic cancer (13% of cases). Trousseau syndrome, a superficial thrombophlebitis, is another classic sign that reflects the hypercoagulable nature of pancreatic cancer (3% of cases).¹⁷ The pathophysiology of this syndrome is not completely understood, but it may occur secondary to the release of cancer microparticles in the blood stream which in turn stimulate the coagulation cascade. Other nonspecific symptoms are dark urine, nausea, vomiting, diarrhea, steatorrhea, and epigastric and back pain. Because symptoms early in the course of the disease are nonspecific, pancreatic cancer is typically diagnosed late, after the cancer has invaded local structures or metastasized. The initial presentation varies depending on tumor location, with 70% of pancreatic head malignancies presenting with jaundice and pain correlating to an advanced stage.¹⁸ Although data supporting an association between new-onset diabetes mellitus and pancreatic cancer are inconclusive, pancreatic cancer should still be a consideration in patients with new-onset diabetes mellitus and other symptoms such as pain and weight loss. Early signs of incurable disease include a palpable mass, ascites, lymphadenopathy (classic Virchow node), and an umbilical mass (Sister Mary Joseph node). Incidentally discovered pancreatic masses on imaging are rare, but the incidence is increasing due to frequent imaging for other reasons and improved diagnostic techniques.

 

• What is the approach to diagnosis and staging?

History and physical examination findings are not sufficiently sensitive or specific to diagnose pancreatic cancer. High clinical suspicion in a patient with risk factors can lead to a comprehensive evaluation and potential early diagnosis. In general, an initial diagnostic work-up for suspected pancreatic cancer will include serologic evaluation (liver function test, lipase, tumor markers) and abdominal imaging (ultrasound, CT scans, or magnetic resonance imaging [MRI]). Ultrasound is a first-line diagnostic tool with a sensitivity of 90% and specificity of 98.8% for pancreatic cancer, but it is investigator-dependent and is less accurate in detecting tumors smaller than 3 cm in diameter.¹⁹ Multiphasic helical CT of the abdomen has better sensitivity (100%) and specificity (100%) for detecting tumors larger than 2 cm, but this modality is less accurate in detecting pancreatic masses smaller than 2 cm (77%).²⁰ Percutaneous fine-needle aspiration (FNA) performed by ultrasound or CT guidance is avoided due to theoretical concerns about intraperitoneal seeding and bleeding.

If a pancreatic mass is detected by ultrasound or CT, additional interventions may be indicated depending on the clinical scenario. EUS-guided biopsy can provide histological confirmation and is currently utilized frequently for diagnosis and early resectability staging. Endoscopic retrograde cholangiopancreatography (ERCP) is indicated for patients with biliary obstruction requiring stent placement, and this procedure may provide tissue confirmation by forceps biopsy or brush cytology (lower accuracy than EUS). In a meta-analysis that evaluated the diagnostic value of tests for pancreatic cancer, ERCP had the highest sensitivity (92%) and specificity (96%) compared to ultrasound and CT,²¹ but this modality carries a risk for pancreatitis, bleeding, and cholangitis. Magnetic resonance cholangiopancreatography has not replaced ERCP, but it but may be an alternative for patients who cannot undergo ERCP (eg, gastric outlet obstruction, duodenal stenosis, anatomical surgical disruption, unsuccessful ERCP). ERCP is used frequently because many patients present with obstructive jaundice due to pancreatic mass compression, specifically if the mass is located in the head, and must undergo ERCP and stenting of the common bile duct.

The carbohydrate antigen (CA) 19-9 level has variable sensitivity and specificity in pancreatic cancer, as levels can be elevated in many benign pancreaticobiliary disorders. Elevated CA 19-9, in the appropriate clinical scenario (ie, a suspicious pancreatic mass and a value greater than 37 U/mL) demonstrated a sensitivity of 77% and specificity of 87% when differentiating pancreaticobiliary cancer from benign clinical conditions such as acute cholangitis or cholestasis.²² CA 19-9 level has prognostic value, as it may predict occult disease and correlates with survival rates, but no specific cutoff value has been established to guide perioperative therapy for high-risk resectable tumors.²³

The American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) tumor, node, metastasis (TNM) system is the preferred method for staging pancreatic cancer (Table 1). 

Stages IA, IB, IIA, IIB, and III disease correlate with median survival durations of 38, 24, 18, 17, and 14 months, respectively.^3,24 Accurate pancreatic cancer staging defines which patients are eligible for resection with curative intent. In a cost-effectiveness analysis, abdominal multidetector CT angiography (triple-phase contrast-enhanced thin-slice helical CT) followed by EUS provided the most accurate and cost-effective strategy in evaluating tumor burden in both local and metastatic disease (eg, liver metastasis or peritoneum).²⁵ Nonetheless, in clinical practice MRI is the preferred imaging modality for determining resectability based on specific anatomic characteristics and for detecting metastatic disease. Localized, nonmetastatic disease is deemed to be resectable, borderline resectable, and unresectable based on the extent of vascular invasion, infiltration of adjacent structures, and involvement of distal lymph nodes, according to criteria established by the National Comprehensive Cancer Network (NCCN, Table 2).^26,27 

Tumors that encase the celiac artery and superior mesenteric artery (> 180°) and infiltrate the portal vein are considered unresectable. Conversely, tumors that completely spare the celiac artery and superior mesenteric artery are considered resectable. Borderline-resectable tumors generally involve the superior mesenteric artery (< 180°) and/or abut the portal vein.

Positron emission tomography with CT scan is occasionally utilized in practice to assess tumor burden by evaluating anatomical structures and assessing physiologic uptake, which aids in establishing the extent of disease in equivocal cases. Staging laparoscopy with or without peritoneal biopsy is sometimes used to establish appropriate staging in cases that are questionable for occult metastatic disease. This procedure helps avoid unnecessary morbid surgeries.

 

Neoadjuvant Therapy

Case Continued

The patient is referred to oncology. Blood work reveals a CA 19-9 level of 100 U/mL (reference range < 35 U/mL) and a staging CT scan of the chest reveals a benign-appearing 3-mm nodule (no prior imaging for comparison). CT scan of the abdomen and pelvis does not define venous vasculature involvement appropriately and hence MRI of the abdomen and pelvis is performed. MRI reveals a pancreatic head mass measuring 3.0 × 2.7 cm, without arterial or venous vasculature invasion. However, the mass is abutting the portal vein and superior mesenteric vein and there is a new nonspecific 8-mm aortocaval lymph node.

• What are the current approaches to treating patients with resectable, unresectable, and metastatic disease?

Accurate staging and assessment of surgical resectability in pancreatic cancer are paramount as these steps prevent a futile morbid Whipple procedure in patients with advanced disease and a high risk of recurrence. Conversely, it allows patients with low-volume disease to undergo a potentially curative surgery. Approximately 20% of patients present with resectable disease, 40% present with locally advanced unresectable tumors (eg, involvement of critical vascular structures), and 40% present with metastatic disease.³ Treatment for resectable pancreatic cancer continues to be upfront surgery, although neoadjuvant therapy with either chemoradiation, radiation alone, or chemotherapy is an option per guidelines from the American Society of Clinical Oncology (ASCO),²⁸ the NCCN,²⁶ and the European Society for Medical Oncology (ESMO),²⁹ particularly for patients with borderline resectable tumors (Table 3). 

Neoadjuvant therapy provides an opportunity to downstage the cancer to allow for surgical resection and achieve negative surgical margins (R0). Unfortunately, even in patients with resectable tumors who achieve a complete resection and are treated with adjuvant therapy, the 5-year recurrence rate is approximately 80% and the survival rate is between 5% and 25%.^24,30 Nonetheless, to improve survival rates all patients with resected pancreatic adenocarcinoma should be treated with adjuvant chemotherapy based on data showing that it decreases the likelihood of recurrence compared with surgical resection alone.³¹

 

Systemic chemotherapy is recommended for fit candidates with locally advanced unresectable or metastatic disease, with an emphasis on supportive palliative measures. Palliative interventions include biliary stenting, duodenal stent for relieving gastric-outlet obstruction, and celiac axis nerve blocks, when indicated. Routine preoperative biliary stent placement/drainage in patients undergoing subsequent surgery for pancreatic cancer located in the head is associated with an increased risk of surgical complications when compared with up-front surgery without prior biliary drainage, and thus stent placement/drainage is not recommended.²⁶ Aggressive supportive management of symptoms, such as cancer-associated pain, anorexia-cachexia syndromes, and anxiety-depression disorders, should remain a primary palliative focus.

Case Continued

A multidisciplinary tumor board discusses the patient’s case and deems the cancer borderline resectable; neoadjuvant therapy is recommended. The patient is started on treatment with gemcitabine and nab-paclitaxel as first-line neoadjuvant therapy. After 4 cycles, the CA 19-9 level drops to 14 U/mL, and MRI reveals a smaller head mass of 1.3 × 1.4 cm with stable effacement of the superior mesenteric vein and no portal vein involvement; the aortocaval lymph node remains stable. At tumor board, it is evident that the patient has responded to therapy and the recommendation is to treat with gemcitabine chemoradiotherapy before surgery.

• What neoadjuvant therapy strategies are used in the treatment of pancreatic adenocarcinoma?

There are no established evidence-based recommendations for neoadjuvant therapy in patients with borderline resectable pancreatic cancer or patients with unresectable locally advanced pancreatic cancer. However, there are ongoing trials to investigate this treatment approach, and it is offered off-label in specific clinical scenarios, such as in the case patient described here. In patients with borderline resectable disease, preoperative chemotherapy followed by chemoradiation is a routine practice in most cancer centers,³² and ongoing clinical trials are an option for this cohort of patients (eg, Southwest Oncology Group Trial 1505, NCT02562716). The definitions of borderline resectable and unresectable pancreatic cancer have been described by the NCCN,²⁶ although most surgeons consider involvement of the major upper abdominal blood vessels the main unresectability criterion; oncologists also consider other parameters such as suspicious lesions on scans, worsening performance status, and a significantly elevated CA 19-9 level suggestive of disseminated disease.²⁸ The goal of a conversion approach by chemotherapy with or without radiation for borderline and unresectable cancers is to deliver a tolerable regimen leading to tumor downstaging, allowing for surgical resection. No randomized clinical trial has shown a survival advantage of this approach. Enrollment in clinical trials is preferred for patients with borderline and unresectable cancer, and there are trials that are currently enrolling patients.

The main treatment strategies for patients with locally advanced borderline and unresectable pancreatic cancer outside of a clinical trial are primary radiotherapy, systemic chemotherapy, and chemoradiation therapy. Guidelines from ASCO, NCCN, and ESMO recommend induction chemotherapy followed by restaging and consolidation chemoradiotherapy in the absence of progression.^26,28,29 There is no standard chemoradiation regimen and the role of chemotherapy sensitizers, including fluorouracil, gemcitabine, and capecitabine (an oral fluoropyrimidine substitute), and targeted agents in combination with different radiation modalities is now being investigated.

Fluorouracil is a radio-sensitizer that has been used in locally advanced pancreatic cancer based on experience in other gastrointestinal malignancies; data shows conflicting results with this drug. Capecitabine and tegafur/gimeracil/oteracil (S-1) are oral prodrugs that can safely replace infusional fluorouracil. Gemcitabine, a more potent radiation sensitizer, is very toxic, even at low-doses twice weekly, and does not provide a survival benefit, as demonstrated in the Cancer and Leukemia Group B (CALGB) 89805 trial, a phase 2 study of patients with surgically staged locally advanced pancreatic cancer.³³ Gemcitabine-based chemoradiotherapy was also evaluated in the Eastern Cooperative Group (ECOG) E4201 trial, which randomly assigned patients to receive gemcitabine alone (at 1000 mg/m²/wk for weeks 1 through 6, followed by 1 week rest, then weekly for 3 out of 4 weeks) or gemcitabine (600 mg/m²/wk for weeks 1 to 5, then 4 weeks later 1000 mg/m² for 3 out of 4 weeks) plus radiotherapy (starting on day 1, 1.8 Gy/fraction for total of 50.4 Gy).³⁴ Patients with locally advanced unresectable pancreatic cancer had a better OS outcome with gemcitabine in combination with radiation therapy (11.1 months) as compared with patients who received gemcitabine alone (9.2 months). Although there was a greater incidence of grade 4 and 5 treatment-related toxicities in the combination arm, no statistical differences in quality-of-life measurements were reported. Gemcitabine-based and capecitabine-based chemoradiotherapy were compared in the open-label phase 2 multicenter randomized SCALOP trial.³⁵ Patients with locally advanced pancreatic cancer were assigned to receive 3 cycles of induction with gemcitabine 1000 mg/m² days 1, 8, and 15 and capecitabine 830 mg/m² days 1 to 21 every 28 days; patients who had stable or responding disease were randomly assigned to receive a fourth cycle followed by capecitabine (830 mg/m² twice daily on weekdays only) or gemcitabine (300 mg/m² weekly) with radiation (50.4 Gy over 28 fractions). Patients treated with capecitabine-based chemoradiotherapy had higher nonsignificant median OS (17.6 months) and median progression-free survival (12 months) compared to those treated with gemcitabine (14.6 months and 10.4 months, respectively).

 

The benefit of radiation therapy in the treatment of locally advanced pancreatic cancer was further explored by the Fédération Francophone de Cancérologie Digestive 2000-01 phase 3 trial. This study compared induction chemoradiotherapy (60 Gy, 2 Gy/fraction; concomitant fluorouracil infusion, 300 mg/m²/day, days 1–5 for 6 weeks; cisplatin, 20 mg/m²/day, days 1–5 during weeks 1 and 5) to gemcitabine alone (1000 mg/m² weekly for 7 weeks) followed by maintenance gemcitabine in both arms.³⁶ Unexpectedly, the median OS was significantly shorter in the chemoradiotherapy arm than in the chemotherapy alone arm (8.6 months versus 13 months, respectively, P = 0.03) and the combination arm had more toxicities. The phase 3 open-label LAP07 study explored the role of radiation therapy in patients with locally advanced pancreatic cancer who had controlled disease after 4 months of induction therapy.³⁷ LAP07 had 2 randomizations: first, patients with locally advanced pancreatic cancer were assigned to receive weekly gemcitabine alone (1000 mg/m²) or this same dose of gemcitabine plus erlotinib 100 mg/day; second, patients with progression-free disease (61% of initial cohort) after 4 months of therapy were assigned to receive 2 months of the same chemotherapy or chemoradiotherapy (54 Gy plus capecitabine). This study showed that the addition of erlotinib to gemcitabine did not improve survival and in fact affected survival adversely. Of note, no survival benefit was observed after the first randomization from chemotherapy to consolidating chemoradiotherapy. Chemoradiotherapy achieved better locoregional tumor control with significantly less local tumor progression (32% versus 46%, P < 0.03) and no increase in toxicity. Based on prior moderate-quality evidence, guidelines recommend consolidative chemoradiotherapy only for surgical resection candidates following induction chemotherapy; for those who are not surgical candidates, guidelines recommend continuing systemic therapy.^26,28,29

Gemcitabine and fluorouracil-based chemotherapies were the standard induction regimens until evidence from studies of metastatic systemic treatment protocols with FOLFIRINOX (ACCORD trial³⁸) and nanoparticle albumin-bound paclitaxel (nab-paclitaxel) plus gemcitabine (MPACT trial³⁹) was extrapolated to clinical practice. These regimens were shown to achieve higher objective response rates when compared to single-agent gemcitabine in patients with metastatic pancreatic cancer. Due to the broad heterogeneity of results in small retrospective series with neoadjuvant trials in borderline resectable pancreatic cancer, the quality of the evidence is low and any recommendation is limited. Many individual series have demonstrated improved complete resection rates and promising survival rates. In the largest single-institution retrospective review of patients with borderline resectable pancreatic adenocarcinoma who completed neoadjuvant gemcitabine-based chemoradiotherapy (50 Gy in 28 fractions or 30 Gy in 10 fractions), 94% achieved a margin-negative pancreatectomy; the median OS in those who completed preoperative therapy and had surgery was 40 months, with a 5-year OS of 36%.⁴⁰ A meta-analysis by Andriulli and colleagues included 20 prospective studies of patients with initially resectable (366 lesions) or unresectable (341 lesions) disease who were treated with neoadjuvant/preoperative gemcitabine with or without radiotherapy.⁴¹ In the group with initially unresectable disease, 39% underwent surgery after restaging and 68% of explored patients were resected; the R0 resection rate was 60%. After restaging, 91% of patients with resectable disease underwent surgery, with 82% of explored patients undergoing surgical resection and 89% of these achieving R0 resection. The estimated 1- and 2-year survival probabilities after resection among patients with initially unresectable disease were 86.3% and 54.2%.⁴¹

The largest single-institution retrospective review of FOLFIRINOX (fluorouracil, oxaliplatin, irinotecan, and leucovorin), an alternative to gemcitabine, for neoadjuvant induction therapy for patients with locally advanced unresectable disease was conducted at Memorial Sloan Kettering Cancer Center. In this study (n = 101), 31% of patients initially deemed unresectable who completed FOLFIRINOX induction therapy with or without chemoradiation underwent resection. The R0 resection rate in these patients was 55%, and patients who did not progress during induction FOLFIRINOX therapy had a median OS of 26 months.⁴² A systematic review and meta-analysis of FOLFIRINOX chemotherapy with or without radiotherapy in patients with locally advanced unresectable pancreatic cancer reported that 25.9% of patients underwent resection after FOLFIRINOX therapy, and the R0 resection rate in these patients was 78.4%.⁴³ The median OS in this study was 24.2 months, which was longer than the previously reported median OS rates for gemcitabine.

There is no strong evidence published for the use of combination nab-paclitaxel plus gemcitabine in the neoadjuvant setting, but it is used in clinical practice based on evidence from the MPACT trial, which showed the combination improved OS and progression-free survival in patients with metastatic pancreatic cancer.³⁹ An early-phase 1-arm clinical trial of neoadjuvant gemcitabine, docetaxel, and capecitabine (GTX) followed by radiotherapy showed an increased response rate and survival for locally advanced disease; however, the NCCN expert panel has reached a consensus but not a uniform recommendation regarding this regimen due to significant toxicities and low patient accrual.²⁶ Selected patients with pancreatic cancer with BRCA1/2 mutations are more sensitive to platinum-based chemotherapy. Although studies of neoadjuvant platinum-based chemotherapy in this population have not been reported, the NCCN guidelines list it as an alternative option based on extrapolated data.²⁶ A clinical trial of gemcitabine, nab-paclitaxel, and cisplatin in the neoadjuvant setting in patients with resectable pancreatic cancer is currently enrolling patients (NGC triple regimen NCT0339257).

Summary

Chemotherapy alone or followed by chemoradiotherapy may be used as initial treatment for patients with borderline and unresectable pancreatic adenocarcinoma without distant metastases who are potential surgical candidates. Chemoradiotherapy remains a preferred treatment option for patients with poorly controlled pain from local tumor invasion, in view of the well-documented analgesic palliative effect of radiation therapy. FOLFIRINOX with or without radiation therapy may offer the highest documented response rates, but it also results in higher rates of treatment-related toxicities. FOLFIRINOX can be offered to selected fit patients (< 65 years old, no comorbidity contraindication, good functional status [ECOG 0–1]) who can tolerate triple therapy with a more toxic adverse-effect profile. A clinical trial evaluating neoadjuvant FOLFIRINOX with or without preoperative chemoradiotherapy in patients with borderline resectable pancreatic cancer is ongoing (PANDAS-PRODIGE 44, NCT02676349). Gemcitabine with or without radiation therapy is a tolerable combination, although it is potentially more toxic when combined with radiation. The addition of nab-paclitaxel to gemcitabine without radiation may emerge as a preferred neoadjuvant treatment for selected patients; a clinical trial investigating this modality in patients with resectable and borderline resectable disease is ongoing (NCT02723331).

 

Adjuvant Therapy

Case Continued

Prior to the planned surgical resection and after undergoing chemoradiation therapy, the patient has an excellent performance status and repeat MRI shows a 1.3 × 1.4 cm head mass with no further vasculature involvement, no evidence of lymphadenopathy, and no distant metastasis. The CA 19-9 level is stable at 18 U/mL. The patient undergoes an uncomplicated partial pancreaticoduodenectomy, and analysis of a surgical pathology specimen reveals T3N0 disease with closest margin of 0.1 cm.

• Would the patient benefit from adjuvant therapy?

Adjuvant chemotherapy for 6 months after pancreatic cancer resection should be offered to all patients based on mature data. Gemcitabine and capecitabine are the current standard of care in adjuvant therapy; alternatively, single-agent gemcitabine can be offered to patients with poor performance status or patients who cannot tolerate the toxicities associated with this combination.²⁸ Adjuvant treatment should be initiated within approximately 8 weeks of surgical resection. The value of radiation therapy remains controversial, but it can be offered within the context of a clinical trial or to patients with positive margins after surgical resection and/or lymph node–positive disease. Based on low-quality supportive evidence, it is strongly recommended that patients who receive neoadjuvant therapy complete a total of 6 months of chemotherapy, factoring in the duration of the preoperative regimen.²⁸ Different adjuvant strategies have been investigated, including chemotherapy alone with a fluoropyrimidine and/or gemcitabine with or without combined chemoradiation therapy.

The European Study Group for Pancreatic Cancer 1 (ESPAC)-1 trial was a randomized clinical trial that evaluated several adjuvant strategies in pancreatic cancer treatment. This trial assigned patients who underwent pancreatic adenocarcinoma resection to adjuvant chemotherapy alone (intravenous fluorouracil 425 mg/m² and leucovorin 20 mg/m² daily for 5 days, monthly for 6 months), chemoradiotherapy (20 Gy in 10 daily fractions over 2 weeks with 500 mg/m² intravenous fluorouracil on days 1–3, repeated after 2 weeks), both chemotherapy and chemoradiation, and observation.⁴⁴ The results showed no added benefit for adjuvant chemoradiotherapy, with a median OS of 15.5 months in the chemoradiotherapy cohort, as compared to a median OS of 16.1 months in the chemotherapy-alone cohort (hazard ratio [HR] 1.18 [95% CI 0.90 to 1.55], P = 0.24). In addition, there was evidence of a survival benefit for the chemotherapy-alone arm when compared to the combined modality arm, with a median OS of 19.7 versus 14.0 months, respectively (HR 0.66 [95% CI 0.52 to 0.83], P = 0.0005). Although ESPAC-1 has been criticized for being underpowered to perform statistical comparison, it is still considered a landmark trial demonstrating benefit with single-agent chemotherapy alone. A follow-up analysis of ESPAC-1 showed that adjuvant chemotherapy alone conferred a significant 5-year survival benefit while the combined modality had a deleterious effect on survival. ⁴⁵ Hence, adjuvant chemotherapy alone became the standard of care in the United States following resection.

The results of the multicenter randomized controlled phase 3 CONKO-001 (CharitéOnkologie 001) trial, which were reported in 2007, supported the use of adjuvant gemcitabine for 6 months in patients with resected pancreatic adenocarcinoma. In this study, patients treated with adjuvant gemcitabine (1000 mg/m² days 1, 8, and 15 every 4 weeks for 6 months) had superior disease-free survival compared with those who received surgery alone.³⁰ A long-term outcome update of this study demonstrated a significant improvement in 5-year OS for patients treated with adjuvant gemcitabine (20.7% [95% CI 14.7% to 26.6%]) compared to those who received surgical resection alone (10.4% [95% CI 5.9% to 15.0%]). This benefit persisted at 10-year follow-up, with an OS of 12.2% (95% CI 7.3% to 17.2%) in the adjuvant gemcitabine group, as compared to 7.7% (95% CI 3.6% to 11.8%) in the resection alone group.³¹

Fluorouracil and gemcitabine remained equivalent adjuvant treatment options until the results of the ESPAC-3 trial were reported in 2010.³² This large phase 3 trial, conducted mainly in the United Kingdom, compared weekly gemcitabine (1000 mg/m² weekly for 3 of every 4 weeks) to leucovorin-modulated fluorouracil (Mayo Clinic regimen: leucovorin 20 mg/m² followed by fluorouracil 425 mg/m² intravenous bolus days 1 through 5 every 28 days) as adjuvant therapy in resected pancreatic adenocarcinoma. After a median follow-up of 34.2 months, the median OS was similar in the 2 groups (fluorouracil/leucovorin 23.0 months versus gemcitabine 23.6 months; P = 0.39). However, the fluorouracil/leucovorin group experienced more grade 3/4 treatment-related toxicities (mucositis, stomatitis, diarrhea, and hosptializations; 14% versus 7.5%; P < 0.001).⁴⁶ Following this trial, gemcitabine became the standard of care for adjuvant chemotherapy for resected pancreatic cancer.

The U.S. Radiation Therapy Oncology Group (RTOG) 9704 trial was conducted to investigate the potential benefit of adding radiation therapy to gemcitabine. This trial demonstrated an improved trend among patients with pancreatic head tumors (but not with cancers of the pancreatic body or tail) who received adjuvant gemcitabine followed by chemoradiotherapy (50.4 Gy in 1.8 Gy daily fractions for 5.5 weeks with concurrent infusional fluorouracil 250 mg/m² daily) and subsequent gemcitabine monotherapy compared to postoperative fluorouracil-based chemoradiotherapy. Results showed a 5-year OS of 22% versus 18%, respectively, although this improvement was not statistically significant (P = 0.08). This trial failed to show a benefit of adding radiotherapy to gemcitabine.⁴⁷

The ESPAC-4 trial, reported in 2017, evaluated the combination of gemcitabine and capecitabine compared to gemcitabine alone as adjuvant therapy for resected pancreatic adenocarcinoma.⁴⁸ Patients were randomly assigned after surgical resection, regardless of margin or node status, to 6 months of gemcitabine alone (1000 mg/m²/day on days 1, 8, and 15 of each 28-day cycle) or gemcitabine plus capecitabine (1660 mg/m²/day on days 1 through 21 of each 28-day cycle). Combination therapy had a significant survival benefit compared to single therapy, with median OS durations of 28 months and 25.5 months, respectively (HR for death 0.82 [95% CI 0.68 to 0.98]). The 5-year OS for patients who received combination treatment was 29 months (95% CI 22.9 to 35.2) versus 16 months (95% CI 10.2 to 23.7) for those in the monotherapy group. As expected, grade 3 or 4 treatment-related toxicities (diarrhea, hand-foot syndrome, and neutropenia) were significantly more common with combined therapy, although there were no significant differences in the rates of serious adverse events. The adjuvant combination of gemcitabine and capecitabine became the current and preferred new standard of care following resection of pancreatic ductal adenocarcinoma,²⁸ but single-agent gemcitabine and fluorouracil/leucovorin continue to be viable options,^26,28,29 particularly for elderly patients, patients with borderline performance status, or patients with multiple comorbidities.

Evidence showing that a more intensive regimen can improve outcome in the adjuvant setting remains elusive. The phase 3 APACT study (Adjuvant Therapy for Patients with Resected Pancreatic Cancer, NCT01964430) comparing gemcitabine alone to gemcitabine plus nab-paclitaxel in patients with surgically resected pancreatic adenocarcinoma has concluded, with the results projected to be released in 2018. Another phase 3 trial investigating the efficacy of FOLFIRINOX versus gemcitabine alone as adjuvant therapy is underway in France and Canada (PRODIGE24/ACCORD24, NCT01526135). Other strategies with newer targeted therapies and immunotherapy are in the development phase.

 

Follow-Up and Surveillance

Case Conclusion

After recovery from surgery, the patient is offered and completes 4 cycles of adjuvant chemotherapy with gemcitabine plus capecitabine. He is started on surveillance at 3 and 6 months, and he maintains an excellent performance status. He develops clinical evidence of pancreatic enzyme insufficiency and is placed on oral replacement therapy. He has no other complaints, and there is no evidence of recurrence on MRI and CA 19-9 levels.

• What is the recommended duration of surveillance following curative resection?

Surveillance after curative resection of pancreatic adenocarcinoma is recommended by NCCN guidelines.²⁶ However, pancreatic adenocarcinoma has a poor prognosis, and surveillance after curative surgical resection with or without perioperative therapy has not been shown to impact survival. Most recurrences will occur within 2 years after treatment. Surveillance recommendations differ among expert groups.^26,28,29 NCCN guidelines recommend evaluating patients by history and physical examination every 3 to 6 months for the first 2 years, then every 6 to 12 months for 3 years. CA 19-9 level and CT scan should be obtained every 3 to 6 months for 2 years and then every 6 to 12 months for 3 years. Follow-up with CA 19-9 levels and CT scans after 5 years is not routinely performed unless guided by signs, symptoms, or laboratory findings that raise suspicion for recurrence. Follow-up visits should also include evaluation of treatment-related toxicities, symptom management, nutrition support of pancreatic insufficiency, and psychosocial support.

Conclusion

Pancreatic cancer is a leading cause of cancer-related death that frequently presents with locally advanced or metastatic disease due to nonspecific symptoms and lack of a screening modality. Histological tissue biopsy confirmation and accurate resectability staging guide treatment planning and prognosis. The only potentially curative therapy is surgical resection plus adjuvant therapy for those with resectable disease. Surgical candidates with borderline resectable and unresectable disease can be offered induction preoperative chemotherapy followed by consolidation chemoradiation, based on clinical consensus practice. Enrollment in clinical trials should be encouraged for all patients, as evidence from clinical trials is essential to making progress in pancreatic cancer treatment.

Introduction

Exocrine pancreatic cancer refers to pancreatic adenocarcinomas that arise from ductal epithelial cells. Pancreatic ductal adenocarcinoma is a highly lethal malignancy, ranking as the fourth most common cause of cancer-related death in the United States¹ and the eighth most common worldwide.² In the United States, the pancreas is the second most common site of gastrointestinal malignancy after the colon.¹ The only potentially curative modality for pancreatic adenocarcinomas is complete resection, followed by adjuvant therapy; unfortunately, only around 20% of patients are surgical candidates at the time of presentation due to delayed development of symptoms and consequently diagnosis.³ Most symptomatic patients with pancreatic cancer have locally advanced disease at diagnosis, and only a select group of patients with good performance status and borderline resectable disease can be offered neoadjuvant therapy. Adjuvant chemotherapy is typically recommended for patients who undergo potentially curative resection for pancreatic cancer.

Epidemiology

In the United States, pancreatic cancer has an annual estimated incidence of 55,440 new cases.¹ It causes an estimated 44,330 deaths per year, with a 5-year overall survival (OS) rate of 8.2%.¹ Worldwide an estimated 138,100 men and 127,900 women die of pancreatic cancer each year.² In general, pancreatic cancers occur more commonly in persons living in Western/industrialized countries, older persons (age > 60 years), males (ratio 1.3:1 female), and African-Americans and native Hawaiians.⁴

Etiology

The major preventable environmental risk factor for pancreatic cancer is cigarette smoking, which accounts for 25% of all cases.⁵ A prospective study that estimated the excess incidence of pancreatic cancer among cigarette smokers and assessed the influence of smoking cessation on the risk for pancreatic cancer showed that persons who quit smoking reduced their risk of pancreatic cancer by 48% after 2 years of cessation, compared with smokers who did not quit, and reduced their risk to near the level of a never smoker after 10 years of cessation.⁵ Risk is higher for heavy smokers and those with homozygous deletions of the glutathione S-transferase theta 1 gene (GSTT1), which results in the absence of the carcinogen-metabolizing function of the glutathione S-transferase enzyme. High body mass index and sedentary lifestyle have been linked to pancreatic cancer.⁶ Data regarding aspirin, diet, coffee, and excess alcohol consumption are insufficient, inconclusive, and even conflicting, and thus the effect of these factors on risk for pancreatic cancer remains unclear. Infectious risk factors such as Helicobacter pylori and hepatitis B and C virus have weak associations with pancreatic cancer. Chronic pancreatitis and pancreatic cysts (eg, intraductal papillary mucinous neoplasm [IPMN] of the pancreas) carry a risk for malignant transformation, and hence may require surveillance. Multiple epidemiologic studies have shown a strong association between pancreatic cancer and recently diagnosed diabetes mellitus (relative risk [RR] 1.97 [95% confidence interval {CI} 1.78 to 2.18]); the presence of diabetes also may be a long-term predisposing factor for pancreatic cancer, and cancer screening needs to be considered for selected patients.⁷

A predisposing genetic anomaly accounts for 15% of all cases of pancreatic cancer.⁸ Hereditary risk factors are divided into 2 broad categories: defined genetic syndromes and familial pancreatic cancer. Familial predispositions that do not meet genetic syndrome criteria account for approximately 5% to 10% of all cases associated with hereditary factors; in one study, 29% of tested kindreds with an incident pancreatic cancer had a germline BRCA2 mutation.⁹ Other predisposing genetic syndromes that have been linked to pancreatic cancer include:

• Peutz-Jeghers syndrome with germline STK11 mutations (RR 132);
• Hereditary pancreatitis with germline PRSS1, SPINK1, and CFTR mutations (RR 26–87);
• Familial atypical multiple mole melanoma syndrome with CDKN2A mutations (RR 20–40);
• Familial breast and ovarian cancer with BRCA2 (RR 10) and BRCA1 (RR 2.8) mutations;
• Hereditary nonpolyposis colorectal cancer (HNPCC, Lynch II syndrome) with MLH1, MSH2, MSH6, and PMS2 mutations (RR 9–11); and
• Familial adenomatous polyposis with APC mutations (RR 5).¹⁰

Other gene mutations with unknown relative risk for pancreatic cancer include mutations affecting PALB2, ATM, and TP53.

The International Cancer of the Pancreas Screening consortium consensus on screening for pancreatic cancer in patients with increased risk for familial pancreatic cancer recommends screening those at high risk: first-degree relatives (FDRs) of patients with pancreatic cancer from a familial pancreatic kindred with at least 2 affected FDRs; patients with Peutz-Jeghers syndrome; and p16, BRCA2, and HNPCC mutation carriers with 1 or more affected FDRs and hereditary pancreatitis. The guidelines emphasize that screening should be done only in those who are surgical candidates and are evaluated at an experienced multidisciplinary center.⁸

Deleterious germline mutations in pancreatic cancer can account for 33% of patients with apparent sporadic cancers and no hereditary risk. These include germline mutations affecting BRCA1/2, PALB2, ATM, MLH1, CHK-2, CDKN2A, and TP53.¹¹

 

Pathogenesis

Pancreatic neoplasms can be benign or malignant and thus a tissue histologic diagnosis is paramount. Pancreatic adenocarcinomas with exocrine features represent more than 95% of all pancreatic neoplasms, with only 5% arising from the endocrine pancreas (ie, neuroendocrine tumors). Pancreatic neuroendocrine tumors and pancreatic adenocarcinoma must be distinguished histologically because treatment of the 2 neoplasms is completely different. Other malignant pancreatic tumors are signet ring cell carcinoma, adenosquamous carcinoma, undifferentiated (anaplastic) carcinoma, and mucinous noncystic (colloid) carcinoma; the latter tumor has a better prognosis.¹² It is essential to characterize and distinguish among benign cystic neoplasms, as some require surgical resection due to the risk of malignant transformation. IPMN, pancreatic intraepithelial neoplasia, and mucinous cystic neoplasms are thought to be premalignant lesions of invasive ductal adenocarcinomas, and the pathological report should highlight the degree of dysplasia for adequate risk stratification.¹³ This information could be the deciding factor in whether a pancreatectomy is recommended by a multidisciplinary team.

Most pancreatic cancers harbor activating or silencing genetic mutations, and multiple combinations of altered genes can be detected by next-generation sequencing (average of 63 genetic alterations per cancer).¹⁴ Mutational activated KRAS is the most frequent (> 90%) genetic alteration in pancreatic cancer, even in early neoplastic precursors (IPMN > 75%). KRAS is a highly complex, dynamic proto-oncogene involved in signaling of various receptor kinases such as the epidermal growth factor receptor and the insulin-like growth factor receptor-I. It also engages in canonical downstream effector pathways, mainly Raf/MEK/ERK, PI3K/PDK1/Akt, and the Ral guanine nucleotide exchange factor pathway, which drive much of the pathogenesis of malignancy. These pathways lead to sustained proliferation, metabolic reprogramming, anti-apoptosis, remodeling of the tumor microenvironment, evasion of the immune response, cell migration, and metastasis. An activating point mutation in codon G12 is the most common (98%) locus of KRAS mutation in pancreatic adenocarcinoma, but all drugs targeting this mutation have failed in clinical practice.¹⁵ Additionally, inactivation of tumor suppressor genes such as p53, DPC4 (SMAD4/MADH4), CDKN2A (p16/MTS1), and BRCA2 can be found in 75%, 30%, 35%, and 4% of pancreatic adenocarcinoma cases, respectively.¹⁴ Another pancreatic cancer hallmark is inactivation of DNA damage repair genes, which include MLH1 and MSH2.¹⁶

Diagnosis and Staging

Case Presentation

A 71-year-old male veteran with no significant past medical history other than hypertension and hyperlipidemia and an excellent performance status presents to the emergency department after noticing a yellowish skin and sclera color. He denies weight loss, abdominal pain, or any other pertinent symptom or sign. Physical examination reveals a healthy developed man with yellowish discoloration of the skin and sclera and a soft, nontender benign abdomen; physical examination is otherwise unremarkable. Laboratory evaluation reveals a direct bilirubin level of 4.5 mg/dL and normal values for complete blood count and renal, liver, and coagulation panels. Abdominal and pelvis computed tomography (CT) with intravenous contrast shows a pancreatic head mass measuring 2.6 × 2.3 cm minimally abutting the anterior surface of the superior mesenteric vein, which remains patent. Follow-up endoscopic ultrasound (EUS) confirms an irregular mass at the head of the pancreas measuring 3.2 × 2.6 cm with sonographic evidence suggesting invasion into the portal vein. During the procedure, the bile duct is successfully stented, the mass is biopsied, and bile duct brushing is performed. Pathology report is consistent with pancreatic adenocarcinoma.

• What is the typical presentation of pancreatic cancer?

The most common symptoms of pancreatic cancer at the time of presentation include weight loss (85%), asthenia/anorexia (86%), and/or abdominal pain (79%).¹⁷ The most frequent signs are jaundice (55%), hepatomegaly (39%), and cachexia (13%). Courvoisier sign, a nontender but palpable distended gallbladder at the right costal margin, is neither sensitive nor specific for pancreatic cancer (13% of cases). Trousseau syndrome, a superficial thrombophlebitis, is another classic sign that reflects the hypercoagulable nature of pancreatic cancer (3% of cases).¹⁷ The pathophysiology of this syndrome is not completely understood, but it may occur secondary to the release of cancer microparticles in the blood stream which in turn stimulate the coagulation cascade. Other nonspecific symptoms are dark urine, nausea, vomiting, diarrhea, steatorrhea, and epigastric and back pain. Because symptoms early in the course of the disease are nonspecific, pancreatic cancer is typically diagnosed late, after the cancer has invaded local structures or metastasized. The initial presentation varies depending on tumor location, with 70% of pancreatic head malignancies presenting with jaundice and pain correlating to an advanced stage.¹⁸ Although data supporting an association between new-onset diabetes mellitus and pancreatic cancer are inconclusive, pancreatic cancer should still be a consideration in patients with new-onset diabetes mellitus and other symptoms such as pain and weight loss. Early signs of incurable disease include a palpable mass, ascites, lymphadenopathy (classic Virchow node), and an umbilical mass (Sister Mary Joseph node). Incidentally discovered pancreatic masses on imaging are rare, but the incidence is increasing due to frequent imaging for other reasons and improved diagnostic techniques.

 

• What is the approach to diagnosis and staging?

History and physical examination findings are not sufficiently sensitive or specific to diagnose pancreatic cancer. High clinical suspicion in a patient with risk factors can lead to a comprehensive evaluation and potential early diagnosis. In general, an initial diagnostic work-up for suspected pancreatic cancer will include serologic evaluation (liver function test, lipase, tumor markers) and abdominal imaging (ultrasound, CT scans, or magnetic resonance imaging [MRI]). Ultrasound is a first-line diagnostic tool with a sensitivity of 90% and specificity of 98.8% for pancreatic cancer, but it is investigator-dependent and is less accurate in detecting tumors smaller than 3 cm in diameter.¹⁹ Multiphasic helical CT of the abdomen has better sensitivity (100%) and specificity (100%) for detecting tumors larger than 2 cm, but this modality is less accurate in detecting pancreatic masses smaller than 2 cm (77%).²⁰ Percutaneous fine-needle aspiration (FNA) performed by ultrasound or CT guidance is avoided due to theoretical concerns about intraperitoneal seeding and bleeding.

If a pancreatic mass is detected by ultrasound or CT, additional interventions may be indicated depending on the clinical scenario. EUS-guided biopsy can provide histological confirmation and is currently utilized frequently for diagnosis and early resectability staging. Endoscopic retrograde cholangiopancreatography (ERCP) is indicated for patients with biliary obstruction requiring stent placement, and this procedure may provide tissue confirmation by forceps biopsy or brush cytology (lower accuracy than EUS). In a meta-analysis that evaluated the diagnostic value of tests for pancreatic cancer, ERCP had the highest sensitivity (92%) and specificity (96%) compared to ultrasound and CT,²¹ but this modality carries a risk for pancreatitis, bleeding, and cholangitis. Magnetic resonance cholangiopancreatography has not replaced ERCP, but it but may be an alternative for patients who cannot undergo ERCP (eg, gastric outlet obstruction, duodenal stenosis, anatomical surgical disruption, unsuccessful ERCP). ERCP is used frequently because many patients present with obstructive jaundice due to pancreatic mass compression, specifically if the mass is located in the head, and must undergo ERCP and stenting of the common bile duct.

The carbohydrate antigen (CA) 19-9 level has variable sensitivity and specificity in pancreatic cancer, as levels can be elevated in many benign pancreaticobiliary disorders. Elevated CA 19-9, in the appropriate clinical scenario (ie, a suspicious pancreatic mass and a value greater than 37 U/mL) demonstrated a sensitivity of 77% and specificity of 87% when differentiating pancreaticobiliary cancer from benign clinical conditions such as acute cholangitis or cholestasis.²² CA 19-9 level has prognostic value, as it may predict occult disease and correlates with survival rates, but no specific cutoff value has been established to guide perioperative therapy for high-risk resectable tumors.²³

The American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) tumor, node, metastasis (TNM) system is the preferred method for staging pancreatic cancer (Table 1). 

Stages IA, IB, IIA, IIB, and III disease correlate with median survival durations of 38, 24, 18, 17, and 14 months, respectively.^3,24 Accurate pancreatic cancer staging defines which patients are eligible for resection with curative intent. In a cost-effectiveness analysis, abdominal multidetector CT angiography (triple-phase contrast-enhanced thin-slice helical CT) followed by EUS provided the most accurate and cost-effective strategy in evaluating tumor burden in both local and metastatic disease (eg, liver metastasis or peritoneum).²⁵ Nonetheless, in clinical practice MRI is the preferred imaging modality for determining resectability based on specific anatomic characteristics and for detecting metastatic disease. Localized, nonmetastatic disease is deemed to be resectable, borderline resectable, and unresectable based on the extent of vascular invasion, infiltration of adjacent structures, and involvement of distal lymph nodes, according to criteria established by the National Comprehensive Cancer Network (NCCN, Table 2).^26,27 

Tumors that encase the celiac artery and superior mesenteric artery (> 180°) and infiltrate the portal vein are considered unresectable. Conversely, tumors that completely spare the celiac artery and superior mesenteric artery are considered resectable. Borderline-resectable tumors generally involve the superior mesenteric artery (< 180°) and/or abut the portal vein.

Positron emission tomography with CT scan is occasionally utilized in practice to assess tumor burden by evaluating anatomical structures and assessing physiologic uptake, which aids in establishing the extent of disease in equivocal cases. Staging laparoscopy with or without peritoneal biopsy is sometimes used to establish appropriate staging in cases that are questionable for occult metastatic disease. This procedure helps avoid unnecessary morbid surgeries.

 

Neoadjuvant Therapy

Case Continued

The patient is referred to oncology. Blood work reveals a CA 19-9 level of 100 U/mL (reference range < 35 U/mL) and a staging CT scan of the chest reveals a benign-appearing 3-mm nodule (no prior imaging for comparison). CT scan of the abdomen and pelvis does not define venous vasculature involvement appropriately and hence MRI of the abdomen and pelvis is performed. MRI reveals a pancreatic head mass measuring 3.0 × 2.7 cm, without arterial or venous vasculature invasion. However, the mass is abutting the portal vein and superior mesenteric vein and there is a new nonspecific 8-mm aortocaval lymph node.

• What are the current approaches to treating patients with resectable, unresectable, and metastatic disease?

Accurate staging and assessment of surgical resectability in pancreatic cancer are paramount as these steps prevent a futile morbid Whipple procedure in patients with advanced disease and a high risk of recurrence. Conversely, it allows patients with low-volume disease to undergo a potentially curative surgery. Approximately 20% of patients present with resectable disease, 40% present with locally advanced unresectable tumors (eg, involvement of critical vascular structures), and 40% present with metastatic disease.³ Treatment for resectable pancreatic cancer continues to be upfront surgery, although neoadjuvant therapy with either chemoradiation, radiation alone, or chemotherapy is an option per guidelines from the American Society of Clinical Oncology (ASCO),²⁸ the NCCN,²⁶ and the European Society for Medical Oncology (ESMO),²⁹ particularly for patients with borderline resectable tumors (Table 3). 

Neoadjuvant therapy provides an opportunity to downstage the cancer to allow for surgical resection and achieve negative surgical margins (R0). Unfortunately, even in patients with resectable tumors who achieve a complete resection and are treated with adjuvant therapy, the 5-year recurrence rate is approximately 80% and the survival rate is between 5% and 25%.^24,30 Nonetheless, to improve survival rates all patients with resected pancreatic adenocarcinoma should be treated with adjuvant chemotherapy based on data showing that it decreases the likelihood of recurrence compared with surgical resection alone.³¹

 

Systemic chemotherapy is recommended for fit candidates with locally advanced unresectable or metastatic disease, with an emphasis on supportive palliative measures. Palliative interventions include biliary stenting, duodenal stent for relieving gastric-outlet obstruction, and celiac axis nerve blocks, when indicated. Routine preoperative biliary stent placement/drainage in patients undergoing subsequent surgery for pancreatic cancer located in the head is associated with an increased risk of surgical complications when compared with up-front surgery without prior biliary drainage, and thus stent placement/drainage is not recommended.²⁶ Aggressive supportive management of symptoms, such as cancer-associated pain, anorexia-cachexia syndromes, and anxiety-depression disorders, should remain a primary palliative focus.

Case Continued

A multidisciplinary tumor board discusses the patient’s case and deems the cancer borderline resectable; neoadjuvant therapy is recommended. The patient is started on treatment with gemcitabine and nab-paclitaxel as first-line neoadjuvant therapy. After 4 cycles, the CA 19-9 level drops to 14 U/mL, and MRI reveals a smaller head mass of 1.3 × 1.4 cm with stable effacement of the superior mesenteric vein and no portal vein involvement; the aortocaval lymph node remains stable. At tumor board, it is evident that the patient has responded to therapy and the recommendation is to treat with gemcitabine chemoradiotherapy before surgery.

• What neoadjuvant therapy strategies are used in the treatment of pancreatic adenocarcinoma?

There are no established evidence-based recommendations for neoadjuvant therapy in patients with borderline resectable pancreatic cancer or patients with unresectable locally advanced pancreatic cancer. However, there are ongoing trials to investigate this treatment approach, and it is offered off-label in specific clinical scenarios, such as in the case patient described here. In patients with borderline resectable disease, preoperative chemotherapy followed by chemoradiation is a routine practice in most cancer centers,³² and ongoing clinical trials are an option for this cohort of patients (eg, Southwest Oncology Group Trial 1505, NCT02562716). The definitions of borderline resectable and unresectable pancreatic cancer have been described by the NCCN,²⁶ although most surgeons consider involvement of the major upper abdominal blood vessels the main unresectability criterion; oncologists also consider other parameters such as suspicious lesions on scans, worsening performance status, and a significantly elevated CA 19-9 level suggestive of disseminated disease.²⁸ The goal of a conversion approach by chemotherapy with or without radiation for borderline and unresectable cancers is to deliver a tolerable regimen leading to tumor downstaging, allowing for surgical resection. No randomized clinical trial has shown a survival advantage of this approach. Enrollment in clinical trials is preferred for patients with borderline and unresectable cancer, and there are trials that are currently enrolling patients.

The main treatment strategies for patients with locally advanced borderline and unresectable pancreatic cancer outside of a clinical trial are primary radiotherapy, systemic chemotherapy, and chemoradiation therapy. Guidelines from ASCO, NCCN, and ESMO recommend induction chemotherapy followed by restaging and consolidation chemoradiotherapy in the absence of progression.^26,28,29 There is no standard chemoradiation regimen and the role of chemotherapy sensitizers, including fluorouracil, gemcitabine, and capecitabine (an oral fluoropyrimidine substitute), and targeted agents in combination with different radiation modalities is now being investigated.

Fluorouracil is a radio-sensitizer that has been used in locally advanced pancreatic cancer based on experience in other gastrointestinal malignancies; data shows conflicting results with this drug. Capecitabine and tegafur/gimeracil/oteracil (S-1) are oral prodrugs that can safely replace infusional fluorouracil. Gemcitabine, a more potent radiation sensitizer, is very toxic, even at low-doses twice weekly, and does not provide a survival benefit, as demonstrated in the Cancer and Leukemia Group B (CALGB) 89805 trial, a phase 2 study of patients with surgically staged locally advanced pancreatic cancer.³³ Gemcitabine-based chemoradiotherapy was also evaluated in the Eastern Cooperative Group (ECOG) E4201 trial, which randomly assigned patients to receive gemcitabine alone (at 1000 mg/m²/wk for weeks 1 through 6, followed by 1 week rest, then weekly for 3 out of 4 weeks) or gemcitabine (600 mg/m²/wk for weeks 1 to 5, then 4 weeks later 1000 mg/m² for 3 out of 4 weeks) plus radiotherapy (starting on day 1, 1.8 Gy/fraction for total of 50.4 Gy).³⁴ Patients with locally advanced unresectable pancreatic cancer had a better OS outcome with gemcitabine in combination with radiation therapy (11.1 months) as compared with patients who received gemcitabine alone (9.2 months). Although there was a greater incidence of grade 4 and 5 treatment-related toxicities in the combination arm, no statistical differences in quality-of-life measurements were reported. Gemcitabine-based and capecitabine-based chemoradiotherapy were compared in the open-label phase 2 multicenter randomized SCALOP trial.³⁵ Patients with locally advanced pancreatic cancer were assigned to receive 3 cycles of induction with gemcitabine 1000 mg/m² days 1, 8, and 15 and capecitabine 830 mg/m² days 1 to 21 every 28 days; patients who had stable or responding disease were randomly assigned to receive a fourth cycle followed by capecitabine (830 mg/m² twice daily on weekdays only) or gemcitabine (300 mg/m² weekly) with radiation (50.4 Gy over 28 fractions). Patients treated with capecitabine-based chemoradiotherapy had higher nonsignificant median OS (17.6 months) and median progression-free survival (12 months) compared to those treated with gemcitabine (14.6 months and 10.4 months, respectively).

 

The benefit of radiation therapy in the treatment of locally advanced pancreatic cancer was further explored by the Fédération Francophone de Cancérologie Digestive 2000-01 phase 3 trial. This study compared induction chemoradiotherapy (60 Gy, 2 Gy/fraction; concomitant fluorouracil infusion, 300 mg/m²/day, days 1–5 for 6 weeks; cisplatin, 20 mg/m²/day, days 1–5 during weeks 1 and 5) to gemcitabine alone (1000 mg/m² weekly for 7 weeks) followed by maintenance gemcitabine in both arms.³⁶ Unexpectedly, the median OS was significantly shorter in the chemoradiotherapy arm than in the chemotherapy alone arm (8.6 months versus 13 months, respectively, P = 0.03) and the combination arm had more toxicities. The phase 3 open-label LAP07 study explored the role of radiation therapy in patients with locally advanced pancreatic cancer who had controlled disease after 4 months of induction therapy.³⁷ LAP07 had 2 randomizations: first, patients with locally advanced pancreatic cancer were assigned to receive weekly gemcitabine alone (1000 mg/m²) or this same dose of gemcitabine plus erlotinib 100 mg/day; second, patients with progression-free disease (61% of initial cohort) after 4 months of therapy were assigned to receive 2 months of the same chemotherapy or chemoradiotherapy (54 Gy plus capecitabine). This study showed that the addition of erlotinib to gemcitabine did not improve survival and in fact affected survival adversely. Of note, no survival benefit was observed after the first randomization from chemotherapy to consolidating chemoradiotherapy. Chemoradiotherapy achieved better locoregional tumor control with significantly less local tumor progression (32% versus 46%, P < 0.03) and no increase in toxicity. Based on prior moderate-quality evidence, guidelines recommend consolidative chemoradiotherapy only for surgical resection candidates following induction chemotherapy; for those who are not surgical candidates, guidelines recommend continuing systemic therapy.^26,28,29

Gemcitabine and fluorouracil-based chemotherapies were the standard induction regimens until evidence from studies of metastatic systemic treatment protocols with FOLFIRINOX (ACCORD trial³⁸) and nanoparticle albumin-bound paclitaxel (nab-paclitaxel) plus gemcitabine (MPACT trial³⁹) was extrapolated to clinical practice. These regimens were shown to achieve higher objective response rates when compared to single-agent gemcitabine in patients with metastatic pancreatic cancer. Due to the broad heterogeneity of results in small retrospective series with neoadjuvant trials in borderline resectable pancreatic cancer, the quality of the evidence is low and any recommendation is limited. Many individual series have demonstrated improved complete resection rates and promising survival rates. In the largest single-institution retrospective review of patients with borderline resectable pancreatic adenocarcinoma who completed neoadjuvant gemcitabine-based chemoradiotherapy (50 Gy in 28 fractions or 30 Gy in 10 fractions), 94% achieved a margin-negative pancreatectomy; the median OS in those who completed preoperative therapy and had surgery was 40 months, with a 5-year OS of 36%.⁴⁰ A meta-analysis by Andriulli and colleagues included 20 prospective studies of patients with initially resectable (366 lesions) or unresectable (341 lesions) disease who were treated with neoadjuvant/preoperative gemcitabine with or without radiotherapy.⁴¹ In the group with initially unresectable disease, 39% underwent surgery after restaging and 68% of explored patients were resected; the R0 resection rate was 60%. After restaging, 91% of patients with resectable disease underwent surgery, with 82% of explored patients undergoing surgical resection and 89% of these achieving R0 resection. The estimated 1- and 2-year survival probabilities after resection among patients with initially unresectable disease were 86.3% and 54.2%.⁴¹

The largest single-institution retrospective review of FOLFIRINOX (fluorouracil, oxaliplatin, irinotecan, and leucovorin), an alternative to gemcitabine, for neoadjuvant induction therapy for patients with locally advanced unresectable disease was conducted at Memorial Sloan Kettering Cancer Center. In this study (n = 101), 31% of patients initially deemed unresectable who completed FOLFIRINOX induction therapy with or without chemoradiation underwent resection. The R0 resection rate in these patients was 55%, and patients who did not progress during induction FOLFIRINOX therapy had a median OS of 26 months.⁴² A systematic review and meta-analysis of FOLFIRINOX chemotherapy with or without radiotherapy in patients with locally advanced unresectable pancreatic cancer reported that 25.9% of patients underwent resection after FOLFIRINOX therapy, and the R0 resection rate in these patients was 78.4%.⁴³ The median OS in this study was 24.2 months, which was longer than the previously reported median OS rates for gemcitabine.

There is no strong evidence published for the use of combination nab-paclitaxel plus gemcitabine in the neoadjuvant setting, but it is used in clinical practice based on evidence from the MPACT trial, which showed the combination improved OS and progression-free survival in patients with metastatic pancreatic cancer.³⁹ An early-phase 1-arm clinical trial of neoadjuvant gemcitabine, docetaxel, and capecitabine (GTX) followed by radiotherapy showed an increased response rate and survival for locally advanced disease; however, the NCCN expert panel has reached a consensus but not a uniform recommendation regarding this regimen due to significant toxicities and low patient accrual.²⁶ Selected patients with pancreatic cancer with BRCA1/2 mutations are more sensitive to platinum-based chemotherapy. Although studies of neoadjuvant platinum-based chemotherapy in this population have not been reported, the NCCN guidelines list it as an alternative option based on extrapolated data.²⁶ A clinical trial of gemcitabine, nab-paclitaxel, and cisplatin in the neoadjuvant setting in patients with resectable pancreatic cancer is currently enrolling patients (NGC triple regimen NCT0339257).

Summary

Chemotherapy alone or followed by chemoradiotherapy may be used as initial treatment for patients with borderline and unresectable pancreatic adenocarcinoma without distant metastases who are potential surgical candidates. Chemoradiotherapy remains a preferred treatment option for patients with poorly controlled pain from local tumor invasion, in view of the well-documented analgesic palliative effect of radiation therapy. FOLFIRINOX with or without radiation therapy may offer the highest documented response rates, but it also results in higher rates of treatment-related toxicities. FOLFIRINOX can be offered to selected fit patients (< 65 years old, no comorbidity contraindication, good functional status [ECOG 0–1]) who can tolerate triple therapy with a more toxic adverse-effect profile. A clinical trial evaluating neoadjuvant FOLFIRINOX with or without preoperative chemoradiotherapy in patients with borderline resectable pancreatic cancer is ongoing (PANDAS-PRODIGE 44, NCT02676349). Gemcitabine with or without radiation therapy is a tolerable combination, although it is potentially more toxic when combined with radiation. The addition of nab-paclitaxel to gemcitabine without radiation may emerge as a preferred neoadjuvant treatment for selected patients; a clinical trial investigating this modality in patients with resectable and borderline resectable disease is ongoing (NCT02723331).

 

Adjuvant Therapy

Case Continued

Prior to the planned surgical resection and after undergoing chemoradiation therapy, the patient has an excellent performance status and repeat MRI shows a 1.3 × 1.4 cm head mass with no further vasculature involvement, no evidence of lymphadenopathy, and no distant metastasis. The CA 19-9 level is stable at 18 U/mL. The patient undergoes an uncomplicated partial pancreaticoduodenectomy, and analysis of a surgical pathology specimen reveals T3N0 disease with closest margin of 0.1 cm.

• Would the patient benefit from adjuvant therapy?

Adjuvant chemotherapy for 6 months after pancreatic cancer resection should be offered to all patients based on mature data. Gemcitabine and capecitabine are the current standard of care in adjuvant therapy; alternatively, single-agent gemcitabine can be offered to patients with poor performance status or patients who cannot tolerate the toxicities associated with this combination.²⁸ Adjuvant treatment should be initiated within approximately 8 weeks of surgical resection. The value of radiation therapy remains controversial, but it can be offered within the context of a clinical trial or to patients with positive margins after surgical resection and/or lymph node–positive disease. Based on low-quality supportive evidence, it is strongly recommended that patients who receive neoadjuvant therapy complete a total of 6 months of chemotherapy, factoring in the duration of the preoperative regimen.²⁸ Different adjuvant strategies have been investigated, including chemotherapy alone with a fluoropyrimidine and/or gemcitabine with or without combined chemoradiation therapy.

The European Study Group for Pancreatic Cancer 1 (ESPAC)-1 trial was a randomized clinical trial that evaluated several adjuvant strategies in pancreatic cancer treatment. This trial assigned patients who underwent pancreatic adenocarcinoma resection to adjuvant chemotherapy alone (intravenous fluorouracil 425 mg/m² and leucovorin 20 mg/m² daily for 5 days, monthly for 6 months), chemoradiotherapy (20 Gy in 10 daily fractions over 2 weeks with 500 mg/m² intravenous fluorouracil on days 1–3, repeated after 2 weeks), both chemotherapy and chemoradiation, and observation.⁴⁴ The results showed no added benefit for adjuvant chemoradiotherapy, with a median OS of 15.5 months in the chemoradiotherapy cohort, as compared to a median OS of 16.1 months in the chemotherapy-alone cohort (hazard ratio [HR] 1.18 [95% CI 0.90 to 1.55], P = 0.24). In addition, there was evidence of a survival benefit for the chemotherapy-alone arm when compared to the combined modality arm, with a median OS of 19.7 versus 14.0 months, respectively (HR 0.66 [95% CI 0.52 to 0.83], P = 0.0005). Although ESPAC-1 has been criticized for being underpowered to perform statistical comparison, it is still considered a landmark trial demonstrating benefit with single-agent chemotherapy alone. A follow-up analysis of ESPAC-1 showed that adjuvant chemotherapy alone conferred a significant 5-year survival benefit while the combined modality had a deleterious effect on survival. ⁴⁵ Hence, adjuvant chemotherapy alone became the standard of care in the United States following resection.

The results of the multicenter randomized controlled phase 3 CONKO-001 (CharitéOnkologie 001) trial, which were reported in 2007, supported the use of adjuvant gemcitabine for 6 months in patients with resected pancreatic adenocarcinoma. In this study, patients treated with adjuvant gemcitabine (1000 mg/m² days 1, 8, and 15 every 4 weeks for 6 months) had superior disease-free survival compared with those who received surgery alone.³⁰ A long-term outcome update of this study demonstrated a significant improvement in 5-year OS for patients treated with adjuvant gemcitabine (20.7% [95% CI 14.7% to 26.6%]) compared to those who received surgical resection alone (10.4% [95% CI 5.9% to 15.0%]). This benefit persisted at 10-year follow-up, with an OS of 12.2% (95% CI 7.3% to 17.2%) in the adjuvant gemcitabine group, as compared to 7.7% (95% CI 3.6% to 11.8%) in the resection alone group.³¹

Fluorouracil and gemcitabine remained equivalent adjuvant treatment options until the results of the ESPAC-3 trial were reported in 2010.³² This large phase 3 trial, conducted mainly in the United Kingdom, compared weekly gemcitabine (1000 mg/m² weekly for 3 of every 4 weeks) to leucovorin-modulated fluorouracil (Mayo Clinic regimen: leucovorin 20 mg/m² followed by fluorouracil 425 mg/m² intravenous bolus days 1 through 5 every 28 days) as adjuvant therapy in resected pancreatic adenocarcinoma. After a median follow-up of 34.2 months, the median OS was similar in the 2 groups (fluorouracil/leucovorin 23.0 months versus gemcitabine 23.6 months; P = 0.39). However, the fluorouracil/leucovorin group experienced more grade 3/4 treatment-related toxicities (mucositis, stomatitis, diarrhea, and hosptializations; 14% versus 7.5%; P < 0.001).⁴⁶ Following this trial, gemcitabine became the standard of care for adjuvant chemotherapy for resected pancreatic cancer.

The U.S. Radiation Therapy Oncology Group (RTOG) 9704 trial was conducted to investigate the potential benefit of adding radiation therapy to gemcitabine. This trial demonstrated an improved trend among patients with pancreatic head tumors (but not with cancers of the pancreatic body or tail) who received adjuvant gemcitabine followed by chemoradiotherapy (50.4 Gy in 1.8 Gy daily fractions for 5.5 weeks with concurrent infusional fluorouracil 250 mg/m² daily) and subsequent gemcitabine monotherapy compared to postoperative fluorouracil-based chemoradiotherapy. Results showed a 5-year OS of 22% versus 18%, respectively, although this improvement was not statistically significant (P = 0.08). This trial failed to show a benefit of adding radiotherapy to gemcitabine.⁴⁷

The ESPAC-4 trial, reported in 2017, evaluated the combination of gemcitabine and capecitabine compared to gemcitabine alone as adjuvant therapy for resected pancreatic adenocarcinoma.⁴⁸ Patients were randomly assigned after surgical resection, regardless of margin or node status, to 6 months of gemcitabine alone (1000 mg/m²/day on days 1, 8, and 15 of each 28-day cycle) or gemcitabine plus capecitabine (1660 mg/m²/day on days 1 through 21 of each 28-day cycle). Combination therapy had a significant survival benefit compared to single therapy, with median OS durations of 28 months and 25.5 months, respectively (HR for death 0.82 [95% CI 0.68 to 0.98]). The 5-year OS for patients who received combination treatment was 29 months (95% CI 22.9 to 35.2) versus 16 months (95% CI 10.2 to 23.7) for those in the monotherapy group. As expected, grade 3 or 4 treatment-related toxicities (diarrhea, hand-foot syndrome, and neutropenia) were significantly more common with combined therapy, although there were no significant differences in the rates of serious adverse events. The adjuvant combination of gemcitabine and capecitabine became the current and preferred new standard of care following resection of pancreatic ductal adenocarcinoma,²⁸ but single-agent gemcitabine and fluorouracil/leucovorin continue to be viable options,^26,28,29 particularly for elderly patients, patients with borderline performance status, or patients with multiple comorbidities.

Evidence showing that a more intensive regimen can improve outcome in the adjuvant setting remains elusive. The phase 3 APACT study (Adjuvant Therapy for Patients with Resected Pancreatic Cancer, NCT01964430) comparing gemcitabine alone to gemcitabine plus nab-paclitaxel in patients with surgically resected pancreatic adenocarcinoma has concluded, with the results projected to be released in 2018. Another phase 3 trial investigating the efficacy of FOLFIRINOX versus gemcitabine alone as adjuvant therapy is underway in France and Canada (PRODIGE24/ACCORD24, NCT01526135). Other strategies with newer targeted therapies and immunotherapy are in the development phase.

 

Follow-Up and Surveillance

Case Conclusion

After recovery from surgery, the patient is offered and completes 4 cycles of adjuvant chemotherapy with gemcitabine plus capecitabine. He is started on surveillance at 3 and 6 months, and he maintains an excellent performance status. He develops clinical evidence of pancreatic enzyme insufficiency and is placed on oral replacement therapy. He has no other complaints, and there is no evidence of recurrence on MRI and CA 19-9 levels.

• What is the recommended duration of surveillance following curative resection?

Surveillance after curative resection of pancreatic adenocarcinoma is recommended by NCCN guidelines.²⁶ However, pancreatic adenocarcinoma has a poor prognosis, and surveillance after curative surgical resection with or without perioperative therapy has not been shown to impact survival. Most recurrences will occur within 2 years after treatment. Surveillance recommendations differ among expert groups.^26,28,29 NCCN guidelines recommend evaluating patients by history and physical examination every 3 to 6 months for the first 2 years, then every 6 to 12 months for 3 years. CA 19-9 level and CT scan should be obtained every 3 to 6 months for 2 years and then every 6 to 12 months for 3 years. Follow-up with CA 19-9 levels and CT scans after 5 years is not routinely performed unless guided by signs, symptoms, or laboratory findings that raise suspicion for recurrence. Follow-up visits should also include evaluation of treatment-related toxicities, symptom management, nutrition support of pancreatic insufficiency, and psychosocial support.

Conclusion

Pancreatic cancer is a leading cause of cancer-related death that frequently presents with locally advanced or metastatic disease due to nonspecific symptoms and lack of a screening modality. Histological tissue biopsy confirmation and accurate resectability staging guide treatment planning and prognosis. The only potentially curative therapy is surgical resection plus adjuvant therapy for those with resectable disease. Surgical candidates with borderline resectable and unresectable disease can be offered induction preoperative chemotherapy followed by consolidation chemoradiation, based on clinical consensus practice. Enrollment in clinical trials should be encouraged for all patients, as evidence from clinical trials is essential to making progress in pancreatic cancer treatment.

Introduction

Exocrine pancreatic cancer refers to pancreatic adenocarcinomas that arise from ductal epithelial cells. Pancreatic ductal adenocarcinoma is a highly lethal malignancy, ranking as the fourth most common cause of cancer-related death in the United States¹ and the eighth most common worldwide.² In the United States, the pancreas is the second most common site of gastrointestinal malignancy after the colon.¹ The only potentially curative modality for pancreatic adenocarcinomas is complete resection, followed by adjuvant therapy; unfortunately, only around 20% of patients are surgical candidates at the time of presentation due to delayed development of symptoms and consequently diagnosis.³ Most symptomatic patients with pancreatic cancer have locally advanced disease at diagnosis, and only a select group of patients with good performance status and borderline resectable disease can be offered neoadjuvant therapy. Adjuvant chemotherapy is typically recommended for patients who undergo potentially curative resection for pancreatic cancer.

Epidemiology

In the United States, pancreatic cancer has an annual estimated incidence of 55,440 new cases.¹ It causes an estimated 44,330 deaths per year, with a 5-year overall survival (OS) rate of 8.2%.¹ Worldwide an estimated 138,100 men and 127,900 women die of pancreatic cancer each year.² In general, pancreatic cancers occur more commonly in persons living in Western/industrialized countries, older persons (age > 60 years), males (ratio 1.3:1 female), and African-Americans and native Hawaiians.⁴

Etiology

The major preventable environmental risk factor for pancreatic cancer is cigarette smoking, which accounts for 25% of all cases.⁵ A prospective study that estimated the excess incidence of pancreatic cancer among cigarette smokers and assessed the influence of smoking cessation on the risk for pancreatic cancer showed that persons who quit smoking reduced their risk of pancreatic cancer by 48% after 2 years of cessation, compared with smokers who did not quit, and reduced their risk to near the level of a never smoker after 10 years of cessation.⁵ Risk is higher for heavy smokers and those with homozygous deletions of the glutathione S-transferase theta 1 gene (GSTT1), which results in the absence of the carcinogen-metabolizing function of the glutathione S-transferase enzyme. High body mass index and sedentary lifestyle have been linked to pancreatic cancer.⁶ Data regarding aspirin, diet, coffee, and excess alcohol consumption are insufficient, inconclusive, and even conflicting, and thus the effect of these factors on risk for pancreatic cancer remains unclear. Infectious risk factors such as Helicobacter pylori and hepatitis B and C virus have weak associations with pancreatic cancer. Chronic pancreatitis and pancreatic cysts (eg, intraductal papillary mucinous neoplasm [IPMN] of the pancreas) carry a risk for malignant transformation, and hence may require surveillance. Multiple epidemiologic studies have shown a strong association between pancreatic cancer and recently diagnosed diabetes mellitus (relative risk [RR] 1.97 [95% confidence interval {CI} 1.78 to 2.18]); the presence of diabetes also may be a long-term predisposing factor for pancreatic cancer, and cancer screening needs to be considered for selected patients.⁷

A predisposing genetic anomaly accounts for 15% of all cases of pancreatic cancer.⁸ Hereditary risk factors are divided into 2 broad categories: defined genetic syndromes and familial pancreatic cancer. Familial predispositions that do not meet genetic syndrome criteria account for approximately 5% to 10% of all cases associated with hereditary factors; in one study, 29% of tested kindreds with an incident pancreatic cancer had a germline BRCA2 mutation.⁹ Other predisposing genetic syndromes that have been linked to pancreatic cancer include:

• Peutz-Jeghers syndrome with germline STK11 mutations (RR 132);
• Hereditary pancreatitis with germline PRSS1, SPINK1, and CFTR mutations (RR 26–87);
• Familial atypical multiple mole melanoma syndrome with CDKN2A mutations (RR 20–40);
• Familial breast and ovarian cancer with BRCA2 (RR 10) and BRCA1 (RR 2.8) mutations;
• Hereditary nonpolyposis colorectal cancer (HNPCC, Lynch II syndrome) with MLH1, MSH2, MSH6, and PMS2 mutations (RR 9–11); and
• Familial adenomatous polyposis with APC mutations (RR 5).¹⁰

Other gene mutations with unknown relative risk for pancreatic cancer include mutations affecting PALB2, ATM, and TP53.

The International Cancer of the Pancreas Screening consortium consensus on screening for pancreatic cancer in patients with increased risk for familial pancreatic cancer recommends screening those at high risk: first-degree relatives (FDRs) of patients with pancreatic cancer from a familial pancreatic kindred with at least 2 affected FDRs; patients with Peutz-Jeghers syndrome; and p16, BRCA2, and HNPCC mutation carriers with 1 or more affected FDRs and hereditary pancreatitis. The guidelines emphasize that screening should be done only in those who are surgical candidates and are evaluated at an experienced multidisciplinary center.⁸

Deleterious germline mutations in pancreatic cancer can account for 33% of patients with apparent sporadic cancers and no hereditary risk. These include germline mutations affecting BRCA1/2, PALB2, ATM, MLH1, CHK-2, CDKN2A, and TP53.¹¹

 

Pathogenesis

Pancreatic neoplasms can be benign or malignant and thus a tissue histologic diagnosis is paramount. Pancreatic adenocarcinomas with exocrine features represent more than 95% of all pancreatic neoplasms, with only 5% arising from the endocrine pancreas (ie, neuroendocrine tumors). Pancreatic neuroendocrine tumors and pancreatic adenocarcinoma must be distinguished histologically because treatment of the 2 neoplasms is completely different. Other malignant pancreatic tumors are signet ring cell carcinoma, adenosquamous carcinoma, undifferentiated (anaplastic) carcinoma, and mucinous noncystic (colloid) carcinoma; the latter tumor has a better prognosis.¹² It is essential to characterize and distinguish among benign cystic neoplasms, as some require surgical resection due to the risk of malignant transformation. IPMN, pancreatic intraepithelial neoplasia, and mucinous cystic neoplasms are thought to be premalignant lesions of invasive ductal adenocarcinomas, and the pathological report should highlight the degree of dysplasia for adequate risk stratification.¹³ This information could be the deciding factor in whether a pancreatectomy is recommended by a multidisciplinary team.

Most pancreatic cancers harbor activating or silencing genetic mutations, and multiple combinations of altered genes can be detected by next-generation sequencing (average of 63 genetic alterations per cancer).¹⁴ Mutational activated KRAS is the most frequent (> 90%) genetic alteration in pancreatic cancer, even in early neoplastic precursors (IPMN > 75%). KRAS is a highly complex, dynamic proto-oncogene involved in signaling of various receptor kinases such as the epidermal growth factor receptor and the insulin-like growth factor receptor-I. It also engages in canonical downstream effector pathways, mainly Raf/MEK/ERK, PI3K/PDK1/Akt, and the Ral guanine nucleotide exchange factor pathway, which drive much of the pathogenesis of malignancy. These pathways lead to sustained proliferation, metabolic reprogramming, anti-apoptosis, remodeling of the tumor microenvironment, evasion of the immune response, cell migration, and metastasis. An activating point mutation in codon G12 is the most common (98%) locus of KRAS mutation in pancreatic adenocarcinoma, but all drugs targeting this mutation have failed in clinical practice.¹⁵ Additionally, inactivation of tumor suppressor genes such as p53, DPC4 (SMAD4/MADH4), CDKN2A (p16/MTS1), and BRCA2 can be found in 75%, 30%, 35%, and 4% of pancreatic adenocarcinoma cases, respectively.¹⁴ Another pancreatic cancer hallmark is inactivation of DNA damage repair genes, which include MLH1 and MSH2.¹⁶

Diagnosis and Staging

Case Presentation

A 71-year-old male veteran with no significant past medical history other than hypertension and hyperlipidemia and an excellent performance status presents to the emergency department after noticing a yellowish skin and sclera color. He denies weight loss, abdominal pain, or any other pertinent symptom or sign. Physical examination reveals a healthy developed man with yellowish discoloration of the skin and sclera and a soft, nontender benign abdomen; physical examination is otherwise unremarkable. Laboratory evaluation reveals a direct bilirubin level of 4.5 mg/dL and normal values for complete blood count and renal, liver, and coagulation panels. Abdominal and pelvis computed tomography (CT) with intravenous contrast shows a pancreatic head mass measuring 2.6 × 2.3 cm minimally abutting the anterior surface of the superior mesenteric vein, which remains patent. Follow-up endoscopic ultrasound (EUS) confirms an irregular mass at the head of the pancreas measuring 3.2 × 2.6 cm with sonographic evidence suggesting invasion into the portal vein. During the procedure, the bile duct is successfully stented, the mass is biopsied, and bile duct brushing is performed. Pathology report is consistent with pancreatic adenocarcinoma.

• What is the typical presentation of pancreatic cancer?

The most common symptoms of pancreatic cancer at the time of presentation include weight loss (85%), asthenia/anorexia (86%), and/or abdominal pain (79%).¹⁷ The most frequent signs are jaundice (55%), hepatomegaly (39%), and cachexia (13%). Courvoisier sign, a nontender but palpable distended gallbladder at the right costal margin, is neither sensitive nor specific for pancreatic cancer (13% of cases). Trousseau syndrome, a superficial thrombophlebitis, is another classic sign that reflects the hypercoagulable nature of pancreatic cancer (3% of cases).¹⁷ The pathophysiology of this syndrome is not completely understood, but it may occur secondary to the release of cancer microparticles in the blood stream which in turn stimulate the coagulation cascade. Other nonspecific symptoms are dark urine, nausea, vomiting, diarrhea, steatorrhea, and epigastric and back pain. Because symptoms early in the course of the disease are nonspecific, pancreatic cancer is typically diagnosed late, after the cancer has invaded local structures or metastasized. The initial presentation varies depending on tumor location, with 70% of pancreatic head malignancies presenting with jaundice and pain correlating to an advanced stage.¹⁸ Although data supporting an association between new-onset diabetes mellitus and pancreatic cancer are inconclusive, pancreatic cancer should still be a consideration in patients with new-onset diabetes mellitus and other symptoms such as pain and weight loss. Early signs of incurable disease include a palpable mass, ascites, lymphadenopathy (classic Virchow node), and an umbilical mass (Sister Mary Joseph node). Incidentally discovered pancreatic masses on imaging are rare, but the incidence is increasing due to frequent imaging for other reasons and improved diagnostic techniques.

 

• What is the approach to diagnosis and staging?

History and physical examination findings are not sufficiently sensitive or specific to diagnose pancreatic cancer. High clinical suspicion in a patient with risk factors can lead to a comprehensive evaluation and potential early diagnosis. In general, an initial diagnostic work-up for suspected pancreatic cancer will include serologic evaluation (liver function test, lipase, tumor markers) and abdominal imaging (ultrasound, CT scans, or magnetic resonance imaging [MRI]). Ultrasound is a first-line diagnostic tool with a sensitivity of 90% and specificity of 98.8% for pancreatic cancer, but it is investigator-dependent and is less accurate in detecting tumors smaller than 3 cm in diameter.¹⁹ Multiphasic helical CT of the abdomen has better sensitivity (100%) and specificity (100%) for detecting tumors larger than 2 cm, but this modality is less accurate in detecting pancreatic masses smaller than 2 cm (77%).²⁰ Percutaneous fine-needle aspiration (FNA) performed by ultrasound or CT guidance is avoided due to theoretical concerns about intraperitoneal seeding and bleeding.

If a pancreatic mass is detected by ultrasound or CT, additional interventions may be indicated depending on the clinical scenario. EUS-guided biopsy can provide histological confirmation and is currently utilized frequently for diagnosis and early resectability staging. Endoscopic retrograde cholangiopancreatography (ERCP) is indicated for patients with biliary obstruction requiring stent placement, and this procedure may provide tissue confirmation by forceps biopsy or brush cytology (lower accuracy than EUS). In a meta-analysis that evaluated the diagnostic value of tests for pancreatic cancer, ERCP had the highest sensitivity (92%) and specificity (96%) compared to ultrasound and CT,²¹ but this modality carries a risk for pancreatitis, bleeding, and cholangitis. Magnetic resonance cholangiopancreatography has not replaced ERCP, but it but may be an alternative for patients who cannot undergo ERCP (eg, gastric outlet obstruction, duodenal stenosis, anatomical surgical disruption, unsuccessful ERCP). ERCP is used frequently because many patients present with obstructive jaundice due to pancreatic mass compression, specifically if the mass is located in the head, and must undergo ERCP and stenting of the common bile duct.

The carbohydrate antigen (CA) 19-9 level has variable sensitivity and specificity in pancreatic cancer, as levels can be elevated in many benign pancreaticobiliary disorders. Elevated CA 19-9, in the appropriate clinical scenario (ie, a suspicious pancreatic mass and a value greater than 37 U/mL) demonstrated a sensitivity of 77% and specificity of 87% when differentiating pancreaticobiliary cancer from benign clinical conditions such as acute cholangitis or cholestasis.²² CA 19-9 level has prognostic value, as it may predict occult disease and correlates with survival rates, but no specific cutoff value has been established to guide perioperative therapy for high-risk resectable tumors.²³

The American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) tumor, node, metastasis (TNM) system is the preferred method for staging pancreatic cancer (Table 1). 

Stages IA, IB, IIA, IIB, and III disease correlate with median survival durations of 38, 24, 18, 17, and 14 months, respectively.^3,24 Accurate pancreatic cancer staging defines which patients are eligible for resection with curative intent. In a cost-effectiveness analysis, abdominal multidetector CT angiography (triple-phase contrast-enhanced thin-slice helical CT) followed by EUS provided the most accurate and cost-effective strategy in evaluating tumor burden in both local and metastatic disease (eg, liver metastasis or peritoneum).²⁵ Nonetheless, in clinical practice MRI is the preferred imaging modality for determining resectability based on specific anatomic characteristics and for detecting metastatic disease. Localized, nonmetastatic disease is deemed to be resectable, borderline resectable, and unresectable based on the extent of vascular invasion, infiltration of adjacent structures, and involvement of distal lymph nodes, according to criteria established by the National Comprehensive Cancer Network (NCCN, Table 2).^26,27 

Tumors that encase the celiac artery and superior mesenteric artery (> 180°) and infiltrate the portal vein are considered unresectable. Conversely, tumors that completely spare the celiac artery and superior mesenteric artery are considered resectable. Borderline-resectable tumors generally involve the superior mesenteric artery (< 180°) and/or abut the portal vein.

Positron emission tomography with CT scan is occasionally utilized in practice to assess tumor burden by evaluating anatomical structures and assessing physiologic uptake, which aids in establishing the extent of disease in equivocal cases. Staging laparoscopy with or without peritoneal biopsy is sometimes used to establish appropriate staging in cases that are questionable for occult metastatic disease. This procedure helps avoid unnecessary morbid surgeries.

 

Neoadjuvant Therapy

Case Continued

The patient is referred to oncology. Blood work reveals a CA 19-9 level of 100 U/mL (reference range < 35 U/mL) and a staging CT scan of the chest reveals a benign-appearing 3-mm nodule (no prior imaging for comparison). CT scan of the abdomen and pelvis does not define venous vasculature involvement appropriately and hence MRI of the abdomen and pelvis is performed. MRI reveals a pancreatic head mass measuring 3.0 × 2.7 cm, without arterial or venous vasculature invasion. However, the mass is abutting the portal vein and superior mesenteric vein and there is a new nonspecific 8-mm aortocaval lymph node.

• What are the current approaches to treating patients with resectable, unresectable, and metastatic disease?

Accurate staging and assessment of surgical resectability in pancreatic cancer are paramount as these steps prevent a futile morbid Whipple procedure in patients with advanced disease and a high risk of recurrence. Conversely, it allows patients with low-volume disease to undergo a potentially curative surgery. Approximately 20% of patients present with resectable disease, 40% present with locally advanced unresectable tumors (eg, involvement of critical vascular structures), and 40% present with metastatic disease.³ Treatment for resectable pancreatic cancer continues to be upfront surgery, although neoadjuvant therapy with either chemoradiation, radiation alone, or chemotherapy is an option per guidelines from the American Society of Clinical Oncology (ASCO),²⁸ the NCCN,²⁶ and the European Society for Medical Oncology (ESMO),²⁹ particularly for patients with borderline resectable tumors (Table 3). 

Neoadjuvant therapy provides an opportunity to downstage the cancer to allow for surgical resection and achieve negative surgical margins (R0). Unfortunately, even in patients with resectable tumors who achieve a complete resection and are treated with adjuvant therapy, the 5-year recurrence rate is approximately 80% and the survival rate is between 5% and 25%.^24,30 Nonetheless, to improve survival rates all patients with resected pancreatic adenocarcinoma should be treated with adjuvant chemotherapy based on data showing that it decreases the likelihood of recurrence compared with surgical resection alone.³¹

 

Systemic chemotherapy is recommended for fit candidates with locally advanced unresectable or metastatic disease, with an emphasis on supportive palliative measures. Palliative interventions include biliary stenting, duodenal stent for relieving gastric-outlet obstruction, and celiac axis nerve blocks, when indicated. Routine preoperative biliary stent placement/drainage in patients undergoing subsequent surgery for pancreatic cancer located in the head is associated with an increased risk of surgical complications when compared with up-front surgery without prior biliary drainage, and thus stent placement/drainage is not recommended.²⁶ Aggressive supportive management of symptoms, such as cancer-associated pain, anorexia-cachexia syndromes, and anxiety-depression disorders, should remain a primary palliative focus.

Case Continued

A multidisciplinary tumor board discusses the patient’s case and deems the cancer borderline resectable; neoadjuvant therapy is recommended. The patient is started on treatment with gemcitabine and nab-paclitaxel as first-line neoadjuvant therapy. After 4 cycles, the CA 19-9 level drops to 14 U/mL, and MRI reveals a smaller head mass of 1.3 × 1.4 cm with stable effacement of the superior mesenteric vein and no portal vein involvement; the aortocaval lymph node remains stable. At tumor board, it is evident that the patient has responded to therapy and the recommendation is to treat with gemcitabine chemoradiotherapy before surgery.

• What neoadjuvant therapy strategies are used in the treatment of pancreatic adenocarcinoma?

There are no established evidence-based recommendations for neoadjuvant therapy in patients with borderline resectable pancreatic cancer or patients with unresectable locally advanced pancreatic cancer. However, there are ongoing trials to investigate this treatment approach, and it is offered off-label in specific clinical scenarios, such as in the case patient described here. In patients with borderline resectable disease, preoperative chemotherapy followed by chemoradiation is a routine practice in most cancer centers,³² and ongoing clinical trials are an option for this cohort of patients (eg, Southwest Oncology Group Trial 1505, NCT02562716). The definitions of borderline resectable and unresectable pancreatic cancer have been described by the NCCN,²⁶ although most surgeons consider involvement of the major upper abdominal blood vessels the main unresectability criterion; oncologists also consider other parameters such as suspicious lesions on scans, worsening performance status, and a significantly elevated CA 19-9 level suggestive of disseminated disease.²⁸ The goal of a conversion approach by chemotherapy with or without radiation for borderline and unresectable cancers is to deliver a tolerable regimen leading to tumor downstaging, allowing for surgical resection. No randomized clinical trial has shown a survival advantage of this approach. Enrollment in clinical trials is preferred for patients with borderline and unresectable cancer, and there are trials that are currently enrolling patients.

The main treatment strategies for patients with locally advanced borderline and unresectable pancreatic cancer outside of a clinical trial are primary radiotherapy, systemic chemotherapy, and chemoradiation therapy. Guidelines from ASCO, NCCN, and ESMO recommend induction chemotherapy followed by restaging and consolidation chemoradiotherapy in the absence of progression.^26,28,29 There is no standard chemoradiation regimen and the role of chemotherapy sensitizers, including fluorouracil, gemcitabine, and capecitabine (an oral fluoropyrimidine substitute), and targeted agents in combination with different radiation modalities is now being investigated.

Fluorouracil is a radio-sensitizer that has been used in locally advanced pancreatic cancer based on experience in other gastrointestinal malignancies; data shows conflicting results with this drug. Capecitabine and tegafur/gimeracil/oteracil (S-1) are oral prodrugs that can safely replace infusional fluorouracil. Gemcitabine, a more potent radiation sensitizer, is very toxic, even at low-doses twice weekly, and does not provide a survival benefit, as demonstrated in the Cancer and Leukemia Group B (CALGB) 89805 trial, a phase 2 study of patients with surgically staged locally advanced pancreatic cancer.³³ Gemcitabine-based chemoradiotherapy was also evaluated in the Eastern Cooperative Group (ECOG) E4201 trial, which randomly assigned patients to receive gemcitabine alone (at 1000 mg/m²/wk for weeks 1 through 6, followed by 1 week rest, then weekly for 3 out of 4 weeks) or gemcitabine (600 mg/m²/wk for weeks 1 to 5, then 4 weeks later 1000 mg/m² for 3 out of 4 weeks) plus radiotherapy (starting on day 1, 1.8 Gy/fraction for total of 50.4 Gy).³⁴ Patients with locally advanced unresectable pancreatic cancer had a better OS outcome with gemcitabine in combination with radiation therapy (11.1 months) as compared with patients who received gemcitabine alone (9.2 months). Although there was a greater incidence of grade 4 and 5 treatment-related toxicities in the combination arm, no statistical differences in quality-of-life measurements were reported. Gemcitabine-based and capecitabine-based chemoradiotherapy were compared in the open-label phase 2 multicenter randomized SCALOP trial.³⁵ Patients with locally advanced pancreatic cancer were assigned to receive 3 cycles of induction with gemcitabine 1000 mg/m² days 1, 8, and 15 and capecitabine 830 mg/m² days 1 to 21 every 28 days; patients who had stable or responding disease were randomly assigned to receive a fourth cycle followed by capecitabine (830 mg/m² twice daily on weekdays only) or gemcitabine (300 mg/m² weekly) with radiation (50.4 Gy over 28 fractions). Patients treated with capecitabine-based chemoradiotherapy had higher nonsignificant median OS (17.6 months) and median progression-free survival (12 months) compared to those treated with gemcitabine (14.6 months and 10.4 months, respectively).

 

The benefit of radiation therapy in the treatment of locally advanced pancreatic cancer was further explored by the Fédération Francophone de Cancérologie Digestive 2000-01 phase 3 trial. This study compared induction chemoradiotherapy (60 Gy, 2 Gy/fraction; concomitant fluorouracil infusion, 300 mg/m²/day, days 1–5 for 6 weeks; cisplatin, 20 mg/m²/day, days 1–5 during weeks 1 and 5) to gemcitabine alone (1000 mg/m² weekly for 7 weeks) followed by maintenance gemcitabine in both arms.³⁶ Unexpectedly, the median OS was significantly shorter in the chemoradiotherapy arm than in the chemotherapy alone arm (8.6 months versus 13 months, respectively, P = 0.03) and the combination arm had more toxicities. The phase 3 open-label LAP07 study explored the role of radiation therapy in patients with locally advanced pancreatic cancer who had controlled disease after 4 months of induction therapy.³⁷ LAP07 had 2 randomizations: first, patients with locally advanced pancreatic cancer were assigned to receive weekly gemcitabine alone (1000 mg/m²) or this same dose of gemcitabine plus erlotinib 100 mg/day; second, patients with progression-free disease (61% of initial cohort) after 4 months of therapy were assigned to receive 2 months of the same chemotherapy or chemoradiotherapy (54 Gy plus capecitabine). This study showed that the addition of erlotinib to gemcitabine did not improve survival and in fact affected survival adversely. Of note, no survival benefit was observed after the first randomization from chemotherapy to consolidating chemoradiotherapy. Chemoradiotherapy achieved better locoregional tumor control with significantly less local tumor progression (32% versus 46%, P < 0.03) and no increase in toxicity. Based on prior moderate-quality evidence, guidelines recommend consolidative chemoradiotherapy only for surgical resection candidates following induction chemotherapy; for those who are not surgical candidates, guidelines recommend continuing systemic therapy.^26,28,29

Gemcitabine and fluorouracil-based chemotherapies were the standard induction regimens until evidence from studies of metastatic systemic treatment protocols with FOLFIRINOX (ACCORD trial³⁸) and nanoparticle albumin-bound paclitaxel (nab-paclitaxel) plus gemcitabine (MPACT trial³⁹) was extrapolated to clinical practice. These regimens were shown to achieve higher objective response rates when compared to single-agent gemcitabine in patients with metastatic pancreatic cancer. Due to the broad heterogeneity of results in small retrospective series with neoadjuvant trials in borderline resectable pancreatic cancer, the quality of the evidence is low and any recommendation is limited. Many individual series have demonstrated improved complete resection rates and promising survival rates. In the largest single-institution retrospective review of patients with borderline resectable pancreatic adenocarcinoma who completed neoadjuvant gemcitabine-based chemoradiotherapy (50 Gy in 28 fractions or 30 Gy in 10 fractions), 94% achieved a margin-negative pancreatectomy; the median OS in those who completed preoperative therapy and had surgery was 40 months, with a 5-year OS of 36%.⁴⁰ A meta-analysis by Andriulli and colleagues included 20 prospective studies of patients with initially resectable (366 lesions) or unresectable (341 lesions) disease who were treated with neoadjuvant/preoperative gemcitabine with or without radiotherapy.⁴¹ In the group with initially unresectable disease, 39% underwent surgery after restaging and 68% of explored patients were resected; the R0 resection rate was 60%. After restaging, 91% of patients with resectable disease underwent surgery, with 82% of explored patients undergoing surgical resection and 89% of these achieving R0 resection. The estimated 1- and 2-year survival probabilities after resection among patients with initially unresectable disease were 86.3% and 54.2%.⁴¹

The largest single-institution retrospective review of FOLFIRINOX (fluorouracil, oxaliplatin, irinotecan, and leucovorin), an alternative to gemcitabine, for neoadjuvant induction therapy for patients with locally advanced unresectable disease was conducted at Memorial Sloan Kettering Cancer Center. In this study (n = 101), 31% of patients initially deemed unresectable who completed FOLFIRINOX induction therapy with or without chemoradiation underwent resection. The R0 resection rate in these patients was 55%, and patients who did not progress during induction FOLFIRINOX therapy had a median OS of 26 months.⁴² A systematic review and meta-analysis of FOLFIRINOX chemotherapy with or without radiotherapy in patients with locally advanced unresectable pancreatic cancer reported that 25.9% of patients underwent resection after FOLFIRINOX therapy, and the R0 resection rate in these patients was 78.4%.⁴³ The median OS in this study was 24.2 months, which was longer than the previously reported median OS rates for gemcitabine.

There is no strong evidence published for the use of combination nab-paclitaxel plus gemcitabine in the neoadjuvant setting, but it is used in clinical practice based on evidence from the MPACT trial, which showed the combination improved OS and progression-free survival in patients with metastatic pancreatic cancer.³⁹ An early-phase 1-arm clinical trial of neoadjuvant gemcitabine, docetaxel, and capecitabine (GTX) followed by radiotherapy showed an increased response rate and survival for locally advanced disease; however, the NCCN expert panel has reached a consensus but not a uniform recommendation regarding this regimen due to significant toxicities and low patient accrual.²⁶ Selected patients with pancreatic cancer with BRCA1/2 mutations are more sensitive to platinum-based chemotherapy. Although studies of neoadjuvant platinum-based chemotherapy in this population have not been reported, the NCCN guidelines list it as an alternative option based on extrapolated data.²⁶ A clinical trial of gemcitabine, nab-paclitaxel, and cisplatin in the neoadjuvant setting in patients with resectable pancreatic cancer is currently enrolling patients (NGC triple regimen NCT0339257).

Summary

Chemotherapy alone or followed by chemoradiotherapy may be used as initial treatment for patients with borderline and unresectable pancreatic adenocarcinoma without distant metastases who are potential surgical candidates. Chemoradiotherapy remains a preferred treatment option for patients with poorly controlled pain from local tumor invasion, in view of the well-documented analgesic palliative effect of radiation therapy. FOLFIRINOX with or without radiation therapy may offer the highest documented response rates, but it also results in higher rates of treatment-related toxicities. FOLFIRINOX can be offered to selected fit patients (< 65 years old, no comorbidity contraindication, good functional status [ECOG 0–1]) who can tolerate triple therapy with a more toxic adverse-effect profile. A clinical trial evaluating neoadjuvant FOLFIRINOX with or without preoperative chemoradiotherapy in patients with borderline resectable pancreatic cancer is ongoing (PANDAS-PRODIGE 44, NCT02676349). Gemcitabine with or without radiation therapy is a tolerable combination, although it is potentially more toxic when combined with radiation. The addition of nab-paclitaxel to gemcitabine without radiation may emerge as a preferred neoadjuvant treatment for selected patients; a clinical trial investigating this modality in patients with resectable and borderline resectable disease is ongoing (NCT02723331).

 

Adjuvant Therapy

Case Continued

Prior to the planned surgical resection and after undergoing chemoradiation therapy, the patient has an excellent performance status and repeat MRI shows a 1.3 × 1.4 cm head mass with no further vasculature involvement, no evidence of lymphadenopathy, and no distant metastasis. The CA 19-9 level is stable at 18 U/mL. The patient undergoes an uncomplicated partial pancreaticoduodenectomy, and analysis of a surgical pathology specimen reveals T3N0 disease with closest margin of 0.1 cm.

• Would the patient benefit from adjuvant therapy?

Adjuvant chemotherapy for 6 months after pancreatic cancer resection should be offered to all patients based on mature data. Gemcitabine and capecitabine are the current standard of care in adjuvant therapy; alternatively, single-agent gemcitabine can be offered to patients with poor performance status or patients who cannot tolerate the toxicities associated with this combination.²⁸ Adjuvant treatment should be initiated within approximately 8 weeks of surgical resection. The value of radiation therapy remains controversial, but it can be offered within the context of a clinical trial or to patients with positive margins after surgical resection and/or lymph node–positive disease. Based on low-quality supportive evidence, it is strongly recommended that patients who receive neoadjuvant therapy complete a total of 6 months of chemotherapy, factoring in the duration of the preoperative regimen.²⁸ Different adjuvant strategies have been investigated, including chemotherapy alone with a fluoropyrimidine and/or gemcitabine with or without combined chemoradiation therapy.

The European Study Group for Pancreatic Cancer 1 (ESPAC)-1 trial was a randomized clinical trial that evaluated several adjuvant strategies in pancreatic cancer treatment. This trial assigned patients who underwent pancreatic adenocarcinoma resection to adjuvant chemotherapy alone (intravenous fluorouracil 425 mg/m² and leucovorin 20 mg/m² daily for 5 days, monthly for 6 months), chemoradiotherapy (20 Gy in 10 daily fractions over 2 weeks with 500 mg/m² intravenous fluorouracil on days 1–3, repeated after 2 weeks), both chemotherapy and chemoradiation, and observation.⁴⁴ The results showed no added benefit for adjuvant chemoradiotherapy, with a median OS of 15.5 months in the chemoradiotherapy cohort, as compared to a median OS of 16.1 months in the chemotherapy-alone cohort (hazard ratio [HR] 1.18 [95% CI 0.90 to 1.55], P = 0.24). In addition, there was evidence of a survival benefit for the chemotherapy-alone arm when compared to the combined modality arm, with a median OS of 19.7 versus 14.0 months, respectively (HR 0.66 [95% CI 0.52 to 0.83], P = 0.0005). Although ESPAC-1 has been criticized for being underpowered to perform statistical comparison, it is still considered a landmark trial demonstrating benefit with single-agent chemotherapy alone. A follow-up analysis of ESPAC-1 showed that adjuvant chemotherapy alone conferred a significant 5-year survival benefit while the combined modality had a deleterious effect on survival. ⁴⁵ Hence, adjuvant chemotherapy alone became the standard of care in the United States following resection.

The results of the multicenter randomized controlled phase 3 CONKO-001 (CharitéOnkologie 001) trial, which were reported in 2007, supported the use of adjuvant gemcitabine for 6 months in patients with resected pancreatic adenocarcinoma. In this study, patients treated with adjuvant gemcitabine (1000 mg/m² days 1, 8, and 15 every 4 weeks for 6 months) had superior disease-free survival compared with those who received surgery alone.³⁰ A long-term outcome update of this study demonstrated a significant improvement in 5-year OS for patients treated with adjuvant gemcitabine (20.7% [95% CI 14.7% to 26.6%]) compared to those who received surgical resection alone (10.4% [95% CI 5.9% to 15.0%]). This benefit persisted at 10-year follow-up, with an OS of 12.2% (95% CI 7.3% to 17.2%) in the adjuvant gemcitabine group, as compared to 7.7% (95% CI 3.6% to 11.8%) in the resection alone group.³¹

Fluorouracil and gemcitabine remained equivalent adjuvant treatment options until the results of the ESPAC-3 trial were reported in 2010.³² This large phase 3 trial, conducted mainly in the United Kingdom, compared weekly gemcitabine (1000 mg/m² weekly for 3 of every 4 weeks) to leucovorin-modulated fluorouracil (Mayo Clinic regimen: leucovorin 20 mg/m² followed by fluorouracil 425 mg/m² intravenous bolus days 1 through 5 every 28 days) as adjuvant therapy in resected pancreatic adenocarcinoma. After a median follow-up of 34.2 months, the median OS was similar in the 2 groups (fluorouracil/leucovorin 23.0 months versus gemcitabine 23.6 months; P = 0.39). However, the fluorouracil/leucovorin group experienced more grade 3/4 treatment-related toxicities (mucositis, stomatitis, diarrhea, and hosptializations; 14% versus 7.5%; P < 0.001).⁴⁶ Following this trial, gemcitabine became the standard of care for adjuvant chemotherapy for resected pancreatic cancer.

The U.S. Radiation Therapy Oncology Group (RTOG) 9704 trial was conducted to investigate the potential benefit of adding radiation therapy to gemcitabine. This trial demonstrated an improved trend among patients with pancreatic head tumors (but not with cancers of the pancreatic body or tail) who received adjuvant gemcitabine followed by chemoradiotherapy (50.4 Gy in 1.8 Gy daily fractions for 5.5 weeks with concurrent infusional fluorouracil 250 mg/m² daily) and subsequent gemcitabine monotherapy compared to postoperative fluorouracil-based chemoradiotherapy. Results showed a 5-year OS of 22% versus 18%, respectively, although this improvement was not statistically significant (P = 0.08). This trial failed to show a benefit of adding radiotherapy to gemcitabine.⁴⁷

The ESPAC-4 trial, reported in 2017, evaluated the combination of gemcitabine and capecitabine compared to gemcitabine alone as adjuvant therapy for resected pancreatic adenocarcinoma.⁴⁸ Patients were randomly assigned after surgical resection, regardless of margin or node status, to 6 months of gemcitabine alone (1000 mg/m²/day on days 1, 8, and 15 of each 28-day cycle) or gemcitabine plus capecitabine (1660 mg/m²/day on days 1 through 21 of each 28-day cycle). Combination therapy had a significant survival benefit compared to single therapy, with median OS durations of 28 months and 25.5 months, respectively (HR for death 0.82 [95% CI 0.68 to 0.98]). The 5-year OS for patients who received combination treatment was 29 months (95% CI 22.9 to 35.2) versus 16 months (95% CI 10.2 to 23.7) for those in the monotherapy group. As expected, grade 3 or 4 treatment-related toxicities (diarrhea, hand-foot syndrome, and neutropenia) were significantly more common with combined therapy, although there were no significant differences in the rates of serious adverse events. The adjuvant combination of gemcitabine and capecitabine became the current and preferred new standard of care following resection of pancreatic ductal adenocarcinoma,²⁸ but single-agent gemcitabine and fluorouracil/leucovorin continue to be viable options,^26,28,29 particularly for elderly patients, patients with borderline performance status, or patients with multiple comorbidities.

Evidence showing that a more intensive regimen can improve outcome in the adjuvant setting remains elusive. The phase 3 APACT study (Adjuvant Therapy for Patients with Resected Pancreatic Cancer, NCT01964430) comparing gemcitabine alone to gemcitabine plus nab-paclitaxel in patients with surgically resected pancreatic adenocarcinoma has concluded, with the results projected to be released in 2018. Another phase 3 trial investigating the efficacy of FOLFIRINOX versus gemcitabine alone as adjuvant therapy is underway in France and Canada (PRODIGE24/ACCORD24, NCT01526135). Other strategies with newer targeted therapies and immunotherapy are in the development phase.

 

Follow-Up and Surveillance

Case Conclusion

After recovery from surgery, the patient is offered and completes 4 cycles of adjuvant chemotherapy with gemcitabine plus capecitabine. He is started on surveillance at 3 and 6 months, and he maintains an excellent performance status. He develops clinical evidence of pancreatic enzyme insufficiency and is placed on oral replacement therapy. He has no other complaints, and there is no evidence of recurrence on MRI and CA 19-9 levels.

• What is the recommended duration of surveillance following curative resection?

Surveillance after curative resection of pancreatic adenocarcinoma is recommended by NCCN guidelines.²⁶ However, pancreatic adenocarcinoma has a poor prognosis, and surveillance after curative surgical resection with or without perioperative therapy has not been shown to impact survival. Most recurrences will occur within 2 years after treatment. Surveillance recommendations differ among expert groups.^26,28,29 NCCN guidelines recommend evaluating patients by history and physical examination every 3 to 6 months for the first 2 years, then every 6 to 12 months for 3 years. CA 19-9 level and CT scan should be obtained every 3 to 6 months for 2 years and then every 6 to 12 months for 3 years. Follow-up with CA 19-9 levels and CT scans after 5 years is not routinely performed unless guided by signs, symptoms, or laboratory findings that raise suspicion for recurrence. Follow-up visits should also include evaluation of treatment-related toxicities, symptom management, nutrition support of pancreatic insufficiency, and psychosocial support.

Conclusion

Pancreatic cancer is a leading cause of cancer-related death that frequently presents with locally advanced or metastatic disease due to nonspecific symptoms and lack of a screening modality. Histological tissue biopsy confirmation and accurate resectability staging guide treatment planning and prognosis. The only potentially curative therapy is surgical resection plus adjuvant therapy for those with resectable disease. Surgical candidates with borderline resectable and unresectable disease can be offered induction preoperative chemotherapy followed by consolidation chemoradiation, based on clinical consensus practice. Enrollment in clinical trials should be encouraged for all patients, as evidence from clinical trials is essential to making progress in pancreatic cancer treatment.

Introduction

Biliary tract carcinoma (BTC) is the term for a heterogeneous group of rare gastrointestinal malignancies¹ that includes both carcinoma arising from the gallbladder and cholangiocarcinoma, which refers to diverse aggressive epithelial cancers involving the intrahepatic, perihilar, and distal biliary tree.^1–3 In this article, we review the epidemiology, clinical features, and diagnostic approach to BTC, with a focus on current evidence-based treatment strategies for localized, locally advanced, and metastatic BTC.

Epidemiology

In the United States, BTC is rare and accounts for approximately 4% of all gastrointestinal malignancies, with an estimated 6000 to 7000 cases of carcinoma of the gallbladder and 3000 to 4000 cases of carcinoma of the bile duct diagnosed annually.⁴ Among women, there is a 26-fold variation in BTC mortality worldwide, ranging from 0.8 deaths per 100,000 in South Africa to 21.2 per 100,000 in Chile.^1,5 Interestingly, for American Indians in New Mexico, gallbladder cancer mortality rates (8.9 per 100,000) surpass those for breast and pancreatic cancers.⁶ The incidence of anatomical cholangiocarcinoma subtypes also varies regionally, reflecting disparities in genetic and environmental predisposing factors.^2,7 In a large, single-center study in the United States, intrahepatic cholangiocarcinoma accounted for less than 10% of cases, perihilar accounted for 50%, and distal accounted for the remaining 40%.⁸ Importantly, intrahepatic cholangiocarcinoma is the second most common primary malignancy of the liver, and its incidence seems to be rising in many western countries. In the United States, there has been an estimated 128% rise over the past 40 years.^4,9

BTC is associated with high mortality rates.¹⁰ Median overall survival (OS) for cholangiocarcinoma is 20 to 28 months and 5-year survival is around 25%.¹⁰ Most cholangiocarcinomas are diagnosed at advanced stages with unresectable tumors.¹⁰ Furthermore, outcomes following resection with curative intent are poor—median disease-free survival (DFS) of 12 to 36 months has been reported.^11,12 Patients with intrahepatic disease have a better prognosis when compared with patients who have extrahepatic tumors.¹² Gallbladder cancer, likewise, carries a poor overall prognosis; median OS is 32 months and 5-year survival is as low as 13%.⁶

Risk factors for BTC include intrinsic and extrinsic elements.⁶ Incidence of BTC increases with age, and diagnosis typically occurs in the sixth to eighth decade of life.^5,6,13 In contrast to gallbladder cancer, the incidence of cholangiocarcinoma is slightly higher in men.⁹ Obesity, diabetes, and consumption of sweetened drinks also increase the risk for BTC.^14–16 Cholelithiasis is the most prevalent risk factor for gallbladder cancer, and the risk is greater for larger stones.⁵ Around 1 in 5 patients with porcelain gallbladder will develop gallbladder carcinoma.¹⁷ Primary sclerosing cholangitis (PSC), chronic calculi of the bile duct, choledochal cysts, cirrhosis, hepatitis C, and liver fluke infections are well established risk factors for cholangiocarcinoma.^7,12,18 PSC is one of the best described entities among these predisposing conditions. Lifetime prevalence of cholangiocarcinoma among patients with PSC ranges from 5% to 10%.^18,19 These patients also present at a younger age; in one series, the median age at diagnosis for BTC arising from PSC was 39 years.¹⁸ It is important to recognize, however, that in most patients diagnosed with cholangiocarcinoma, no predisposing factors are identified.⁸

Diagnosis

Clinical Presentation

Clinical presentation of BTC depends upon anatomic location.²⁰ Patients with early invasive gallbladder cancer are most often asymptomatic.²¹ When symptoms occur, they may be nonspecific and mimic cholelithiasis.²¹ The most common clinical presentations include jaundice, weight loss, and abdominal pain.²¹ Prior to widespread availability of imaging studies, the preoperative diagnosis rate for gallbladder cancer was as low as 10%.²² However, the accuracy of computed tomography (CT) has changed this scenario, with sensitivity ranging from 73% to 87% and specificity from 88% to 100%.²¹ As a result of its silent clinical character, cholangiocarcinoma is frequently difficult to diagnose.²³ Perihilar and distal cholangiocarcinoma characteristically present with signs of biliary obstruction, and imaging and laboratory data can corroborate the presence of cholestasis.²⁴ On examination, patients with extrahepatic cholangiocarcinoma may present with jaundice, hepatomegaly, and a palpable right upper quadrant mass.²⁵ A palpable gallbladder (Courvoisier sign) can also be present.²⁵ Intrahepatic cholangiocarcinoma presents differently, and patients are less likely to be jaundiced.²³ Typical clinical features are nonspecific and include dull right upper quadrant pain, weight loss, and an elevated alkaline phosphatase level.²³ Alternatively, asymptomatic patients can present with incidentally detected lesions, when imaging is obtained as part of the workup for other causes or during screening for hepatocellular carcinoma in patients with viral hepatitis or cirrhosis.^23,26 Uncommonly, BTC patients present because of signs or symptoms related to metastatic disease or evidence of metastatic disease on imaging.

 

Pathology and Grading

The majority of BTCs are adenocarcinomas, corresponding to 90% of cholangiocarcinomas and 99% of gallbladder cancers.^27,28 They are graded as well, moderately, or poorly differentiated.² Adenosquamous and squamous cell carcinoma are responsible for most of the remaining cases.^2,29 Cholangiocarcinomas are divided into 3 types, defined by the Liver Cancer Study Group of Japan: (1) mass-forming, (2) periductal-infiltrating, and (3) intraductal-growing.^30,31 Mass-forming intrahepatic cholangiocarcinomas are characterized morphologically by a homogeneous gray-yellow mass with frequent satellite nodules and irregular but well-defined margins.^17,30 Central necrosis and fibrosis are also common.³⁰ In the periductal-infiltrating type, tumor typically grows along the bile duct wall without mass formation, resulting in concentric mural thickening and proximal biliary dilation.³⁰ Intraductal-growing papillary cholangiocarcinoma is characterized by the presence of intraluminal papillary or tubular polypoid tumors of the intra- or extrahepatic bile ducts, with partial obstruction and proximal biliary dilation.³⁰

Cholangiocarcinoma

Case Presentation

A previously healthy 59-year-old man presents to his primary care physician with a 3-month history of dull right upper quadrant pain associated with weight loss. The patient is markedly cachectic and abdominal examination reveals upper quadrant tenderness. Laboratory exams are significant for elevated alkaline phosphatase (500 U/L; reference range 45–115 U/L), cancer antigen 19-9 (CA 19-9, 73 U/mL; reference range ≤ 37 U/mL), and carcinoembryonic antigen (CEA , 20 ng/mL; reference range for nonsmokers ≤ 3.0 ng/mL). Aspartate aminotransferase, alanine aminotransferase, total bilirubin, and coagulation studies are within normal range. Ultrasound demonstrates a homogeneous mass with irregular borders in the right lobe of the liver. Triphasic contrast-enhanced CT scan demonstrates a tumor with ragged rim enhancement at the periphery, and portal venous phase shows gradual centripetal enhancement of the tumor with capsular retraction. No abdominal lymph nodes or extrahepatic tumors are noted (Figure 1, Image A).

• What are the next diagnostic steps?

The most critical differential diagnosis of solid liver mass in patients without cirrhosis is cholangiocarcinoma and metastases from another primary site.³² Alternatively, when an intrahepatic lesion is noted on an imaging study in the setting of cirrhosis, the next diagnostic step is differentiation between cholangiocarcinoma and hepatocellular carcinoma (HCC).³² Triphasic contrast-enhanced CT and dynamic magnetic resonance imaging (MRI) are key diagnostic procedures.^32,33 In the appropriate setting, classical imaging features in the arterial phase with washout in portal venous or delayed phase can be diagnostic of HCC and may obviate the need for a biopsy (Figure 2).

Typical radiographic features of cholangiocarcinoma include a hypodense hepatic lesion that can be either well-defined or infiltrative and is frequently associated with biliary dilatation (Figure 1, Image A).³³ The dense fibrotic nature of the tumor may cause capsular retraction, which is seen in up to 20% of cases.¹⁷ This finding is highly suggestive of cholangiocarcinoma and is rarely present in HCC.³³ Following contrast administration, there is peripheral (rim) enhancement throughout both arterial and venous phases.^32–34 However, these classic features were present in only 70% of cases in one study.³⁵ Although intrahepatic cholangiocarcinomas are most commonly hypovascular, small mass-forming intrahepatic cholangiocarcinomas can often be arterially hyperenhancing and mimic HCC.³³ Tumor enhancement on delayed CT imaging has been correlated with survival. Asayama et al demonstrated that tumors that exhibited delayed enhancement on CT in more than two-thirds of their volume were associated with a worse prognosis.³⁶

Patients without cirrhosis who present with a localized lesion of the liver should undergo extensive evaluation for a primary cancer site.³⁷ CT of the chest, abdomen, and pelvis with contrast should be obtained.³⁷ Additionally, mammogram and endoscopic evaluation with esophagogastroduodenoscopy (EGD) and colonoscopy should be included in the work-up.³⁷

Preoperative tumor markers are also included in the work-up. All patients with a solid liver lesion should have serum alpha-fetoprotein (AFP) levels checked. AFP is a serum glycoprotein recognized as a marker for HCC and is reported to detect preclinical HCC.³⁸ However, serum concentrations are normal in up to 40% of small HCCs.³⁸ Although no specific marker for cholangiocarcinoma has yet been identified, the presence of certain tumor markers in the serum of patients may be of diagnostic value, especially in patients with PSC. CA 19-9 and CEA are the best studied. Elevated levels of CA 19-9 prior to treatment are associated with a poorer prognosis, and CA 19-9 concentrations greater than 1000 U/mL are consistent with advanced disease.^39,40 One large series evaluated the diagnostic value of serum CEA levels in 333 patients with PSC, 13% of whom were diagnosed with cholangiocarcinoma.³⁴ A serum CEA level greater than 5.2 ng/mL had a sensitivity of 68.0% and specificity of 81.5%.³⁸

If a biopsy is obtained, appropriate immunohistochemistry (IHC) can facilitate the diagnosis. BTC is strongly positive for CK-7 and CK-19.⁴¹ CK-7 positivity is not specific and is also common among metastatic cancers of the lung and breast; therefore, in some cases cholangiocarcinoma may be a diagnosis of exclusion. Immunostaining for monoclonal CEA is diffusely positive in up to 75% of cases.⁴¹ An IHC panel consisting of Hep Par-1, arginase-1, monoclonal CEA, CK-7, CK-20, TTF-1, MOC-31, and CDX-2 has been proposed to optimize the differential diagnosis of HCC, metastatic adenocarcinoma, and cholangiocarcinoma.⁴¹

 

Case Continued

CT of the chest, abdomen, and pelvis reveals no concerns for metastasis and no evidence of primary cancer elsewhere. EGD and colonoscopy are clear. AFP levels are within normal limits (2 ng/mL). Biopsy is performed and demonstrates adenocarcinoma. IHC studies demonstrate cells positive for monoclonal CEA, CK-7, CK-19, and MOC-31, and negative for Napsin A, TTF-1, and CK-20.

• How is cholangiocarcinoma staged and classified?

The purpose of the staging system is to provide information on prognosis and guidance for therapy. Prognostic factors and the therapeutic approaches for BTC differ depending upon their location in the biliary tree. Accordingly, TNM classification systems for intrahepatic, hilar, and distal cholangiocarcinoma and gallbladder cancer have been separated (Table 1 and Table 2).²³

For all the subtypes, T stage is mainly dependent upon invasion of adjacent structures rather than size. For perihilar tumors, N category has been reclassified in the newest version of the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) staging system based upon the number of involved lymph nodes rather than location.

The Bismuth-Corlette classification is used to further classify perihilar cholangiocarcinoma according to patterns of hepatic duct involvement. Type I tumors are located below the confluence of the left and right hepatic ducts.⁴² Type II reach the confluence of the hepatic ducts.⁴² Type III occlude the common hepatic duct and either the right or left hepatic duct (IIIa and IIIb, respectively).⁴² Finally, type IV are multicentric, or involve the confluence and both the right and left hepatic ducts.⁴² Tumors that involve the common hepatic duct bifurcation are named Klatskin tumors.⁴²

• What is the first-line treatment for localized cholangiocarcinomas?

Surgical resection is the only potentially curative treatment for localized cholangiocarcinoma, although fewer than 20% of patients are suitable for curative treatment, due to the presence of advanced disease at diagnosis.^43,44 Available evidence supports the recommendation that resection with negative margins, regardless of extent, should be the goal of therapy for patients with potentially resectable disease.⁴⁴ Extensive hepatic resections are often necessary to achieve clear margins since the majority of patients present with large masses. Substantial evidence corroborates that R0 resection is associated with better survival, whereas the benefit of wide compared to narrow (< 5–10 mm) margins is unclear.⁴⁵ A recent analysis of 96 patients suggests that the proximal resection margin has more prognostic implications than distal margins.⁴⁵

Surgical options and resectability criteria depend upon tumor location. Extent of tumor in the bile duct is one of the most important factors that determine resectability.¹⁷ Although multifocal liver tumors (including satellite lesions), lymph node metastases to the porta hepatis, and distant metastases are considered relative contraindications to surgery, surgical approaches can be considered in selected patients.⁴³ Patient selection for surgery is facilitated by careful preoperative staging, which may include laparoscopy. Laparoscopic staging prior to resection may prevent unnecessary laparotomy in 30% to 45% of patients.^42,46

• Is there a role for adjuvant treatment?

Recurrence following complete resection is a primary limitation for cure in BTC, which provides a rationale for the use of adjuvant therapy.^47,48 In a sample of 79 patients with extrahepatic cholangiocarcinoma who underwent curative resection, the cumulative recurrence rate after 4 years was 56%.⁴⁷ Initial recurrence at a distant site occurs in 40% to 50% of patients.⁴⁸

Lymphovascular and perineural invasion, lymph node metastasis, and tumor size ≥ 5 cm have been reported as independent predictors of recurrence and mortality following resection.⁴⁹ A 2017 meta-analysis which included 30 studies involving more than 22,499 patients reported a 41% reduction in the risk of death with adjuvant chemotherapy, which translated to a mean OS benefit of 4 months in an unselected population.⁴⁹ Moreover, this study revealed inferior OS in patients given adjuvant radiation therapy (RT) in combination with chemotherapy.⁴⁹ These results are in line with the previous meta-analysis by Horgan et al, which demonstrated that adjuvant RT seems to benefit only patients with R1 resections, with a possible detrimental effect in R0 disease.⁵⁰ Therefore, adjuvant chemoradiation cannot be viewed as a standard practice following R0 resection, and should be reserved for those patients with positive margins (R1/ 2) to reduce local progression.

In the phase 3 BILCAP trial presented at ASCO 2017, 447 patients with completely resected cholangiocarcinoma or gallbladder cancer with adequate biliary drainage and Eastern Cooperative Oncology Group (ECOG) performance score ≤ 2 were randomly assigned to observation or capecitabine (1250 mg/m² twice daily for days 1–14 every 21 days for 8 cycles).⁵¹ Surgical treatment achieved R0 resection in 62% of patients and 46% were node-negative. Median OS was 51 months for the capecitabine group and 36 months for the control arm (hazard ratio [HR] 0.80, 95% CI 0.63 to 1.04, P = 0.097). Analyses with adjustment for nodal status, grade of disease, and gender indicated a HR of 0.71 (P < 0.01). Median DFS was 25 months versus 18 months favoring the capecitabine group, and rates of grade 3 or 4 toxicity were less than anticipated. Following the results of this trial, adjuvant capecitabine should become the new standard of care.

 

• What is the treatment for locally advanced cholangiocarcinoma?

The optimal approach to patients with locally advanced unresectable cholangiocarcinoma has not been established. The prognosis for patients with either locally unresectable or locally recurrent disease is typically measured in months. Goals of palliative therapy are relief of symptoms and improvement in quality of life, and there is no role for surgical debulking.

Liver transplantation is a potentially curative option for selected patients with hilar or intrahepatic cholangiocarcinoma. Patients with lymph node-negative, non-disseminated, locally advanced hilar cholangiocarcinomas have 5-year survival rates ranging from 25% to 42% following transplantation.⁵² Retrospective data suggests that neoadjuvant chemoradiation followed by liver transplantation is highly effective for selected patients with hilar cholangiocarcinoma.⁵² However, these results require confirmation from prospective clinical evidence. It is important to recognize that liver transplantation plays no role in the management of distal cholangiocarcinoma or gallbladder cancer.

Rarely, patients with borderline resectable intrahepatic cholangiocarcinoma will have a sufficient response to chemotherapy to permit later resection, and, in such cases, starting with chemotherapy and then restaging to evaluate resectability is appropriate.⁵⁴ A single-center, retrospective analysis including 186 patients by Le Roy et al evaluated survival in patients with locally advanced, unresectable intrahepatic cholangiocarcinoma who received primary chemotherapy, followed by surgery in those with secondary resectability.⁵⁴ After a median of 6 cycles of chemotherapy, 53% of patients achieved resectability and underwent surgery with curative intent. These patients had similar short- and long-term results compared to patients with initially resectable intrahepatic cholangiocarcinoma who had surgery alone, with median OS reaching 24 months.⁵⁴

Ablative radiotherapy is an additional option for localized inoperable intrahepatic cholangiocarcinoma. Tao and colleagues evaluated 79 consecutive patients with inoperable intrahepatic cholangiocarcinoma treated with definitive RT.⁵⁵ Median tumor size was 7.9 cm and 89% of patients received chemotherapy before RT. Median OS was 30 months and 3-year OS was 44%. Radiation dose was the single most important prognostic factor, and higher doses correlated with improved local control and OS. A biologic equivalent dose (BED) greater than 80.5 Gy was identified as an ablative dose of RT for large intrahepatic cholangiocarcinomas. The 3-year OS for patients receiving BED greater than 80.5 Gy was 73% versus 38% for those receiving lower doses.

Case Continued

The patient is deemed to have resectable disease and undergoes surgical resection followed by adjuvant capecitabine for 8 cycles. Unfortunately, after 1 year, follow-up imaging identifies bilateral enlarging lung nodules. Biopsy is performed and confirms metastatic cholangiocarcinoma.

• What is the treatment for metastatic BTC?

The prognosis of patients with advanced BTC is poor and OS for those undergoing supportive care alone is short. A benefit of chemotherapy over best supportive care for cholangiocarcinoma was demonstrated in an early phase 3 trial that randomly assigned 90 patients with advanced pancreatic or biliary cancer (37 with bile duct cancer) to receive either fluorouracil (FU) -based systemic chemotherapy or best supportive care. Results showed that chemotherapy significantly improved OS (6 months versus 2.5 months).⁵⁶ Chemotherapy is also beneficial for patients with unresectable gallbladder cancer. In a single-center randomized study including 81 patients with unresectable gallbladder cancer, gemcitabine and oxaliplatin (GEMOX) improved progression-free survival (PFS) and OS compared to best supportive care.⁵⁷ Treatment for metastatic cholangiocarcinoma and gallbladder cancer follows the same algorithm.

In 2010, cisplatin plus gemcitabine was established as a reference regimen for first-line therapy by the ABC-02 study, in which 410 patients with locally advanced or metastatic bile duct, gallbladder, or ampullary cancer were randomly assigned to 6 courses of cisplatin (25 mg/m²) plus gemcitabine (1000 mg/m² on days 1 and 8, every 21 days) or gemcitabine alone (1000 mg/m² days 1, 8, 15, every 28 days).⁵⁸ OS was significantly greater with combination therapy (11.7 versus 8.1 months), and PFS also favored the combination arm (8 versus 5 months). Toxicity was comparable in both groups, with the exception of significantly higher rates of grade 3 or 4 neutropenia with gemcitabine plus cisplatin (25% versus 17%), and higher rates of grade 3 or 4 abnormal liver function with gemcitabine alone (27% versus 17%). Most quality-of-life scales showed a trend favoring combined therapy.⁵⁸ A smaller, identically designed Japanese phase 3 randomized trial achieved similar results, demonstrating greater OS with cisplatin plus gemcitabine compared to gemcitabine alone (11.2 versus 7.7 months).⁵⁹

The gemcitabine plus cisplatin combination has not been directly compared with other gemcitabine combinations in phase 3 trials. A pooled analysis of 104 trials of a variety of chemotherapy regimens in advanced biliary cancer concluded that the gemcitabine plus cisplatin regimen offered the highest rates of objective response and tumor control compared with either gemcitabine-free or cisplatin-free regimens.⁶⁰ However, this did not translate into significant benefit in terms of either time to tumor progression or median OS. It is important to note that this analysis did not include results of the subsequent ABC-02 trial.

There is no standard treatment for patients with cholangiocarcinoma for whom first-line gemcitabine-based therapy fails. There are no completed prospective phase 3 trials supporting the use of second-line chemotherapy after failure of first-line chemotherapy in BTC, and the selection of candidates for second-line therapy as well as the optimal regimen are not established.⁶¹ The ongoing phase 2 multicenter ABC-06 trial is evaluating oxaliplatin plus short-term infusional FU and leucovorin (FOLFOX) versus best supportive care for second-line therapy. In a systematic review including 23 studies (14 phase 2 clinical trials and 9 retrospective studies) with 761 patients with BTC, the median OS was 7.2 months.

The optimal selection of candidates for second-line chemotherapy is not established. Two independent studies suggest that patients who have a good performance status (0 or 1), disease control with the first-line chemotherapy, low CA 19-9 level, and possibly previous surgery on their primary tumor, have the longest survival with second-line chemotherapy. However, whether these characteristics predict for chemotherapy responsiveness or more favorable biologic behavior is not clear.^62,63 No particular regimen has proved superior to any other, and the choice of second-line regimen remains empiric.

For patients with adequate performance status, examples of other conventional chemotherapy regimens with demonstrated activity that could be considered for second-line therapy include: FOLFOX or capecitabine, gemcitabine plus capecitabine, capecitabine plus cisplatin, or irinotecan plus short-term infusional FU and leucovorin (FOLFIRI) with or without bevacizumab.⁶⁴ For selected patients, second-line molecularly targeted therapy using erlotinib plus bevacizumab may be considered. However, this regimen is very costly.⁶⁴ Examples of other regimens with demonstrated activity in phase 2 trials include GEMOX, gemcitabine plus fluoropyrimidine, and fluoropyrimidine plus oxaliplatin or cisplatin.⁶⁴

There is promising data from studies of targeted therapy for specific molecular subgroups. A recent phase 2 trial evaluated the activity of BGJ398, an orally bioavailable, selective, ATP-competitive pan inhibitor of human fibroblast growth factor receptor (FGFR) kinase, in patients with FGFR-altered advanced cholangiocarcinoma.⁶⁵ The overall response rate was 14.8% (18.8% FGFR2 fusions only) and disease control rate was 75.4% (83.3% FGFR2 fusions only). All responsive tumors contained FGFR2 fusions. Adverse events were manageable, and grade 3 or 4 treatment-related adverse events occurred in 25 patients (41%). Those included hyperphosphatemia, stomatitis, and palmar-plantar erythrodysesthesia. Javle and colleagues also identified HER2/neu blockade as a promising treatment strategy for gallbladder cancer patients with this gene amplification.⁶⁶ This retrospective analysis included 9 patients with gallbladder cancer and 5 patients with cholangiocarcinoma who received HER2/neu-directed therapy (trastuzumab, lapatinib, or pertuzumab). In the gallbladder cancer group, HER2/neu gene amplification or overexpression was detected in 8 cases. These patients experienced disease stability (n = 3), partial response (n = 4), or complete response (n = 1) with HER2/neu–directed therapy. Median duration of response was 40 weeks. The cholangiocarcinoma cases treated in this series had no radiological responses despite HER2/neu mutations or amplification.

 

Gallbladder Cancer

Case Presentation

A 57-year-old woman from Chile presents with a 3-week history of progressive right upper quadrant abdominal pain. She denies nausea, vomiting, dysphagia, odynophagia, alterations in bowel habits, fever, or jaundice. Her past medical history is significant for obesity and hypertension. She has no history of smoking, alcohol, or illicit drug use. Laboratory studies show marked leukocytosis (23,800/µL) with neutrophilia (91%). Liver function test results are within normal limits. Ultrasound of the abdomen reveals gallbladder wall thickening and cholelithiasis.

The patient undergoes an uneventful laparoscopic cholecystectomy and is discharged from the hospital after 48 hours. Pathology report reveals a moderately differentiated adenocarcinoma of the gallbladder invading the perimuscular connective tissue (T2). No lymph nodes are identified in the specimen.

• What is the appropriate surgical management of gallbladder cancer?

Gallbladder cancer can be diagnosed preoperatively or can be found incidentally by intraoperative or pathological findings. In one large series, gallbladder cancer was incidentally found during 0.25% of laparoscopic cholecystectomies.⁶⁷

For patients who are diagnosed with previously unsuspected gallbladder cancer by pathology findings, the extent of tumor invasion (T stage) indicates the need for re-resection (Figure 3).⁶⁴

Surgical exploration and re-resection are recommended if disease is stage T1b (involving the muscular layer) or higher (Table 2).^64,68 In these patients, re-resection is associated with significantly improved OS.⁶⁸ Patients found to have incidental T1a tumors with negative margins are generally felt to be curable with simple cholecystectomy, and re-resection for T1a tumors does not appear to provide an OS benefit.^69,70 The majority of patients diagnosed under these circumstances have T2 or higher disease, and will ultimately require additional surgical exploration.⁷¹ A German series that analyzed 439 cases of incidentally diagnosed gallbladder cancer demonstrated that positive lymph nodes were found in 21% and 44% of the re-resected patients with T2 and T3 tumors, respectively.⁷¹ There is retrospective data suggesting that the optimal timing of the reoperation is between 4 and 8 weeks following the initial cholecystectomy.⁷² This interval is believed to be ideal, as it allows for reduced inflammation and does not permit too much time for disease dissemination.⁷²

Alternatively, when gallbladder cancer is documented or suspected preoperatively, adequate imaging is important to identify patients with absolute contraindications to resection. Contraindications to surgery include metastasis, extensive involvement of the hepatoduodenal ligament, encasement of major vessels, and involvement of celiac, peripancreatic, periduodenal, or superior mesenteric nodes.⁷² Notwithstanding, retrospective series suggest individual patients may benefit, and surgical indications in advanced disease should be determined on an individual basis.⁷³ Staging imaging should be obtained using multiphasic contrast-enhanced CT or MRI of the chest, abdomen, and pelvis. PET-scan can be used in selected cases where metastatic disease is suspected.⁶⁴ Laparoscopic diagnostic staging should be considered prior to resection.⁶⁴ This procedure can identify previously unknown contraindications to tumor resection in as much as 23% of patients, and the yield is significantly higher in locally advanced tumors.⁷³

Patients with a diagnosis of potentially resectable, localized gallbladder cancer should be offered definitive surgery. Extended cholecystectomy is recommended for patients stage T2 or above. This procedure involves wedge resection of the gallbladder bed or a segmentectomy IVb/V and lymph node dissection, which should include the cystic duct, common bile duct, posterior superior pancreaticoduodenal lymph nodes, and those around the hepatoduodenal ligament.⁷² Bile duct excision should be performed if there is malignant involvement.⁶⁴

Conclusion

BTCs are anatomically and clinically heterogeneous tumors. Prognostic factors and therapeutic approaches for BTCs differ depending upon their location in the biliary tree and, accordingly, TNM classification systems for intrahepatic, hilar, and distal cholangiocarcinoma and gallbladder cancer have been separated. Surgical resection is the only potentially curative treatment for localized BTC. However, recurrence following complete resection is a primary limitation for cure, which provides a rationale for the use of adjuvant therapy. The prognosis of patients with advanced BTC is poor and OS for those undergoing supportive care alone is short. Multiple randomized clinical trials have demonstrated a benefit of chemotherapy for metastatic disease. For patients with adequate performance status, second-line therapy can be considered, and data from studies that evaluated targeted therapy for specific molecular subgroups is promising.

Introduction

Biliary tract carcinoma (BTC) is the term for a heterogeneous group of rare gastrointestinal malignancies¹ that includes both carcinoma arising from the gallbladder and cholangiocarcinoma, which refers to diverse aggressive epithelial cancers involving the intrahepatic, perihilar, and distal biliary tree.^1–3 In this article, we review the epidemiology, clinical features, and diagnostic approach to BTC, with a focus on current evidence-based treatment strategies for localized, locally advanced, and metastatic BTC.

Epidemiology

In the United States, BTC is rare and accounts for approximately 4% of all gastrointestinal malignancies, with an estimated 6000 to 7000 cases of carcinoma of the gallbladder and 3000 to 4000 cases of carcinoma of the bile duct diagnosed annually.⁴ Among women, there is a 26-fold variation in BTC mortality worldwide, ranging from 0.8 deaths per 100,000 in South Africa to 21.2 per 100,000 in Chile.^1,5 Interestingly, for American Indians in New Mexico, gallbladder cancer mortality rates (8.9 per 100,000) surpass those for breast and pancreatic cancers.⁶ The incidence of anatomical cholangiocarcinoma subtypes also varies regionally, reflecting disparities in genetic and environmental predisposing factors.^2,7 In a large, single-center study in the United States, intrahepatic cholangiocarcinoma accounted for less than 10% of cases, perihilar accounted for 50%, and distal accounted for the remaining 40%.⁸ Importantly, intrahepatic cholangiocarcinoma is the second most common primary malignancy of the liver, and its incidence seems to be rising in many western countries. In the United States, there has been an estimated 128% rise over the past 40 years.^4,9

BTC is associated with high mortality rates.¹⁰ Median overall survival (OS) for cholangiocarcinoma is 20 to 28 months and 5-year survival is around 25%.¹⁰ Most cholangiocarcinomas are diagnosed at advanced stages with unresectable tumors.¹⁰ Furthermore, outcomes following resection with curative intent are poor—median disease-free survival (DFS) of 12 to 36 months has been reported.^11,12 Patients with intrahepatic disease have a better prognosis when compared with patients who have extrahepatic tumors.¹² Gallbladder cancer, likewise, carries a poor overall prognosis; median OS is 32 months and 5-year survival is as low as 13%.⁶

Risk factors for BTC include intrinsic and extrinsic elements.⁶ Incidence of BTC increases with age, and diagnosis typically occurs in the sixth to eighth decade of life.^5,6,13 In contrast to gallbladder cancer, the incidence of cholangiocarcinoma is slightly higher in men.⁹ Obesity, diabetes, and consumption of sweetened drinks also increase the risk for BTC.^14–16 Cholelithiasis is the most prevalent risk factor for gallbladder cancer, and the risk is greater for larger stones.⁵ Around 1 in 5 patients with porcelain gallbladder will develop gallbladder carcinoma.¹⁷ Primary sclerosing cholangitis (PSC), chronic calculi of the bile duct, choledochal cysts, cirrhosis, hepatitis C, and liver fluke infections are well established risk factors for cholangiocarcinoma.^7,12,18 PSC is one of the best described entities among these predisposing conditions. Lifetime prevalence of cholangiocarcinoma among patients with PSC ranges from 5% to 10%.^18,19 These patients also present at a younger age; in one series, the median age at diagnosis for BTC arising from PSC was 39 years.¹⁸ It is important to recognize, however, that in most patients diagnosed with cholangiocarcinoma, no predisposing factors are identified.⁸

Diagnosis

Clinical Presentation

Clinical presentation of BTC depends upon anatomic location.²⁰ Patients with early invasive gallbladder cancer are most often asymptomatic.²¹ When symptoms occur, they may be nonspecific and mimic cholelithiasis.²¹ The most common clinical presentations include jaundice, weight loss, and abdominal pain.²¹ Prior to widespread availability of imaging studies, the preoperative diagnosis rate for gallbladder cancer was as low as 10%.²² However, the accuracy of computed tomography (CT) has changed this scenario, with sensitivity ranging from 73% to 87% and specificity from 88% to 100%.²¹ As a result of its silent clinical character, cholangiocarcinoma is frequently difficult to diagnose.²³ Perihilar and distal cholangiocarcinoma characteristically present with signs of biliary obstruction, and imaging and laboratory data can corroborate the presence of cholestasis.²⁴ On examination, patients with extrahepatic cholangiocarcinoma may present with jaundice, hepatomegaly, and a palpable right upper quadrant mass.²⁵ A palpable gallbladder (Courvoisier sign) can also be present.²⁵ Intrahepatic cholangiocarcinoma presents differently, and patients are less likely to be jaundiced.²³ Typical clinical features are nonspecific and include dull right upper quadrant pain, weight loss, and an elevated alkaline phosphatase level.²³ Alternatively, asymptomatic patients can present with incidentally detected lesions, when imaging is obtained as part of the workup for other causes or during screening for hepatocellular carcinoma in patients with viral hepatitis or cirrhosis.^23,26 Uncommonly, BTC patients present because of signs or symptoms related to metastatic disease or evidence of metastatic disease on imaging.

 

Pathology and Grading

The majority of BTCs are adenocarcinomas, corresponding to 90% of cholangiocarcinomas and 99% of gallbladder cancers.^27,28 They are graded as well, moderately, or poorly differentiated.² Adenosquamous and squamous cell carcinoma are responsible for most of the remaining cases.^2,29 Cholangiocarcinomas are divided into 3 types, defined by the Liver Cancer Study Group of Japan: (1) mass-forming, (2) periductal-infiltrating, and (3) intraductal-growing.^30,31 Mass-forming intrahepatic cholangiocarcinomas are characterized morphologically by a homogeneous gray-yellow mass with frequent satellite nodules and irregular but well-defined margins.^17,30 Central necrosis and fibrosis are also common.³⁰ In the periductal-infiltrating type, tumor typically grows along the bile duct wall without mass formation, resulting in concentric mural thickening and proximal biliary dilation.³⁰ Intraductal-growing papillary cholangiocarcinoma is characterized by the presence of intraluminal papillary or tubular polypoid tumors of the intra- or extrahepatic bile ducts, with partial obstruction and proximal biliary dilation.³⁰

Cholangiocarcinoma

Case Presentation

A previously healthy 59-year-old man presents to his primary care physician with a 3-month history of dull right upper quadrant pain associated with weight loss. The patient is markedly cachectic and abdominal examination reveals upper quadrant tenderness. Laboratory exams are significant for elevated alkaline phosphatase (500 U/L; reference range 45–115 U/L), cancer antigen 19-9 (CA 19-9, 73 U/mL; reference range ≤ 37 U/mL), and carcinoembryonic antigen (CEA , 20 ng/mL; reference range for nonsmokers ≤ 3.0 ng/mL). Aspartate aminotransferase, alanine aminotransferase, total bilirubin, and coagulation studies are within normal range. Ultrasound demonstrates a homogeneous mass with irregular borders in the right lobe of the liver. Triphasic contrast-enhanced CT scan demonstrates a tumor with ragged rim enhancement at the periphery, and portal venous phase shows gradual centripetal enhancement of the tumor with capsular retraction. No abdominal lymph nodes or extrahepatic tumors are noted (Figure 1, Image A).

• What are the next diagnostic steps?

The most critical differential diagnosis of solid liver mass in patients without cirrhosis is cholangiocarcinoma and metastases from another primary site.³² Alternatively, when an intrahepatic lesion is noted on an imaging study in the setting of cirrhosis, the next diagnostic step is differentiation between cholangiocarcinoma and hepatocellular carcinoma (HCC).³² Triphasic contrast-enhanced CT and dynamic magnetic resonance imaging (MRI) are key diagnostic procedures.^32,33 In the appropriate setting, classical imaging features in the arterial phase with washout in portal venous or delayed phase can be diagnostic of HCC and may obviate the need for a biopsy (Figure 2).

Typical radiographic features of cholangiocarcinoma include a hypodense hepatic lesion that can be either well-defined or infiltrative and is frequently associated with biliary dilatation (Figure 1, Image A).³³ The dense fibrotic nature of the tumor may cause capsular retraction, which is seen in up to 20% of cases.¹⁷ This finding is highly suggestive of cholangiocarcinoma and is rarely present in HCC.³³ Following contrast administration, there is peripheral (rim) enhancement throughout both arterial and venous phases.^32–34 However, these classic features were present in only 70% of cases in one study.³⁵ Although intrahepatic cholangiocarcinomas are most commonly hypovascular, small mass-forming intrahepatic cholangiocarcinomas can often be arterially hyperenhancing and mimic HCC.³³ Tumor enhancement on delayed CT imaging has been correlated with survival. Asayama et al demonstrated that tumors that exhibited delayed enhancement on CT in more than two-thirds of their volume were associated with a worse prognosis.³⁶

Patients without cirrhosis who present with a localized lesion of the liver should undergo extensive evaluation for a primary cancer site.³⁷ CT of the chest, abdomen, and pelvis with contrast should be obtained.³⁷ Additionally, mammogram and endoscopic evaluation with esophagogastroduodenoscopy (EGD) and colonoscopy should be included in the work-up.³⁷

Preoperative tumor markers are also included in the work-up. All patients with a solid liver lesion should have serum alpha-fetoprotein (AFP) levels checked. AFP is a serum glycoprotein recognized as a marker for HCC and is reported to detect preclinical HCC.³⁸ However, serum concentrations are normal in up to 40% of small HCCs.³⁸ Although no specific marker for cholangiocarcinoma has yet been identified, the presence of certain tumor markers in the serum of patients may be of diagnostic value, especially in patients with PSC. CA 19-9 and CEA are the best studied. Elevated levels of CA 19-9 prior to treatment are associated with a poorer prognosis, and CA 19-9 concentrations greater than 1000 U/mL are consistent with advanced disease.^39,40 One large series evaluated the diagnostic value of serum CEA levels in 333 patients with PSC, 13% of whom were diagnosed with cholangiocarcinoma.³⁴ A serum CEA level greater than 5.2 ng/mL had a sensitivity of 68.0% and specificity of 81.5%.³⁸

If a biopsy is obtained, appropriate immunohistochemistry (IHC) can facilitate the diagnosis. BTC is strongly positive for CK-7 and CK-19.⁴¹ CK-7 positivity is not specific and is also common among metastatic cancers of the lung and breast; therefore, in some cases cholangiocarcinoma may be a diagnosis of exclusion. Immunostaining for monoclonal CEA is diffusely positive in up to 75% of cases.⁴¹ An IHC panel consisting of Hep Par-1, arginase-1, monoclonal CEA, CK-7, CK-20, TTF-1, MOC-31, and CDX-2 has been proposed to optimize the differential diagnosis of HCC, metastatic adenocarcinoma, and cholangiocarcinoma.⁴¹

 

Case Continued

CT of the chest, abdomen, and pelvis reveals no concerns for metastasis and no evidence of primary cancer elsewhere. EGD and colonoscopy are clear. AFP levels are within normal limits (2 ng/mL). Biopsy is performed and demonstrates adenocarcinoma. IHC studies demonstrate cells positive for monoclonal CEA, CK-7, CK-19, and MOC-31, and negative for Napsin A, TTF-1, and CK-20.

• How is cholangiocarcinoma staged and classified?

The purpose of the staging system is to provide information on prognosis and guidance for therapy. Prognostic factors and the therapeutic approaches for BTC differ depending upon their location in the biliary tree. Accordingly, TNM classification systems for intrahepatic, hilar, and distal cholangiocarcinoma and gallbladder cancer have been separated (Table 1 and Table 2).²³

For all the subtypes, T stage is mainly dependent upon invasion of adjacent structures rather than size. For perihilar tumors, N category has been reclassified in the newest version of the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) staging system based upon the number of involved lymph nodes rather than location.

The Bismuth-Corlette classification is used to further classify perihilar cholangiocarcinoma according to patterns of hepatic duct involvement. Type I tumors are located below the confluence of the left and right hepatic ducts.⁴² Type II reach the confluence of the hepatic ducts.⁴² Type III occlude the common hepatic duct and either the right or left hepatic duct (IIIa and IIIb, respectively).⁴² Finally, type IV are multicentric, or involve the confluence and both the right and left hepatic ducts.⁴² Tumors that involve the common hepatic duct bifurcation are named Klatskin tumors.⁴²

• What is the first-line treatment for localized cholangiocarcinomas?

Surgical resection is the only potentially curative treatment for localized cholangiocarcinoma, although fewer than 20% of patients are suitable for curative treatment, due to the presence of advanced disease at diagnosis.^43,44 Available evidence supports the recommendation that resection with negative margins, regardless of extent, should be the goal of therapy for patients with potentially resectable disease.⁴⁴ Extensive hepatic resections are often necessary to achieve clear margins since the majority of patients present with large masses. Substantial evidence corroborates that R0 resection is associated with better survival, whereas the benefit of wide compared to narrow (< 5–10 mm) margins is unclear.⁴⁵ A recent analysis of 96 patients suggests that the proximal resection margin has more prognostic implications than distal margins.⁴⁵

Surgical options and resectability criteria depend upon tumor location. Extent of tumor in the bile duct is one of the most important factors that determine resectability.¹⁷ Although multifocal liver tumors (including satellite lesions), lymph node metastases to the porta hepatis, and distant metastases are considered relative contraindications to surgery, surgical approaches can be considered in selected patients.⁴³ Patient selection for surgery is facilitated by careful preoperative staging, which may include laparoscopy. Laparoscopic staging prior to resection may prevent unnecessary laparotomy in 30% to 45% of patients.^42,46

• Is there a role for adjuvant treatment?

Recurrence following complete resection is a primary limitation for cure in BTC, which provides a rationale for the use of adjuvant therapy.^47,48 In a sample of 79 patients with extrahepatic cholangiocarcinoma who underwent curative resection, the cumulative recurrence rate after 4 years was 56%.⁴⁷ Initial recurrence at a distant site occurs in 40% to 50% of patients.⁴⁸

Lymphovascular and perineural invasion, lymph node metastasis, and tumor size ≥ 5 cm have been reported as independent predictors of recurrence and mortality following resection.⁴⁹ A 2017 meta-analysis which included 30 studies involving more than 22,499 patients reported a 41% reduction in the risk of death with adjuvant chemotherapy, which translated to a mean OS benefit of 4 months in an unselected population.⁴⁹ Moreover, this study revealed inferior OS in patients given adjuvant radiation therapy (RT) in combination with chemotherapy.⁴⁹ These results are in line with the previous meta-analysis by Horgan et al, which demonstrated that adjuvant RT seems to benefit only patients with R1 resections, with a possible detrimental effect in R0 disease.⁵⁰ Therefore, adjuvant chemoradiation cannot be viewed as a standard practice following R0 resection, and should be reserved for those patients with positive margins (R1/ 2) to reduce local progression.

In the phase 3 BILCAP trial presented at ASCO 2017, 447 patients with completely resected cholangiocarcinoma or gallbladder cancer with adequate biliary drainage and Eastern Cooperative Oncology Group (ECOG) performance score ≤ 2 were randomly assigned to observation or capecitabine (1250 mg/m² twice daily for days 1–14 every 21 days for 8 cycles).⁵¹ Surgical treatment achieved R0 resection in 62% of patients and 46% were node-negative. Median OS was 51 months for the capecitabine group and 36 months for the control arm (hazard ratio [HR] 0.80, 95% CI 0.63 to 1.04, P = 0.097). Analyses with adjustment for nodal status, grade of disease, and gender indicated a HR of 0.71 (P < 0.01). Median DFS was 25 months versus 18 months favoring the capecitabine group, and rates of grade 3 or 4 toxicity were less than anticipated. Following the results of this trial, adjuvant capecitabine should become the new standard of care.

 

• What is the treatment for locally advanced cholangiocarcinoma?

The optimal approach to patients with locally advanced unresectable cholangiocarcinoma has not been established. The prognosis for patients with either locally unresectable or locally recurrent disease is typically measured in months. Goals of palliative therapy are relief of symptoms and improvement in quality of life, and there is no role for surgical debulking.

Liver transplantation is a potentially curative option for selected patients with hilar or intrahepatic cholangiocarcinoma. Patients with lymph node-negative, non-disseminated, locally advanced hilar cholangiocarcinomas have 5-year survival rates ranging from 25% to 42% following transplantation.⁵² Retrospective data suggests that neoadjuvant chemoradiation followed by liver transplantation is highly effective for selected patients with hilar cholangiocarcinoma.⁵² However, these results require confirmation from prospective clinical evidence. It is important to recognize that liver transplantation plays no role in the management of distal cholangiocarcinoma or gallbladder cancer.

Rarely, patients with borderline resectable intrahepatic cholangiocarcinoma will have a sufficient response to chemotherapy to permit later resection, and, in such cases, starting with chemotherapy and then restaging to evaluate resectability is appropriate.⁵⁴ A single-center, retrospective analysis including 186 patients by Le Roy et al evaluated survival in patients with locally advanced, unresectable intrahepatic cholangiocarcinoma who received primary chemotherapy, followed by surgery in those with secondary resectability.⁵⁴ After a median of 6 cycles of chemotherapy, 53% of patients achieved resectability and underwent surgery with curative intent. These patients had similar short- and long-term results compared to patients with initially resectable intrahepatic cholangiocarcinoma who had surgery alone, with median OS reaching 24 months.⁵⁴

Ablative radiotherapy is an additional option for localized inoperable intrahepatic cholangiocarcinoma. Tao and colleagues evaluated 79 consecutive patients with inoperable intrahepatic cholangiocarcinoma treated with definitive RT.⁵⁵ Median tumor size was 7.9 cm and 89% of patients received chemotherapy before RT. Median OS was 30 months and 3-year OS was 44%. Radiation dose was the single most important prognostic factor, and higher doses correlated with improved local control and OS. A biologic equivalent dose (BED) greater than 80.5 Gy was identified as an ablative dose of RT for large intrahepatic cholangiocarcinomas. The 3-year OS for patients receiving BED greater than 80.5 Gy was 73% versus 38% for those receiving lower doses.

Case Continued

The patient is deemed to have resectable disease and undergoes surgical resection followed by adjuvant capecitabine for 8 cycles. Unfortunately, after 1 year, follow-up imaging identifies bilateral enlarging lung nodules. Biopsy is performed and confirms metastatic cholangiocarcinoma.

• What is the treatment for metastatic BTC?

The prognosis of patients with advanced BTC is poor and OS for those undergoing supportive care alone is short. A benefit of chemotherapy over best supportive care for cholangiocarcinoma was demonstrated in an early phase 3 trial that randomly assigned 90 patients with advanced pancreatic or biliary cancer (37 with bile duct cancer) to receive either fluorouracil (FU) -based systemic chemotherapy or best supportive care. Results showed that chemotherapy significantly improved OS (6 months versus 2.5 months).⁵⁶ Chemotherapy is also beneficial for patients with unresectable gallbladder cancer. In a single-center randomized study including 81 patients with unresectable gallbladder cancer, gemcitabine and oxaliplatin (GEMOX) improved progression-free survival (PFS) and OS compared to best supportive care.⁵⁷ Treatment for metastatic cholangiocarcinoma and gallbladder cancer follows the same algorithm.

In 2010, cisplatin plus gemcitabine was established as a reference regimen for first-line therapy by the ABC-02 study, in which 410 patients with locally advanced or metastatic bile duct, gallbladder, or ampullary cancer were randomly assigned to 6 courses of cisplatin (25 mg/m²) plus gemcitabine (1000 mg/m² on days 1 and 8, every 21 days) or gemcitabine alone (1000 mg/m² days 1, 8, 15, every 28 days).⁵⁸ OS was significantly greater with combination therapy (11.7 versus 8.1 months), and PFS also favored the combination arm (8 versus 5 months). Toxicity was comparable in both groups, with the exception of significantly higher rates of grade 3 or 4 neutropenia with gemcitabine plus cisplatin (25% versus 17%), and higher rates of grade 3 or 4 abnormal liver function with gemcitabine alone (27% versus 17%). Most quality-of-life scales showed a trend favoring combined therapy.⁵⁸ A smaller, identically designed Japanese phase 3 randomized trial achieved similar results, demonstrating greater OS with cisplatin plus gemcitabine compared to gemcitabine alone (11.2 versus 7.7 months).⁵⁹

The gemcitabine plus cisplatin combination has not been directly compared with other gemcitabine combinations in phase 3 trials. A pooled analysis of 104 trials of a variety of chemotherapy regimens in advanced biliary cancer concluded that the gemcitabine plus cisplatin regimen offered the highest rates of objective response and tumor control compared with either gemcitabine-free or cisplatin-free regimens.⁶⁰ However, this did not translate into significant benefit in terms of either time to tumor progression or median OS. It is important to note that this analysis did not include results of the subsequent ABC-02 trial.

There is no standard treatment for patients with cholangiocarcinoma for whom first-line gemcitabine-based therapy fails. There are no completed prospective phase 3 trials supporting the use of second-line chemotherapy after failure of first-line chemotherapy in BTC, and the selection of candidates for second-line therapy as well as the optimal regimen are not established.⁶¹ The ongoing phase 2 multicenter ABC-06 trial is evaluating oxaliplatin plus short-term infusional FU and leucovorin (FOLFOX) versus best supportive care for second-line therapy. In a systematic review including 23 studies (14 phase 2 clinical trials and 9 retrospective studies) with 761 patients with BTC, the median OS was 7.2 months.

The optimal selection of candidates for second-line chemotherapy is not established. Two independent studies suggest that patients who have a good performance status (0 or 1), disease control with the first-line chemotherapy, low CA 19-9 level, and possibly previous surgery on their primary tumor, have the longest survival with second-line chemotherapy. However, whether these characteristics predict for chemotherapy responsiveness or more favorable biologic behavior is not clear.^62,63 No particular regimen has proved superior to any other, and the choice of second-line regimen remains empiric.

For patients with adequate performance status, examples of other conventional chemotherapy regimens with demonstrated activity that could be considered for second-line therapy include: FOLFOX or capecitabine, gemcitabine plus capecitabine, capecitabine plus cisplatin, or irinotecan plus short-term infusional FU and leucovorin (FOLFIRI) with or without bevacizumab.⁶⁴ For selected patients, second-line molecularly targeted therapy using erlotinib plus bevacizumab may be considered. However, this regimen is very costly.⁶⁴ Examples of other regimens with demonstrated activity in phase 2 trials include GEMOX, gemcitabine plus fluoropyrimidine, and fluoropyrimidine plus oxaliplatin or cisplatin.⁶⁴

There is promising data from studies of targeted therapy for specific molecular subgroups. A recent phase 2 trial evaluated the activity of BGJ398, an orally bioavailable, selective, ATP-competitive pan inhibitor of human fibroblast growth factor receptor (FGFR) kinase, in patients with FGFR-altered advanced cholangiocarcinoma.⁶⁵ The overall response rate was 14.8% (18.8% FGFR2 fusions only) and disease control rate was 75.4% (83.3% FGFR2 fusions only). All responsive tumors contained FGFR2 fusions. Adverse events were manageable, and grade 3 or 4 treatment-related adverse events occurred in 25 patients (41%). Those included hyperphosphatemia, stomatitis, and palmar-plantar erythrodysesthesia. Javle and colleagues also identified HER2/neu blockade as a promising treatment strategy for gallbladder cancer patients with this gene amplification.⁶⁶ This retrospective analysis included 9 patients with gallbladder cancer and 5 patients with cholangiocarcinoma who received HER2/neu-directed therapy (trastuzumab, lapatinib, or pertuzumab). In the gallbladder cancer group, HER2/neu gene amplification or overexpression was detected in 8 cases. These patients experienced disease stability (n = 3), partial response (n = 4), or complete response (n = 1) with HER2/neu–directed therapy. Median duration of response was 40 weeks. The cholangiocarcinoma cases treated in this series had no radiological responses despite HER2/neu mutations or amplification.

 

Gallbladder Cancer

Case Presentation

A 57-year-old woman from Chile presents with a 3-week history of progressive right upper quadrant abdominal pain. She denies nausea, vomiting, dysphagia, odynophagia, alterations in bowel habits, fever, or jaundice. Her past medical history is significant for obesity and hypertension. She has no history of smoking, alcohol, or illicit drug use. Laboratory studies show marked leukocytosis (23,800/µL) with neutrophilia (91%). Liver function test results are within normal limits. Ultrasound of the abdomen reveals gallbladder wall thickening and cholelithiasis.

The patient undergoes an uneventful laparoscopic cholecystectomy and is discharged from the hospital after 48 hours. Pathology report reveals a moderately differentiated adenocarcinoma of the gallbladder invading the perimuscular connective tissue (T2). No lymph nodes are identified in the specimen.

• What is the appropriate surgical management of gallbladder cancer?

Gallbladder cancer can be diagnosed preoperatively or can be found incidentally by intraoperative or pathological findings. In one large series, gallbladder cancer was incidentally found during 0.25% of laparoscopic cholecystectomies.⁶⁷

For patients who are diagnosed with previously unsuspected gallbladder cancer by pathology findings, the extent of tumor invasion (T stage) indicates the need for re-resection (Figure 3).⁶⁴

Surgical exploration and re-resection are recommended if disease is stage T1b (involving the muscular layer) or higher (Table 2).^64,68 In these patients, re-resection is associated with significantly improved OS.⁶⁸ Patients found to have incidental T1a tumors with negative margins are generally felt to be curable with simple cholecystectomy, and re-resection for T1a tumors does not appear to provide an OS benefit.^69,70 The majority of patients diagnosed under these circumstances have T2 or higher disease, and will ultimately require additional surgical exploration.⁷¹ A German series that analyzed 439 cases of incidentally diagnosed gallbladder cancer demonstrated that positive lymph nodes were found in 21% and 44% of the re-resected patients with T2 and T3 tumors, respectively.⁷¹ There is retrospective data suggesting that the optimal timing of the reoperation is between 4 and 8 weeks following the initial cholecystectomy.⁷² This interval is believed to be ideal, as it allows for reduced inflammation and does not permit too much time for disease dissemination.⁷²

Alternatively, when gallbladder cancer is documented or suspected preoperatively, adequate imaging is important to identify patients with absolute contraindications to resection. Contraindications to surgery include metastasis, extensive involvement of the hepatoduodenal ligament, encasement of major vessels, and involvement of celiac, peripancreatic, periduodenal, or superior mesenteric nodes.⁷² Notwithstanding, retrospective series suggest individual patients may benefit, and surgical indications in advanced disease should be determined on an individual basis.⁷³ Staging imaging should be obtained using multiphasic contrast-enhanced CT or MRI of the chest, abdomen, and pelvis. PET-scan can be used in selected cases where metastatic disease is suspected.⁶⁴ Laparoscopic diagnostic staging should be considered prior to resection.⁶⁴ This procedure can identify previously unknown contraindications to tumor resection in as much as 23% of patients, and the yield is significantly higher in locally advanced tumors.⁷³

Patients with a diagnosis of potentially resectable, localized gallbladder cancer should be offered definitive surgery. Extended cholecystectomy is recommended for patients stage T2 or above. This procedure involves wedge resection of the gallbladder bed or a segmentectomy IVb/V and lymph node dissection, which should include the cystic duct, common bile duct, posterior superior pancreaticoduodenal lymph nodes, and those around the hepatoduodenal ligament.⁷² Bile duct excision should be performed if there is malignant involvement.⁶⁴

Conclusion

BTCs are anatomically and clinically heterogeneous tumors. Prognostic factors and therapeutic approaches for BTCs differ depending upon their location in the biliary tree and, accordingly, TNM classification systems for intrahepatic, hilar, and distal cholangiocarcinoma and gallbladder cancer have been separated. Surgical resection is the only potentially curative treatment for localized BTC. However, recurrence following complete resection is a primary limitation for cure, which provides a rationale for the use of adjuvant therapy. The prognosis of patients with advanced BTC is poor and OS for those undergoing supportive care alone is short. Multiple randomized clinical trials have demonstrated a benefit of chemotherapy for metastatic disease. For patients with adequate performance status, second-line therapy can be considered, and data from studies that evaluated targeted therapy for specific molecular subgroups is promising.

Introduction

Biliary tract carcinoma (BTC) is the term for a heterogeneous group of rare gastrointestinal malignancies¹ that includes both carcinoma arising from the gallbladder and cholangiocarcinoma, which refers to diverse aggressive epithelial cancers involving the intrahepatic, perihilar, and distal biliary tree.^1–3 In this article, we review the epidemiology, clinical features, and diagnostic approach to BTC, with a focus on current evidence-based treatment strategies for localized, locally advanced, and metastatic BTC.

Epidemiology

In the United States, BTC is rare and accounts for approximately 4% of all gastrointestinal malignancies, with an estimated 6000 to 7000 cases of carcinoma of the gallbladder and 3000 to 4000 cases of carcinoma of the bile duct diagnosed annually.⁴ Among women, there is a 26-fold variation in BTC mortality worldwide, ranging from 0.8 deaths per 100,000 in South Africa to 21.2 per 100,000 in Chile.^1,5 Interestingly, for American Indians in New Mexico, gallbladder cancer mortality rates (8.9 per 100,000) surpass those for breast and pancreatic cancers.⁶ The incidence of anatomical cholangiocarcinoma subtypes also varies regionally, reflecting disparities in genetic and environmental predisposing factors.^2,7 In a large, single-center study in the United States, intrahepatic cholangiocarcinoma accounted for less than 10% of cases, perihilar accounted for 50%, and distal accounted for the remaining 40%.⁸ Importantly, intrahepatic cholangiocarcinoma is the second most common primary malignancy of the liver, and its incidence seems to be rising in many western countries. In the United States, there has been an estimated 128% rise over the past 40 years.^4,9

BTC is associated with high mortality rates.¹⁰ Median overall survival (OS) for cholangiocarcinoma is 20 to 28 months and 5-year survival is around 25%.¹⁰ Most cholangiocarcinomas are diagnosed at advanced stages with unresectable tumors.¹⁰ Furthermore, outcomes following resection with curative intent are poor—median disease-free survival (DFS) of 12 to 36 months has been reported.^11,12 Patients with intrahepatic disease have a better prognosis when compared with patients who have extrahepatic tumors.¹² Gallbladder cancer, likewise, carries a poor overall prognosis; median OS is 32 months and 5-year survival is as low as 13%.⁶

Risk factors for BTC include intrinsic and extrinsic elements.⁶ Incidence of BTC increases with age, and diagnosis typically occurs in the sixth to eighth decade of life.^5,6,13 In contrast to gallbladder cancer, the incidence of cholangiocarcinoma is slightly higher in men.⁹ Obesity, diabetes, and consumption of sweetened drinks also increase the risk for BTC.^14–16 Cholelithiasis is the most prevalent risk factor for gallbladder cancer, and the risk is greater for larger stones.⁵ Around 1 in 5 patients with porcelain gallbladder will develop gallbladder carcinoma.¹⁷ Primary sclerosing cholangitis (PSC), chronic calculi of the bile duct, choledochal cysts, cirrhosis, hepatitis C, and liver fluke infections are well established risk factors for cholangiocarcinoma.^7,12,18 PSC is one of the best described entities among these predisposing conditions. Lifetime prevalence of cholangiocarcinoma among patients with PSC ranges from 5% to 10%.^18,19 These patients also present at a younger age; in one series, the median age at diagnosis for BTC arising from PSC was 39 years.¹⁸ It is important to recognize, however, that in most patients diagnosed with cholangiocarcinoma, no predisposing factors are identified.⁸

Diagnosis

Clinical Presentation

Clinical presentation of BTC depends upon anatomic location.²⁰ Patients with early invasive gallbladder cancer are most often asymptomatic.²¹ When symptoms occur, they may be nonspecific and mimic cholelithiasis.²¹ The most common clinical presentations include jaundice, weight loss, and abdominal pain.²¹ Prior to widespread availability of imaging studies, the preoperative diagnosis rate for gallbladder cancer was as low as 10%.²² However, the accuracy of computed tomography (CT) has changed this scenario, with sensitivity ranging from 73% to 87% and specificity from 88% to 100%.²¹ As a result of its silent clinical character, cholangiocarcinoma is frequently difficult to diagnose.²³ Perihilar and distal cholangiocarcinoma characteristically present with signs of biliary obstruction, and imaging and laboratory data can corroborate the presence of cholestasis.²⁴ On examination, patients with extrahepatic cholangiocarcinoma may present with jaundice, hepatomegaly, and a palpable right upper quadrant mass.²⁵ A palpable gallbladder (Courvoisier sign) can also be present.²⁵ Intrahepatic cholangiocarcinoma presents differently, and patients are less likely to be jaundiced.²³ Typical clinical features are nonspecific and include dull right upper quadrant pain, weight loss, and an elevated alkaline phosphatase level.²³ Alternatively, asymptomatic patients can present with incidentally detected lesions, when imaging is obtained as part of the workup for other causes or during screening for hepatocellular carcinoma in patients with viral hepatitis or cirrhosis.^23,26 Uncommonly, BTC patients present because of signs or symptoms related to metastatic disease or evidence of metastatic disease on imaging.

 

Pathology and Grading

The majority of BTCs are adenocarcinomas, corresponding to 90% of cholangiocarcinomas and 99% of gallbladder cancers.^27,28 They are graded as well, moderately, or poorly differentiated.² Adenosquamous and squamous cell carcinoma are responsible for most of the remaining cases.^2,29 Cholangiocarcinomas are divided into 3 types, defined by the Liver Cancer Study Group of Japan: (1) mass-forming, (2) periductal-infiltrating, and (3) intraductal-growing.^30,31 Mass-forming intrahepatic cholangiocarcinomas are characterized morphologically by a homogeneous gray-yellow mass with frequent satellite nodules and irregular but well-defined margins.^17,30 Central necrosis and fibrosis are also common.³⁰ In the periductal-infiltrating type, tumor typically grows along the bile duct wall without mass formation, resulting in concentric mural thickening and proximal biliary dilation.³⁰ Intraductal-growing papillary cholangiocarcinoma is characterized by the presence of intraluminal papillary or tubular polypoid tumors of the intra- or extrahepatic bile ducts, with partial obstruction and proximal biliary dilation.³⁰

Cholangiocarcinoma

Case Presentation

A previously healthy 59-year-old man presents to his primary care physician with a 3-month history of dull right upper quadrant pain associated with weight loss. The patient is markedly cachectic and abdominal examination reveals upper quadrant tenderness. Laboratory exams are significant for elevated alkaline phosphatase (500 U/L; reference range 45–115 U/L), cancer antigen 19-9 (CA 19-9, 73 U/mL; reference range ≤ 37 U/mL), and carcinoembryonic antigen (CEA , 20 ng/mL; reference range for nonsmokers ≤ 3.0 ng/mL). Aspartate aminotransferase, alanine aminotransferase, total bilirubin, and coagulation studies are within normal range. Ultrasound demonstrates a homogeneous mass with irregular borders in the right lobe of the liver. Triphasic contrast-enhanced CT scan demonstrates a tumor with ragged rim enhancement at the periphery, and portal venous phase shows gradual centripetal enhancement of the tumor with capsular retraction. No abdominal lymph nodes or extrahepatic tumors are noted (Figure 1, Image A).

• What are the next diagnostic steps?

The most critical differential diagnosis of solid liver mass in patients without cirrhosis is cholangiocarcinoma and metastases from another primary site.³² Alternatively, when an intrahepatic lesion is noted on an imaging study in the setting of cirrhosis, the next diagnostic step is differentiation between cholangiocarcinoma and hepatocellular carcinoma (HCC).³² Triphasic contrast-enhanced CT and dynamic magnetic resonance imaging (MRI) are key diagnostic procedures.^32,33 In the appropriate setting, classical imaging features in the arterial phase with washout in portal venous or delayed phase can be diagnostic of HCC and may obviate the need for a biopsy (Figure 2).

Typical radiographic features of cholangiocarcinoma include a hypodense hepatic lesion that can be either well-defined or infiltrative and is frequently associated with biliary dilatation (Figure 1, Image A).³³ The dense fibrotic nature of the tumor may cause capsular retraction, which is seen in up to 20% of cases.¹⁷ This finding is highly suggestive of cholangiocarcinoma and is rarely present in HCC.³³ Following contrast administration, there is peripheral (rim) enhancement throughout both arterial and venous phases.^32–34 However, these classic features were present in only 70% of cases in one study.³⁵ Although intrahepatic cholangiocarcinomas are most commonly hypovascular, small mass-forming intrahepatic cholangiocarcinomas can often be arterially hyperenhancing and mimic HCC.³³ Tumor enhancement on delayed CT imaging has been correlated with survival. Asayama et al demonstrated that tumors that exhibited delayed enhancement on CT in more than two-thirds of their volume were associated with a worse prognosis.³⁶

Patients without cirrhosis who present with a localized lesion of the liver should undergo extensive evaluation for a primary cancer site.³⁷ CT of the chest, abdomen, and pelvis with contrast should be obtained.³⁷ Additionally, mammogram and endoscopic evaluation with esophagogastroduodenoscopy (EGD) and colonoscopy should be included in the work-up.³⁷

Preoperative tumor markers are also included in the work-up. All patients with a solid liver lesion should have serum alpha-fetoprotein (AFP) levels checked. AFP is a serum glycoprotein recognized as a marker for HCC and is reported to detect preclinical HCC.³⁸ However, serum concentrations are normal in up to 40% of small HCCs.³⁸ Although no specific marker for cholangiocarcinoma has yet been identified, the presence of certain tumor markers in the serum of patients may be of diagnostic value, especially in patients with PSC. CA 19-9 and CEA are the best studied. Elevated levels of CA 19-9 prior to treatment are associated with a poorer prognosis, and CA 19-9 concentrations greater than 1000 U/mL are consistent with advanced disease.^39,40 One large series evaluated the diagnostic value of serum CEA levels in 333 patients with PSC, 13% of whom were diagnosed with cholangiocarcinoma.³⁴ A serum CEA level greater than 5.2 ng/mL had a sensitivity of 68.0% and specificity of 81.5%.³⁸

If a biopsy is obtained, appropriate immunohistochemistry (IHC) can facilitate the diagnosis. BTC is strongly positive for CK-7 and CK-19.⁴¹ CK-7 positivity is not specific and is also common among metastatic cancers of the lung and breast; therefore, in some cases cholangiocarcinoma may be a diagnosis of exclusion. Immunostaining for monoclonal CEA is diffusely positive in up to 75% of cases.⁴¹ An IHC panel consisting of Hep Par-1, arginase-1, monoclonal CEA, CK-7, CK-20, TTF-1, MOC-31, and CDX-2 has been proposed to optimize the differential diagnosis of HCC, metastatic adenocarcinoma, and cholangiocarcinoma.⁴¹

 

Case Continued

CT of the chest, abdomen, and pelvis reveals no concerns for metastasis and no evidence of primary cancer elsewhere. EGD and colonoscopy are clear. AFP levels are within normal limits (2 ng/mL). Biopsy is performed and demonstrates adenocarcinoma. IHC studies demonstrate cells positive for monoclonal CEA, CK-7, CK-19, and MOC-31, and negative for Napsin A, TTF-1, and CK-20.

• How is cholangiocarcinoma staged and classified?

The purpose of the staging system is to provide information on prognosis and guidance for therapy. Prognostic factors and the therapeutic approaches for BTC differ depending upon their location in the biliary tree. Accordingly, TNM classification systems for intrahepatic, hilar, and distal cholangiocarcinoma and gallbladder cancer have been separated (Table 1 and Table 2).²³

For all the subtypes, T stage is mainly dependent upon invasion of adjacent structures rather than size. For perihilar tumors, N category has been reclassified in the newest version of the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) staging system based upon the number of involved lymph nodes rather than location.

The Bismuth-Corlette classification is used to further classify perihilar cholangiocarcinoma according to patterns of hepatic duct involvement. Type I tumors are located below the confluence of the left and right hepatic ducts.⁴² Type II reach the confluence of the hepatic ducts.⁴² Type III occlude the common hepatic duct and either the right or left hepatic duct (IIIa and IIIb, respectively).⁴² Finally, type IV are multicentric, or involve the confluence and both the right and left hepatic ducts.⁴² Tumors that involve the common hepatic duct bifurcation are named Klatskin tumors.⁴²

• What is the first-line treatment for localized cholangiocarcinomas?

Surgical resection is the only potentially curative treatment for localized cholangiocarcinoma, although fewer than 20% of patients are suitable for curative treatment, due to the presence of advanced disease at diagnosis.^43,44 Available evidence supports the recommendation that resection with negative margins, regardless of extent, should be the goal of therapy for patients with potentially resectable disease.⁴⁴ Extensive hepatic resections are often necessary to achieve clear margins since the majority of patients present with large masses. Substantial evidence corroborates that R0 resection is associated with better survival, whereas the benefit of wide compared to narrow (< 5–10 mm) margins is unclear.⁴⁵ A recent analysis of 96 patients suggests that the proximal resection margin has more prognostic implications than distal margins.⁴⁵

Surgical options and resectability criteria depend upon tumor location. Extent of tumor in the bile duct is one of the most important factors that determine resectability.¹⁷ Although multifocal liver tumors (including satellite lesions), lymph node metastases to the porta hepatis, and distant metastases are considered relative contraindications to surgery, surgical approaches can be considered in selected patients.⁴³ Patient selection for surgery is facilitated by careful preoperative staging, which may include laparoscopy. Laparoscopic staging prior to resection may prevent unnecessary laparotomy in 30% to 45% of patients.^42,46

• Is there a role for adjuvant treatment?

Recurrence following complete resection is a primary limitation for cure in BTC, which provides a rationale for the use of adjuvant therapy.^47,48 In a sample of 79 patients with extrahepatic cholangiocarcinoma who underwent curative resection, the cumulative recurrence rate after 4 years was 56%.⁴⁷ Initial recurrence at a distant site occurs in 40% to 50% of patients.⁴⁸

Lymphovascular and perineural invasion, lymph node metastasis, and tumor size ≥ 5 cm have been reported as independent predictors of recurrence and mortality following resection.⁴⁹ A 2017 meta-analysis which included 30 studies involving more than 22,499 patients reported a 41% reduction in the risk of death with adjuvant chemotherapy, which translated to a mean OS benefit of 4 months in an unselected population.⁴⁹ Moreover, this study revealed inferior OS in patients given adjuvant radiation therapy (RT) in combination with chemotherapy.⁴⁹ These results are in line with the previous meta-analysis by Horgan et al, which demonstrated that adjuvant RT seems to benefit only patients with R1 resections, with a possible detrimental effect in R0 disease.⁵⁰ Therefore, adjuvant chemoradiation cannot be viewed as a standard practice following R0 resection, and should be reserved for those patients with positive margins (R1/ 2) to reduce local progression.

In the phase 3 BILCAP trial presented at ASCO 2017, 447 patients with completely resected cholangiocarcinoma or gallbladder cancer with adequate biliary drainage and Eastern Cooperative Oncology Group (ECOG) performance score ≤ 2 were randomly assigned to observation or capecitabine (1250 mg/m² twice daily for days 1–14 every 21 days for 8 cycles).⁵¹ Surgical treatment achieved R0 resection in 62% of patients and 46% were node-negative. Median OS was 51 months for the capecitabine group and 36 months for the control arm (hazard ratio [HR] 0.80, 95% CI 0.63 to 1.04, P = 0.097). Analyses with adjustment for nodal status, grade of disease, and gender indicated a HR of 0.71 (P < 0.01). Median DFS was 25 months versus 18 months favoring the capecitabine group, and rates of grade 3 or 4 toxicity were less than anticipated. Following the results of this trial, adjuvant capecitabine should become the new standard of care.

 

• What is the treatment for locally advanced cholangiocarcinoma?

The optimal approach to patients with locally advanced unresectable cholangiocarcinoma has not been established. The prognosis for patients with either locally unresectable or locally recurrent disease is typically measured in months. Goals of palliative therapy are relief of symptoms and improvement in quality of life, and there is no role for surgical debulking.

Liver transplantation is a potentially curative option for selected patients with hilar or intrahepatic cholangiocarcinoma. Patients with lymph node-negative, non-disseminated, locally advanced hilar cholangiocarcinomas have 5-year survival rates ranging from 25% to 42% following transplantation.⁵² Retrospective data suggests that neoadjuvant chemoradiation followed by liver transplantation is highly effective for selected patients with hilar cholangiocarcinoma.⁵² However, these results require confirmation from prospective clinical evidence. It is important to recognize that liver transplantation plays no role in the management of distal cholangiocarcinoma or gallbladder cancer.

Rarely, patients with borderline resectable intrahepatic cholangiocarcinoma will have a sufficient response to chemotherapy to permit later resection, and, in such cases, starting with chemotherapy and then restaging to evaluate resectability is appropriate.⁵⁴ A single-center, retrospective analysis including 186 patients by Le Roy et al evaluated survival in patients with locally advanced, unresectable intrahepatic cholangiocarcinoma who received primary chemotherapy, followed by surgery in those with secondary resectability.⁵⁴ After a median of 6 cycles of chemotherapy, 53% of patients achieved resectability and underwent surgery with curative intent. These patients had similar short- and long-term results compared to patients with initially resectable intrahepatic cholangiocarcinoma who had surgery alone, with median OS reaching 24 months.⁵⁴

Ablative radiotherapy is an additional option for localized inoperable intrahepatic cholangiocarcinoma. Tao and colleagues evaluated 79 consecutive patients with inoperable intrahepatic cholangiocarcinoma treated with definitive RT.⁵⁵ Median tumor size was 7.9 cm and 89% of patients received chemotherapy before RT. Median OS was 30 months and 3-year OS was 44%. Radiation dose was the single most important prognostic factor, and higher doses correlated with improved local control and OS. A biologic equivalent dose (BED) greater than 80.5 Gy was identified as an ablative dose of RT for large intrahepatic cholangiocarcinomas. The 3-year OS for patients receiving BED greater than 80.5 Gy was 73% versus 38% for those receiving lower doses.

Case Continued

The patient is deemed to have resectable disease and undergoes surgical resection followed by adjuvant capecitabine for 8 cycles. Unfortunately, after 1 year, follow-up imaging identifies bilateral enlarging lung nodules. Biopsy is performed and confirms metastatic cholangiocarcinoma.

• What is the treatment for metastatic BTC?

The prognosis of patients with advanced BTC is poor and OS for those undergoing supportive care alone is short. A benefit of chemotherapy over best supportive care for cholangiocarcinoma was demonstrated in an early phase 3 trial that randomly assigned 90 patients with advanced pancreatic or biliary cancer (37 with bile duct cancer) to receive either fluorouracil (FU) -based systemic chemotherapy or best supportive care. Results showed that chemotherapy significantly improved OS (6 months versus 2.5 months).⁵⁶ Chemotherapy is also beneficial for patients with unresectable gallbladder cancer. In a single-center randomized study including 81 patients with unresectable gallbladder cancer, gemcitabine and oxaliplatin (GEMOX) improved progression-free survival (PFS) and OS compared to best supportive care.⁵⁷ Treatment for metastatic cholangiocarcinoma and gallbladder cancer follows the same algorithm.

In 2010, cisplatin plus gemcitabine was established as a reference regimen for first-line therapy by the ABC-02 study, in which 410 patients with locally advanced or metastatic bile duct, gallbladder, or ampullary cancer were randomly assigned to 6 courses of cisplatin (25 mg/m²) plus gemcitabine (1000 mg/m² on days 1 and 8, every 21 days) or gemcitabine alone (1000 mg/m² days 1, 8, 15, every 28 days).⁵⁸ OS was significantly greater with combination therapy (11.7 versus 8.1 months), and PFS also favored the combination arm (8 versus 5 months). Toxicity was comparable in both groups, with the exception of significantly higher rates of grade 3 or 4 neutropenia with gemcitabine plus cisplatin (25% versus 17%), and higher rates of grade 3 or 4 abnormal liver function with gemcitabine alone (27% versus 17%). Most quality-of-life scales showed a trend favoring combined therapy.⁵⁸ A smaller, identically designed Japanese phase 3 randomized trial achieved similar results, demonstrating greater OS with cisplatin plus gemcitabine compared to gemcitabine alone (11.2 versus 7.7 months).⁵⁹

The gemcitabine plus cisplatin combination has not been directly compared with other gemcitabine combinations in phase 3 trials. A pooled analysis of 104 trials of a variety of chemotherapy regimens in advanced biliary cancer concluded that the gemcitabine plus cisplatin regimen offered the highest rates of objective response and tumor control compared with either gemcitabine-free or cisplatin-free regimens.⁶⁰ However, this did not translate into significant benefit in terms of either time to tumor progression or median OS. It is important to note that this analysis did not include results of the subsequent ABC-02 trial.

There is no standard treatment for patients with cholangiocarcinoma for whom first-line gemcitabine-based therapy fails. There are no completed prospective phase 3 trials supporting the use of second-line chemotherapy after failure of first-line chemotherapy in BTC, and the selection of candidates for second-line therapy as well as the optimal regimen are not established.⁶¹ The ongoing phase 2 multicenter ABC-06 trial is evaluating oxaliplatin plus short-term infusional FU and leucovorin (FOLFOX) versus best supportive care for second-line therapy. In a systematic review including 23 studies (14 phase 2 clinical trials and 9 retrospective studies) with 761 patients with BTC, the median OS was 7.2 months.

The optimal selection of candidates for second-line chemotherapy is not established. Two independent studies suggest that patients who have a good performance status (0 or 1), disease control with the first-line chemotherapy, low CA 19-9 level, and possibly previous surgery on their primary tumor, have the longest survival with second-line chemotherapy. However, whether these characteristics predict for chemotherapy responsiveness or more favorable biologic behavior is not clear.^62,63 No particular regimen has proved superior to any other, and the choice of second-line regimen remains empiric.

For patients with adequate performance status, examples of other conventional chemotherapy regimens with demonstrated activity that could be considered for second-line therapy include: FOLFOX or capecitabine, gemcitabine plus capecitabine, capecitabine plus cisplatin, or irinotecan plus short-term infusional FU and leucovorin (FOLFIRI) with or without bevacizumab.⁶⁴ For selected patients, second-line molecularly targeted therapy using erlotinib plus bevacizumab may be considered. However, this regimen is very costly.⁶⁴ Examples of other regimens with demonstrated activity in phase 2 trials include GEMOX, gemcitabine plus fluoropyrimidine, and fluoropyrimidine plus oxaliplatin or cisplatin.⁶⁴

There is promising data from studies of targeted therapy for specific molecular subgroups. A recent phase 2 trial evaluated the activity of BGJ398, an orally bioavailable, selective, ATP-competitive pan inhibitor of human fibroblast growth factor receptor (FGFR) kinase, in patients with FGFR-altered advanced cholangiocarcinoma.⁶⁵ The overall response rate was 14.8% (18.8% FGFR2 fusions only) and disease control rate was 75.4% (83.3% FGFR2 fusions only). All responsive tumors contained FGFR2 fusions. Adverse events were manageable, and grade 3 or 4 treatment-related adverse events occurred in 25 patients (41%). Those included hyperphosphatemia, stomatitis, and palmar-plantar erythrodysesthesia. Javle and colleagues also identified HER2/neu blockade as a promising treatment strategy for gallbladder cancer patients with this gene amplification.⁶⁶ This retrospective analysis included 9 patients with gallbladder cancer and 5 patients with cholangiocarcinoma who received HER2/neu-directed therapy (trastuzumab, lapatinib, or pertuzumab). In the gallbladder cancer group, HER2/neu gene amplification or overexpression was detected in 8 cases. These patients experienced disease stability (n = 3), partial response (n = 4), or complete response (n = 1) with HER2/neu–directed therapy. Median duration of response was 40 weeks. The cholangiocarcinoma cases treated in this series had no radiological responses despite HER2/neu mutations or amplification.

 

Gallbladder Cancer

Case Presentation

A 57-year-old woman from Chile presents with a 3-week history of progressive right upper quadrant abdominal pain. She denies nausea, vomiting, dysphagia, odynophagia, alterations in bowel habits, fever, or jaundice. Her past medical history is significant for obesity and hypertension. She has no history of smoking, alcohol, or illicit drug use. Laboratory studies show marked leukocytosis (23,800/µL) with neutrophilia (91%). Liver function test results are within normal limits. Ultrasound of the abdomen reveals gallbladder wall thickening and cholelithiasis.

The patient undergoes an uneventful laparoscopic cholecystectomy and is discharged from the hospital after 48 hours. Pathology report reveals a moderately differentiated adenocarcinoma of the gallbladder invading the perimuscular connective tissue (T2). No lymph nodes are identified in the specimen.

• What is the appropriate surgical management of gallbladder cancer?

Gallbladder cancer can be diagnosed preoperatively or can be found incidentally by intraoperative or pathological findings. In one large series, gallbladder cancer was incidentally found during 0.25% of laparoscopic cholecystectomies.⁶⁷

For patients who are diagnosed with previously unsuspected gallbladder cancer by pathology findings, the extent of tumor invasion (T stage) indicates the need for re-resection (Figure 3).⁶⁴

Surgical exploration and re-resection are recommended if disease is stage T1b (involving the muscular layer) or higher (Table 2).^64,68 In these patients, re-resection is associated with significantly improved OS.⁶⁸ Patients found to have incidental T1a tumors with negative margins are generally felt to be curable with simple cholecystectomy, and re-resection for T1a tumors does not appear to provide an OS benefit.^69,70 The majority of patients diagnosed under these circumstances have T2 or higher disease, and will ultimately require additional surgical exploration.⁷¹ A German series that analyzed 439 cases of incidentally diagnosed gallbladder cancer demonstrated that positive lymph nodes were found in 21% and 44% of the re-resected patients with T2 and T3 tumors, respectively.⁷¹ There is retrospective data suggesting that the optimal timing of the reoperation is between 4 and 8 weeks following the initial cholecystectomy.⁷² This interval is believed to be ideal, as it allows for reduced inflammation and does not permit too much time for disease dissemination.⁷²

Alternatively, when gallbladder cancer is documented or suspected preoperatively, adequate imaging is important to identify patients with absolute contraindications to resection. Contraindications to surgery include metastasis, extensive involvement of the hepatoduodenal ligament, encasement of major vessels, and involvement of celiac, peripancreatic, periduodenal, or superior mesenteric nodes.⁷² Notwithstanding, retrospective series suggest individual patients may benefit, and surgical indications in advanced disease should be determined on an individual basis.⁷³ Staging imaging should be obtained using multiphasic contrast-enhanced CT or MRI of the chest, abdomen, and pelvis. PET-scan can be used in selected cases where metastatic disease is suspected.⁶⁴ Laparoscopic diagnostic staging should be considered prior to resection.⁶⁴ This procedure can identify previously unknown contraindications to tumor resection in as much as 23% of patients, and the yield is significantly higher in locally advanced tumors.⁷³

Patients with a diagnosis of potentially resectable, localized gallbladder cancer should be offered definitive surgery. Extended cholecystectomy is recommended for patients stage T2 or above. This procedure involves wedge resection of the gallbladder bed or a segmentectomy IVb/V and lymph node dissection, which should include the cystic duct, common bile duct, posterior superior pancreaticoduodenal lymph nodes, and those around the hepatoduodenal ligament.⁷² Bile duct excision should be performed if there is malignant involvement.⁶⁴

Conclusion

BTCs are anatomically and clinically heterogeneous tumors. Prognostic factors and therapeutic approaches for BTCs differ depending upon their location in the biliary tree and, accordingly, TNM classification systems for intrahepatic, hilar, and distal cholangiocarcinoma and gallbladder cancer have been separated. Surgical resection is the only potentially curative treatment for localized BTC. However, recurrence following complete resection is a primary limitation for cure, which provides a rationale for the use of adjuvant therapy. The prognosis of patients with advanced BTC is poor and OS for those undergoing supportive care alone is short. Multiple randomized clinical trials have demonstrated a benefit of chemotherapy for metastatic disease. For patients with adequate performance status, second-line therapy can be considered, and data from studies that evaluated targeted therapy for specific molecular subgroups is promising.

Introduction

Polycythemia vera (PV) and essential thrombocythemia (ET), along with primary myelofibrosis (PMF), belong to the group of Philadelphia-negative myeloproliferative neoplasms (MPN). All these malignancies arise from the clonal proliferation of an aberrant hematopoietic stem cell, but are characterized by distinct clinical phenotypes.^1,2 Although the clinical course of PV and ET is indolent, it can be complicated by thrombohemorrhagic episodes and/or evolution into myelofibrosis and/or acute myeloid leukemia (AML).³ Since vascular events are the most frequent life-threatening complications of PV and ET, therapeutic strategies are aimed at reducing this risk. Treatment may also help control other disease-associated symptoms.⁴ No therapy has been shown to prevent evolution of PV or ET into myelofibrosis or AML. The discovery of the Janus kinase 2 (JAK2)/V617F mutation in most patients with PV and over half of those with ET (and PMF)^5,6 has opened new avenues of research and led to the development of targeted therapies, such as the JAK1/2 inhibitor ruxolitinib, for patients with MPN.^7,8

Epidemiology

PV and ET are typically diagnosed in the fifth to seventh decade of life.⁹ Although these disorders are generally associated with a long clinical course, survival of patients with PV or ET may be shorter than that of the general population.^10–13 Estimating the incidence and prevalence of MPN is a challenge because most patients remain asymptomatic for long periods of time and do not seek medical attention.¹³ The annual incidence rates of PV and ET are estimated at 0.01 to 2.61 and 0.21 to 2.53 per 100,000, respectively. PV occurs slightly more frequently in males, whereas ET has a predilection for females.¹⁴ Given the long course and low mortality associated with these disorders, the prevalence of PV and ET are significantly higher than the respective incidence: up to 47 and 57 per 100,000, respectively.^15–17

Molecular Pathogenesis

In 2005 researchers discovered a gain-of-function mutation of the JAK2 gene in nearly all patients with PV and more than half of those with ET and PMF.^5,6,18,19 JAK2 is a non-receptor tyrosine kinase that plays a central role in normal hematopoiesis. Substitution of a valine for a phenylalanine at codon 617 (ie, V617F) leads to its constitutive activation and signaling through the JAK-STAT pathway.^5,6,18,19 More rarely (and exclusively in patients with PV), JAK2 mutations involve exon 12.^20–22 The vast majority of JAK2-negative ET patients harbor mutations in either the myeloproliferative leukemia (MPL) gene, which encodes the thrombopoietin receptor,^23–25 or the calreticulin (CALR) gene,^26,27 which encodes for a chaperone protein that plays a role in cellular proliferation, differentiation, and apoptosis.²⁸ Both the MPL and CALR mutations ultimately result in the constitutive activation of the JAK-STAT pathway. Thus, JAK2, MPL, and CALR alterations are collectively referred to as driver mutations. Moreover, because these mutations affect the same oncogenic pathway (ie, JAK-STAT), they are almost always mutually exclusive in a given patient. Patients with ET (or myelofibrosis) who are wild-type for JAK2, MPL, and CALR are referred to as having “triple-negative” disease. Many recurrent non-driver mutations are also found in patients with MPN that are not exclusive of each other (ie, patients may have many at the same time), and involve for example ten-eleven translocation-2 (TET2), additional sex combs like 1 (ASXL1), enhancer of zeste homolog 2 (EZH2), isocitrate dehydrogenase 1 and isocitrate dehydrogenase 2 (IDH1/2), and DNA methyltransferase 3A (DNMT3A) genes, among others.²⁹ The biologic and prognostic significance of these non-driver alterations remain to be fully defined in ET and PV.

Diagnosis and Risk Assessment

Case Presentations

Patient A is a 68-year-old man with a history of gouty arthritis who presents with a 6-month history of recurrent headaches and itching that increases after a hot shower. Over the past 2 months, he has also noticed worsening fatigue and redness of his face. He is a nonsmoker. Physical exam reveals erythromelalgia (ie, erythema, edema, and warmth) of the upper and lower extremities, scattered scratch marks, and splenomegaly 4 cm below the costal margin. Complete blood count (CBC) shows a white blood cell (WBC) count of 8100/µL, hemoglobin 194 g/L, and platelets 582 × 10³/µL. Serum erythropoietin level is decreased at 2 mU/mL. Peripheral blood testing reveals a JAK2V617F mutation.

Patient B is a 51-year-old woman with a history of severe depression treated with sertraline and hypertension controlled with lisinopril and amlodipine who presents to her primary care physician for her “50-year-old physical.” She denies symptoms and is a nonsmoker. Physical exam is unrevealing. CBC shows a WBC count of 7400/µL (normal differential), hemoglobin 135 g/L, and platelets 1282 × 10³/µL. A bone marrow biopsy shows normal cellularity with clusters of large, hyperlobulated megakaryocytes. Reverse transcriptase-polymerase chain reaction fails to reveal a BCR-ABL fusion product. The patient is diagnosed with ET.

 

Diagnostic Criteria

Diagnostic criteria for PV and ET according to the World Health Organization (WHO) classification³⁰ are summarized in Table 1. Criteria for the diagnosis of prefibrotic myelofibrosis are included as well since this entity was formally recognized as separate from ET and part of the PMF spectrum in the 2016 WHO classification of myeloid tumors.³⁰

Clinically, both PV and ET generally remain asymptomatic for a long time. PV tends to be more symptomatic than ET and can present with debilitating constitutional symptoms (fatigue, night sweats, weight loss, pruritus), microvascular symptoms (headache, lightheadedness, acral paresthesias, erythromelalgia, atypical chest pain, and pruritus),³¹ or macrovascular accidents (larger vein thrombosis, stroke, or myocardial ischemia).³² ET is often diagnosed incidentally, but patients can suffer from similar general symptoms and vascular complications. Causes of secondary absolute erythrocytosis (altitude, chronic hypoxemia, heavy smoking, cardiomyopathy, use of corticosteroids, erythropoietin, or other anabolic hormones, familial or congenital forms) or thrombocytosis (iron deficiency, acute blood loss, trauma or injury, acute coronary syndrome, systemic autoimmune disorders, chronic kidney failure, other malignancies, splenectomy) should be considered and appropriately excluded. Once the diagnosis is made, symptom assessment tools such as the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF)³³ or the abbreviated version, the MPN-SAF Total Symptom Score (MPN-SAF TSS),³⁴ are generally used to assess patients’ symptom burden and response to treatment in everyday practice.

Risk Stratification

Thrombohemorrhagic events, evolution into myelofibrosis, and leukemic transformation are the most serious complications in the course of PV or ET. Only thrombohemorrhagic events are, at least partially, preventable. Arterial or venous thrombotic complications are observed at rates of 1.8 to 10.9 per 100 patient-years in PV (arterial thrombosis being more common than venous) and 0.74 to 7.7 per 100 patient-years in ET, depending on the risk group³⁵ and the presence of other factors (see below).

Thrombosis Risk Stratification in PV

The risk stratification of patients with PV is based on 2 factors: age ≥ 60 years and prior history of thrombosis. If either is present the patient is assigned to the high-risk category, whereas if none is present the patient is considered at low risk.³⁶ In addition, high hematocrit³⁷ and high WBC,³⁸ but not thrombocytosis, have been associated with the development of vascular complications. In one study, the risk of new arterial thrombosis was increased by the presence of leukoerythroblastosis, hypertension, and prior arterial thrombosis, while karyotypic abnormalities and prior venous thrombosis were predictors of new venous thrombosis.³⁹ Another emerging risk factor for thrombosis in patients with PV is high JAK2 allele burden (ie, the normal-to-mutated gene product ratio), although the evidence supporting this conclusion is equivocal.⁴⁰

Thrombosis Risk Stratification in ET

Traditionally, in ET patients, thrombotic risk was assessed using the same 2 factors (age ≥ 60 years and prior history of thrombosis), separating patients into low- and high-risk groups. However, the prognostication of ET patients has been refined recently with the identification of new relevant factors. In particular, the impact of JAK2 mutations on thrombotic risk has been thoroughly studied. Clinically, the presence of JAK2V617F is associated with older age, higher hemoglobin and hematocrit, lower platelet counts, more frequent need for cytoreductive treatment, and greater tendency to evolve into PV (a rare event).^41,42 Many,^41,43–46 but not all,^47–51 studies suggested a correlation between JAK2 mutation and risk of both arterial and venous thrombosis. Although infrequent, a JAK2V617F homozygous state (ie, the mutation is present in both alleles) might confer an even higher thrombotic risk.⁵² Moreover, the impact of the JAK2 mutation on vascular events persists over time,⁵³ particularly in patients with high or unstable mutation burden.⁵⁴ Based on JAK2V617F’s influence on the thrombotic risk of ET patients, a new prognostic score was proposed, the International Prognostic Score for ET (IPSET)-thrombosis (Table 2). The revised version of this model is currently endorsed by the National Comprehensive Cancer Network and divides patients into 4 risk groups: high, intermediate, low, and very low. Treatment recommendations vary according to the risk group (as described below).⁵⁵

Other thrombotic risk factors have been identified, but deemed not significant enough to be included in the model. Cardiovascular risk factors (hypercholesterolemia, hypertension, smoking, diabetes mellitus) can increase the risk of vascular events,^56–59 as can splenomegaly⁶⁰ and baseline or persistent leukocytosis.^61–63 Thrombocytosis has been correlated with thrombotic risk in some studies,^64–68 whereas others did not support this conclusion and/or suggested a lower rate of thrombosis and, in some cases, increased risk of bleeding in ET patients with platelet counts greater than 1000 × 10³/µL (due to acquired von Willebrand syndrome).^{56,61,63,68,69}

CALR mutations tend to occur in younger males with lower hemoglobin and WBC count, higher platelet count, and greater marrow megakaryocytic predominance as compared to JAK2 mutations.^{26,27,70–72} The associated incidence of thrombosis was less than 10% at 15 years in patients with CALR mutations, lower than the incidence reported for ET patients with JAK2V617F mutations.⁷³ The presence of the mutation per se does not appear to affect the thrombotic risk.^74–76 Information on the thrombotic risk associated with MPL mutations or a triple-negative state is scarce. In both instances, however, the risk appears to be lower than with the JAK2 mutation.^73,77–79

Venous thromboembolism in patients with PV or ET may occur at unusual sites, such as the splanchnic or cerebral venous systems.⁸⁰ Risk factors for unusual venous thromboembolism include younger age,⁸¹ female gender (especially with concomitant use of oral contraceptive pills),⁸² and splenomegaly/splenectomy.⁸³JAK2 mutation has also been associated with thrombosis at unusual sites. However, the prevalence of MPN or JAK2V617F in patients presenting with splanchnic venous thromboembolism has varied.⁸⁰ In addition, MPN may be occult (ie, no clinical or laboratory abnormalities) in around 15% of patients.⁸⁴ Screening for JAK2V617F and underlying MPN is recommended in patients presenting with isolated unexplained splanchnic venous thromboembolism. Treatment entails long-term anticoagulation therapy. JAK2V617F screening in patients with nonsplanchnic venous thromboembolism is not recommended, as its prevalence in this group is low (< 3%).^85,86

 

Treatment

Cases Continued

Patient A is diagnosed with PV based on the presence of 2 major criteria (elevated hemoglobin and presence of the JAK2V617F mutation) and 1 minor criterion (low erythropoietin level). Given his age, he belongs to the high-risk disease category. He is now seeking advice regarding the management of his newly diagnosed PV.

Patient B presents to the emergency department with right lower extremity swelling and is found to have deep femoral thrombosis extending to the iliac vein. Five days after being discharged from the emergency department, she presents for follow-up. She is taking warfarin compliantly and her INR is within therapeutic range. The patient now has high-risk ET and would like to know more about thrombosis in her condition and how to best manage her risk.

Risk-Adapted Therapy

Low-Risk PV

All patients with PV should receive counseling to mitigate cardiovascular risk factors, including smoking cessation, lifestyle modifications, and lipid-lowering therapy, as indicated. Furthermore, all PV patients should receive acetylsalicylic acid (ASA) to decrease their risk for thrombosis and control vasomotor symptoms.^55,87 Aspirin 81 to 100 mg daily is the preferred regimen because it provides adequate antithrombotic effect without the associated bleeding risk of higher-dose aspirin.⁸⁸ Low-risk PV patients should also receive periodic phlebotomies to reduce and maintain their hematocrit below 45%. This recommendation is based on the results of the Cytoreductive Therapy in Polycythemia Vera (CYTO PV) randomized controlled trial. In the CYTO PV study, patients receiving more intense therapy to maintain the hematocrit below 45% had a lower incidence of cardiovascular-related deaths or major thrombotic events than those with hematocrit goals of 45% to 50% (2.7% versus 9.8%).⁸⁹ Cytoreduction is an option for low-risk patients who do not tolerate phlebotomy or require frequent phlebotomy, or who have disease-related bleeding, severe symptoms, symptomatic splenomegaly, or progressive leukocytosis.³⁸

High-Risk PV

Patients older than 60 years and/or with a history of thrombosis should be considered for cytoreductive therapy in addition to the above measures. Front-line cytoreductive therapies include hydroxyurea or interferon (IFN)- alfa.⁸⁷ Hydroxyurea is a potent ribonucleotide reductase inhibitor that interferes with DNA repair and is the treatment of choice for most high-risk patients with PV.⁹⁰ In a small trial hydroxyurea reduced the risk of thrombosis compared with historical controls treated with phlebotomy alone.⁹¹ Hydroxyurea is generally well tolerated; common side effects include cytopenias, nail changes, and mucosal and/or skin ulcers. Although never formally proven to be leukemogenic, this agent should be used with caution in younger patients.⁸⁷ Indeed, in the original study, the rates of transformation were 5.9% and 1.5% for patients receiving hydroxyurea and phlebotomy alone,⁹² respectively, although an independent role for hydroxyurea in leukemic transformation was not supported in the much larger European Collaboration on Low-dose Aspirin in Polycythemia Vera (ECLAP) study.⁹³ About 70% of patients will have a sustained response to hydroxyurea,⁹⁴ while the remaining patients become resistant to or intolerant of the drug. Resistant individuals have a higher risk of progression to acute leukemia and death.⁹⁵

IFN alfa is a pleiotropic antitumor agent that has found application in many types of malignancies⁹⁶ and is sometimes employed as treatment for patients with newly diagnosed high-risk PV. Early studies showed responses in up to 100% of cases,^97,98 albeit at the expense of a high discontinuation rate due to adverse events, such as flu-like symptoms, fatigue, and neuropsychiatric manifestations.⁹⁹ A newer formulation of the drug obtained by adding a polyethylene glycol (PEG) moiety to the native IFN alfa molecule (PEG-IFN alfa) was shown to have a longer half-life, greater stability, less immunogenicity, and, potentially, better tolerability.¹⁰⁰ Pilot phase 2 trials of PEG-IFN alfa-2a demonstrated its remarkable activity, with symptomatic and hematologic responses seen in the majority of patients (which, in some cases, persisted beyond discontinuation), and reasonable tolerability, with long-term discontinuation rates of around 20% to 30%.^101–103 In some patients JAK2V617F became undetectable over time.¹⁰⁴ Results of 2 ongoing trials, MDP-RC111 (single-arm study, PEG-IFN alfa-2a in high-risk PV or ET [NCT01259817]) and MPD-RC112 (randomized controlled trial, PEG-IFN alfa-2a versus hydroxyurea in the same population [NCT01258856]), will shed light on the role of PEG-IFN alfa in the management of patients with high-risk PV or ET. In 2 phase 2 studies of PEG-IFN alfa-2b, complete responses were seen in 70% to 100% of patients and discontinuation occurred in around a third of cases.^105,106 A new, longer-acting formulation of PEG-IFN alfa-2a (peg-proline INF alfa-2b, AOP2014) is also undergoing clinical development.^107,108

The approach to treatment of PV based on thrombotic risk level is illustrated in Figure 1.

 

 

Very Low- and Low-Risk ET

Like patients with PV, individuals with ET should undergo rigorous cardiovascular risk management and generally receive ASA to decrease their thrombotic risk and improve symptom control. Antiplatelet therapy may not be warranted in patients with documented acquired von Willebrand syndrome, with or without extreme thrombocytosis, or in those in the very low-risk category according to the IPSET-thrombosis model.^55,87 The risk/benefit ratio of antiplatelet agents in patients with ET at different thrombotic risk levels was assessed in poor-quality studies and thus remains highly uncertain. Platelet-lowering agents are sometimes recommended in patients with low-risk disease who have platelet counts ≥ 1500 × 10³/µL, due to the potential risk of acquired von Willebrand syndrome and a risk of bleeding (this would require stopping ASA).¹⁰⁹ Cytoreduction may also be used in low-risk patients with progressive symptoms despite ASA, symptomatic or progressive splenomegaly, and progressive leukocytosis.

Intermediate-Risk ET

This category includes patients older than 60 years but without thrombosis or JAK2 mutations. These individuals would have been considered high risk (and thus candidates for cytoreductive therapy) according to the traditional risk stratification. Guidelines currently recommend ASA as the sole therapy for these patients, while reserving cytoreduction for those who experience thrombosis (ie, become high-risk) or have uncontrolled vasomotor or general symptoms, symptomatic splenomegaly, symptomatic thrombocytosis, or progressive leukocytosis.

High-Risk ET

For patients with ET in need of cytoreductive therapy (ie, those with prior thrombosis or older than 60 years with a JAK2V617F mutation), first-line options include hydroxyurea, IFN, and anagrelide. Hydroxyurea remains the treatment of choice in the majority of patients.¹¹⁰ In a seminal study, 114 patients with ET were randomly assigned to either observation or hydroxyurea treatment with the goal of maintaining the platelet count below 600 × 10³/µL. At a median follow-up of 27 months, patients in the hydroxyurea group had a lower thrombosis rate (3.6% versus 24%, P = 0.003) and longer thrombosis-free survival, regardless of the use of antiplatelet drugs.⁶⁴

Anagrelide, a selective inhibitor of megakaryocytic differentiation and proliferation, was compared with hydroxyurea in patients with ET in 2 randomized trials. In the first (N = 809), the group receiving anagrelide had a higher risk of arterial thrombosis, major bleeding, and fibrotic evolution, but lower incidence of venous thrombosis. Hydroxyurea was better tolerated, mainly due to anagrelide-related cardiovascular adverse events.¹¹¹ As a result of this study, hydroxyurea is often preferred to anagrelide as front-line therapy for patients with newly diagnosed high-risk ET. In the second, more recent study (N = 259), however, the 2 agents proved equivalent in terms of major or minor arterial or venous thrombosis, as well as discontinuation rate.¹¹² The discrepancy between the 2 trials may be partly explained by the different ET diagnostic criteria used, with the latter only enrolling patients with WHO-defined true ET, while the former utilized Polycythemia Vera Study Group-ET diagnostic criteria that included patients with increases in other blood counts or varying degrees of marrow fibrosis.

Interferons were studied in ET in parallel with PV. PEG-IFN alfa-2a proved effective in patients with ET, with responses observed in 80% of patients.¹⁰³ PEG-IFN alfa-2b produced similar results, with responses in 70% to 90% of patients in small studies and discontinuation observed in 20% to 38% of cases.^105,106,113 Because the very long-term leukemogenic potential of hydroxyurea has remained somewhat uncertain, anagrelide or IFN might be preferable choices in younger patients.

The approach to treatment of ET based on thrombotic risk level is illustrated in Figure 2.

Assessing Response to Therapy

For both patients with PV and ET the endpoint of treatment set forth for clinical trials has been the achievement of a clinicohematologic response. However, studies have failed to show a correlation between response and reduction of the thrombohemorrhagic risk.¹¹⁴ Therefore, proposed clinical trial response criteria were revised to include absence of hemorrhagic or thrombotic events as part of the definition of response (Table 3).⁹⁴

Cases Continued

Patient A was initially treated with phlebotomies and his blood counts were subsequently controlled with hydroxyurea, which he took uninterruptedly at an average dose of 2.5 g daily. He also took ASA daily throughout. Now, 18 months after the start of therapy, he presents with a complaint of fatigue for the past 3 months, which more recently has been associated with recurrent itching. A repeat CBC shows a WBC count of 17,200/µL, hemoglobin 181 g/L, and platelets 940 × 10³/µL.

Patient B presents for scheduled follow-up. She has had no further thrombotic episodes. However, she spontaneously discontinued hydroxyurea 1 month ago because of worsening mouth ulcers that impaired her ability to eat even small meals. She seeks recommendations for further treatment options.

 

Approach to Patients Refractory to or Intolerant of First-Line Therapy

According to the European LeukemiaNet recommendations, an inadequate response to hydroxyurea in patients with PV (or myelofibrosis) is defined as a need for phlebotomy to maintain hematocrit below < 45%, platelet count > 400 × 10³/µL, and a WBC count > 10,000/µL, or failure to reduce splenomegaly > 10 cm by > 50% at a dose of ≥ 2 g/day or maximum tolerated dose. Historically, treatment options for patients with PV or ET who failed first-line therapy (most commonly hydroxyurea) have included alkylating agents, such as busulfan, chlorambucil, or pipobroman, and phosphorus (P)-32. However, the use of these drugs is limited by the associated risk of leukemic transformation.^93,115,116 The use of IFN (or anagrelide for ET) is often considered in patients previously treated with hydroxyurea, and vice versa.

Ruxolitinib is a JAK1 and JAK2 inhibitor currently approved for the treatment of PV patients refractory to or intolerant of hydroxyurea.⁷ Following promising results of a phase 2 trial,¹¹⁷ ruxolitinib 10 mg twice daily was compared with best available therapy in the pivotal RESPONSE trial (N = 222). Ruxolitinib proved superior in achieving hematocrit control, reduction of spleen volume, and improvement of symptoms. Grade 3-4 hematologic toxicity was infrequent and similar in the 2 arms.¹¹⁸ In addition, longer follow-up of that study suggested a lower rate of thrombotic events in patients receiving ruxolitinib (1.8 versus 8.2 per 100 patient-years).¹¹⁹ In a similarly designed randomized phase 3 study in PV patients without splenomegaly (RESPONSE-2), more patients in the ruxolitinib arm had hematocrit reduction without an increase in toxicity. Based on the results of the above studies, ruxolitinib can be considered a standard of care for second-line therapy in this post-hydroxyurea patient population.¹²⁰

Ruxolitinib is also being tested in patients with high-risk ET who have become resistant to, or were intolerant of hydroxyurea, but currently has no approved indication in this setting.^121,122 Common side effects of ruxolitinib include cytopenias (especially anemia), increased risk of infections, hyperlipidemia, and increased risk of non-melanoma skin cancer.

Novel Agents

Novel agents that have been studied in patients with PV and ET are histone deacetylase inhibitors, murine double minute 2 (MDM2, or HDM2 for their human counterpart) inhibitors (which restore the function of p53), Bcl-2 homology domain 3 mimetics such as navitoclax and venetoclax, and, for patients with ET, the telomerase inhibitor imetelstat.¹²³

Disease Evolution

Cases Continued

Patient A’s PV has been well controlled with PEG-IFN alfa-2a 90 μg subcutaneously weekly. However, he now presents with a complaint of worsening fatigue and early satiety. On exam the patient appears ill and splenomegaly is appreciated 12 cm below the costal margin. CBC shows a WBC count of 2600/µL, hemoglobin 73 g/L, and platelets 122 × 10³/µL. Peripheral blood smear reveals leukoerythroblastosis and dacro­cytosis. CBC 6 months ago was normal. A bone marrow biopsy is consistent with myelofibrosis.

After discontinuing hydroxyurea, patient B’s ET has been well controlled with anagrelide. However, for the past 4 weeks she has complained of severe fatigue and easy bruising. Physical exam reveals a pale, ill-appearing woman with scattered bruises. CBC shows a WBC count of 14,600/µL with 44% myeloblasts, hemoglobin 73 g/L, and platelets 22 × 10³/µL. CBC 6 months ago was normal. A bone marrow biopsy is consistent with leukemic transformation of ET.

Post-PV/Post-ET Myelofibrosis

Diagnostic criteria for post-PV and post-ET myelofibrosis are outlined in Table 4.

Fibrotic transformation represents a natural evolution of the clinical course of PV or ET. It occurs in up to 15% and 9% of patients with PV and ET, respectively, in western countries.¹²⁴ The true percentage of ET patients who develop myelofibrosis is confounded by the inclusion of prefibrotic myelofibrosis cases in earlier series. The survival of patients who develop myelofibrosis is shortened compared to those who do not. In PV patients risk factors for myelofibrosis evolution include advanced age, leukocytosis, JAK2V617F homozygosity or higher allele burden, and hydroxyurea therapy. Once post-PV myelofibrosis has occurred, hemoglobin < 10 g/dL, platelet count < 100 × 10³/µL, and WBC count > 30,000/µL are associated with worse outcomes.¹²⁵ In patients with ET, risk factors for myelofibrosis transformation include age, anemia, bone marrow hypercellularity and increased reticulin, increased lactate dehydrogenase, leukocytosis, and male gender. Management of post-PV/post-ET myelofibrosis recapitulates that of PMF.

Leukemic Transformation

The presence of more than 20% blasts in peripheral blood or bone marrow in a patient with MPN defines leukemic transformation. This occurs in up to 5% to 10% of patients and may or may not be preceded by a myelofibrosis phase.¹²⁶ In cases of extramedullary transformation, a lower percentage of blasts can be seen in the bone marrow compared to the peripheral blood. The pathogenesis of leukemic transformation has remained elusive, but it is believed to be associated with genetic instability, which facilitates the acquisition of additional mutations, including those of TET2, ASXL1, EZH2 and DNMT3, IDH1/2, and TP53.¹²⁷

 

Clinical risk factors for leukemic transformation include advanced age, karyotypic abnormalities, prior therapy with alkylating agents or P-32, splenectomy, increased peripheral blood or bone marrow blasts, leukocytosis, anemia, thrombocytopenia, and cytogenetic abnormalities. Hydroxyurea, interferon, and ruxolitinib have not been shown to have leukemogenic potential thus far. Prognosis of leukemic transformation is uniformly poor and patient survival rarely exceeds 6 months.

There is no standard of care for leukemic transformation of MPN (MPN-LT). Treatment options range from low-intensity regimens to more aggressive AML-type induction chemotherapy. No strategy appears clearly superior to others.¹²⁸ Hematopoietic stem cell transplantation is the only therapy that provides clinically meaningful benefit to patients,¹²⁹ but it is applicable only to a minority of patients with chemosensitive disease and good performance status.¹³⁰ Notable experimental approaches to MPN–LT include hypomethylating agents, such as decitabine¹³¹ or azacitidine,¹³² with or without ruxolitinib.^133-135

Conclusion

PV and ET are rare, chronic myeloid disorders. Patients typically experience a long clinical course and enjoy near-normal quality of life if properly managed. The 2 most important life-limiting complications of PV and ET are thrombohemorrhagic events and myelofibrosis/AML transformation. Vascular events are at least in part preventable with counseling on risk factors, phlebotomy (for patients with PV), antiplatelet therapy, and cytoreduction with hydroxyurea, IFNs, or anagrelide (for patients with ET). In addition, ruxolitinib was recently approved for PV patients after hydroxyurea failure. PV/ET transformation in myelofibrosis or AML is part of the natural history of the disease and no therapy has been shown to prevent it. Treatment follows recommendations set forth for PMF and AML, but results are generally poorer and novel strategies are needed to improve patients’ outcomes.

Introduction

Polycythemia vera (PV) and essential thrombocythemia (ET), along with primary myelofibrosis (PMF), belong to the group of Philadelphia-negative myeloproliferative neoplasms (MPN). All these malignancies arise from the clonal proliferation of an aberrant hematopoietic stem cell, but are characterized by distinct clinical phenotypes.^1,2 Although the clinical course of PV and ET is indolent, it can be complicated by thrombohemorrhagic episodes and/or evolution into myelofibrosis and/or acute myeloid leukemia (AML).³ Since vascular events are the most frequent life-threatening complications of PV and ET, therapeutic strategies are aimed at reducing this risk. Treatment may also help control other disease-associated symptoms.⁴ No therapy has been shown to prevent evolution of PV or ET into myelofibrosis or AML. The discovery of the Janus kinase 2 (JAK2)/V617F mutation in most patients with PV and over half of those with ET (and PMF)^5,6 has opened new avenues of research and led to the development of targeted therapies, such as the JAK1/2 inhibitor ruxolitinib, for patients with MPN.^7,8

Epidemiology

PV and ET are typically diagnosed in the fifth to seventh decade of life.⁹ Although these disorders are generally associated with a long clinical course, survival of patients with PV or ET may be shorter than that of the general population.^10–13 Estimating the incidence and prevalence of MPN is a challenge because most patients remain asymptomatic for long periods of time and do not seek medical attention.¹³ The annual incidence rates of PV and ET are estimated at 0.01 to 2.61 and 0.21 to 2.53 per 100,000, respectively. PV occurs slightly more frequently in males, whereas ET has a predilection for females.¹⁴ Given the long course and low mortality associated with these disorders, the prevalence of PV and ET are significantly higher than the respective incidence: up to 47 and 57 per 100,000, respectively.^15–17

Molecular Pathogenesis

In 2005 researchers discovered a gain-of-function mutation of the JAK2 gene in nearly all patients with PV and more than half of those with ET and PMF.^5,6,18,19 JAK2 is a non-receptor tyrosine kinase that plays a central role in normal hematopoiesis. Substitution of a valine for a phenylalanine at codon 617 (ie, V617F) leads to its constitutive activation and signaling through the JAK-STAT pathway.^5,6,18,19 More rarely (and exclusively in patients with PV), JAK2 mutations involve exon 12.^20–22 The vast majority of JAK2-negative ET patients harbor mutations in either the myeloproliferative leukemia (MPL) gene, which encodes the thrombopoietin receptor,^23–25 or the calreticulin (CALR) gene,^26,27 which encodes for a chaperone protein that plays a role in cellular proliferation, differentiation, and apoptosis.²⁸ Both the MPL and CALR mutations ultimately result in the constitutive activation of the JAK-STAT pathway. Thus, JAK2, MPL, and CALR alterations are collectively referred to as driver mutations. Moreover, because these mutations affect the same oncogenic pathway (ie, JAK-STAT), they are almost always mutually exclusive in a given patient. Patients with ET (or myelofibrosis) who are wild-type for JAK2, MPL, and CALR are referred to as having “triple-negative” disease. Many recurrent non-driver mutations are also found in patients with MPN that are not exclusive of each other (ie, patients may have many at the same time), and involve for example ten-eleven translocation-2 (TET2), additional sex combs like 1 (ASXL1), enhancer of zeste homolog 2 (EZH2), isocitrate dehydrogenase 1 and isocitrate dehydrogenase 2 (IDH1/2), and DNA methyltransferase 3A (DNMT3A) genes, among others.²⁹ The biologic and prognostic significance of these non-driver alterations remain to be fully defined in ET and PV.

Diagnosis and Risk Assessment

Case Presentations

Patient A is a 68-year-old man with a history of gouty arthritis who presents with a 6-month history of recurrent headaches and itching that increases after a hot shower. Over the past 2 months, he has also noticed worsening fatigue and redness of his face. He is a nonsmoker. Physical exam reveals erythromelalgia (ie, erythema, edema, and warmth) of the upper and lower extremities, scattered scratch marks, and splenomegaly 4 cm below the costal margin. Complete blood count (CBC) shows a white blood cell (WBC) count of 8100/µL, hemoglobin 194 g/L, and platelets 582 × 10³/µL. Serum erythropoietin level is decreased at 2 mU/mL. Peripheral blood testing reveals a JAK2V617F mutation.

Patient B is a 51-year-old woman with a history of severe depression treated with sertraline and hypertension controlled with lisinopril and amlodipine who presents to her primary care physician for her “50-year-old physical.” She denies symptoms and is a nonsmoker. Physical exam is unrevealing. CBC shows a WBC count of 7400/µL (normal differential), hemoglobin 135 g/L, and platelets 1282 × 10³/µL. A bone marrow biopsy shows normal cellularity with clusters of large, hyperlobulated megakaryocytes. Reverse transcriptase-polymerase chain reaction fails to reveal a BCR-ABL fusion product. The patient is diagnosed with ET.

 

Diagnostic Criteria

Diagnostic criteria for PV and ET according to the World Health Organization (WHO) classification³⁰ are summarized in Table 1. Criteria for the diagnosis of prefibrotic myelofibrosis are included as well since this entity was formally recognized as separate from ET and part of the PMF spectrum in the 2016 WHO classification of myeloid tumors.³⁰

Clinically, both PV and ET generally remain asymptomatic for a long time. PV tends to be more symptomatic than ET and can present with debilitating constitutional symptoms (fatigue, night sweats, weight loss, pruritus), microvascular symptoms (headache, lightheadedness, acral paresthesias, erythromelalgia, atypical chest pain, and pruritus),³¹ or macrovascular accidents (larger vein thrombosis, stroke, or myocardial ischemia).³² ET is often diagnosed incidentally, but patients can suffer from similar general symptoms and vascular complications. Causes of secondary absolute erythrocytosis (altitude, chronic hypoxemia, heavy smoking, cardiomyopathy, use of corticosteroids, erythropoietin, or other anabolic hormones, familial or congenital forms) or thrombocytosis (iron deficiency, acute blood loss, trauma or injury, acute coronary syndrome, systemic autoimmune disorders, chronic kidney failure, other malignancies, splenectomy) should be considered and appropriately excluded. Once the diagnosis is made, symptom assessment tools such as the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF)³³ or the abbreviated version, the MPN-SAF Total Symptom Score (MPN-SAF TSS),³⁴ are generally used to assess patients’ symptom burden and response to treatment in everyday practice.

Risk Stratification

Thrombohemorrhagic events, evolution into myelofibrosis, and leukemic transformation are the most serious complications in the course of PV or ET. Only thrombohemorrhagic events are, at least partially, preventable. Arterial or venous thrombotic complications are observed at rates of 1.8 to 10.9 per 100 patient-years in PV (arterial thrombosis being more common than venous) and 0.74 to 7.7 per 100 patient-years in ET, depending on the risk group³⁵ and the presence of other factors (see below).

Thrombosis Risk Stratification in PV

The risk stratification of patients with PV is based on 2 factors: age ≥ 60 years and prior history of thrombosis. If either is present the patient is assigned to the high-risk category, whereas if none is present the patient is considered at low risk.³⁶ In addition, high hematocrit³⁷ and high WBC,³⁸ but not thrombocytosis, have been associated with the development of vascular complications. In one study, the risk of new arterial thrombosis was increased by the presence of leukoerythroblastosis, hypertension, and prior arterial thrombosis, while karyotypic abnormalities and prior venous thrombosis were predictors of new venous thrombosis.³⁹ Another emerging risk factor for thrombosis in patients with PV is high JAK2 allele burden (ie, the normal-to-mutated gene product ratio), although the evidence supporting this conclusion is equivocal.⁴⁰

Thrombosis Risk Stratification in ET

Traditionally, in ET patients, thrombotic risk was assessed using the same 2 factors (age ≥ 60 years and prior history of thrombosis), separating patients into low- and high-risk groups. However, the prognostication of ET patients has been refined recently with the identification of new relevant factors. In particular, the impact of JAK2 mutations on thrombotic risk has been thoroughly studied. Clinically, the presence of JAK2V617F is associated with older age, higher hemoglobin and hematocrit, lower platelet counts, more frequent need for cytoreductive treatment, and greater tendency to evolve into PV (a rare event).^41,42 Many,^41,43–46 but not all,^47–51 studies suggested a correlation between JAK2 mutation and risk of both arterial and venous thrombosis. Although infrequent, a JAK2V617F homozygous state (ie, the mutation is present in both alleles) might confer an even higher thrombotic risk.⁵² Moreover, the impact of the JAK2 mutation on vascular events persists over time,⁵³ particularly in patients with high or unstable mutation burden.⁵⁴ Based on JAK2V617F’s influence on the thrombotic risk of ET patients, a new prognostic score was proposed, the International Prognostic Score for ET (IPSET)-thrombosis (Table 2). The revised version of this model is currently endorsed by the National Comprehensive Cancer Network and divides patients into 4 risk groups: high, intermediate, low, and very low. Treatment recommendations vary according to the risk group (as described below).⁵⁵

Other thrombotic risk factors have been identified, but deemed not significant enough to be included in the model. Cardiovascular risk factors (hypercholesterolemia, hypertension, smoking, diabetes mellitus) can increase the risk of vascular events,^56–59 as can splenomegaly⁶⁰ and baseline or persistent leukocytosis.^61–63 Thrombocytosis has been correlated with thrombotic risk in some studies,^64–68 whereas others did not support this conclusion and/or suggested a lower rate of thrombosis and, in some cases, increased risk of bleeding in ET patients with platelet counts greater than 1000 × 10³/µL (due to acquired von Willebrand syndrome).^{56,61,63,68,69}

CALR mutations tend to occur in younger males with lower hemoglobin and WBC count, higher platelet count, and greater marrow megakaryocytic predominance as compared to JAK2 mutations.^{26,27,70–72} The associated incidence of thrombosis was less than 10% at 15 years in patients with CALR mutations, lower than the incidence reported for ET patients with JAK2V617F mutations.⁷³ The presence of the mutation per se does not appear to affect the thrombotic risk.^74–76 Information on the thrombotic risk associated with MPL mutations or a triple-negative state is scarce. In both instances, however, the risk appears to be lower than with the JAK2 mutation.^73,77–79

Venous thromboembolism in patients with PV or ET may occur at unusual sites, such as the splanchnic or cerebral venous systems.⁸⁰ Risk factors for unusual venous thromboembolism include younger age,⁸¹ female gender (especially with concomitant use of oral contraceptive pills),⁸² and splenomegaly/splenectomy.⁸³JAK2 mutation has also been associated with thrombosis at unusual sites. However, the prevalence of MPN or JAK2V617F in patients presenting with splanchnic venous thromboembolism has varied.⁸⁰ In addition, MPN may be occult (ie, no clinical or laboratory abnormalities) in around 15% of patients.⁸⁴ Screening for JAK2V617F and underlying MPN is recommended in patients presenting with isolated unexplained splanchnic venous thromboembolism. Treatment entails long-term anticoagulation therapy. JAK2V617F screening in patients with nonsplanchnic venous thromboembolism is not recommended, as its prevalence in this group is low (< 3%).^85,86

 

Treatment

Cases Continued

Patient A is diagnosed with PV based on the presence of 2 major criteria (elevated hemoglobin and presence of the JAK2V617F mutation) and 1 minor criterion (low erythropoietin level). Given his age, he belongs to the high-risk disease category. He is now seeking advice regarding the management of his newly diagnosed PV.

Patient B presents to the emergency department with right lower extremity swelling and is found to have deep femoral thrombosis extending to the iliac vein. Five days after being discharged from the emergency department, she presents for follow-up. She is taking warfarin compliantly and her INR is within therapeutic range. The patient now has high-risk ET and would like to know more about thrombosis in her condition and how to best manage her risk.

Risk-Adapted Therapy

Low-Risk PV

All patients with PV should receive counseling to mitigate cardiovascular risk factors, including smoking cessation, lifestyle modifications, and lipid-lowering therapy, as indicated. Furthermore, all PV patients should receive acetylsalicylic acid (ASA) to decrease their risk for thrombosis and control vasomotor symptoms.^55,87 Aspirin 81 to 100 mg daily is the preferred regimen because it provides adequate antithrombotic effect without the associated bleeding risk of higher-dose aspirin.⁸⁸ Low-risk PV patients should also receive periodic phlebotomies to reduce and maintain their hematocrit below 45%. This recommendation is based on the results of the Cytoreductive Therapy in Polycythemia Vera (CYTO PV) randomized controlled trial. In the CYTO PV study, patients receiving more intense therapy to maintain the hematocrit below 45% had a lower incidence of cardiovascular-related deaths or major thrombotic events than those with hematocrit goals of 45% to 50% (2.7% versus 9.8%).⁸⁹ Cytoreduction is an option for low-risk patients who do not tolerate phlebotomy or require frequent phlebotomy, or who have disease-related bleeding, severe symptoms, symptomatic splenomegaly, or progressive leukocytosis.³⁸

High-Risk PV

Patients older than 60 years and/or with a history of thrombosis should be considered for cytoreductive therapy in addition to the above measures. Front-line cytoreductive therapies include hydroxyurea or interferon (IFN)- alfa.⁸⁷ Hydroxyurea is a potent ribonucleotide reductase inhibitor that interferes with DNA repair and is the treatment of choice for most high-risk patients with PV.⁹⁰ In a small trial hydroxyurea reduced the risk of thrombosis compared with historical controls treated with phlebotomy alone.⁹¹ Hydroxyurea is generally well tolerated; common side effects include cytopenias, nail changes, and mucosal and/or skin ulcers. Although never formally proven to be leukemogenic, this agent should be used with caution in younger patients.⁸⁷ Indeed, in the original study, the rates of transformation were 5.9% and 1.5% for patients receiving hydroxyurea and phlebotomy alone,⁹² respectively, although an independent role for hydroxyurea in leukemic transformation was not supported in the much larger European Collaboration on Low-dose Aspirin in Polycythemia Vera (ECLAP) study.⁹³ About 70% of patients will have a sustained response to hydroxyurea,⁹⁴ while the remaining patients become resistant to or intolerant of the drug. Resistant individuals have a higher risk of progression to acute leukemia and death.⁹⁵

IFN alfa is a pleiotropic antitumor agent that has found application in many types of malignancies⁹⁶ and is sometimes employed as treatment for patients with newly diagnosed high-risk PV. Early studies showed responses in up to 100% of cases,^97,98 albeit at the expense of a high discontinuation rate due to adverse events, such as flu-like symptoms, fatigue, and neuropsychiatric manifestations.⁹⁹ A newer formulation of the drug obtained by adding a polyethylene glycol (PEG) moiety to the native IFN alfa molecule (PEG-IFN alfa) was shown to have a longer half-life, greater stability, less immunogenicity, and, potentially, better tolerability.¹⁰⁰ Pilot phase 2 trials of PEG-IFN alfa-2a demonstrated its remarkable activity, with symptomatic and hematologic responses seen in the majority of patients (which, in some cases, persisted beyond discontinuation), and reasonable tolerability, with long-term discontinuation rates of around 20% to 30%.^101–103 In some patients JAK2V617F became undetectable over time.¹⁰⁴ Results of 2 ongoing trials, MDP-RC111 (single-arm study, PEG-IFN alfa-2a in high-risk PV or ET [NCT01259817]) and MPD-RC112 (randomized controlled trial, PEG-IFN alfa-2a versus hydroxyurea in the same population [NCT01258856]), will shed light on the role of PEG-IFN alfa in the management of patients with high-risk PV or ET. In 2 phase 2 studies of PEG-IFN alfa-2b, complete responses were seen in 70% to 100% of patients and discontinuation occurred in around a third of cases.^105,106 A new, longer-acting formulation of PEG-IFN alfa-2a (peg-proline INF alfa-2b, AOP2014) is also undergoing clinical development.^107,108

The approach to treatment of PV based on thrombotic risk level is illustrated in Figure 1.

 

 

Very Low- and Low-Risk ET

Like patients with PV, individuals with ET should undergo rigorous cardiovascular risk management and generally receive ASA to decrease their thrombotic risk and improve symptom control. Antiplatelet therapy may not be warranted in patients with documented acquired von Willebrand syndrome, with or without extreme thrombocytosis, or in those in the very low-risk category according to the IPSET-thrombosis model.^55,87 The risk/benefit ratio of antiplatelet agents in patients with ET at different thrombotic risk levels was assessed in poor-quality studies and thus remains highly uncertain. Platelet-lowering agents are sometimes recommended in patients with low-risk disease who have platelet counts ≥ 1500 × 10³/µL, due to the potential risk of acquired von Willebrand syndrome and a risk of bleeding (this would require stopping ASA).¹⁰⁹ Cytoreduction may also be used in low-risk patients with progressive symptoms despite ASA, symptomatic or progressive splenomegaly, and progressive leukocytosis.

Intermediate-Risk ET

This category includes patients older than 60 years but without thrombosis or JAK2 mutations. These individuals would have been considered high risk (and thus candidates for cytoreductive therapy) according to the traditional risk stratification. Guidelines currently recommend ASA as the sole therapy for these patients, while reserving cytoreduction for those who experience thrombosis (ie, become high-risk) or have uncontrolled vasomotor or general symptoms, symptomatic splenomegaly, symptomatic thrombocytosis, or progressive leukocytosis.

High-Risk ET

For patients with ET in need of cytoreductive therapy (ie, those with prior thrombosis or older than 60 years with a JAK2V617F mutation), first-line options include hydroxyurea, IFN, and anagrelide. Hydroxyurea remains the treatment of choice in the majority of patients.¹¹⁰ In a seminal study, 114 patients with ET were randomly assigned to either observation or hydroxyurea treatment with the goal of maintaining the platelet count below 600 × 10³/µL. At a median follow-up of 27 months, patients in the hydroxyurea group had a lower thrombosis rate (3.6% versus 24%, P = 0.003) and longer thrombosis-free survival, regardless of the use of antiplatelet drugs.⁶⁴

Anagrelide, a selective inhibitor of megakaryocytic differentiation and proliferation, was compared with hydroxyurea in patients with ET in 2 randomized trials. In the first (N = 809), the group receiving anagrelide had a higher risk of arterial thrombosis, major bleeding, and fibrotic evolution, but lower incidence of venous thrombosis. Hydroxyurea was better tolerated, mainly due to anagrelide-related cardiovascular adverse events.¹¹¹ As a result of this study, hydroxyurea is often preferred to anagrelide as front-line therapy for patients with newly diagnosed high-risk ET. In the second, more recent study (N = 259), however, the 2 agents proved equivalent in terms of major or minor arterial or venous thrombosis, as well as discontinuation rate.¹¹² The discrepancy between the 2 trials may be partly explained by the different ET diagnostic criteria used, with the latter only enrolling patients with WHO-defined true ET, while the former utilized Polycythemia Vera Study Group-ET diagnostic criteria that included patients with increases in other blood counts or varying degrees of marrow fibrosis.

Interferons were studied in ET in parallel with PV. PEG-IFN alfa-2a proved effective in patients with ET, with responses observed in 80% of patients.¹⁰³ PEG-IFN alfa-2b produced similar results, with responses in 70% to 90% of patients in small studies and discontinuation observed in 20% to 38% of cases.^105,106,113 Because the very long-term leukemogenic potential of hydroxyurea has remained somewhat uncertain, anagrelide or IFN might be preferable choices in younger patients.

The approach to treatment of ET based on thrombotic risk level is illustrated in Figure 2.

Assessing Response to Therapy

For both patients with PV and ET the endpoint of treatment set forth for clinical trials has been the achievement of a clinicohematologic response. However, studies have failed to show a correlation between response and reduction of the thrombohemorrhagic risk.¹¹⁴ Therefore, proposed clinical trial response criteria were revised to include absence of hemorrhagic or thrombotic events as part of the definition of response (Table 3).⁹⁴

Cases Continued

Patient A was initially treated with phlebotomies and his blood counts were subsequently controlled with hydroxyurea, which he took uninterruptedly at an average dose of 2.5 g daily. He also took ASA daily throughout. Now, 18 months after the start of therapy, he presents with a complaint of fatigue for the past 3 months, which more recently has been associated with recurrent itching. A repeat CBC shows a WBC count of 17,200/µL, hemoglobin 181 g/L, and platelets 940 × 10³/µL.

Patient B presents for scheduled follow-up. She has had no further thrombotic episodes. However, she spontaneously discontinued hydroxyurea 1 month ago because of worsening mouth ulcers that impaired her ability to eat even small meals. She seeks recommendations for further treatment options.

 

Approach to Patients Refractory to or Intolerant of First-Line Therapy

According to the European LeukemiaNet recommendations, an inadequate response to hydroxyurea in patients with PV (or myelofibrosis) is defined as a need for phlebotomy to maintain hematocrit below < 45%, platelet count > 400 × 10³/µL, and a WBC count > 10,000/µL, or failure to reduce splenomegaly > 10 cm by > 50% at a dose of ≥ 2 g/day or maximum tolerated dose. Historically, treatment options for patients with PV or ET who failed first-line therapy (most commonly hydroxyurea) have included alkylating agents, such as busulfan, chlorambucil, or pipobroman, and phosphorus (P)-32. However, the use of these drugs is limited by the associated risk of leukemic transformation.^93,115,116 The use of IFN (or anagrelide for ET) is often considered in patients previously treated with hydroxyurea, and vice versa.

Ruxolitinib is a JAK1 and JAK2 inhibitor currently approved for the treatment of PV patients refractory to or intolerant of hydroxyurea.⁷ Following promising results of a phase 2 trial,¹¹⁷ ruxolitinib 10 mg twice daily was compared with best available therapy in the pivotal RESPONSE trial (N = 222). Ruxolitinib proved superior in achieving hematocrit control, reduction of spleen volume, and improvement of symptoms. Grade 3-4 hematologic toxicity was infrequent and similar in the 2 arms.¹¹⁸ In addition, longer follow-up of that study suggested a lower rate of thrombotic events in patients receiving ruxolitinib (1.8 versus 8.2 per 100 patient-years).¹¹⁹ In a similarly designed randomized phase 3 study in PV patients without splenomegaly (RESPONSE-2), more patients in the ruxolitinib arm had hematocrit reduction without an increase in toxicity. Based on the results of the above studies, ruxolitinib can be considered a standard of care for second-line therapy in this post-hydroxyurea patient population.¹²⁰

Ruxolitinib is also being tested in patients with high-risk ET who have become resistant to, or were intolerant of hydroxyurea, but currently has no approved indication in this setting.^121,122 Common side effects of ruxolitinib include cytopenias (especially anemia), increased risk of infections, hyperlipidemia, and increased risk of non-melanoma skin cancer.

Novel Agents

Novel agents that have been studied in patients with PV and ET are histone deacetylase inhibitors, murine double minute 2 (MDM2, or HDM2 for their human counterpart) inhibitors (which restore the function of p53), Bcl-2 homology domain 3 mimetics such as navitoclax and venetoclax, and, for patients with ET, the telomerase inhibitor imetelstat.¹²³

Disease Evolution

Cases Continued

Patient A’s PV has been well controlled with PEG-IFN alfa-2a 90 μg subcutaneously weekly. However, he now presents with a complaint of worsening fatigue and early satiety. On exam the patient appears ill and splenomegaly is appreciated 12 cm below the costal margin. CBC shows a WBC count of 2600/µL, hemoglobin 73 g/L, and platelets 122 × 10³/µL. Peripheral blood smear reveals leukoerythroblastosis and dacro­cytosis. CBC 6 months ago was normal. A bone marrow biopsy is consistent with myelofibrosis.

After discontinuing hydroxyurea, patient B’s ET has been well controlled with anagrelide. However, for the past 4 weeks she has complained of severe fatigue and easy bruising. Physical exam reveals a pale, ill-appearing woman with scattered bruises. CBC shows a WBC count of 14,600/µL with 44% myeloblasts, hemoglobin 73 g/L, and platelets 22 × 10³/µL. CBC 6 months ago was normal. A bone marrow biopsy is consistent with leukemic transformation of ET.

Post-PV/Post-ET Myelofibrosis

Diagnostic criteria for post-PV and post-ET myelofibrosis are outlined in Table 4.

Fibrotic transformation represents a natural evolution of the clinical course of PV or ET. It occurs in up to 15% and 9% of patients with PV and ET, respectively, in western countries.¹²⁴ The true percentage of ET patients who develop myelofibrosis is confounded by the inclusion of prefibrotic myelofibrosis cases in earlier series. The survival of patients who develop myelofibrosis is shortened compared to those who do not. In PV patients risk factors for myelofibrosis evolution include advanced age, leukocytosis, JAK2V617F homozygosity or higher allele burden, and hydroxyurea therapy. Once post-PV myelofibrosis has occurred, hemoglobin < 10 g/dL, platelet count < 100 × 10³/µL, and WBC count > 30,000/µL are associated with worse outcomes.¹²⁵ In patients with ET, risk factors for myelofibrosis transformation include age, anemia, bone marrow hypercellularity and increased reticulin, increased lactate dehydrogenase, leukocytosis, and male gender. Management of post-PV/post-ET myelofibrosis recapitulates that of PMF.

Leukemic Transformation

The presence of more than 20% blasts in peripheral blood or bone marrow in a patient with MPN defines leukemic transformation. This occurs in up to 5% to 10% of patients and may or may not be preceded by a myelofibrosis phase.¹²⁶ In cases of extramedullary transformation, a lower percentage of blasts can be seen in the bone marrow compared to the peripheral blood. The pathogenesis of leukemic transformation has remained elusive, but it is believed to be associated with genetic instability, which facilitates the acquisition of additional mutations, including those of TET2, ASXL1, EZH2 and DNMT3, IDH1/2, and TP53.¹²⁷

 

Clinical risk factors for leukemic transformation include advanced age, karyotypic abnormalities, prior therapy with alkylating agents or P-32, splenectomy, increased peripheral blood or bone marrow blasts, leukocytosis, anemia, thrombocytopenia, and cytogenetic abnormalities. Hydroxyurea, interferon, and ruxolitinib have not been shown to have leukemogenic potential thus far. Prognosis of leukemic transformation is uniformly poor and patient survival rarely exceeds 6 months.

There is no standard of care for leukemic transformation of MPN (MPN-LT). Treatment options range from low-intensity regimens to more aggressive AML-type induction chemotherapy. No strategy appears clearly superior to others.¹²⁸ Hematopoietic stem cell transplantation is the only therapy that provides clinically meaningful benefit to patients,¹²⁹ but it is applicable only to a minority of patients with chemosensitive disease and good performance status.¹³⁰ Notable experimental approaches to MPN–LT include hypomethylating agents, such as decitabine¹³¹ or azacitidine,¹³² with or without ruxolitinib.^133-135

Conclusion

PV and ET are rare, chronic myeloid disorders. Patients typically experience a long clinical course and enjoy near-normal quality of life if properly managed. The 2 most important life-limiting complications of PV and ET are thrombohemorrhagic events and myelofibrosis/AML transformation. Vascular events are at least in part preventable with counseling on risk factors, phlebotomy (for patients with PV), antiplatelet therapy, and cytoreduction with hydroxyurea, IFNs, or anagrelide (for patients with ET). In addition, ruxolitinib was recently approved for PV patients after hydroxyurea failure. PV/ET transformation in myelofibrosis or AML is part of the natural history of the disease and no therapy has been shown to prevent it. Treatment follows recommendations set forth for PMF and AML, but results are generally poorer and novel strategies are needed to improve patients’ outcomes.

Introduction

Polycythemia vera (PV) and essential thrombocythemia (ET), along with primary myelofibrosis (PMF), belong to the group of Philadelphia-negative myeloproliferative neoplasms (MPN). All these malignancies arise from the clonal proliferation of an aberrant hematopoietic stem cell, but are characterized by distinct clinical phenotypes.^1,2 Although the clinical course of PV and ET is indolent, it can be complicated by thrombohemorrhagic episodes and/or evolution into myelofibrosis and/or acute myeloid leukemia (AML).³ Since vascular events are the most frequent life-threatening complications of PV and ET, therapeutic strategies are aimed at reducing this risk. Treatment may also help control other disease-associated symptoms.⁴ No therapy has been shown to prevent evolution of PV or ET into myelofibrosis or AML. The discovery of the Janus kinase 2 (JAK2)/V617F mutation in most patients with PV and over half of those with ET (and PMF)^5,6 has opened new avenues of research and led to the development of targeted therapies, such as the JAK1/2 inhibitor ruxolitinib, for patients with MPN.^7,8

Epidemiology

PV and ET are typically diagnosed in the fifth to seventh decade of life.⁹ Although these disorders are generally associated with a long clinical course, survival of patients with PV or ET may be shorter than that of the general population.^10–13 Estimating the incidence and prevalence of MPN is a challenge because most patients remain asymptomatic for long periods of time and do not seek medical attention.¹³ The annual incidence rates of PV and ET are estimated at 0.01 to 2.61 and 0.21 to 2.53 per 100,000, respectively. PV occurs slightly more frequently in males, whereas ET has a predilection for females.¹⁴ Given the long course and low mortality associated with these disorders, the prevalence of PV and ET are significantly higher than the respective incidence: up to 47 and 57 per 100,000, respectively.^15–17

Molecular Pathogenesis

In 2005 researchers discovered a gain-of-function mutation of the JAK2 gene in nearly all patients with PV and more than half of those with ET and PMF.^5,6,18,19 JAK2 is a non-receptor tyrosine kinase that plays a central role in normal hematopoiesis. Substitution of a valine for a phenylalanine at codon 617 (ie, V617F) leads to its constitutive activation and signaling through the JAK-STAT pathway.^5,6,18,19 More rarely (and exclusively in patients with PV), JAK2 mutations involve exon 12.^20–22 The vast majority of JAK2-negative ET patients harbor mutations in either the myeloproliferative leukemia (MPL) gene, which encodes the thrombopoietin receptor,^23–25 or the calreticulin (CALR) gene,^26,27 which encodes for a chaperone protein that plays a role in cellular proliferation, differentiation, and apoptosis.²⁸ Both the MPL and CALR mutations ultimately result in the constitutive activation of the JAK-STAT pathway. Thus, JAK2, MPL, and CALR alterations are collectively referred to as driver mutations. Moreover, because these mutations affect the same oncogenic pathway (ie, JAK-STAT), they are almost always mutually exclusive in a given patient. Patients with ET (or myelofibrosis) who are wild-type for JAK2, MPL, and CALR are referred to as having “triple-negative” disease. Many recurrent non-driver mutations are also found in patients with MPN that are not exclusive of each other (ie, patients may have many at the same time), and involve for example ten-eleven translocation-2 (TET2), additional sex combs like 1 (ASXL1), enhancer of zeste homolog 2 (EZH2), isocitrate dehydrogenase 1 and isocitrate dehydrogenase 2 (IDH1/2), and DNA methyltransferase 3A (DNMT3A) genes, among others.²⁹ The biologic and prognostic significance of these non-driver alterations remain to be fully defined in ET and PV.

Diagnosis and Risk Assessment

Case Presentations

Patient A is a 68-year-old man with a history of gouty arthritis who presents with a 6-month history of recurrent headaches and itching that increases after a hot shower. Over the past 2 months, he has also noticed worsening fatigue and redness of his face. He is a nonsmoker. Physical exam reveals erythromelalgia (ie, erythema, edema, and warmth) of the upper and lower extremities, scattered scratch marks, and splenomegaly 4 cm below the costal margin. Complete blood count (CBC) shows a white blood cell (WBC) count of 8100/µL, hemoglobin 194 g/L, and platelets 582 × 10³/µL. Serum erythropoietin level is decreased at 2 mU/mL. Peripheral blood testing reveals a JAK2V617F mutation.

Patient B is a 51-year-old woman with a history of severe depression treated with sertraline and hypertension controlled with lisinopril and amlodipine who presents to her primary care physician for her “50-year-old physical.” She denies symptoms and is a nonsmoker. Physical exam is unrevealing. CBC shows a WBC count of 7400/µL (normal differential), hemoglobin 135 g/L, and platelets 1282 × 10³/µL. A bone marrow biopsy shows normal cellularity with clusters of large, hyperlobulated megakaryocytes. Reverse transcriptase-polymerase chain reaction fails to reveal a BCR-ABL fusion product. The patient is diagnosed with ET.

 

Diagnostic Criteria

Diagnostic criteria for PV and ET according to the World Health Organization (WHO) classification³⁰ are summarized in Table 1. Criteria for the diagnosis of prefibrotic myelofibrosis are included as well since this entity was formally recognized as separate from ET and part of the PMF spectrum in the 2016 WHO classification of myeloid tumors.³⁰

Clinically, both PV and ET generally remain asymptomatic for a long time. PV tends to be more symptomatic than ET and can present with debilitating constitutional symptoms (fatigue, night sweats, weight loss, pruritus), microvascular symptoms (headache, lightheadedness, acral paresthesias, erythromelalgia, atypical chest pain, and pruritus),³¹ or macrovascular accidents (larger vein thrombosis, stroke, or myocardial ischemia).³² ET is often diagnosed incidentally, but patients can suffer from similar general symptoms and vascular complications. Causes of secondary absolute erythrocytosis (altitude, chronic hypoxemia, heavy smoking, cardiomyopathy, use of corticosteroids, erythropoietin, or other anabolic hormones, familial or congenital forms) or thrombocytosis (iron deficiency, acute blood loss, trauma or injury, acute coronary syndrome, systemic autoimmune disorders, chronic kidney failure, other malignancies, splenectomy) should be considered and appropriately excluded. Once the diagnosis is made, symptom assessment tools such as the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF)³³ or the abbreviated version, the MPN-SAF Total Symptom Score (MPN-SAF TSS),³⁴ are generally used to assess patients’ symptom burden and response to treatment in everyday practice.

Risk Stratification

Thrombohemorrhagic events, evolution into myelofibrosis, and leukemic transformation are the most serious complications in the course of PV or ET. Only thrombohemorrhagic events are, at least partially, preventable. Arterial or venous thrombotic complications are observed at rates of 1.8 to 10.9 per 100 patient-years in PV (arterial thrombosis being more common than venous) and 0.74 to 7.7 per 100 patient-years in ET, depending on the risk group³⁵ and the presence of other factors (see below).

Thrombosis Risk Stratification in PV

The risk stratification of patients with PV is based on 2 factors: age ≥ 60 years and prior history of thrombosis. If either is present the patient is assigned to the high-risk category, whereas if none is present the patient is considered at low risk.³⁶ In addition, high hematocrit³⁷ and high WBC,³⁸ but not thrombocytosis, have been associated with the development of vascular complications. In one study, the risk of new arterial thrombosis was increased by the presence of leukoerythroblastosis, hypertension, and prior arterial thrombosis, while karyotypic abnormalities and prior venous thrombosis were predictors of new venous thrombosis.³⁹ Another emerging risk factor for thrombosis in patients with PV is high JAK2 allele burden (ie, the normal-to-mutated gene product ratio), although the evidence supporting this conclusion is equivocal.⁴⁰

Thrombosis Risk Stratification in ET

Traditionally, in ET patients, thrombotic risk was assessed using the same 2 factors (age ≥ 60 years and prior history of thrombosis), separating patients into low- and high-risk groups. However, the prognostication of ET patients has been refined recently with the identification of new relevant factors. In particular, the impact of JAK2 mutations on thrombotic risk has been thoroughly studied. Clinically, the presence of JAK2V617F is associated with older age, higher hemoglobin and hematocrit, lower platelet counts, more frequent need for cytoreductive treatment, and greater tendency to evolve into PV (a rare event).^41,42 Many,^41,43–46 but not all,^47–51 studies suggested a correlation between JAK2 mutation and risk of both arterial and venous thrombosis. Although infrequent, a JAK2V617F homozygous state (ie, the mutation is present in both alleles) might confer an even higher thrombotic risk.⁵² Moreover, the impact of the JAK2 mutation on vascular events persists over time,⁵³ particularly in patients with high or unstable mutation burden.⁵⁴ Based on JAK2V617F’s influence on the thrombotic risk of ET patients, a new prognostic score was proposed, the International Prognostic Score for ET (IPSET)-thrombosis (Table 2). The revised version of this model is currently endorsed by the National Comprehensive Cancer Network and divides patients into 4 risk groups: high, intermediate, low, and very low. Treatment recommendations vary according to the risk group (as described below).⁵⁵

Other thrombotic risk factors have been identified, but deemed not significant enough to be included in the model. Cardiovascular risk factors (hypercholesterolemia, hypertension, smoking, diabetes mellitus) can increase the risk of vascular events,^56–59 as can splenomegaly⁶⁰ and baseline or persistent leukocytosis.^61–63 Thrombocytosis has been correlated with thrombotic risk in some studies,^64–68 whereas others did not support this conclusion and/or suggested a lower rate of thrombosis and, in some cases, increased risk of bleeding in ET patients with platelet counts greater than 1000 × 10³/µL (due to acquired von Willebrand syndrome).^{56,61,63,68,69}

CALR mutations tend to occur in younger males with lower hemoglobin and WBC count, higher platelet count, and greater marrow megakaryocytic predominance as compared to JAK2 mutations.^{26,27,70–72} The associated incidence of thrombosis was less than 10% at 15 years in patients with CALR mutations, lower than the incidence reported for ET patients with JAK2V617F mutations.⁷³ The presence of the mutation per se does not appear to affect the thrombotic risk.^74–76 Information on the thrombotic risk associated with MPL mutations or a triple-negative state is scarce. In both instances, however, the risk appears to be lower than with the JAK2 mutation.^73,77–79

Venous thromboembolism in patients with PV or ET may occur at unusual sites, such as the splanchnic or cerebral venous systems.⁸⁰ Risk factors for unusual venous thromboembolism include younger age,⁸¹ female gender (especially with concomitant use of oral contraceptive pills),⁸² and splenomegaly/splenectomy.⁸³JAK2 mutation has also been associated with thrombosis at unusual sites. However, the prevalence of MPN or JAK2V617F in patients presenting with splanchnic venous thromboembolism has varied.⁸⁰ In addition, MPN may be occult (ie, no clinical or laboratory abnormalities) in around 15% of patients.⁸⁴ Screening for JAK2V617F and underlying MPN is recommended in patients presenting with isolated unexplained splanchnic venous thromboembolism. Treatment entails long-term anticoagulation therapy. JAK2V617F screening in patients with nonsplanchnic venous thromboembolism is not recommended, as its prevalence in this group is low (< 3%).^85,86

 

Treatment

Cases Continued

Patient A is diagnosed with PV based on the presence of 2 major criteria (elevated hemoglobin and presence of the JAK2V617F mutation) and 1 minor criterion (low erythropoietin level). Given his age, he belongs to the high-risk disease category. He is now seeking advice regarding the management of his newly diagnosed PV.

Patient B presents to the emergency department with right lower extremity swelling and is found to have deep femoral thrombosis extending to the iliac vein. Five days after being discharged from the emergency department, she presents for follow-up. She is taking warfarin compliantly and her INR is within therapeutic range. The patient now has high-risk ET and would like to know more about thrombosis in her condition and how to best manage her risk.

Risk-Adapted Therapy

Low-Risk PV

All patients with PV should receive counseling to mitigate cardiovascular risk factors, including smoking cessation, lifestyle modifications, and lipid-lowering therapy, as indicated. Furthermore, all PV patients should receive acetylsalicylic acid (ASA) to decrease their risk for thrombosis and control vasomotor symptoms.^55,87 Aspirin 81 to 100 mg daily is the preferred regimen because it provides adequate antithrombotic effect without the associated bleeding risk of higher-dose aspirin.⁸⁸ Low-risk PV patients should also receive periodic phlebotomies to reduce and maintain their hematocrit below 45%. This recommendation is based on the results of the Cytoreductive Therapy in Polycythemia Vera (CYTO PV) randomized controlled trial. In the CYTO PV study, patients receiving more intense therapy to maintain the hematocrit below 45% had a lower incidence of cardiovascular-related deaths or major thrombotic events than those with hematocrit goals of 45% to 50% (2.7% versus 9.8%).⁸⁹ Cytoreduction is an option for low-risk patients who do not tolerate phlebotomy or require frequent phlebotomy, or who have disease-related bleeding, severe symptoms, symptomatic splenomegaly, or progressive leukocytosis.³⁸

High-Risk PV

Patients older than 60 years and/or with a history of thrombosis should be considered for cytoreductive therapy in addition to the above measures. Front-line cytoreductive therapies include hydroxyurea or interferon (IFN)- alfa.⁸⁷ Hydroxyurea is a potent ribonucleotide reductase inhibitor that interferes with DNA repair and is the treatment of choice for most high-risk patients with PV.⁹⁰ In a small trial hydroxyurea reduced the risk of thrombosis compared with historical controls treated with phlebotomy alone.⁹¹ Hydroxyurea is generally well tolerated; common side effects include cytopenias, nail changes, and mucosal and/or skin ulcers. Although never formally proven to be leukemogenic, this agent should be used with caution in younger patients.⁸⁷ Indeed, in the original study, the rates of transformation were 5.9% and 1.5% for patients receiving hydroxyurea and phlebotomy alone,⁹² respectively, although an independent role for hydroxyurea in leukemic transformation was not supported in the much larger European Collaboration on Low-dose Aspirin in Polycythemia Vera (ECLAP) study.⁹³ About 70% of patients will have a sustained response to hydroxyurea,⁹⁴ while the remaining patients become resistant to or intolerant of the drug. Resistant individuals have a higher risk of progression to acute leukemia and death.⁹⁵

IFN alfa is a pleiotropic antitumor agent that has found application in many types of malignancies⁹⁶ and is sometimes employed as treatment for patients with newly diagnosed high-risk PV. Early studies showed responses in up to 100% of cases,^97,98 albeit at the expense of a high discontinuation rate due to adverse events, such as flu-like symptoms, fatigue, and neuropsychiatric manifestations.⁹⁹ A newer formulation of the drug obtained by adding a polyethylene glycol (PEG) moiety to the native IFN alfa molecule (PEG-IFN alfa) was shown to have a longer half-life, greater stability, less immunogenicity, and, potentially, better tolerability.¹⁰⁰ Pilot phase 2 trials of PEG-IFN alfa-2a demonstrated its remarkable activity, with symptomatic and hematologic responses seen in the majority of patients (which, in some cases, persisted beyond discontinuation), and reasonable tolerability, with long-term discontinuation rates of around 20% to 30%.^101–103 In some patients JAK2V617F became undetectable over time.¹⁰⁴ Results of 2 ongoing trials, MDP-RC111 (single-arm study, PEG-IFN alfa-2a in high-risk PV or ET [NCT01259817]) and MPD-RC112 (randomized controlled trial, PEG-IFN alfa-2a versus hydroxyurea in the same population [NCT01258856]), will shed light on the role of PEG-IFN alfa in the management of patients with high-risk PV or ET. In 2 phase 2 studies of PEG-IFN alfa-2b, complete responses were seen in 70% to 100% of patients and discontinuation occurred in around a third of cases.^105,106 A new, longer-acting formulation of PEG-IFN alfa-2a (peg-proline INF alfa-2b, AOP2014) is also undergoing clinical development.^107,108

The approach to treatment of PV based on thrombotic risk level is illustrated in Figure 1.

 

 

Very Low- and Low-Risk ET

Like patients with PV, individuals with ET should undergo rigorous cardiovascular risk management and generally receive ASA to decrease their thrombotic risk and improve symptom control. Antiplatelet therapy may not be warranted in patients with documented acquired von Willebrand syndrome, with or without extreme thrombocytosis, or in those in the very low-risk category according to the IPSET-thrombosis model.^55,87 The risk/benefit ratio of antiplatelet agents in patients with ET at different thrombotic risk levels was assessed in poor-quality studies and thus remains highly uncertain. Platelet-lowering agents are sometimes recommended in patients with low-risk disease who have platelet counts ≥ 1500 × 10³/µL, due to the potential risk of acquired von Willebrand syndrome and a risk of bleeding (this would require stopping ASA).¹⁰⁹ Cytoreduction may also be used in low-risk patients with progressive symptoms despite ASA, symptomatic or progressive splenomegaly, and progressive leukocytosis.

Intermediate-Risk ET

This category includes patients older than 60 years but without thrombosis or JAK2 mutations. These individuals would have been considered high risk (and thus candidates for cytoreductive therapy) according to the traditional risk stratification. Guidelines currently recommend ASA as the sole therapy for these patients, while reserving cytoreduction for those who experience thrombosis (ie, become high-risk) or have uncontrolled vasomotor or general symptoms, symptomatic splenomegaly, symptomatic thrombocytosis, or progressive leukocytosis.

High-Risk ET

For patients with ET in need of cytoreductive therapy (ie, those with prior thrombosis or older than 60 years with a JAK2V617F mutation), first-line options include hydroxyurea, IFN, and anagrelide. Hydroxyurea remains the treatment of choice in the majority of patients.¹¹⁰ In a seminal study, 114 patients with ET were randomly assigned to either observation or hydroxyurea treatment with the goal of maintaining the platelet count below 600 × 10³/µL. At a median follow-up of 27 months, patients in the hydroxyurea group had a lower thrombosis rate (3.6% versus 24%, P = 0.003) and longer thrombosis-free survival, regardless of the use of antiplatelet drugs.⁶⁴

Anagrelide, a selective inhibitor of megakaryocytic differentiation and proliferation, was compared with hydroxyurea in patients with ET in 2 randomized trials. In the first (N = 809), the group receiving anagrelide had a higher risk of arterial thrombosis, major bleeding, and fibrotic evolution, but lower incidence of venous thrombosis. Hydroxyurea was better tolerated, mainly due to anagrelide-related cardiovascular adverse events.¹¹¹ As a result of this study, hydroxyurea is often preferred to anagrelide as front-line therapy for patients with newly diagnosed high-risk ET. In the second, more recent study (N = 259), however, the 2 agents proved equivalent in terms of major or minor arterial or venous thrombosis, as well as discontinuation rate.¹¹² The discrepancy between the 2 trials may be partly explained by the different ET diagnostic criteria used, with the latter only enrolling patients with WHO-defined true ET, while the former utilized Polycythemia Vera Study Group-ET diagnostic criteria that included patients with increases in other blood counts or varying degrees of marrow fibrosis.

Interferons were studied in ET in parallel with PV. PEG-IFN alfa-2a proved effective in patients with ET, with responses observed in 80% of patients.¹⁰³ PEG-IFN alfa-2b produced similar results, with responses in 70% to 90% of patients in small studies and discontinuation observed in 20% to 38% of cases.^105,106,113 Because the very long-term leukemogenic potential of hydroxyurea has remained somewhat uncertain, anagrelide or IFN might be preferable choices in younger patients.

The approach to treatment of ET based on thrombotic risk level is illustrated in Figure 2.

Assessing Response to Therapy

For both patients with PV and ET the endpoint of treatment set forth for clinical trials has been the achievement of a clinicohematologic response. However, studies have failed to show a correlation between response and reduction of the thrombohemorrhagic risk.¹¹⁴ Therefore, proposed clinical trial response criteria were revised to include absence of hemorrhagic or thrombotic events as part of the definition of response (Table 3).⁹⁴

Cases Continued

Patient A was initially treated with phlebotomies and his blood counts were subsequently controlled with hydroxyurea, which he took uninterruptedly at an average dose of 2.5 g daily. He also took ASA daily throughout. Now, 18 months after the start of therapy, he presents with a complaint of fatigue for the past 3 months, which more recently has been associated with recurrent itching. A repeat CBC shows a WBC count of 17,200/µL, hemoglobin 181 g/L, and platelets 940 × 10³/µL.

Patient B presents for scheduled follow-up. She has had no further thrombotic episodes. However, she spontaneously discontinued hydroxyurea 1 month ago because of worsening mouth ulcers that impaired her ability to eat even small meals. She seeks recommendations for further treatment options.

 

Approach to Patients Refractory to or Intolerant of First-Line Therapy

According to the European LeukemiaNet recommendations, an inadequate response to hydroxyurea in patients with PV (or myelofibrosis) is defined as a need for phlebotomy to maintain hematocrit below < 45%, platelet count > 400 × 10³/µL, and a WBC count > 10,000/µL, or failure to reduce splenomegaly > 10 cm by > 50% at a dose of ≥ 2 g/day or maximum tolerated dose. Historically, treatment options for patients with PV or ET who failed first-line therapy (most commonly hydroxyurea) have included alkylating agents, such as busulfan, chlorambucil, or pipobroman, and phosphorus (P)-32. However, the use of these drugs is limited by the associated risk of leukemic transformation.^93,115,116 The use of IFN (or anagrelide for ET) is often considered in patients previously treated with hydroxyurea, and vice versa.

Ruxolitinib is a JAK1 and JAK2 inhibitor currently approved for the treatment of PV patients refractory to or intolerant of hydroxyurea.⁷ Following promising results of a phase 2 trial,¹¹⁷ ruxolitinib 10 mg twice daily was compared with best available therapy in the pivotal RESPONSE trial (N = 222). Ruxolitinib proved superior in achieving hematocrit control, reduction of spleen volume, and improvement of symptoms. Grade 3-4 hematologic toxicity was infrequent and similar in the 2 arms.¹¹⁸ In addition, longer follow-up of that study suggested a lower rate of thrombotic events in patients receiving ruxolitinib (1.8 versus 8.2 per 100 patient-years).¹¹⁹ In a similarly designed randomized phase 3 study in PV patients without splenomegaly (RESPONSE-2), more patients in the ruxolitinib arm had hematocrit reduction without an increase in toxicity. Based on the results of the above studies, ruxolitinib can be considered a standard of care for second-line therapy in this post-hydroxyurea patient population.¹²⁰

Ruxolitinib is also being tested in patients with high-risk ET who have become resistant to, or were intolerant of hydroxyurea, but currently has no approved indication in this setting.^121,122 Common side effects of ruxolitinib include cytopenias (especially anemia), increased risk of infections, hyperlipidemia, and increased risk of non-melanoma skin cancer.

Novel Agents

Novel agents that have been studied in patients with PV and ET are histone deacetylase inhibitors, murine double minute 2 (MDM2, or HDM2 for their human counterpart) inhibitors (which restore the function of p53), Bcl-2 homology domain 3 mimetics such as navitoclax and venetoclax, and, for patients with ET, the telomerase inhibitor imetelstat.¹²³

Disease Evolution

Cases Continued

Patient A’s PV has been well controlled with PEG-IFN alfa-2a 90 μg subcutaneously weekly. However, he now presents with a complaint of worsening fatigue and early satiety. On exam the patient appears ill and splenomegaly is appreciated 12 cm below the costal margin. CBC shows a WBC count of 2600/µL, hemoglobin 73 g/L, and platelets 122 × 10³/µL. Peripheral blood smear reveals leukoerythroblastosis and dacro­cytosis. CBC 6 months ago was normal. A bone marrow biopsy is consistent with myelofibrosis.

After discontinuing hydroxyurea, patient B’s ET has been well controlled with anagrelide. However, for the past 4 weeks she has complained of severe fatigue and easy bruising. Physical exam reveals a pale, ill-appearing woman with scattered bruises. CBC shows a WBC count of 14,600/µL with 44% myeloblasts, hemoglobin 73 g/L, and platelets 22 × 10³/µL. CBC 6 months ago was normal. A bone marrow biopsy is consistent with leukemic transformation of ET.

Post-PV/Post-ET Myelofibrosis

Diagnostic criteria for post-PV and post-ET myelofibrosis are outlined in Table 4.

Fibrotic transformation represents a natural evolution of the clinical course of PV or ET. It occurs in up to 15% and 9% of patients with PV and ET, respectively, in western countries.¹²⁴ The true percentage of ET patients who develop myelofibrosis is confounded by the inclusion of prefibrotic myelofibrosis cases in earlier series. The survival of patients who develop myelofibrosis is shortened compared to those who do not. In PV patients risk factors for myelofibrosis evolution include advanced age, leukocytosis, JAK2V617F homozygosity or higher allele burden, and hydroxyurea therapy. Once post-PV myelofibrosis has occurred, hemoglobin < 10 g/dL, platelet count < 100 × 10³/µL, and WBC count > 30,000/µL are associated with worse outcomes.¹²⁵ In patients with ET, risk factors for myelofibrosis transformation include age, anemia, bone marrow hypercellularity and increased reticulin, increased lactate dehydrogenase, leukocytosis, and male gender. Management of post-PV/post-ET myelofibrosis recapitulates that of PMF.

Leukemic Transformation

The presence of more than 20% blasts in peripheral blood or bone marrow in a patient with MPN defines leukemic transformation. This occurs in up to 5% to 10% of patients and may or may not be preceded by a myelofibrosis phase.¹²⁶ In cases of extramedullary transformation, a lower percentage of blasts can be seen in the bone marrow compared to the peripheral blood. The pathogenesis of leukemic transformation has remained elusive, but it is believed to be associated with genetic instability, which facilitates the acquisition of additional mutations, including those of TET2, ASXL1, EZH2 and DNMT3, IDH1/2, and TP53.¹²⁷

 

Clinical risk factors for leukemic transformation include advanced age, karyotypic abnormalities, prior therapy with alkylating agents or P-32, splenectomy, increased peripheral blood or bone marrow blasts, leukocytosis, anemia, thrombocytopenia, and cytogenetic abnormalities. Hydroxyurea, interferon, and ruxolitinib have not been shown to have leukemogenic potential thus far. Prognosis of leukemic transformation is uniformly poor and patient survival rarely exceeds 6 months.

There is no standard of care for leukemic transformation of MPN (MPN-LT). Treatment options range from low-intensity regimens to more aggressive AML-type induction chemotherapy. No strategy appears clearly superior to others.¹²⁸ Hematopoietic stem cell transplantation is the only therapy that provides clinically meaningful benefit to patients,¹²⁹ but it is applicable only to a minority of patients with chemosensitive disease and good performance status.¹³⁰ Notable experimental approaches to MPN–LT include hypomethylating agents, such as decitabine¹³¹ or azacitidine,¹³² with or without ruxolitinib.^133-135

Conclusion

PV and ET are rare, chronic myeloid disorders. Patients typically experience a long clinical course and enjoy near-normal quality of life if properly managed. The 2 most important life-limiting complications of PV and ET are thrombohemorrhagic events and myelofibrosis/AML transformation. Vascular events are at least in part preventable with counseling on risk factors, phlebotomy (for patients with PV), antiplatelet therapy, and cytoreduction with hydroxyurea, IFNs, or anagrelide (for patients with ET). In addition, ruxolitinib was recently approved for PV patients after hydroxyurea failure. PV/ET transformation in myelofibrosis or AML is part of the natural history of the disease and no therapy has been shown to prevent it. Treatment follows recommendations set forth for PMF and AML, but results are generally poorer and novel strategies are needed to improve patients’ outcomes.

Introduction

Immune thrombocytopenia (ITP) is a common acquired autoimmune disease characterized by low platelet counts and an increased risk of bleeding. The incidence of ITP is approximately 3.3 per 100,000 adults.¹ There is considerable controversy about all aspects of the disease, with little “hard” data on which to base decisions given the lack of randomized clinical trials to address most clinical questions. This article reviews the presentation and diagnosis of ITP and its treatment options and discusses management of ITP in specific clinical situations.

Pathogenesis and Epidemiology

ITP is caused by autoantibodies binding to platelet surface proteins, most often to the platelet receptor GP IIb/IIIa.^2-4 These antibody-coated platelets then bind to Fc receptors in macrophages and are removed from circulation. The initiating event in ITP is unknown. It is speculated that the patient responds to a viral or bacterial infection by creating antibodies which cross-react with the platelet receptors. Continued exposure to platelets perpetuates the immune response. ITP that occurs in childhood appears to be an acute response to viral infection and usually resolves. ITP in adults may occur in any age group but is seen especially in young women.

Despite the increased platelet destruction that occurs in ITP, the production of new platelets often is not significantly increased. This is most likely due to lack of an increase in thrombopoietin, the predominant platelet growth factor.⁵

It had been thought that most adult patients who present with ITP go on to have a chronic course, but more recent studies have shown this is not the case. In modern series the percentage of patients who are “cured” with steroids ranges from 30% to 70%.^6–9 In addition, it has been appreciated that even in patients with modest thrombocytopenia, no therapy is required if the platelet count remains higher than 30 × 10³/µL. However, this leaves a considerable number of patients who will require chronic therapy.

Clinical Presentation

Presentation can range from a symptomatic patient with low platelets found on a routine blood count to a patient with massive bleeding. Typically, patients first present with petechiae (small bruises 1 mm in size) on the shins. True petechiae are seen only in severe thrombocytopenia. Patients will also report frequent bruising and bleeding from the gums. Patients with very low platelet counts will notice “wet purpura,” which is characterized by blood-filled bullae in the oral cavity. Life-threatening bleeding is a very unusual presenting sign unless other problems (trauma, ulcers) are present. The physical examination is only remarkable for stigmata of bleeding such as the petechiae. The presence of splenomegaly or lymphadenopathy weighs strongly against a diagnosis of ITP. Many patients with ITP will note fatigue when their platelets counts are lower.¹⁰

Diagnosis

Extremely low platelet counts with a normal blood smear and an otherwise healthy patient are diagnostic of ITP. The platelet count cutoff for considering ITP is 100 × 10³/µL as the majority of patients with counts in the 100 to 150 × 10³/µL range will not develop greater thrombocytopenia.¹¹ Also, the platelet count decreases with age (9 × 10³/µL per decade in one study), and this also needs to be factored into the evaluation.¹² The finding of relatives with ITP should raise suspicion for congenital thrombocytopenia.¹³ One should question the patient carefully about drug exposure (see Drug-Induced Thrombocytopenia), especially about over-the-counter medicines, “natural” remedies, or recreational drugs.

There is no laboratory test that rules in ITP; rather, it is a diagnosis of exclusion. The blood smear should be carefully examined for evidence of microangiopathic hemolytic anemias (schistocytes), bone marrow disease (blasts, teardrop cells), or any other evidence of a primary bone marrow disease. In ITP, the platelets can be larger than normal, but finding some platelets the size of red cells should raise the issue of congenital thrombocytopenia.¹⁴ Pseudo-thrombocytopenia, which is the clumping of platelets due to a reaction to the EDTA anticoagulant in the tube, should be excluded. The diagnosis is established by drawing the blood in a citrated (blue-top) tube to perform the platelet count. There is no role for antiplatelet antibody assay because this test lacks sensitivity and specificity. In a patient without a history of autoimmune disease or symptoms, empiric testing for autoimmune disease is not recommended.

Patients who present with ITP should be tested for both HIV and hepatitis C infection.^15,16 These are the most common viral causes of secondary ITP, and both have prognostic and treatment implications. Some authorities also recommend checking thyroid function as hypothyroidism can present or aggravate the thrombocytopenia.

 

The role of bone marrow examination is controversial.¹⁷ Patients with a classic presentation of ITP (young woman, normal blood smear) do not require a bone marrow exam before therapy is initiated, although patients who do not respond to initial therapy should have a bone marrow aspiration. The rare entity amegakaryocytic thrombocytopenia can present with a clinical picture similar to that of ITP, but amegakaryocytic thrombocytopenia will not respond to steroids. Bone marrow aspiration reveals the absence of megakaryocytes in this entity. It is rare, however, that another hematologic disease is diagnosed in patients with a classic clinical presentation of ITP.

In the future, measurement of thrombopoietin and reticulated platelets may provide clues to the diagnosis.⁴ Patients with ITP paradoxically have normal or only mildly elevated thrombopoietin levels. The finding of a significantly elevated thrombopoietin level should lead to questioning of the diagnosis. One can also measure “reticulated platelets,” which are analogous to red cell reticulocytes. Patients with ITP (or any platelet destructive disorders) will have high levels of reticulated platelets. These tests are not recommended for routine evaluation, but may be helpful in difficult cases.

Treatment

In general, therapy in ITP should be guided by the patient’s signs of bleeding and not by unquestioning adherence to measuring platelet levels,¹⁵ as patients tolerate thrombocytopenia well. It is unusual to have life-threatening bleeding with platelet counts greater than 5 × 10³/µL in the absence of mechanical lesions. Despite the low platelet count in patients with ITP, the overall mortality is estimated to be only 0.3% to 1.3%.¹⁸ It is sobering that in one study the rate of death from infections was twice as high as that from bleeding.¹⁹ Rare patients will have antibodies that interfere with the function of the platelet, and these patients can have profound bleeding with only modestly lowered platelet counts.²⁰ A suggested cut-off for treating newly diagnosed patients is 30 × 10³/µL.²¹

Initial Therapy

The primary therapy of ITP is glucocorticoids, either prednisone or dexamethasone. In the past prednisone at a dose of 60 to 80 mg/day was started at the time of diagnosis (Table 1).

Most patients will respond by 1 week, although some patients may take up to 4 weeks to respond. When the platelet count is greater than 50 × 10³/µL, the prednisone should be tapered over the course of several weeks. An alternative that is being used more frequently is dexamethasone 40 mg/day for 4 days, which offers the advantage of requiring patients to take medication for only 4 days. In European studies better responses were seen with multiple cycles of dexamethasone: 4-day pulses every 28 days for 6 cycles (overall response was 89.2% and relapse-free survival at 15 months was 90%) or 4-day pulses every 14 days for 4 cycles (85.6% response rate with 81% relapse-free survival at 15 months).²² Two randomized trials have shown higher response rates with pulsed dexamethasone repeated 2 or 3 times every 2 weeks, and this is now the preferred option.^8,23

For rapid induction of a response, there are 2 options. A single dose of intravenous immune globulin (IVIG) at 1 g/kg or intravenous anti-D immunoglobulin (anti-D) at 50 to 75 µg/kg can induce a response in more than 80% of patients in 24 to 48 hours.^21,24 IVIG has several drawbacks. It can cause aseptic meningitis, and in patients with vascular disease the increased viscosity can induce ischemia. There is also a considerable fluid load delivered with the IVIG, and it needs to be given over several hours.

The use of anti-D is limited to Rh-positive patients who have not had a splenectomy. It should not be used in patients who are Coombs positive due to the risk of provoking more hemolysis. Rarely anti-D has been reported to cause a severe hemolytic disseminated intravascular coagulation syndrome (1:20,000 patients), which has led to restrictions in its use.²⁵ Although the drug can be rapidly given over 15 minutes, due to these concerns current recommendations are now to observe patients for 8 hours after their dose and to perform a urine dipstick test for blood at 2, 4, and 8 hours. Concerns about this rare but serious side effect have led to a dramatic decrease in the use of anti-D.

For patients who are severely thrombocytopenic and do not respond to initial therapy, there are 2 options for raising the platelet counts. One is to use a combination of IVIG, methylprednisolone, vincristine, and/or anti-D.²⁶ The combination of IVIG and anti-D may be synergistic since these agents block different Fc receptors. A response of 71% has been reported for this 3- or 4-drug combination in a series of 35 patients.²⁶ The other option is to treat with a continuous infusion of platelets (1 unit over 6 hours) and IVIG 1 g/kg for 24 hours. Response rates of 62.7% have been reported with this combination, and this rapid rise in platelets can allow time for other therapies to take effect.^27,28

 

Patients with severe thrombocytopenia who relapse with reduction of steroids or who do not respond to steroids have several options for further management. Repeated doses of IVIG can transiently raise the platelet count, and some patients may only need several courses of therapy over the course of many months. One study showed that 60% of patients could delay or defer therapy by receiving multiple doses of anti-D. However, 30% of patients did eventually receive splenectomy and 20% of patients required ongoing therapy with anti-D.²⁹ In a randomized trial comparing early use of anti-D to steroids to avoid splenectomy, there was no difference in splenectomy rate (38% versus 42%).³⁰ Finally, an option as mentioned above is to try a 6-month course of pulse dexamethasone 40 mg/day for 4 days, repeated every 28 days.

Options for Refractory ITP

There are multiple options for patients who do not respond to initial ITP therapies. These can be divided into several broad groups: curative therapies (splenectomy and rituximab), thrombopoietin receptor agonists, and anecdotal therapies.

Splenectomy

In patients with severe thrombocytopenia who do not respond or who relapse with lower doses of prednisone, splenectomy should be strongly considered. Splenectomy will induce a good response in 60% to 70% of patients and is durable in most patients. In 2 recently published reviews of splenectomy, the complete response rate was 67% and the total response rate was 88% to 90%%.^8,31 Between 15% and 28% of patients relapsed over 5 years, with most recurrences occurring in the first 2 years. Splenectomy carries a short-term surgical risk, and the life-long risk of increased susceptibility to overwhelming sepsis is discussed below. However, the absolute magnitude of these risks is low and is often lower than the risks of continued prednisone therapy or of continued cytotoxic therapy.

Timing of splenectomy depends on the patient’s presentation. Most patients should be given a 6-month trial of steroids or other therapies before proceeding to splenectomy.³¹ However, patients who persist with severe thrombocytopenia despite initial therapies or who are suffering intolerable side effects from therapy should be considered sooner for splenectomy.³¹ In the George review, multiple factors such as responding to IVIG were found not to be predictive of response to splenectomy.⁸

Method of splenectomy appears not to matter.²¹ Rates of finding accessory spleens are just as high or higher with laparoscopic splenectomy and the patient can recover faster. In patients who are severely thrombocytopenic, open splenectomy can allow for quicker control of the vascular access of the spleen.

Rates of splenectomy in recent years have decreased for many reasons,³² including the acceptance of lower platelet counts in asymptomatic patients and the availability of alternative therapies such as rituximab. In addition, despite abundant data for good outcomes, there is a concern that splenectomy responses are not durable. Although splenectomy will not cure every patient with ITP, splenectomy is the therapy with the most patients, the longest follow-up, and the most consistent rate of cure, and it should be discussed with every ITP patient who does not respond to initial therapy and needs further treatment.

The risk of overwhelming sepsis varies by indications for splenectomy but appears to be about 1%.^33,34 The use of pneumococcal vaccine and recognition of this syndrome have helped reduce the risk. Asplenic patients need to be counseled about the risk of overwhelming infections, should be vaccinated for pneumococcus, meningococcus, and Haemophilus influenzae, and should wear an ID bracelet.^35–37 Patients previously vaccinated for pneumococcus should be re-vaccinated every 3 to 5 years. The role of prophylactic antibiotics in adults is controversial, but patients under the age of 18 should be on penicillin VK 250 mg orally twice daily.

Rituximab

Rituximab has been shown to be very active in ITP. Most studies used the standard dose of 375 mg/m² weekly for 4 weeks, but other studies have shown that 1000 mg twice 14 days apart (ie, on days 1 and 15) resulted in the same response rate and may be more convenient for patients.^38,39 The response time can vary, with patients either showing a rapid response or requiring up to 8 weeks for their counts to go up. Although experience is limited, the response seems to be durable, especially in those patients whose counts rise higher than 150 × 10³/µL; in patients who relapse, a response can be re-induced with a repeat course. Overall the response rate for rituximab is about 60%, but only approximately 20% to 40% of patients will remain in long-term remission.^40–42 There is no evidence yet that “maintenance” therapy or monitoring CD19/CD20 cells can help further the duration of remission.

 

Whether to give rituximab pre- or post-splenectomy is also uncertain. An advantage of presplenectomy rituximab is that many patients will achieve remission, delaying the need for surgery. Also, rituximab is a good option for patients whose medical conditions put them at high risk for complications with splenectomy. However, it is unknown whether rituximab poses any long-term risks, while the long-term risks of splenectomy are well-defined. Rituximab is the only curative option left for patients who have failed splenectomy and is a reasonable option for these patients.

There is an intriguing trial in which patients were randomly assigned to dexamethasone alone versus dexamethasone plus rituximab upon presentation with ITP; those who were refractory to dexamethasone alone received salvage therapy with dexamethasone plus rituximab.⁴³ The dexamethasone plus rituximab group had an overall higher rate of sustained remission at 6 months than the dexamethasone group, 63% versus 36%. Interestingly, patients who failed their first course of dexamethasone but then were “salvaged” with dexamethasone/rituximab had a similar overall response rate of 56%, suggesting that saving the addition of rituximab for steroid failures may be an effective option.

Although not “chemotherapy,” rituximab is not without risks. Patients can develop infusion reactions, which can be severe in 1% to 2% of patients. In a meta-analysis the fatal reaction rate was 2.9%.⁴⁰ Patients with chronic hepatitis B infections can experience reactivation with rituximab, and thus all patients should be screened before treatment. Finally, the very rare but devastating complication of progressive multifocal leukoencephalopathy has been reported.

Thrombopoietin Receptor Agonists

Although patients with ITP have low platelet counts, studies starting with Dameshek have shown that these patients also have reduced production of platelets.⁴⁴ Despite the very low circulating platelet count, levels of the platelet growth factor thrombopoietin (TPO) are not raised.⁴⁵ Seminal studies with recombinant TPO in the 1990s showed that ITP patients responded to thrombopoietin-stimulating protein, but the formation of anti-TPO antibodies halted trials with the first generation of these agents. Two TPO receptor agonists (TPO-RA) are approved for use in patients with ITP.

Romiplostim. Romiplostim is a peptibody, a combination of a peptide that binds and stimulates the TPO receptor and an Fc domain to extend its half-life.⁴⁶ It is administered in a weekly subcutaneous dose starting at 1 to 3 µg/kg. Use of romiplostim in ITP patients produces a response rate of 80% to 88%, with 87% of patients being able to wean off or decrease other anti-ITP medications.⁴⁷ In a long-term extension study, the response was again high at 87%.⁴⁸ These studies have also shown a reduced incidence of bleeding.

The major side effect of romiplostim seen in clinical trials was marrow reticulin formation, which occurred in up to 5.6% of patients.^47,48 The clinical course in these patients is the development of anemia and a myelophthisic blood smear with teardrop cells and nucleated red cells. These changes appear to reverse with cessation of the drug. The bone marrow shows increased reticulin formation but rarely, if ever, shows the collagen deposition seen with primary myelofibrosis.

Thrombosis has also been seen, with a rate of 0.08 to 0.1 cases per 100 patient-weeks,⁴⁹ but it remains unclear if this is due to the drug, part of the natural history of ITP, or expected complications in older patients undergoing any type of medical therapy. Surprisingly, despite the low platelet counts, patients with ITP in one study had double the risk of venous thrombosis, demonstrating that ITP itself can be a risk factor for thrombosis.⁵⁰ These trials have shown no long-term concerns for other clinical problems such as liver disease.

Eltrombopag. The other available TPO-RA is eltrombopag,⁵¹ an oral agent that stimulates the TPO receptor by binding the transmembrane domain and activating it. The drug is given orally starting at 50 mg/day (25 mg for patients of Asian ancestry or with liver disease) and can be dose escalated to 75 mg/day. The drug needs to be taken on an empty stomach. Eltrombopag has been shown to be effective in chronic ITP, with response rates of 59% to 80% and reduction in use of rescue medications.^47,51,52 As with romiplostim, the incidence of bleeding was also decreased with eltrombopag in these trials.^47,51

Clinical trials demonstrated that eltrombopag shares with romiplostim the risk for marrow fibrosis. A side effect unique to eltrombopag observed in these trials was a 3% to 7% incidence of elevated liver function tests.^21,52 These abnormal findings appeared to resolve in most patients, but liver function tests need to be monitored in patients receiving eltrombopag.

Clinical use. The clearest indication for the use of TPO-RAs is in patients who have failed several therapies and remain symptomatic or are on intolerable doses of other medications such as prednisone. The clear benefits are their relative safety and high rates of success. The main drawback of TPO-RAs is the need for continuing therapy as the platelet count will return to baseline shortly after these agents are stopped. Currently there is no clear indication for one medication over the other. The advantages of romiplostim are great flexibility in dosing (1–10 µg/kg week) and no concerns about drug interaction. The current drawback of romiplostim is the Food and Drug Administration’s requirement for patients to receive the drug from a clinic and not at home. Eltrombopag offers the advantage of oral use, but it has a limited dose range and potential for drug interactions. Both agents have been associated with marrow reticulin formation, although in clinical use this risk appears to be very low.⁵³

 

Other Options

In the literature there are numerous options for the treatment of ITP.^54,55 Most of these studies are anecdotal, enrolled small number of patients, and sometimes included patients with mild thrombocytopenia, but these therapeutic options can be tried in patients who are refractory to standard therapies and have bleeding. The agents with the greatest amount of supporting data are danazol, vincristine, azathioprine, cyclophosphamide, and fostamatinib.

Danazol 200 mg 4 times daily is thought to downregulate the macrophage Fc receptor. The onset of action may be delayed and a therapeutic trial of up to 4 to 6 months is advised. Danazol is very effective in patients with antiphospholipid antibody syndrome who develop ITP and may be more effective in premenopausal women.⁵⁶ Once a response is seen, danazol should be continued for 6 months and then an attempt to wean the patient off the agent should be made. A partial response can be seen in 70% to 90% of patients, but a complete response is rare.⁵⁴

Vincristine 1.4 mg/m² weekly has a low response rate, but if a response is going to occur, it will occur rapidly within 2 weeks. Thus, a prolonged trial of vincristine is not needed; if no platelet rise is seen in several weeks, the drug should be stopped. Again, partial responses are more common than complete response—50% to 63% versus 0% to 6%.⁵⁴Azathioprine 150 mg orally daily, like danazol, demonstrates a delayed response and requires several months to assess for response. However, 19% to 25% of patients may have a complete response.⁵⁴ It has been reported that the related agent mycophenolate 1000 mg twice daily is also effective in ITP.⁵⁷

Cyclophosphamide 1 g/m² intravenously repeated every 28 days has been reported to have a response rate of up to 40%.⁵⁸ Although considered more aggressive, this is a standard immunosuppressive dose and should be considered in patients with very low platelet counts. Patients who have not responded to single-agent cyclophosphamide may respond to multi-agent chemotherapy with agents such as etoposide and vincristine plus cyclophosphamide.⁵⁹

Fostamatinib, a spleen tyrosine kinase (SYK) inhibitor, is currently under investigation for the treatment of ITP.⁶⁰ This agent prevents phagocytosis of antibody-coated platelets by macrophages. In early studies fostamatinib has been well tolerated at a dose of 150 mg twice daily, with 75% of patients showing a response. Large phase 3 trials are underway, and if the earlier promising results hold up fostamatinib may be a novel option for refractory patients.

A Practical Approach to Refractory ITP

One approach is to divide patients into bleeders, or those with either very low platelet counts (< 5 × 10³/µL) or who have had significant bleeding in the past, and nonbleeders, or those with platelet counts above 5 × 10³/µL and no history of severe bleeding. Bleeders who do not respond adequately to splenectomy should first start with rituximab since it is not cytotoxic and is the only other “curative” therapy (Table 2).

Patients who do not respond to rituximab should then be tried on TPO-RAs. Patients who are unresponsive to these agents and still have severe disease with bleeding should receive aggressive therapy with immunosuppression. One approach to consider is bolus cyclophosphamide. If this is unsuccessful, then using a combination of azathioprine plus danazol can be considered. Since this combination may take 4 to 6 months to work, these patients may need frequent IVIG infusions to maintain a safe platelet count.

Nonbleeders should be tried on danazol and other relatively safe agents. If this fails, rituximab or TPO-RAs can be considered. Before one considers cytotoxic therapy, the risk of the therapy must be weighed against the risk posed by the thrombocytopenia. The mortality from ITP is fairly low (5%) and is restricted to patients with severe disease. Patients with only moderate thrombocytopenia and no bleeding are better served with conservative management. There is little justification for the use of continuous steroid therapy in this group of patients given the long-term risks of this therapy.

Special Situations

Surgery

Patients with ITP who need surgery either for splenectomy or for other reasons should have their platelet counts raised to a level greater than 20 to 30 × 10³/µL before surgery. Most patients with ITP have increased platelet function and will not have excessive bleeding with these platelet counts. For patients with platelet counts below this level, an infusion of immune globulin or anti-D may rapidly increase the platelet counts. If the surgery is elective, short-term use of TPO-RAs to raise the counts can also be considered.

 

Pregnancy

Up to 10% of pregnant women will develop low platelet counts during their pregnancy.^61,62 The most common etiology is gestational thrombocytopenia, which is an exaggeration of the lowered platelet count seen in pregnancy. Counts may fall as low as 50 × 10³/µL at the time of delivery. No therapy is required as the fetus is not affected and the mother does not have an increased risk of bleeding. Pregnancy complications such as HELLP syndrome and thrombotic microangiopathies also present with low platelet counts, but these can be diagnosed by history.^61,63

Women with ITP can either develop the disease during pregnancy or have a worsening of the symptoms.⁶⁴ Counts often drop dramatically during the first trimester. Early management should be conservative with low doses of prednisone to keep the count above 10 × 10³/µL.²¹ Immunoglobulin is also effective,⁶⁵ but there are rare reports of pulmonary edema. Rarely patients who are refractory will require splenectomy, which may be safely performed in the second trimester. For delivery the count should be greater than 30 × 10³/µL and for an epidural greater than 50 × 10³/µL.⁶⁴ There are reports of the use of TPO-RAs in pregnancy, and this can be considered for refractory cases.⁶⁶

Most controversy centers on management of the delivery. In the past it was feared that fetal thrombocytopenia could lead to intracranial hemorrhage, and Caesarean section was always recommended. It now appears that most cases of intracranial hemorrhage were due to alloimmune thrombocytopenia and not ITP. Furthermore, the nadir of the baby’s platelet count is not at birth but several days after. It appears the safest course is to proceed with a vaginal or C-section delivery determined by obstetrical indications and then immediately check the baby’s platelet count. If the platelet count is low in the neonate, immunoglobulin will raise the count. Since the neonatal thrombocytopenia is due to passive transfer of maternal antibody, the platelet destruction will abate in 4 to 6 weeks.

Pediatric Patients

The incidence of ITP in children is 2.2 to 5.3 per 100,000 children.¹ There are several distinct differences in pediatric ITP. Most cases will resolve in weeks, with only a minority of patients transforming into chronic ITP (5%–10%). Also, the rates of serious bleeding are lower in children than in adults, with intracranial hemorrhage rates of 0.1% to 0.5% being seen.⁶⁷ For most patients with no or mild bleeding, management now is observation alone regardless of platelet count because it is felt that the risks of therapies are higher than the risk of bleeding.²¹ For patients with bleeding, IVIG, anti-D, or a short course of steroids can be used. Given the risk of overwhelming sepsis, splenectomy is often deferred as long as possible. Rituximab is increasingly being used in children due to concerns about use of agents such a cyclophosphamide or azathioprine in children.⁶⁸ Abundant data on use of TPO-RAs in children showing high response rates and safety support their use, and these should be considered in refractory ITP before any cytotoxic agent.^69–71

Helicobacter Pylori Infection

There has been much interest in the relationship between H. pylori and ITP.^16,72,73H. pylori infections have been associated with a variety of autoimmune diseases, and there is a confusing literature on this infection and ITP. Several meta-analyses have shown that eradication of H. pylori will result in an ITP response rate of 20% to 30%, but responses curiously appear to be limited to certain geographic areas such as Japan and Italy but not the United States. In patients with recalcitrant ITP, especially in geographic areas with high incidence, it may be worthwhile to check for H. pylori infection and treat accordingly if positive.

Drug-Induced Thrombocytopenia

Patients with drug-induced thrombocytopenia present with very low (< 10 × 10³/µL) platelet counts 1 to 3 weeks after starting a new medication.^74–76 In patients with a possible drug-induced thrombocytopenia, the primary therapy is to stop the suspect drug.⁷⁷ If there are multiple new medications, the best approach is to stop any drug that has been strongly associated with thrombocytopenia (Table 3).^74,78,79

Immune globulin, corticosteroids, or intravenous anti‑D have been suggested as useful in drug‑related thrombocytopenia. However, since most of these thrombocytopenic patients recover when the agent is cleared from the body, this therapy is probably not necessary and withholding treatment avoids exposing the patients to the adverse events associated with further therapy.

 

Evans Syndrome

Evans syndrome is defined as the combination of autoimmune hemolytic anemia (AIHA) and ITP.^80,81 These cytopenias can present simultaneously or sequentially. Patients with Evans syndrome are thought to have a more severe disease process, to be more prone to bleeding, and to be more difficult to treat, but the rarity of this syndrome makes this hard to quantify.

The classic clinical presentation of Evans syndrome is severe anemia and thrombocytopenia. Children with Evans syndrome often have complex immunodeficiencies such as autoimmune lymphoproliferative syndrome.^82,83 In adults, Evans syndrome most often complicates other autoimmune diseases such as lupus. There are increasing reports of Evans syndrome occurring as a complication of T-cell lymphomas. Often the autoimmune disease can predate the lymphoma diagnosis by months or even years.

In theory the diagnostic approach is straightforward by showing a Coombs-positive hemolytic anemia in the setting of a clinical diagnosis of immune thrombocytopenia. The blood smear will show spherocytes and a diminished platelet count. The presence of other abnormal red cell forms should raise the possibility of an alternative diagnosis. It is unclear how vigorously one should search for other underlying diseases. Many patients will already have the diagnosis of an underlying autoimmune disease. The presence of lymphadenopathy should raise concern for lymphoma.

Initial therapy is high-dose steroids (2 mg/kg/day). IVIG should be added if severe thrombocytopenia is present. Patients who cannot be weaned off prednisone or relapse after prednisone should be considered for splenectomy, although these patients are at higher risk of relapsing.⁸⁰ Increasingly rituximab is being used with success.^84,85 For patients who fail splenectomy and rituximab, aggressive immunosuppression should be considered. Increasing data support the benefits of sirolimus, and this should be considered for refractory patients.⁸⁶ For patients with Evans syndrome due to underlying lymphoma, antineoplastic therapy often results in prompt resolution of the symptoms. Recurrence of the autoimmune cytopenias often heralds relapse.

Introduction

Immune thrombocytopenia (ITP) is a common acquired autoimmune disease characterized by low platelet counts and an increased risk of bleeding. The incidence of ITP is approximately 3.3 per 100,000 adults.¹ There is considerable controversy about all aspects of the disease, with little “hard” data on which to base decisions given the lack of randomized clinical trials to address most clinical questions. This article reviews the presentation and diagnosis of ITP and its treatment options and discusses management of ITP in specific clinical situations.

Pathogenesis and Epidemiology

ITP is caused by autoantibodies binding to platelet surface proteins, most often to the platelet receptor GP IIb/IIIa.^2-4 These antibody-coated platelets then bind to Fc receptors in macrophages and are removed from circulation. The initiating event in ITP is unknown. It is speculated that the patient responds to a viral or bacterial infection by creating antibodies which cross-react with the platelet receptors. Continued exposure to platelets perpetuates the immune response. ITP that occurs in childhood appears to be an acute response to viral infection and usually resolves. ITP in adults may occur in any age group but is seen especially in young women.

Despite the increased platelet destruction that occurs in ITP, the production of new platelets often is not significantly increased. This is most likely due to lack of an increase in thrombopoietin, the predominant platelet growth factor.⁵

It had been thought that most adult patients who present with ITP go on to have a chronic course, but more recent studies have shown this is not the case. In modern series the percentage of patients who are “cured” with steroids ranges from 30% to 70%.^6–9 In addition, it has been appreciated that even in patients with modest thrombocytopenia, no therapy is required if the platelet count remains higher than 30 × 10³/µL. However, this leaves a considerable number of patients who will require chronic therapy.

Clinical Presentation

Presentation can range from a symptomatic patient with low platelets found on a routine blood count to a patient with massive bleeding. Typically, patients first present with petechiae (small bruises 1 mm in size) on the shins. True petechiae are seen only in severe thrombocytopenia. Patients will also report frequent bruising and bleeding from the gums. Patients with very low platelet counts will notice “wet purpura,” which is characterized by blood-filled bullae in the oral cavity. Life-threatening bleeding is a very unusual presenting sign unless other problems (trauma, ulcers) are present. The physical examination is only remarkable for stigmata of bleeding such as the petechiae. The presence of splenomegaly or lymphadenopathy weighs strongly against a diagnosis of ITP. Many patients with ITP will note fatigue when their platelets counts are lower.¹⁰

Diagnosis

Extremely low platelet counts with a normal blood smear and an otherwise healthy patient are diagnostic of ITP. The platelet count cutoff for considering ITP is 100 × 10³/µL as the majority of patients with counts in the 100 to 150 × 10³/µL range will not develop greater thrombocytopenia.¹¹ Also, the platelet count decreases with age (9 × 10³/µL per decade in one study), and this also needs to be factored into the evaluation.¹² The finding of relatives with ITP should raise suspicion for congenital thrombocytopenia.¹³ One should question the patient carefully about drug exposure (see Drug-Induced Thrombocytopenia), especially about over-the-counter medicines, “natural” remedies, or recreational drugs.

There is no laboratory test that rules in ITP; rather, it is a diagnosis of exclusion. The blood smear should be carefully examined for evidence of microangiopathic hemolytic anemias (schistocytes), bone marrow disease (blasts, teardrop cells), or any other evidence of a primary bone marrow disease. In ITP, the platelets can be larger than normal, but finding some platelets the size of red cells should raise the issue of congenital thrombocytopenia.¹⁴ Pseudo-thrombocytopenia, which is the clumping of platelets due to a reaction to the EDTA anticoagulant in the tube, should be excluded. The diagnosis is established by drawing the blood in a citrated (blue-top) tube to perform the platelet count. There is no role for antiplatelet antibody assay because this test lacks sensitivity and specificity. In a patient without a history of autoimmune disease or symptoms, empiric testing for autoimmune disease is not recommended.

Patients who present with ITP should be tested for both HIV and hepatitis C infection.^15,16 These are the most common viral causes of secondary ITP, and both have prognostic and treatment implications. Some authorities also recommend checking thyroid function as hypothyroidism can present or aggravate the thrombocytopenia.

 

The role of bone marrow examination is controversial.¹⁷ Patients with a classic presentation of ITP (young woman, normal blood smear) do not require a bone marrow exam before therapy is initiated, although patients who do not respond to initial therapy should have a bone marrow aspiration. The rare entity amegakaryocytic thrombocytopenia can present with a clinical picture similar to that of ITP, but amegakaryocytic thrombocytopenia will not respond to steroids. Bone marrow aspiration reveals the absence of megakaryocytes in this entity. It is rare, however, that another hematologic disease is diagnosed in patients with a classic clinical presentation of ITP.

In the future, measurement of thrombopoietin and reticulated platelets may provide clues to the diagnosis.⁴ Patients with ITP paradoxically have normal or only mildly elevated thrombopoietin levels. The finding of a significantly elevated thrombopoietin level should lead to questioning of the diagnosis. One can also measure “reticulated platelets,” which are analogous to red cell reticulocytes. Patients with ITP (or any platelet destructive disorders) will have high levels of reticulated platelets. These tests are not recommended for routine evaluation, but may be helpful in difficult cases.

Treatment

In general, therapy in ITP should be guided by the patient’s signs of bleeding and not by unquestioning adherence to measuring platelet levels,¹⁵ as patients tolerate thrombocytopenia well. It is unusual to have life-threatening bleeding with platelet counts greater than 5 × 10³/µL in the absence of mechanical lesions. Despite the low platelet count in patients with ITP, the overall mortality is estimated to be only 0.3% to 1.3%.¹⁸ It is sobering that in one study the rate of death from infections was twice as high as that from bleeding.¹⁹ Rare patients will have antibodies that interfere with the function of the platelet, and these patients can have profound bleeding with only modestly lowered platelet counts.²⁰ A suggested cut-off for treating newly diagnosed patients is 30 × 10³/µL.²¹

Initial Therapy

The primary therapy of ITP is glucocorticoids, either prednisone or dexamethasone. In the past prednisone at a dose of 60 to 80 mg/day was started at the time of diagnosis (Table 1).

Most patients will respond by 1 week, although some patients may take up to 4 weeks to respond. When the platelet count is greater than 50 × 10³/µL, the prednisone should be tapered over the course of several weeks. An alternative that is being used more frequently is dexamethasone 40 mg/day for 4 days, which offers the advantage of requiring patients to take medication for only 4 days. In European studies better responses were seen with multiple cycles of dexamethasone: 4-day pulses every 28 days for 6 cycles (overall response was 89.2% and relapse-free survival at 15 months was 90%) or 4-day pulses every 14 days for 4 cycles (85.6% response rate with 81% relapse-free survival at 15 months).²² Two randomized trials have shown higher response rates with pulsed dexamethasone repeated 2 or 3 times every 2 weeks, and this is now the preferred option.^8,23

For rapid induction of a response, there are 2 options. A single dose of intravenous immune globulin (IVIG) at 1 g/kg or intravenous anti-D immunoglobulin (anti-D) at 50 to 75 µg/kg can induce a response in more than 80% of patients in 24 to 48 hours.^21,24 IVIG has several drawbacks. It can cause aseptic meningitis, and in patients with vascular disease the increased viscosity can induce ischemia. There is also a considerable fluid load delivered with the IVIG, and it needs to be given over several hours.

The use of anti-D is limited to Rh-positive patients who have not had a splenectomy. It should not be used in patients who are Coombs positive due to the risk of provoking more hemolysis. Rarely anti-D has been reported to cause a severe hemolytic disseminated intravascular coagulation syndrome (1:20,000 patients), which has led to restrictions in its use.²⁵ Although the drug can be rapidly given over 15 minutes, due to these concerns current recommendations are now to observe patients for 8 hours after their dose and to perform a urine dipstick test for blood at 2, 4, and 8 hours. Concerns about this rare but serious side effect have led to a dramatic decrease in the use of anti-D.

For patients who are severely thrombocytopenic and do not respond to initial therapy, there are 2 options for raising the platelet counts. One is to use a combination of IVIG, methylprednisolone, vincristine, and/or anti-D.²⁶ The combination of IVIG and anti-D may be synergistic since these agents block different Fc receptors. A response of 71% has been reported for this 3- or 4-drug combination in a series of 35 patients.²⁶ The other option is to treat with a continuous infusion of platelets (1 unit over 6 hours) and IVIG 1 g/kg for 24 hours. Response rates of 62.7% have been reported with this combination, and this rapid rise in platelets can allow time for other therapies to take effect.^27,28

 

Patients with severe thrombocytopenia who relapse with reduction of steroids or who do not respond to steroids have several options for further management. Repeated doses of IVIG can transiently raise the platelet count, and some patients may only need several courses of therapy over the course of many months. One study showed that 60% of patients could delay or defer therapy by receiving multiple doses of anti-D. However, 30% of patients did eventually receive splenectomy and 20% of patients required ongoing therapy with anti-D.²⁹ In a randomized trial comparing early use of anti-D to steroids to avoid splenectomy, there was no difference in splenectomy rate (38% versus 42%).³⁰ Finally, an option as mentioned above is to try a 6-month course of pulse dexamethasone 40 mg/day for 4 days, repeated every 28 days.

Options for Refractory ITP

There are multiple options for patients who do not respond to initial ITP therapies. These can be divided into several broad groups: curative therapies (splenectomy and rituximab), thrombopoietin receptor agonists, and anecdotal therapies.

Splenectomy

In patients with severe thrombocytopenia who do not respond or who relapse with lower doses of prednisone, splenectomy should be strongly considered. Splenectomy will induce a good response in 60% to 70% of patients and is durable in most patients. In 2 recently published reviews of splenectomy, the complete response rate was 67% and the total response rate was 88% to 90%%.^8,31 Between 15% and 28% of patients relapsed over 5 years, with most recurrences occurring in the first 2 years. Splenectomy carries a short-term surgical risk, and the life-long risk of increased susceptibility to overwhelming sepsis is discussed below. However, the absolute magnitude of these risks is low and is often lower than the risks of continued prednisone therapy or of continued cytotoxic therapy.

Timing of splenectomy depends on the patient’s presentation. Most patients should be given a 6-month trial of steroids or other therapies before proceeding to splenectomy.³¹ However, patients who persist with severe thrombocytopenia despite initial therapies or who are suffering intolerable side effects from therapy should be considered sooner for splenectomy.³¹ In the George review, multiple factors such as responding to IVIG were found not to be predictive of response to splenectomy.⁸

Method of splenectomy appears not to matter.²¹ Rates of finding accessory spleens are just as high or higher with laparoscopic splenectomy and the patient can recover faster. In patients who are severely thrombocytopenic, open splenectomy can allow for quicker control of the vascular access of the spleen.

Rates of splenectomy in recent years have decreased for many reasons,³² including the acceptance of lower platelet counts in asymptomatic patients and the availability of alternative therapies such as rituximab. In addition, despite abundant data for good outcomes, there is a concern that splenectomy responses are not durable. Although splenectomy will not cure every patient with ITP, splenectomy is the therapy with the most patients, the longest follow-up, and the most consistent rate of cure, and it should be discussed with every ITP patient who does not respond to initial therapy and needs further treatment.

The risk of overwhelming sepsis varies by indications for splenectomy but appears to be about 1%.^33,34 The use of pneumococcal vaccine and recognition of this syndrome have helped reduce the risk. Asplenic patients need to be counseled about the risk of overwhelming infections, should be vaccinated for pneumococcus, meningococcus, and Haemophilus influenzae, and should wear an ID bracelet.^35–37 Patients previously vaccinated for pneumococcus should be re-vaccinated every 3 to 5 years. The role of prophylactic antibiotics in adults is controversial, but patients under the age of 18 should be on penicillin VK 250 mg orally twice daily.

Rituximab

Rituximab has been shown to be very active in ITP. Most studies used the standard dose of 375 mg/m² weekly for 4 weeks, but other studies have shown that 1000 mg twice 14 days apart (ie, on days 1 and 15) resulted in the same response rate and may be more convenient for patients.^38,39 The response time can vary, with patients either showing a rapid response or requiring up to 8 weeks for their counts to go up. Although experience is limited, the response seems to be durable, especially in those patients whose counts rise higher than 150 × 10³/µL; in patients who relapse, a response can be re-induced with a repeat course. Overall the response rate for rituximab is about 60%, but only approximately 20% to 40% of patients will remain in long-term remission.^40–42 There is no evidence yet that “maintenance” therapy or monitoring CD19/CD20 cells can help further the duration of remission.

 

Whether to give rituximab pre- or post-splenectomy is also uncertain. An advantage of presplenectomy rituximab is that many patients will achieve remission, delaying the need for surgery. Also, rituximab is a good option for patients whose medical conditions put them at high risk for complications with splenectomy. However, it is unknown whether rituximab poses any long-term risks, while the long-term risks of splenectomy are well-defined. Rituximab is the only curative option left for patients who have failed splenectomy and is a reasonable option for these patients.

There is an intriguing trial in which patients were randomly assigned to dexamethasone alone versus dexamethasone plus rituximab upon presentation with ITP; those who were refractory to dexamethasone alone received salvage therapy with dexamethasone plus rituximab.⁴³ The dexamethasone plus rituximab group had an overall higher rate of sustained remission at 6 months than the dexamethasone group, 63% versus 36%. Interestingly, patients who failed their first course of dexamethasone but then were “salvaged” with dexamethasone/rituximab had a similar overall response rate of 56%, suggesting that saving the addition of rituximab for steroid failures may be an effective option.

Although not “chemotherapy,” rituximab is not without risks. Patients can develop infusion reactions, which can be severe in 1% to 2% of patients. In a meta-analysis the fatal reaction rate was 2.9%.⁴⁰ Patients with chronic hepatitis B infections can experience reactivation with rituximab, and thus all patients should be screened before treatment. Finally, the very rare but devastating complication of progressive multifocal leukoencephalopathy has been reported.

Thrombopoietin Receptor Agonists

Although patients with ITP have low platelet counts, studies starting with Dameshek have shown that these patients also have reduced production of platelets.⁴⁴ Despite the very low circulating platelet count, levels of the platelet growth factor thrombopoietin (TPO) are not raised.⁴⁵ Seminal studies with recombinant TPO in the 1990s showed that ITP patients responded to thrombopoietin-stimulating protein, but the formation of anti-TPO antibodies halted trials with the first generation of these agents. Two TPO receptor agonists (TPO-RA) are approved for use in patients with ITP.

Romiplostim. Romiplostim is a peptibody, a combination of a peptide that binds and stimulates the TPO receptor and an Fc domain to extend its half-life.⁴⁶ It is administered in a weekly subcutaneous dose starting at 1 to 3 µg/kg. Use of romiplostim in ITP patients produces a response rate of 80% to 88%, with 87% of patients being able to wean off or decrease other anti-ITP medications.⁴⁷ In a long-term extension study, the response was again high at 87%.⁴⁸ These studies have also shown a reduced incidence of bleeding.

The major side effect of romiplostim seen in clinical trials was marrow reticulin formation, which occurred in up to 5.6% of patients.^47,48 The clinical course in these patients is the development of anemia and a myelophthisic blood smear with teardrop cells and nucleated red cells. These changes appear to reverse with cessation of the drug. The bone marrow shows increased reticulin formation but rarely, if ever, shows the collagen deposition seen with primary myelofibrosis.

Thrombosis has also been seen, with a rate of 0.08 to 0.1 cases per 100 patient-weeks,⁴⁹ but it remains unclear if this is due to the drug, part of the natural history of ITP, or expected complications in older patients undergoing any type of medical therapy. Surprisingly, despite the low platelet counts, patients with ITP in one study had double the risk of venous thrombosis, demonstrating that ITP itself can be a risk factor for thrombosis.⁵⁰ These trials have shown no long-term concerns for other clinical problems such as liver disease.

Eltrombopag. The other available TPO-RA is eltrombopag,⁵¹ an oral agent that stimulates the TPO receptor by binding the transmembrane domain and activating it. The drug is given orally starting at 50 mg/day (25 mg for patients of Asian ancestry or with liver disease) and can be dose escalated to 75 mg/day. The drug needs to be taken on an empty stomach. Eltrombopag has been shown to be effective in chronic ITP, with response rates of 59% to 80% and reduction in use of rescue medications.^47,51,52 As with romiplostim, the incidence of bleeding was also decreased with eltrombopag in these trials.^47,51

Clinical trials demonstrated that eltrombopag shares with romiplostim the risk for marrow fibrosis. A side effect unique to eltrombopag observed in these trials was a 3% to 7% incidence of elevated liver function tests.^21,52 These abnormal findings appeared to resolve in most patients, but liver function tests need to be monitored in patients receiving eltrombopag.

Clinical use. The clearest indication for the use of TPO-RAs is in patients who have failed several therapies and remain symptomatic or are on intolerable doses of other medications such as prednisone. The clear benefits are their relative safety and high rates of success. The main drawback of TPO-RAs is the need for continuing therapy as the platelet count will return to baseline shortly after these agents are stopped. Currently there is no clear indication for one medication over the other. The advantages of romiplostim are great flexibility in dosing (1–10 µg/kg week) and no concerns about drug interaction. The current drawback of romiplostim is the Food and Drug Administration’s requirement for patients to receive the drug from a clinic and not at home. Eltrombopag offers the advantage of oral use, but it has a limited dose range and potential for drug interactions. Both agents have been associated with marrow reticulin formation, although in clinical use this risk appears to be very low.⁵³

 

Other Options

In the literature there are numerous options for the treatment of ITP.^54,55 Most of these studies are anecdotal, enrolled small number of patients, and sometimes included patients with mild thrombocytopenia, but these therapeutic options can be tried in patients who are refractory to standard therapies and have bleeding. The agents with the greatest amount of supporting data are danazol, vincristine, azathioprine, cyclophosphamide, and fostamatinib.

Danazol 200 mg 4 times daily is thought to downregulate the macrophage Fc receptor. The onset of action may be delayed and a therapeutic trial of up to 4 to 6 months is advised. Danazol is very effective in patients with antiphospholipid antibody syndrome who develop ITP and may be more effective in premenopausal women.⁵⁶ Once a response is seen, danazol should be continued for 6 months and then an attempt to wean the patient off the agent should be made. A partial response can be seen in 70% to 90% of patients, but a complete response is rare.⁵⁴

Vincristine 1.4 mg/m² weekly has a low response rate, but if a response is going to occur, it will occur rapidly within 2 weeks. Thus, a prolonged trial of vincristine is not needed; if no platelet rise is seen in several weeks, the drug should be stopped. Again, partial responses are more common than complete response—50% to 63% versus 0% to 6%.⁵⁴Azathioprine 150 mg orally daily, like danazol, demonstrates a delayed response and requires several months to assess for response. However, 19% to 25% of patients may have a complete response.⁵⁴ It has been reported that the related agent mycophenolate 1000 mg twice daily is also effective in ITP.⁵⁷

Cyclophosphamide 1 g/m² intravenously repeated every 28 days has been reported to have a response rate of up to 40%.⁵⁸ Although considered more aggressive, this is a standard immunosuppressive dose and should be considered in patients with very low platelet counts. Patients who have not responded to single-agent cyclophosphamide may respond to multi-agent chemotherapy with agents such as etoposide and vincristine plus cyclophosphamide.⁵⁹

Fostamatinib, a spleen tyrosine kinase (SYK) inhibitor, is currently under investigation for the treatment of ITP.⁶⁰ This agent prevents phagocytosis of antibody-coated platelets by macrophages. In early studies fostamatinib has been well tolerated at a dose of 150 mg twice daily, with 75% of patients showing a response. Large phase 3 trials are underway, and if the earlier promising results hold up fostamatinib may be a novel option for refractory patients.

A Practical Approach to Refractory ITP

One approach is to divide patients into bleeders, or those with either very low platelet counts (< 5 × 10³/µL) or who have had significant bleeding in the past, and nonbleeders, or those with platelet counts above 5 × 10³/µL and no history of severe bleeding. Bleeders who do not respond adequately to splenectomy should first start with rituximab since it is not cytotoxic and is the only other “curative” therapy (Table 2).

Patients who do not respond to rituximab should then be tried on TPO-RAs. Patients who are unresponsive to these agents and still have severe disease with bleeding should receive aggressive therapy with immunosuppression. One approach to consider is bolus cyclophosphamide. If this is unsuccessful, then using a combination of azathioprine plus danazol can be considered. Since this combination may take 4 to 6 months to work, these patients may need frequent IVIG infusions to maintain a safe platelet count.

Nonbleeders should be tried on danazol and other relatively safe agents. If this fails, rituximab or TPO-RAs can be considered. Before one considers cytotoxic therapy, the risk of the therapy must be weighed against the risk posed by the thrombocytopenia. The mortality from ITP is fairly low (5%) and is restricted to patients with severe disease. Patients with only moderate thrombocytopenia and no bleeding are better served with conservative management. There is little justification for the use of continuous steroid therapy in this group of patients given the long-term risks of this therapy.

Special Situations

Surgery

Patients with ITP who need surgery either for splenectomy or for other reasons should have their platelet counts raised to a level greater than 20 to 30 × 10³/µL before surgery. Most patients with ITP have increased platelet function and will not have excessive bleeding with these platelet counts. For patients with platelet counts below this level, an infusion of immune globulin or anti-D may rapidly increase the platelet counts. If the surgery is elective, short-term use of TPO-RAs to raise the counts can also be considered.

 

Pregnancy

Up to 10% of pregnant women will develop low platelet counts during their pregnancy.^61,62 The most common etiology is gestational thrombocytopenia, which is an exaggeration of the lowered platelet count seen in pregnancy. Counts may fall as low as 50 × 10³/µL at the time of delivery. No therapy is required as the fetus is not affected and the mother does not have an increased risk of bleeding. Pregnancy complications such as HELLP syndrome and thrombotic microangiopathies also present with low platelet counts, but these can be diagnosed by history.^61,63

Women with ITP can either develop the disease during pregnancy or have a worsening of the symptoms.⁶⁴ Counts often drop dramatically during the first trimester. Early management should be conservative with low doses of prednisone to keep the count above 10 × 10³/µL.²¹ Immunoglobulin is also effective,⁶⁵ but there are rare reports of pulmonary edema. Rarely patients who are refractory will require splenectomy, which may be safely performed in the second trimester. For delivery the count should be greater than 30 × 10³/µL and for an epidural greater than 50 × 10³/µL.⁶⁴ There are reports of the use of TPO-RAs in pregnancy, and this can be considered for refractory cases.⁶⁶

Most controversy centers on management of the delivery. In the past it was feared that fetal thrombocytopenia could lead to intracranial hemorrhage, and Caesarean section was always recommended. It now appears that most cases of intracranial hemorrhage were due to alloimmune thrombocytopenia and not ITP. Furthermore, the nadir of the baby’s platelet count is not at birth but several days after. It appears the safest course is to proceed with a vaginal or C-section delivery determined by obstetrical indications and then immediately check the baby’s platelet count. If the platelet count is low in the neonate, immunoglobulin will raise the count. Since the neonatal thrombocytopenia is due to passive transfer of maternal antibody, the platelet destruction will abate in 4 to 6 weeks.

Pediatric Patients

The incidence of ITP in children is 2.2 to 5.3 per 100,000 children.¹ There are several distinct differences in pediatric ITP. Most cases will resolve in weeks, with only a minority of patients transforming into chronic ITP (5%–10%). Also, the rates of serious bleeding are lower in children than in adults, with intracranial hemorrhage rates of 0.1% to 0.5% being seen.⁶⁷ For most patients with no or mild bleeding, management now is observation alone regardless of platelet count because it is felt that the risks of therapies are higher than the risk of bleeding.²¹ For patients with bleeding, IVIG, anti-D, or a short course of steroids can be used. Given the risk of overwhelming sepsis, splenectomy is often deferred as long as possible. Rituximab is increasingly being used in children due to concerns about use of agents such a cyclophosphamide or azathioprine in children.⁶⁸ Abundant data on use of TPO-RAs in children showing high response rates and safety support their use, and these should be considered in refractory ITP before any cytotoxic agent.^69–71

Helicobacter Pylori Infection

There has been much interest in the relationship between H. pylori and ITP.^16,72,73H. pylori infections have been associated with a variety of autoimmune diseases, and there is a confusing literature on this infection and ITP. Several meta-analyses have shown that eradication of H. pylori will result in an ITP response rate of 20% to 30%, but responses curiously appear to be limited to certain geographic areas such as Japan and Italy but not the United States. In patients with recalcitrant ITP, especially in geographic areas with high incidence, it may be worthwhile to check for H. pylori infection and treat accordingly if positive.

Drug-Induced Thrombocytopenia

Patients with drug-induced thrombocytopenia present with very low (< 10 × 10³/µL) platelet counts 1 to 3 weeks after starting a new medication.^74–76 In patients with a possible drug-induced thrombocytopenia, the primary therapy is to stop the suspect drug.⁷⁷ If there are multiple new medications, the best approach is to stop any drug that has been strongly associated with thrombocytopenia (Table 3).^74,78,79

Immune globulin, corticosteroids, or intravenous anti‑D have been suggested as useful in drug‑related thrombocytopenia. However, since most of these thrombocytopenic patients recover when the agent is cleared from the body, this therapy is probably not necessary and withholding treatment avoids exposing the patients to the adverse events associated with further therapy.

 

Evans Syndrome

Evans syndrome is defined as the combination of autoimmune hemolytic anemia (AIHA) and ITP.^80,81 These cytopenias can present simultaneously or sequentially. Patients with Evans syndrome are thought to have a more severe disease process, to be more prone to bleeding, and to be more difficult to treat, but the rarity of this syndrome makes this hard to quantify.

The classic clinical presentation of Evans syndrome is severe anemia and thrombocytopenia. Children with Evans syndrome often have complex immunodeficiencies such as autoimmune lymphoproliferative syndrome.^82,83 In adults, Evans syndrome most often complicates other autoimmune diseases such as lupus. There are increasing reports of Evans syndrome occurring as a complication of T-cell lymphomas. Often the autoimmune disease can predate the lymphoma diagnosis by months or even years.

In theory the diagnostic approach is straightforward by showing a Coombs-positive hemolytic anemia in the setting of a clinical diagnosis of immune thrombocytopenia. The blood smear will show spherocytes and a diminished platelet count. The presence of other abnormal red cell forms should raise the possibility of an alternative diagnosis. It is unclear how vigorously one should search for other underlying diseases. Many patients will already have the diagnosis of an underlying autoimmune disease. The presence of lymphadenopathy should raise concern for lymphoma.

Initial therapy is high-dose steroids (2 mg/kg/day). IVIG should be added if severe thrombocytopenia is present. Patients who cannot be weaned off prednisone or relapse after prednisone should be considered for splenectomy, although these patients are at higher risk of relapsing.⁸⁰ Increasingly rituximab is being used with success.^84,85 For patients who fail splenectomy and rituximab, aggressive immunosuppression should be considered. Increasing data support the benefits of sirolimus, and this should be considered for refractory patients.⁸⁶ For patients with Evans syndrome due to underlying lymphoma, antineoplastic therapy often results in prompt resolution of the symptoms. Recurrence of the autoimmune cytopenias often heralds relapse.

Introduction

Immune thrombocytopenia (ITP) is a common acquired autoimmune disease characterized by low platelet counts and an increased risk of bleeding. The incidence of ITP is approximately 3.3 per 100,000 adults.¹ There is considerable controversy about all aspects of the disease, with little “hard” data on which to base decisions given the lack of randomized clinical trials to address most clinical questions. This article reviews the presentation and diagnosis of ITP and its treatment options and discusses management of ITP in specific clinical situations.

Pathogenesis and Epidemiology

ITP is caused by autoantibodies binding to platelet surface proteins, most often to the platelet receptor GP IIb/IIIa.^2-4 These antibody-coated platelets then bind to Fc receptors in macrophages and are removed from circulation. The initiating event in ITP is unknown. It is speculated that the patient responds to a viral or bacterial infection by creating antibodies which cross-react with the platelet receptors. Continued exposure to platelets perpetuates the immune response. ITP that occurs in childhood appears to be an acute response to viral infection and usually resolves. ITP in adults may occur in any age group but is seen especially in young women.

Despite the increased platelet destruction that occurs in ITP, the production of new platelets often is not significantly increased. This is most likely due to lack of an increase in thrombopoietin, the predominant platelet growth factor.⁵

It had been thought that most adult patients who present with ITP go on to have a chronic course, but more recent studies have shown this is not the case. In modern series the percentage of patients who are “cured” with steroids ranges from 30% to 70%.^6–9 In addition, it has been appreciated that even in patients with modest thrombocytopenia, no therapy is required if the platelet count remains higher than 30 × 10³/µL. However, this leaves a considerable number of patients who will require chronic therapy.

Clinical Presentation

Presentation can range from a symptomatic patient with low platelets found on a routine blood count to a patient with massive bleeding. Typically, patients first present with petechiae (small bruises 1 mm in size) on the shins. True petechiae are seen only in severe thrombocytopenia. Patients will also report frequent bruising and bleeding from the gums. Patients with very low platelet counts will notice “wet purpura,” which is characterized by blood-filled bullae in the oral cavity. Life-threatening bleeding is a very unusual presenting sign unless other problems (trauma, ulcers) are present. The physical examination is only remarkable for stigmata of bleeding such as the petechiae. The presence of splenomegaly or lymphadenopathy weighs strongly against a diagnosis of ITP. Many patients with ITP will note fatigue when their platelets counts are lower.¹⁰

Diagnosis

Extremely low platelet counts with a normal blood smear and an otherwise healthy patient are diagnostic of ITP. The platelet count cutoff for considering ITP is 100 × 10³/µL as the majority of patients with counts in the 100 to 150 × 10³/µL range will not develop greater thrombocytopenia.¹¹ Also, the platelet count decreases with age (9 × 10³/µL per decade in one study), and this also needs to be factored into the evaluation.¹² The finding of relatives with ITP should raise suspicion for congenital thrombocytopenia.¹³ One should question the patient carefully about drug exposure (see Drug-Induced Thrombocytopenia), especially about over-the-counter medicines, “natural” remedies, or recreational drugs.

There is no laboratory test that rules in ITP; rather, it is a diagnosis of exclusion. The blood smear should be carefully examined for evidence of microangiopathic hemolytic anemias (schistocytes), bone marrow disease (blasts, teardrop cells), or any other evidence of a primary bone marrow disease. In ITP, the platelets can be larger than normal, but finding some platelets the size of red cells should raise the issue of congenital thrombocytopenia.¹⁴ Pseudo-thrombocytopenia, which is the clumping of platelets due to a reaction to the EDTA anticoagulant in the tube, should be excluded. The diagnosis is established by drawing the blood in a citrated (blue-top) tube to perform the platelet count. There is no role for antiplatelet antibody assay because this test lacks sensitivity and specificity. In a patient without a history of autoimmune disease or symptoms, empiric testing for autoimmune disease is not recommended.

Patients who present with ITP should be tested for both HIV and hepatitis C infection.^15,16 These are the most common viral causes of secondary ITP, and both have prognostic and treatment implications. Some authorities also recommend checking thyroid function as hypothyroidism can present or aggravate the thrombocytopenia.

 

The role of bone marrow examination is controversial.¹⁷ Patients with a classic presentation of ITP (young woman, normal blood smear) do not require a bone marrow exam before therapy is initiated, although patients who do not respond to initial therapy should have a bone marrow aspiration. The rare entity amegakaryocytic thrombocytopenia can present with a clinical picture similar to that of ITP, but amegakaryocytic thrombocytopenia will not respond to steroids. Bone marrow aspiration reveals the absence of megakaryocytes in this entity. It is rare, however, that another hematologic disease is diagnosed in patients with a classic clinical presentation of ITP.

In the future, measurement of thrombopoietin and reticulated platelets may provide clues to the diagnosis.⁴ Patients with ITP paradoxically have normal or only mildly elevated thrombopoietin levels. The finding of a significantly elevated thrombopoietin level should lead to questioning of the diagnosis. One can also measure “reticulated platelets,” which are analogous to red cell reticulocytes. Patients with ITP (or any platelet destructive disorders) will have high levels of reticulated platelets. These tests are not recommended for routine evaluation, but may be helpful in difficult cases.

Treatment

In general, therapy in ITP should be guided by the patient’s signs of bleeding and not by unquestioning adherence to measuring platelet levels,¹⁵ as patients tolerate thrombocytopenia well. It is unusual to have life-threatening bleeding with platelet counts greater than 5 × 10³/µL in the absence of mechanical lesions. Despite the low platelet count in patients with ITP, the overall mortality is estimated to be only 0.3% to 1.3%.¹⁸ It is sobering that in one study the rate of death from infections was twice as high as that from bleeding.¹⁹ Rare patients will have antibodies that interfere with the function of the platelet, and these patients can have profound bleeding with only modestly lowered platelet counts.²⁰ A suggested cut-off for treating newly diagnosed patients is 30 × 10³/µL.²¹

Initial Therapy

The primary therapy of ITP is glucocorticoids, either prednisone or dexamethasone. In the past prednisone at a dose of 60 to 80 mg/day was started at the time of diagnosis (Table 1).

Most patients will respond by 1 week, although some patients may take up to 4 weeks to respond. When the platelet count is greater than 50 × 10³/µL, the prednisone should be tapered over the course of several weeks. An alternative that is being used more frequently is dexamethasone 40 mg/day for 4 days, which offers the advantage of requiring patients to take medication for only 4 days. In European studies better responses were seen with multiple cycles of dexamethasone: 4-day pulses every 28 days for 6 cycles (overall response was 89.2% and relapse-free survival at 15 months was 90%) or 4-day pulses every 14 days for 4 cycles (85.6% response rate with 81% relapse-free survival at 15 months).²² Two randomized trials have shown higher response rates with pulsed dexamethasone repeated 2 or 3 times every 2 weeks, and this is now the preferred option.^8,23

For rapid induction of a response, there are 2 options. A single dose of intravenous immune globulin (IVIG) at 1 g/kg or intravenous anti-D immunoglobulin (anti-D) at 50 to 75 µg/kg can induce a response in more than 80% of patients in 24 to 48 hours.^21,24 IVIG has several drawbacks. It can cause aseptic meningitis, and in patients with vascular disease the increased viscosity can induce ischemia. There is also a considerable fluid load delivered with the IVIG, and it needs to be given over several hours.

The use of anti-D is limited to Rh-positive patients who have not had a splenectomy. It should not be used in patients who are Coombs positive due to the risk of provoking more hemolysis. Rarely anti-D has been reported to cause a severe hemolytic disseminated intravascular coagulation syndrome (1:20,000 patients), which has led to restrictions in its use.²⁵ Although the drug can be rapidly given over 15 minutes, due to these concerns current recommendations are now to observe patients for 8 hours after their dose and to perform a urine dipstick test for blood at 2, 4, and 8 hours. Concerns about this rare but serious side effect have led to a dramatic decrease in the use of anti-D.

For patients who are severely thrombocytopenic and do not respond to initial therapy, there are 2 options for raising the platelet counts. One is to use a combination of IVIG, methylprednisolone, vincristine, and/or anti-D.²⁶ The combination of IVIG and anti-D may be synergistic since these agents block different Fc receptors. A response of 71% has been reported for this 3- or 4-drug combination in a series of 35 patients.²⁶ The other option is to treat with a continuous infusion of platelets (1 unit over 6 hours) and IVIG 1 g/kg for 24 hours. Response rates of 62.7% have been reported with this combination, and this rapid rise in platelets can allow time for other therapies to take effect.^27,28

 

Patients with severe thrombocytopenia who relapse with reduction of steroids or who do not respond to steroids have several options for further management. Repeated doses of IVIG can transiently raise the platelet count, and some patients may only need several courses of therapy over the course of many months. One study showed that 60% of patients could delay or defer therapy by receiving multiple doses of anti-D. However, 30% of patients did eventually receive splenectomy and 20% of patients required ongoing therapy with anti-D.²⁹ In a randomized trial comparing early use of anti-D to steroids to avoid splenectomy, there was no difference in splenectomy rate (38% versus 42%).³⁰ Finally, an option as mentioned above is to try a 6-month course of pulse dexamethasone 40 mg/day for 4 days, repeated every 28 days.

Options for Refractory ITP

There are multiple options for patients who do not respond to initial ITP therapies. These can be divided into several broad groups: curative therapies (splenectomy and rituximab), thrombopoietin receptor agonists, and anecdotal therapies.

Splenectomy

In patients with severe thrombocytopenia who do not respond or who relapse with lower doses of prednisone, splenectomy should be strongly considered. Splenectomy will induce a good response in 60% to 70% of patients and is durable in most patients. In 2 recently published reviews of splenectomy, the complete response rate was 67% and the total response rate was 88% to 90%%.^8,31 Between 15% and 28% of patients relapsed over 5 years, with most recurrences occurring in the first 2 years. Splenectomy carries a short-term surgical risk, and the life-long risk of increased susceptibility to overwhelming sepsis is discussed below. However, the absolute magnitude of these risks is low and is often lower than the risks of continued prednisone therapy or of continued cytotoxic therapy.

Timing of splenectomy depends on the patient’s presentation. Most patients should be given a 6-month trial of steroids or other therapies before proceeding to splenectomy.³¹ However, patients who persist with severe thrombocytopenia despite initial therapies or who are suffering intolerable side effects from therapy should be considered sooner for splenectomy.³¹ In the George review, multiple factors such as responding to IVIG were found not to be predictive of response to splenectomy.⁸

Method of splenectomy appears not to matter.²¹ Rates of finding accessory spleens are just as high or higher with laparoscopic splenectomy and the patient can recover faster. In patients who are severely thrombocytopenic, open splenectomy can allow for quicker control of the vascular access of the spleen.

Rates of splenectomy in recent years have decreased for many reasons,³² including the acceptance of lower platelet counts in asymptomatic patients and the availability of alternative therapies such as rituximab. In addition, despite abundant data for good outcomes, there is a concern that splenectomy responses are not durable. Although splenectomy will not cure every patient with ITP, splenectomy is the therapy with the most patients, the longest follow-up, and the most consistent rate of cure, and it should be discussed with every ITP patient who does not respond to initial therapy and needs further treatment.

The risk of overwhelming sepsis varies by indications for splenectomy but appears to be about 1%.^33,34 The use of pneumococcal vaccine and recognition of this syndrome have helped reduce the risk. Asplenic patients need to be counseled about the risk of overwhelming infections, should be vaccinated for pneumococcus, meningococcus, and Haemophilus influenzae, and should wear an ID bracelet.^35–37 Patients previously vaccinated for pneumococcus should be re-vaccinated every 3 to 5 years. The role of prophylactic antibiotics in adults is controversial, but patients under the age of 18 should be on penicillin VK 250 mg orally twice daily.

Rituximab

Rituximab has been shown to be very active in ITP. Most studies used the standard dose of 375 mg/m² weekly for 4 weeks, but other studies have shown that 1000 mg twice 14 days apart (ie, on days 1 and 15) resulted in the same response rate and may be more convenient for patients.^38,39 The response time can vary, with patients either showing a rapid response or requiring up to 8 weeks for their counts to go up. Although experience is limited, the response seems to be durable, especially in those patients whose counts rise higher than 150 × 10³/µL; in patients who relapse, a response can be re-induced with a repeat course. Overall the response rate for rituximab is about 60%, but only approximately 20% to 40% of patients will remain in long-term remission.^40–42 There is no evidence yet that “maintenance” therapy or monitoring CD19/CD20 cells can help further the duration of remission.

 

Whether to give rituximab pre- or post-splenectomy is also uncertain. An advantage of presplenectomy rituximab is that many patients will achieve remission, delaying the need for surgery. Also, rituximab is a good option for patients whose medical conditions put them at high risk for complications with splenectomy. However, it is unknown whether rituximab poses any long-term risks, while the long-term risks of splenectomy are well-defined. Rituximab is the only curative option left for patients who have failed splenectomy and is a reasonable option for these patients.

There is an intriguing trial in which patients were randomly assigned to dexamethasone alone versus dexamethasone plus rituximab upon presentation with ITP; those who were refractory to dexamethasone alone received salvage therapy with dexamethasone plus rituximab.⁴³ The dexamethasone plus rituximab group had an overall higher rate of sustained remission at 6 months than the dexamethasone group, 63% versus 36%. Interestingly, patients who failed their first course of dexamethasone but then were “salvaged” with dexamethasone/rituximab had a similar overall response rate of 56%, suggesting that saving the addition of rituximab for steroid failures may be an effective option.

Although not “chemotherapy,” rituximab is not without risks. Patients can develop infusion reactions, which can be severe in 1% to 2% of patients. In a meta-analysis the fatal reaction rate was 2.9%.⁴⁰ Patients with chronic hepatitis B infections can experience reactivation with rituximab, and thus all patients should be screened before treatment. Finally, the very rare but devastating complication of progressive multifocal leukoencephalopathy has been reported.

Thrombopoietin Receptor Agonists

Although patients with ITP have low platelet counts, studies starting with Dameshek have shown that these patients also have reduced production of platelets.⁴⁴ Despite the very low circulating platelet count, levels of the platelet growth factor thrombopoietin (TPO) are not raised.⁴⁵ Seminal studies with recombinant TPO in the 1990s showed that ITP patients responded to thrombopoietin-stimulating protein, but the formation of anti-TPO antibodies halted trials with the first generation of these agents. Two TPO receptor agonists (TPO-RA) are approved for use in patients with ITP.

Romiplostim. Romiplostim is a peptibody, a combination of a peptide that binds and stimulates the TPO receptor and an Fc domain to extend its half-life.⁴⁶ It is administered in a weekly subcutaneous dose starting at 1 to 3 µg/kg. Use of romiplostim in ITP patients produces a response rate of 80% to 88%, with 87% of patients being able to wean off or decrease other anti-ITP medications.⁴⁷ In a long-term extension study, the response was again high at 87%.⁴⁸ These studies have also shown a reduced incidence of bleeding.

The major side effect of romiplostim seen in clinical trials was marrow reticulin formation, which occurred in up to 5.6% of patients.^47,48 The clinical course in these patients is the development of anemia and a myelophthisic blood smear with teardrop cells and nucleated red cells. These changes appear to reverse with cessation of the drug. The bone marrow shows increased reticulin formation but rarely, if ever, shows the collagen deposition seen with primary myelofibrosis.

Thrombosis has also been seen, with a rate of 0.08 to 0.1 cases per 100 patient-weeks,⁴⁹ but it remains unclear if this is due to the drug, part of the natural history of ITP, or expected complications in older patients undergoing any type of medical therapy. Surprisingly, despite the low platelet counts, patients with ITP in one study had double the risk of venous thrombosis, demonstrating that ITP itself can be a risk factor for thrombosis.⁵⁰ These trials have shown no long-term concerns for other clinical problems such as liver disease.

Eltrombopag. The other available TPO-RA is eltrombopag,⁵¹ an oral agent that stimulates the TPO receptor by binding the transmembrane domain and activating it. The drug is given orally starting at 50 mg/day (25 mg for patients of Asian ancestry or with liver disease) and can be dose escalated to 75 mg/day. The drug needs to be taken on an empty stomach. Eltrombopag has been shown to be effective in chronic ITP, with response rates of 59% to 80% and reduction in use of rescue medications.^47,51,52 As with romiplostim, the incidence of bleeding was also decreased with eltrombopag in these trials.^47,51

Clinical trials demonstrated that eltrombopag shares with romiplostim the risk for marrow fibrosis. A side effect unique to eltrombopag observed in these trials was a 3% to 7% incidence of elevated liver function tests.^21,52 These abnormal findings appeared to resolve in most patients, but liver function tests need to be monitored in patients receiving eltrombopag.

Clinical use. The clearest indication for the use of TPO-RAs is in patients who have failed several therapies and remain symptomatic or are on intolerable doses of other medications such as prednisone. The clear benefits are their relative safety and high rates of success. The main drawback of TPO-RAs is the need for continuing therapy as the platelet count will return to baseline shortly after these agents are stopped. Currently there is no clear indication for one medication over the other. The advantages of romiplostim are great flexibility in dosing (1–10 µg/kg week) and no concerns about drug interaction. The current drawback of romiplostim is the Food and Drug Administration’s requirement for patients to receive the drug from a clinic and not at home. Eltrombopag offers the advantage of oral use, but it has a limited dose range and potential for drug interactions. Both agents have been associated with marrow reticulin formation, although in clinical use this risk appears to be very low.⁵³

 

Other Options

In the literature there are numerous options for the treatment of ITP.^54,55 Most of these studies are anecdotal, enrolled small number of patients, and sometimes included patients with mild thrombocytopenia, but these therapeutic options can be tried in patients who are refractory to standard therapies and have bleeding. The agents with the greatest amount of supporting data are danazol, vincristine, azathioprine, cyclophosphamide, and fostamatinib.

Danazol 200 mg 4 times daily is thought to downregulate the macrophage Fc receptor. The onset of action may be delayed and a therapeutic trial of up to 4 to 6 months is advised. Danazol is very effective in patients with antiphospholipid antibody syndrome who develop ITP and may be more effective in premenopausal women.⁵⁶ Once a response is seen, danazol should be continued for 6 months and then an attempt to wean the patient off the agent should be made. A partial response can be seen in 70% to 90% of patients, but a complete response is rare.⁵⁴

Vincristine 1.4 mg/m² weekly has a low response rate, but if a response is going to occur, it will occur rapidly within 2 weeks. Thus, a prolonged trial of vincristine is not needed; if no platelet rise is seen in several weeks, the drug should be stopped. Again, partial responses are more common than complete response—50% to 63% versus 0% to 6%.⁵⁴Azathioprine 150 mg orally daily, like danazol, demonstrates a delayed response and requires several months to assess for response. However, 19% to 25% of patients may have a complete response.⁵⁴ It has been reported that the related agent mycophenolate 1000 mg twice daily is also effective in ITP.⁵⁷

Cyclophosphamide 1 g/m² intravenously repeated every 28 days has been reported to have a response rate of up to 40%.⁵⁸ Although considered more aggressive, this is a standard immunosuppressive dose and should be considered in patients with very low platelet counts. Patients who have not responded to single-agent cyclophosphamide may respond to multi-agent chemotherapy with agents such as etoposide and vincristine plus cyclophosphamide.⁵⁹

Fostamatinib, a spleen tyrosine kinase (SYK) inhibitor, is currently under investigation for the treatment of ITP.⁶⁰ This agent prevents phagocytosis of antibody-coated platelets by macrophages. In early studies fostamatinib has been well tolerated at a dose of 150 mg twice daily, with 75% of patients showing a response. Large phase 3 trials are underway, and if the earlier promising results hold up fostamatinib may be a novel option for refractory patients.

A Practical Approach to Refractory ITP

One approach is to divide patients into bleeders, or those with either very low platelet counts (< 5 × 10³/µL) or who have had significant bleeding in the past, and nonbleeders, or those with platelet counts above 5 × 10³/µL and no history of severe bleeding. Bleeders who do not respond adequately to splenectomy should first start with rituximab since it is not cytotoxic and is the only other “curative” therapy (Table 2).

Patients who do not respond to rituximab should then be tried on TPO-RAs. Patients who are unresponsive to these agents and still have severe disease with bleeding should receive aggressive therapy with immunosuppression. One approach to consider is bolus cyclophosphamide. If this is unsuccessful, then using a combination of azathioprine plus danazol can be considered. Since this combination may take 4 to 6 months to work, these patients may need frequent IVIG infusions to maintain a safe platelet count.

Nonbleeders should be tried on danazol and other relatively safe agents. If this fails, rituximab or TPO-RAs can be considered. Before one considers cytotoxic therapy, the risk of the therapy must be weighed against the risk posed by the thrombocytopenia. The mortality from ITP is fairly low (5%) and is restricted to patients with severe disease. Patients with only moderate thrombocytopenia and no bleeding are better served with conservative management. There is little justification for the use of continuous steroid therapy in this group of patients given the long-term risks of this therapy.

Special Situations

Surgery

Patients with ITP who need surgery either for splenectomy or for other reasons should have their platelet counts raised to a level greater than 20 to 30 × 10³/µL before surgery. Most patients with ITP have increased platelet function and will not have excessive bleeding with these platelet counts. For patients with platelet counts below this level, an infusion of immune globulin or anti-D may rapidly increase the platelet counts. If the surgery is elective, short-term use of TPO-RAs to raise the counts can also be considered.

 

Pregnancy

Up to 10% of pregnant women will develop low platelet counts during their pregnancy.^61,62 The most common etiology is gestational thrombocytopenia, which is an exaggeration of the lowered platelet count seen in pregnancy. Counts may fall as low as 50 × 10³/µL at the time of delivery. No therapy is required as the fetus is not affected and the mother does not have an increased risk of bleeding. Pregnancy complications such as HELLP syndrome and thrombotic microangiopathies also present with low platelet counts, but these can be diagnosed by history.^61,63

Women with ITP can either develop the disease during pregnancy or have a worsening of the symptoms.⁶⁴ Counts often drop dramatically during the first trimester. Early management should be conservative with low doses of prednisone to keep the count above 10 × 10³/µL.²¹ Immunoglobulin is also effective,⁶⁵ but there are rare reports of pulmonary edema. Rarely patients who are refractory will require splenectomy, which may be safely performed in the second trimester. For delivery the count should be greater than 30 × 10³/µL and for an epidural greater than 50 × 10³/µL.⁶⁴ There are reports of the use of TPO-RAs in pregnancy, and this can be considered for refractory cases.⁶⁶

Most controversy centers on management of the delivery. In the past it was feared that fetal thrombocytopenia could lead to intracranial hemorrhage, and Caesarean section was always recommended. It now appears that most cases of intracranial hemorrhage were due to alloimmune thrombocytopenia and not ITP. Furthermore, the nadir of the baby’s platelet count is not at birth but several days after. It appears the safest course is to proceed with a vaginal or C-section delivery determined by obstetrical indications and then immediately check the baby’s platelet count. If the platelet count is low in the neonate, immunoglobulin will raise the count. Since the neonatal thrombocytopenia is due to passive transfer of maternal antibody, the platelet destruction will abate in 4 to 6 weeks.

Pediatric Patients

The incidence of ITP in children is 2.2 to 5.3 per 100,000 children.¹ There are several distinct differences in pediatric ITP. Most cases will resolve in weeks, with only a minority of patients transforming into chronic ITP (5%–10%). Also, the rates of serious bleeding are lower in children than in adults, with intracranial hemorrhage rates of 0.1% to 0.5% being seen.⁶⁷ For most patients with no or mild bleeding, management now is observation alone regardless of platelet count because it is felt that the risks of therapies are higher than the risk of bleeding.²¹ For patients with bleeding, IVIG, anti-D, or a short course of steroids can be used. Given the risk of overwhelming sepsis, splenectomy is often deferred as long as possible. Rituximab is increasingly being used in children due to concerns about use of agents such a cyclophosphamide or azathioprine in children.⁶⁸ Abundant data on use of TPO-RAs in children showing high response rates and safety support their use, and these should be considered in refractory ITP before any cytotoxic agent.^69–71

Helicobacter Pylori Infection

There has been much interest in the relationship between H. pylori and ITP.^16,72,73H. pylori infections have been associated with a variety of autoimmune diseases, and there is a confusing literature on this infection and ITP. Several meta-analyses have shown that eradication of H. pylori will result in an ITP response rate of 20% to 30%, but responses curiously appear to be limited to certain geographic areas such as Japan and Italy but not the United States. In patients with recalcitrant ITP, especially in geographic areas with high incidence, it may be worthwhile to check for H. pylori infection and treat accordingly if positive.

Drug-Induced Thrombocytopenia

Patients with drug-induced thrombocytopenia present with very low (< 10 × 10³/µL) platelet counts 1 to 3 weeks after starting a new medication.^74–76 In patients with a possible drug-induced thrombocytopenia, the primary therapy is to stop the suspect drug.⁷⁷ If there are multiple new medications, the best approach is to stop any drug that has been strongly associated with thrombocytopenia (Table 3).^74,78,79

Immune globulin, corticosteroids, or intravenous anti‑D have been suggested as useful in drug‑related thrombocytopenia. However, since most of these thrombocytopenic patients recover when the agent is cleared from the body, this therapy is probably not necessary and withholding treatment avoids exposing the patients to the adverse events associated with further therapy.

 

Evans Syndrome

Evans syndrome is defined as the combination of autoimmune hemolytic anemia (AIHA) and ITP.^80,81 These cytopenias can present simultaneously or sequentially. Patients with Evans syndrome are thought to have a more severe disease process, to be more prone to bleeding, and to be more difficult to treat, but the rarity of this syndrome makes this hard to quantify.

The classic clinical presentation of Evans syndrome is severe anemia and thrombocytopenia. Children with Evans syndrome often have complex immunodeficiencies such as autoimmune lymphoproliferative syndrome.^82,83 In adults, Evans syndrome most often complicates other autoimmune diseases such as lupus. There are increasing reports of Evans syndrome occurring as a complication of T-cell lymphomas. Often the autoimmune disease can predate the lymphoma diagnosis by months or even years.

In theory the diagnostic approach is straightforward by showing a Coombs-positive hemolytic anemia in the setting of a clinical diagnosis of immune thrombocytopenia. The blood smear will show spherocytes and a diminished platelet count. The presence of other abnormal red cell forms should raise the possibility of an alternative diagnosis. It is unclear how vigorously one should search for other underlying diseases. Many patients will already have the diagnosis of an underlying autoimmune disease. The presence of lymphadenopathy should raise concern for lymphoma.

Initial therapy is high-dose steroids (2 mg/kg/day). IVIG should be added if severe thrombocytopenia is present. Patients who cannot be weaned off prednisone or relapse after prednisone should be considered for splenectomy, although these patients are at higher risk of relapsing.⁸⁰ Increasingly rituximab is being used with success.^84,85 For patients who fail splenectomy and rituximab, aggressive immunosuppression should be considered. Increasing data support the benefits of sirolimus, and this should be considered for refractory patients.⁸⁶ For patients with Evans syndrome due to underlying lymphoma, antineoplastic therapy often results in prompt resolution of the symptoms. Recurrence of the autoimmune cytopenias often heralds relapse.

Introduction

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder, with only approximately 2000 new cases diagnosed in the United States each year.¹ It is now recognized that there are 2 distinct categories of HCL, classic HCL (cHCL) and variant HCL (vHCL), with vHCL now classified as a separate entity under the World Health Organization Classification of Hematopoietic Tumors.² For this reason, the 2 diseases will be discussed separately. However, they do bear many clinical and microscopic similarities and because of this were originally indistinguishable using diagnostic techniques previously available. Even in the modern era using immunophenotypic, molecular, and genetic testing, differentiating between the classic and variant disease subtypes is sometimes difficult.

For cHCL the median age of diagnosis is 55 years, with vHCL occurring in patients who are somewhat older; HCL has been described only in the adult population, with 1 exception.^3,4 There is a 4:1 male predominance, and Caucasians are more frequently affected than other ethnic groups. While the cause of the disease remains largely unknown, it has been observed to occur more frequently in farmers and in persons exposed to pesticides and/or herbicides, petroleum products, and ionizing radiation.⁴ The Institute of Medicine recently updated their position regarding veterans and Agent Orange, stating that there is sufficient evidence of an association between herbicides and chronic lymphoid leukemias (including HCL) to consider these diseases linked to exposure.⁵ Familial forms have also been described that are associated with specific HLA haplotypes, indicating a possible hereditary component.⁶ Most likely, a combination of environmental and genetic factors ultimately contributes to the development of HCL.

In recent years enormous progress has been made with respect to new insights into the biology of cHCL and vHCL, with significant refinement of diagnostic criteria. In addition, tremendous advances have occurred in both treatment and supportive care regimens, which have resulted in a dramatically increased overall life expectancy as well as decreased disease-related morbidity. This has meant that more patients are affected by HCL over time and are more likely to require care for relapsed HCL or associated comorbidities. Although no curative treatment options exist outside of allogeneic transplantation, therapeutic improvements have resulted in patients with cHCL having a life expectancy similar to that of unaffected patients, increasing the need for vigilance to prevent foreseeable complications.

Biology and Patheogenisis

The family of HCLs are chronic B-cell malignancies that account for approximately 2% of all diagnosed leukemias.⁷ The first detailed characterization of HCL as a distinct clinical entity was performed by Dr. Bouroncle and colleagues at the Ohio State University in 1958.⁸ Originally called leukemic reticuloendotheliosis, it was renamed HCL following more detailed description of the unique morphology of these malignant cells.⁹ Significant advances have recently been made in identifying distinctive genetic, immunophenotypic, and morphologic features that distinguish HCL from other B-cell malignancies.

HCL B cells tend to accumulate in the bone marrow, splenic red pulp, and (in some cases) peripheral blood. Unlike other lymphoproliferative disorders, HCL only rarely results in lymphadenopathy. HCL derives its name from the distinct appearance of the malignant hairy cells (Figure). Morphologically, HCL cells are mature, small lymphoid B-cells with a round or oval nucleus and abundant pale blue cytoplasm. Irregular projections of cytoplasm and microvilli give the cells a serrated, “hairy” appearance.¹⁰ The biological significance of these fine hair-like projections remains unknown and is an area of ongoing investigation. Gene expression profiling has revealed that HCL B cells are most similar to splenic marginal zone B cells and memory B cells.^11–13 A recent analysis of common genetic alterations in HCL suggests that the cell of origin is in fact the hematopoietic stem cell.¹⁴

Compared to other hematologic malignancies, the genomic profile of HCL is relatively stable, with few chromosomal defects or translocations observed. A seminal study by Tiacci and colleagues revealed that the BRAF V600E mutation was present in 47 out of 47 cHCL cases examined, results that have since been replicated by other groups, confirming that BRAF V600E is a hallmark mutation in cHCL.¹⁵ The BRAF V600E gain-of-function mutation results in constitutive activation of the serine-threonine protein kinase B-Raf, which regulates the mitogen-activated protein kinase (MAPK)/RAF-MEK-ERK pathway. Indeed, cHCL B cells have elevated MAPK signaling, leading to enhancement of growth and survival.¹⁶ This specific mutation in the BRAF gene is also seen in a number of solid tumor malignancies including melanoma and thyroid cancer, and represents a therapeutic target using BRAF inhibitors already developed to treat these malignancies.¹⁷ Testing for BRAF V600E by polymerase chain reaction or immunohistochemical staining is now routinely performed when HCL is suspected.

 

While BRAF V600E is identified in nearly all cases of cHCL, it is rare in vHCL.¹⁸ The variant type of HCL was classified as a distinct clinical entity in 2008 and can now often be distinguished from cHCL on the basis of BRAF mutational status, among other differences. Interestingly, in the rare cases of BRAF V600E–negative cHCL, other mutations in BRAF or downstream targets as well as aberrant activation of the RAF-MEK-ERK signaling cascade are observed, indicating that this pathway is critical in HCL and may still represent a viable therapeutic target. Expression of the IGHV4-34 immunoglobulin rearrangement, while more common in vHCL, has also been identified in 10% of cHCL cases and appears to confer poor prognosis.¹⁹ Other mutated genes that have been identified in HCL include CDKN1B, TP53, U2AF1, ARID1A, EZH2, and KDM6A.²⁰

Classic HCL is characterized by the immunophenotypic expression of CD11c, CD25, CD103, and CD123, with kappa or lambda light chain restriction indicating clonality; HCL B cells are generally negative for CD5, CD10, CD23, CD27, and CD79b. In contrast, vHCL often lacks expression of CD25 and CD123.¹⁸ The B-cell receptor (BCR) is expressed on hairy cells and its activation promotes proliferation and survival in vitro.²¹ The role of BCR signaling in B-cell malignancies is increasingly recognized, and therapies that target the BCR and associated signaling molecules offer an attractive treatment strategy.²² HCL B cells also typically express CD19, CD20, CD22, CD79a, CD200, CD1d, and annexin A1. Tartrate-resistant acid phosphatase (TRAP) positivity by immunohistochemistry is a hallmark of cHCL. Interestingly, changes to the patient’s original immunophenotype have been observed following treatment and upon disease recurrence, highlighting the importance of tracking immunophenotype throughout the course of disease.

Diagnosis

Prior to the advent of annual screening evaluations with routine examination of complete blood counts (CBC), patients were most often diagnosed with HCL when they presented with symptoms of the disease such as splenomegaly, infections, or complications of anemia or thrombocytopenia.²³ In the current era, patients are more likely to be incidentally diagnosed when they are found to have an abnormal value on a CBC. Any blood lineage may be affected and patients may have pancytopenia or isolated cytopenias. Of note, monocytopenia is a common finding in cHCL that is not entirely understood. The cells typical of cHCL do not usually circulate in the peripheral blood, but if present would appear as mature lymphocytes with villous cytoplasmic projections, pale blue cytoplasm, and reniform nuclei with open chromatin (Figure).⁹ Even if the morphologic examination is highly suggestive of HCL, additional testing is required to differentiate between cHCL, vHCL, and other hematologic malignancies which may also have cytoplasmic projections. A complete assessment of the immunophenotype, molecular profile, and cytogenetic features is required to arrive at this diagnosis.

The international Hairy Cell Leukemia Foundation recently published consensus guidelines for the diagnosis and treatment of HCL.²⁴ These guidelines recommend that patients undergo examination of the peripheral blood for morphology and immunophenotyping and further recommend obtaining bone marrow core and aspirate biopsy samples for immunophenotyping via immunohistochemical staining and flow cytometry. The characteristic immunophenotype of cHCL is a population of monoclonal B lymphocytes which co-express CD19, CD20, CD11c, CD25, CD103, and CD123. Variant HCL is characterized by a very similar immunophenotype but is usually negative for CD25 and CD123. It is notable that CD25 positivity may be lost following treatment, and the absence of this marker should not be used as the sole basis of a cHCL versus vHCL diagnosis. Because marrow fibrosis in HCL may prevent a marrow aspirate from being obtained, many of the key diagnostic studies are performed on the core biopsy, including morphological evaluation and immunohistochemical stains such as CD20 (a pan-B cell antigen), annexin-1 (an anti-inflammatory protein expressed only in cHCL), and VE1 (a BRAF V600E stain).

As noted above, recurrent cytogenetic abnormalities have now been identified that may inform the diagnosis or prognosis of HCL. Next-generation sequencing and other testing of the genetic landscape are taking on a larger role in subtype differentiation, and it is likely that future guidelines will recommend evaluation for significant mutations. Given that BRAF V600E mutation status is a key feature of cHCL and is absent in vHCL, it is important to perform this testing at the time of diagnosis whenever possible. The mutation may be detected via VE1 immunohistochemical staining, allele-specific polymerase chain reaction, or next-generation sequencing. Other less sensitive tests exist but are utilized less frequently.

 

Minimal Residual Disease

There is currently no accepted standard for minimal residual disease (MRD) monitoring in HCL. While detection of MRD has been clearly associated with increased risk of disease progression, cHCL cells typically do not circulate in the peripheral blood, limiting the use of peripheral blood immunophenotyping for quantitative MRD assessment. For quantitative monitoring of marrow involvement by HCL, immunohistochemical staining of the bone marrow core biopsy is usually required. Staining may be performed for CD20, or, in patients who have received anti-CD20 therapy, DBA.44, VE-1, or CD79a. There is currently not a consensus regarding what level of disease involvement constitutes MRD. One group studied this issue and found that relapse could be predicted by evaluating MRD by percentage of positive cells in the marrow by immunohistochemical staining, with less than 1% involvement having the lowest risk for disease relapse and greater than 5% having the highest risk for disease relapse.²⁵ A recent study evaluated MRD patterns in the peripheral blood of 32 cHCL patients who had completed frontline therapy. This group performed flow cytometry on the peripheral blood of patients at 1, 3, 6, and 12 months following therapy. All patients had achieved a complete response with initial therapy and peripheral blood MRD negativity at the completion of therapy. At a median follow-up of 100 months post therapy, 5 patients converted from peripheral blood–MRD negative to peripheral blood–MRD positive, and 6 patients developed overt disease progression. In all patients who progressed, progression was preceded by an increase in detectable peripheral blood MRD cells.²⁶ Although larger studies are needed, peripheral blood flow cytometric monitoring for MRD may be a useful adjunct to predict ongoing response or impending relapse. In addition, newer, more sensitive methods of disease monitoring may ultimately supplant flow cytometry.

Risk Stratification

Although much progress has been made in the risk stratification profiling of hematologic malignancies in general, HCL has unfortunately lagged behind in this effort. The most recent risk stratification analysis was performed in 1982 by Jansen and colleagues.²⁷ This group of researchers performed a retrospective analysis of 391 HCL patients treated at 22 centers. One of the central questions in their analysis was survival time from diagnosis in patients who had not yet undergone splenectomy (a standard treatment at the time). This group consisted of a total of 154 patients. As this study predated modern pathological and molecular testing, clinical and laboratory features were examined, and these mostly consisted of physical exam findings and analysis of the peripheral blood. This group found that several factors influenced the survival of these patients, including duration of symptoms prior to diagnosis, the degree of splenomegaly, hemoglobin level, and number of hairy cells in the peripheral blood. However, because of interobserver variation for the majority of these variables, only hemoglobin and spleen size were included in the proportional hazard model. Using only these 2 variables, the authors were able to determine 3 clinical stages for HCL (Table 1). The stages were found to correlate with median survival: patients with stage 1 disease had a median survival not reached at 72 months, but patients with stage 2 disease had a median survival of 18 months, which decreased to only 12 months in patients with stage 3 disease.

Because the majority of patients with HCL in the modern era will be diagnosed prior to reaching stage 3, a risk stratification system incorporating clinical features, laboratory parameters, and molecular and genetic testing is of considerable interest and is a subject of ongoing research. Ultimately, the goal will be to identify patients at higher risk of early relapse so that more intensive therapies can be applied to initial treatment that will result in longer treatment-free intervals.

Treatment

Because there is no curative treatment for either cHCL or vHCL outside allogeneic transplantation, and it is not clear that early treatment leads to better outcomes in HCL, patients do not always receive treatment at the time of diagnosis or relapse. The general consensus is that patients should be treated if there is a declining trend in hematologic parameters or they experience symptoms from the disease.²⁴ Current consensus guidelines recommend treatment when any of the following hematologic parameters are met: hemoglobin less than 11 g/dL, platelet count less than 100 × 10³/µL, or absolute neutrophil count less than 1000/µL.²⁴ These parameters are surrogate markers that indicate compromised bone marrow function. Cytopenias may also be caused by splenomegaly, and symptomatic splenomegaly with or without cytopenias is an indication for treatment. A small number of patients with HCL (approximately 10%) do not require immediate therapy after diagnosis and are monitored by their provider until treatment is indicated.

 

First-Line Therapy

Despite advances in targeted therapies for HCL, because no treatment has been shown to extend the treatment-free interval longer than chemotherapy, treatment with a purine nucleoside analog is usually the recommended first-line therapy. This includes either cladribine or pentostatin. Both agents appear to be equally effective, and the choice of therapy is determined by the treating physician based on his or her experience. Cladribine administration has been studied using a number of different schedules and routes: intravenous continuous infusion (0.1 mg/kg) for 7 days, intravenous infusion (0.14 mg/kg/day) over 2 hours on a 5-day regimen, or alternatively subcutaneously (0.1–0.14 mg/kg/day) on a once-per-day or once-per-week regimen (Table 2).^28,29

Pentostatin is administered intravenously (4 mg/m²) in an outpatient setting once every other week.³⁰ Patients should be followed closely for evidence of fever or active infection, and routine blood counts should be obtained weekly until recovery. Both drugs cause myelosuppression, and titration of both dose and frequency of administration may be required if complications such as life-threatening infection or renal insufficiency arise (Table 2).³⁰ Note that chemotherapy is not recommended for patients with active infections, and an alternative agent may need to be selected in these cases.

Unlike cHCL, vHCL remains difficult to treat and early disease progression is common. The best outcomes have been seen in patients who have received combination chemo-immunotherapy such as purine nucleoside analog therapy plus rituximab or bendamustine plus rituximab.³¹ One pilot study of bendamustine plus rituximab in 12 patients found an overall response rate of 100%, with the majority of patients achieving a complete response.³¹ For patients who achieved a complete response, the median duration of response had not been reached, but patients achieving only a partial response had a median duration of response of only 20 months, indicating there is a subgroup of patients who will require a different treatment approach.³² A randomized phase 2 trial of rituximab with either pentostatin or bendamustine is ongoing.³³

Assessment of Response

Response assessment involves physical examination for estimation of spleen size, assessment of hematologic parameters, and a bone marrow biopsy for evaluation of marrow response. It is recommended that the bone marrow biopsy be performed 4 to 6 months following cladribine administration, or after completion of 12 doses of pentostatin. Detailed response assessment criteria are shown in Table 3.

 

 

Second-Line Therapy

Although the majority of patients treated with purine analogs will achieve durable remissions, approximately 40% of patients will eventually require second-line therapy. Criteria for treatment at relapse are the same as the criteria for initial therapy, including symptomatic disease or progressive anemia, thrombocytopenia, or neutropenia. The choice of treatment is based on clinical parameters and the duration of the previous remission. If the initial remission was longer than 65 months and the patient is eligible to receive chemotherapy, re-treatment with initial therapy is recommended. For a remission between 24 and 65 months, re-treatment with a purine analog combined with an anti-CD20 monoclonal antibody may be considered.³⁴ If the first remission is shorter than 24 months, confirmation of the original diagnosis as well as consideration for testing for additional mutations with therapeutic targets (BRAF V600E, MAP2K1) should be considered before a treatment decision is made. For these patients, alternative therapies, including investigational agents, should be considered.²⁴

Monoclonal antibody therapy has been studied in both the up-front setting and in relapsed or refractory HCL.³⁵ An initial study of 15 patients with relapsed HCL found an overall response rate of 80%, with 8 patients achieving a complete response. A subsequent study of 26 patients who relapsed after cladribine therapy found an overall response rate of 80%, with a complete response rate of 32%. Median relapse-free survival was 27 months.³⁶ Ravandi and others studied rituximab in the up-front setting in combination with cladribine, and found an overall response rate of 100%, including in patients with vHCL. At the time of publication of the study results, the median survival had not been reached.³⁷ As has been seen with other lymphoid malignancies, concurrent therapy with rituximab appears to enhance the activity of the agent with which it is combined. While its use in the up-front setting remains an area of active investigation, there is a clear role for chemo-immunotherapy in the relapsed setting.

 

In patients with cHCL, excellent results including complete remissions have been reported with the use of BRAF inhibitors, both as a single agent and when combined with anti-CD20 therapy. The 2 commercially available BRAF inhibitors are vemurafenib and dabrafenib, and both have been tested in relapsed cHCL.^38,39 The first study of vemurafenib was reported by Tiacci and colleagues, who found an overall response rate of 96% after a median of 8 weeks and a 100% response rate after a median of 12 weeks, with complete response rates up to 42%.³⁸ The median relapse-free survival was 23 months (decreasing to only 6 months in patients who achieved only a partial remission), indicating that these agents will likely need to be administered in combination with other effective therapies with non-overlapping toxicities. Vemurafenib has been administered concurrently with rituximab, and preliminary results of this combination therapy showed early rates of complete responses.⁴⁰ Dabrafenib has been reported for use as a single agent in cHCL and clinical trials are underway evaluating its efficacy when administered with trametinib, a MEK inhibitor.^39,41 Of note, patients receiving BRAF inhibitors frequently develop cutaneous complications of RAF inhibition including cutaneous squamous cell carcinomas and keratoacanthomas, and close dermatologic surveillance is required.

Variant HCL does not harbor the BRAF V600E mutation, but up to half of patients have been found to have mutations of MAP2K1, which upregulates MEK1 expression.⁴² Trametinib is approved by the US Food and Drug Administration for the treatment of patients with melanoma at a dose of 2 mg orally daily, and has been successfully used to treat 1 patient with vHCL.⁴³ Further evaluation of this targeted therapy is underway.

Ibrutinib, a Bruton tyrosine kinase inhibitor, and moxetumomab pasudotox, an immunotoxin conjugate, are currently being studied in National Institutes of Health–sponsored multi-institutional trials for patients with HCL. Ibrutinib is administered orally at 420 mg per day until relapse.⁴⁴ Moxetumomab pasudotox was tested at different doses between 5 and 50 μg/kg intravenously every other day for 3 doses for up to 16 cycles unless they experienced disease progression or developed neutralizing antibodies.⁴⁵ Both agents have been shown to have significant activity in cHCL and vHCL and will likely be included in the treatment armamentarium once trials are completed. Second-line therapy options are summarized in Table 4.

 

 

Complications and Supportive Care

The complications of HCL may be separated into the pre-, intra-, and post-treatment periods. At the time of diagnosis and prior to the initiation of therapy, marrow infiltration by HCL frequently leads to cytopenias which cause symptomatic anemia, infection, and/or bleeding complications. Many patients develop splenomegaly, which may further lower the blood counts and which is experienced as abdominal fullness or distention, with early satiety leading to weight loss. Patients may also experience constitutional symptoms with fatigue, fevers in the absence of infection, and unintentional weight loss even without splenomegaly.

For patients who initiate therapy with purine nucleoside analogs, the early part of treatment is associated with the greatest risk of morbidity and mortality. Chemotherapy leads to both immunosuppression (altered cellular immunity) as well as myelosuppression. Thus, patients who are already in need of treatment because of disease-related cytopenias will experience an abrupt and sometimes significant decline in the peripheral blood counts. The treatment period prior to recovery of neutrophils requires the greatest vigilance. Because patients are profoundly immunocompromised, febrile neutropenia is a common complication leading to hospital admission and the cause is often difficult to identify. Treatment with broad-spectrum antibiotics, investigation for opportunistic and viral infections, and considerations for antifungal prophylaxis or therapy are required in this setting. It is recommended that all patients treated with purine nucleoside analogs receive prophylactic antimicrobials for herpes simplex virus and varicella zoster virus, as well as prophylaxis against Pneumocystis jirovecii. Unfortunately, growth factor support has not proven successful in this patient population but is not contraindicated.⁴⁶

Following successful completion of therapy, patients may remain functionally immunocompromised for a significant period of time even with a normal neutrophil count. Monitoring of the CD4 count may help to determine when prophylactic antimicrobials may be discontinued. A CD4 count greater than 200 cells/µL is generally considered to be adequate for prevention of opportunistic infections. Although immunizations have not been well studied in HCL, it is recommended that patients receive annual influenza immunizations as well as age-appropriate immunizations against Streptococcus pneumoniae and other infectious illnesses as indicated. Live viral vaccines such as the currently available herpes zoster vaccine can lead to infections in this patient population and are not recommended.

 

Like many hematologic malignancies, HCL may be associated with comorbid conditions related to immune dysfunction. There is a known association with an increased risk of second primary malignancies, which may predate the diagnosis of HCL.⁴⁷ Therefore, it is recommended that patients continue annual cancer screenings as well as undergo prompt evaluation for potential symptoms of second malignancies. In addition, it is thought that there may be an increased risk for autoimmune disorders such as inflammatory arthritis or immune-mediated cytopenias. One case-control study found a possible association between autoimmune diseases and HCL, noting that at times these diseases are diagnosed concurrently.⁴⁸ However, because of the rarity of the disease it has been difficult to quantify these associated conditions in a systematic way. There is currently an international patient data registry under development for the systematic study of HCL and its complications which may answer many of these questions.

Survivorship and quality of life are important considerations in chronic diseases. It is not uncommon for patients to develop anxiety related to the trauma of diagnosis and treatment, especially when intensive care has been required. Patients may have lingering fears regarding concerns of developing infections due to exposure to ill persons or fears regarding risk of relapse and need for re-treatment. A proactive approach with partnership with psychosocial oncology may be of benefit, especially when symptoms of post-traumatic stress disorder are evident.

Conclusion

HCL is a rare, chronic lymphoid malignancy that is now subclassified into classic and variant HCL. Further investigations into the disease subtypes will allow more precise disease definitions, and these studies are underway. Renewed efforts toward updated risk stratification and clinical staging systems will be important aspects of these investigations. Refinements in treatment and supportive care have resulted in greatly improved overall survival, which has translated into larger numbers of people living with HCL. However, new treatment paradigms for vHCL are needed as the progression-free survival in this disease remains significantly lower than that of cHCL. Future efforts toward understanding survivorship issues and management of long-term treatment and disease-related complications will be critical for ensuring good quality of life for patients living with HCL.

Introduction

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder, with only approximately 2000 new cases diagnosed in the United States each year.¹ It is now recognized that there are 2 distinct categories of HCL, classic HCL (cHCL) and variant HCL (vHCL), with vHCL now classified as a separate entity under the World Health Organization Classification of Hematopoietic Tumors.² For this reason, the 2 diseases will be discussed separately. However, they do bear many clinical and microscopic similarities and because of this were originally indistinguishable using diagnostic techniques previously available. Even in the modern era using immunophenotypic, molecular, and genetic testing, differentiating between the classic and variant disease subtypes is sometimes difficult.

For cHCL the median age of diagnosis is 55 years, with vHCL occurring in patients who are somewhat older; HCL has been described only in the adult population, with 1 exception.^3,4 There is a 4:1 male predominance, and Caucasians are more frequently affected than other ethnic groups. While the cause of the disease remains largely unknown, it has been observed to occur more frequently in farmers and in persons exposed to pesticides and/or herbicides, petroleum products, and ionizing radiation.⁴ The Institute of Medicine recently updated their position regarding veterans and Agent Orange, stating that there is sufficient evidence of an association between herbicides and chronic lymphoid leukemias (including HCL) to consider these diseases linked to exposure.⁵ Familial forms have also been described that are associated with specific HLA haplotypes, indicating a possible hereditary component.⁶ Most likely, a combination of environmental and genetic factors ultimately contributes to the development of HCL.

In recent years enormous progress has been made with respect to new insights into the biology of cHCL and vHCL, with significant refinement of diagnostic criteria. In addition, tremendous advances have occurred in both treatment and supportive care regimens, which have resulted in a dramatically increased overall life expectancy as well as decreased disease-related morbidity. This has meant that more patients are affected by HCL over time and are more likely to require care for relapsed HCL or associated comorbidities. Although no curative treatment options exist outside of allogeneic transplantation, therapeutic improvements have resulted in patients with cHCL having a life expectancy similar to that of unaffected patients, increasing the need for vigilance to prevent foreseeable complications.

Biology and Patheogenisis

The family of HCLs are chronic B-cell malignancies that account for approximately 2% of all diagnosed leukemias.⁷ The first detailed characterization of HCL as a distinct clinical entity was performed by Dr. Bouroncle and colleagues at the Ohio State University in 1958.⁸ Originally called leukemic reticuloendotheliosis, it was renamed HCL following more detailed description of the unique morphology of these malignant cells.⁹ Significant advances have recently been made in identifying distinctive genetic, immunophenotypic, and morphologic features that distinguish HCL from other B-cell malignancies.

HCL B cells tend to accumulate in the bone marrow, splenic red pulp, and (in some cases) peripheral blood. Unlike other lymphoproliferative disorders, HCL only rarely results in lymphadenopathy. HCL derives its name from the distinct appearance of the malignant hairy cells (Figure). Morphologically, HCL cells are mature, small lymphoid B-cells with a round or oval nucleus and abundant pale blue cytoplasm. Irregular projections of cytoplasm and microvilli give the cells a serrated, “hairy” appearance.¹⁰ The biological significance of these fine hair-like projections remains unknown and is an area of ongoing investigation. Gene expression profiling has revealed that HCL B cells are most similar to splenic marginal zone B cells and memory B cells.^11–13 A recent analysis of common genetic alterations in HCL suggests that the cell of origin is in fact the hematopoietic stem cell.¹⁴

Compared to other hematologic malignancies, the genomic profile of HCL is relatively stable, with few chromosomal defects or translocations observed. A seminal study by Tiacci and colleagues revealed that the BRAF V600E mutation was present in 47 out of 47 cHCL cases examined, results that have since been replicated by other groups, confirming that BRAF V600E is a hallmark mutation in cHCL.¹⁵ The BRAF V600E gain-of-function mutation results in constitutive activation of the serine-threonine protein kinase B-Raf, which regulates the mitogen-activated protein kinase (MAPK)/RAF-MEK-ERK pathway. Indeed, cHCL B cells have elevated MAPK signaling, leading to enhancement of growth and survival.¹⁶ This specific mutation in the BRAF gene is also seen in a number of solid tumor malignancies including melanoma and thyroid cancer, and represents a therapeutic target using BRAF inhibitors already developed to treat these malignancies.¹⁷ Testing for BRAF V600E by polymerase chain reaction or immunohistochemical staining is now routinely performed when HCL is suspected.

 

While BRAF V600E is identified in nearly all cases of cHCL, it is rare in vHCL.¹⁸ The variant type of HCL was classified as a distinct clinical entity in 2008 and can now often be distinguished from cHCL on the basis of BRAF mutational status, among other differences. Interestingly, in the rare cases of BRAF V600E–negative cHCL, other mutations in BRAF or downstream targets as well as aberrant activation of the RAF-MEK-ERK signaling cascade are observed, indicating that this pathway is critical in HCL and may still represent a viable therapeutic target. Expression of the IGHV4-34 immunoglobulin rearrangement, while more common in vHCL, has also been identified in 10% of cHCL cases and appears to confer poor prognosis.¹⁹ Other mutated genes that have been identified in HCL include CDKN1B, TP53, U2AF1, ARID1A, EZH2, and KDM6A.²⁰

Classic HCL is characterized by the immunophenotypic expression of CD11c, CD25, CD103, and CD123, with kappa or lambda light chain restriction indicating clonality; HCL B cells are generally negative for CD5, CD10, CD23, CD27, and CD79b. In contrast, vHCL often lacks expression of CD25 and CD123.¹⁸ The B-cell receptor (BCR) is expressed on hairy cells and its activation promotes proliferation and survival in vitro.²¹ The role of BCR signaling in B-cell malignancies is increasingly recognized, and therapies that target the BCR and associated signaling molecules offer an attractive treatment strategy.²² HCL B cells also typically express CD19, CD20, CD22, CD79a, CD200, CD1d, and annexin A1. Tartrate-resistant acid phosphatase (TRAP) positivity by immunohistochemistry is a hallmark of cHCL. Interestingly, changes to the patient’s original immunophenotype have been observed following treatment and upon disease recurrence, highlighting the importance of tracking immunophenotype throughout the course of disease.

Diagnosis

Prior to the advent of annual screening evaluations with routine examination of complete blood counts (CBC), patients were most often diagnosed with HCL when they presented with symptoms of the disease such as splenomegaly, infections, or complications of anemia or thrombocytopenia.²³ In the current era, patients are more likely to be incidentally diagnosed when they are found to have an abnormal value on a CBC. Any blood lineage may be affected and patients may have pancytopenia or isolated cytopenias. Of note, monocytopenia is a common finding in cHCL that is not entirely understood. The cells typical of cHCL do not usually circulate in the peripheral blood, but if present would appear as mature lymphocytes with villous cytoplasmic projections, pale blue cytoplasm, and reniform nuclei with open chromatin (Figure).⁹ Even if the morphologic examination is highly suggestive of HCL, additional testing is required to differentiate between cHCL, vHCL, and other hematologic malignancies which may also have cytoplasmic projections. A complete assessment of the immunophenotype, molecular profile, and cytogenetic features is required to arrive at this diagnosis.

The international Hairy Cell Leukemia Foundation recently published consensus guidelines for the diagnosis and treatment of HCL.²⁴ These guidelines recommend that patients undergo examination of the peripheral blood for morphology and immunophenotyping and further recommend obtaining bone marrow core and aspirate biopsy samples for immunophenotyping via immunohistochemical staining and flow cytometry. The characteristic immunophenotype of cHCL is a population of monoclonal B lymphocytes which co-express CD19, CD20, CD11c, CD25, CD103, and CD123. Variant HCL is characterized by a very similar immunophenotype but is usually negative for CD25 and CD123. It is notable that CD25 positivity may be lost following treatment, and the absence of this marker should not be used as the sole basis of a cHCL versus vHCL diagnosis. Because marrow fibrosis in HCL may prevent a marrow aspirate from being obtained, many of the key diagnostic studies are performed on the core biopsy, including morphological evaluation and immunohistochemical stains such as CD20 (a pan-B cell antigen), annexin-1 (an anti-inflammatory protein expressed only in cHCL), and VE1 (a BRAF V600E stain).

As noted above, recurrent cytogenetic abnormalities have now been identified that may inform the diagnosis or prognosis of HCL. Next-generation sequencing and other testing of the genetic landscape are taking on a larger role in subtype differentiation, and it is likely that future guidelines will recommend evaluation for significant mutations. Given that BRAF V600E mutation status is a key feature of cHCL and is absent in vHCL, it is important to perform this testing at the time of diagnosis whenever possible. The mutation may be detected via VE1 immunohistochemical staining, allele-specific polymerase chain reaction, or next-generation sequencing. Other less sensitive tests exist but are utilized less frequently.

 

Minimal Residual Disease

There is currently no accepted standard for minimal residual disease (MRD) monitoring in HCL. While detection of MRD has been clearly associated with increased risk of disease progression, cHCL cells typically do not circulate in the peripheral blood, limiting the use of peripheral blood immunophenotyping for quantitative MRD assessment. For quantitative monitoring of marrow involvement by HCL, immunohistochemical staining of the bone marrow core biopsy is usually required. Staining may be performed for CD20, or, in patients who have received anti-CD20 therapy, DBA.44, VE-1, or CD79a. There is currently not a consensus regarding what level of disease involvement constitutes MRD. One group studied this issue and found that relapse could be predicted by evaluating MRD by percentage of positive cells in the marrow by immunohistochemical staining, with less than 1% involvement having the lowest risk for disease relapse and greater than 5% having the highest risk for disease relapse.²⁵ A recent study evaluated MRD patterns in the peripheral blood of 32 cHCL patients who had completed frontline therapy. This group performed flow cytometry on the peripheral blood of patients at 1, 3, 6, and 12 months following therapy. All patients had achieved a complete response with initial therapy and peripheral blood MRD negativity at the completion of therapy. At a median follow-up of 100 months post therapy, 5 patients converted from peripheral blood–MRD negative to peripheral blood–MRD positive, and 6 patients developed overt disease progression. In all patients who progressed, progression was preceded by an increase in detectable peripheral blood MRD cells.²⁶ Although larger studies are needed, peripheral blood flow cytometric monitoring for MRD may be a useful adjunct to predict ongoing response or impending relapse. In addition, newer, more sensitive methods of disease monitoring may ultimately supplant flow cytometry.

Risk Stratification

Although much progress has been made in the risk stratification profiling of hematologic malignancies in general, HCL has unfortunately lagged behind in this effort. The most recent risk stratification analysis was performed in 1982 by Jansen and colleagues.²⁷ This group of researchers performed a retrospective analysis of 391 HCL patients treated at 22 centers. One of the central questions in their analysis was survival time from diagnosis in patients who had not yet undergone splenectomy (a standard treatment at the time). This group consisted of a total of 154 patients. As this study predated modern pathological and molecular testing, clinical and laboratory features were examined, and these mostly consisted of physical exam findings and analysis of the peripheral blood. This group found that several factors influenced the survival of these patients, including duration of symptoms prior to diagnosis, the degree of splenomegaly, hemoglobin level, and number of hairy cells in the peripheral blood. However, because of interobserver variation for the majority of these variables, only hemoglobin and spleen size were included in the proportional hazard model. Using only these 2 variables, the authors were able to determine 3 clinical stages for HCL (Table 1). The stages were found to correlate with median survival: patients with stage 1 disease had a median survival not reached at 72 months, but patients with stage 2 disease had a median survival of 18 months, which decreased to only 12 months in patients with stage 3 disease.

Because the majority of patients with HCL in the modern era will be diagnosed prior to reaching stage 3, a risk stratification system incorporating clinical features, laboratory parameters, and molecular and genetic testing is of considerable interest and is a subject of ongoing research. Ultimately, the goal will be to identify patients at higher risk of early relapse so that more intensive therapies can be applied to initial treatment that will result in longer treatment-free intervals.

Treatment

Because there is no curative treatment for either cHCL or vHCL outside allogeneic transplantation, and it is not clear that early treatment leads to better outcomes in HCL, patients do not always receive treatment at the time of diagnosis or relapse. The general consensus is that patients should be treated if there is a declining trend in hematologic parameters or they experience symptoms from the disease.²⁴ Current consensus guidelines recommend treatment when any of the following hematologic parameters are met: hemoglobin less than 11 g/dL, platelet count less than 100 × 10³/µL, or absolute neutrophil count less than 1000/µL.²⁴ These parameters are surrogate markers that indicate compromised bone marrow function. Cytopenias may also be caused by splenomegaly, and symptomatic splenomegaly with or without cytopenias is an indication for treatment. A small number of patients with HCL (approximately 10%) do not require immediate therapy after diagnosis and are monitored by their provider until treatment is indicated.

 

First-Line Therapy

Despite advances in targeted therapies for HCL, because no treatment has been shown to extend the treatment-free interval longer than chemotherapy, treatment with a purine nucleoside analog is usually the recommended first-line therapy. This includes either cladribine or pentostatin. Both agents appear to be equally effective, and the choice of therapy is determined by the treating physician based on his or her experience. Cladribine administration has been studied using a number of different schedules and routes: intravenous continuous infusion (0.1 mg/kg) for 7 days, intravenous infusion (0.14 mg/kg/day) over 2 hours on a 5-day regimen, or alternatively subcutaneously (0.1–0.14 mg/kg/day) on a once-per-day or once-per-week regimen (Table 2).^28,29

Pentostatin is administered intravenously (4 mg/m²) in an outpatient setting once every other week.³⁰ Patients should be followed closely for evidence of fever or active infection, and routine blood counts should be obtained weekly until recovery. Both drugs cause myelosuppression, and titration of both dose and frequency of administration may be required if complications such as life-threatening infection or renal insufficiency arise (Table 2).³⁰ Note that chemotherapy is not recommended for patients with active infections, and an alternative agent may need to be selected in these cases.

Unlike cHCL, vHCL remains difficult to treat and early disease progression is common. The best outcomes have been seen in patients who have received combination chemo-immunotherapy such as purine nucleoside analog therapy plus rituximab or bendamustine plus rituximab.³¹ One pilot study of bendamustine plus rituximab in 12 patients found an overall response rate of 100%, with the majority of patients achieving a complete response.³¹ For patients who achieved a complete response, the median duration of response had not been reached, but patients achieving only a partial response had a median duration of response of only 20 months, indicating there is a subgroup of patients who will require a different treatment approach.³² A randomized phase 2 trial of rituximab with either pentostatin or bendamustine is ongoing.³³

Assessment of Response

Response assessment involves physical examination for estimation of spleen size, assessment of hematologic parameters, and a bone marrow biopsy for evaluation of marrow response. It is recommended that the bone marrow biopsy be performed 4 to 6 months following cladribine administration, or after completion of 12 doses of pentostatin. Detailed response assessment criteria are shown in Table 3.

 

 

Second-Line Therapy

Although the majority of patients treated with purine analogs will achieve durable remissions, approximately 40% of patients will eventually require second-line therapy. Criteria for treatment at relapse are the same as the criteria for initial therapy, including symptomatic disease or progressive anemia, thrombocytopenia, or neutropenia. The choice of treatment is based on clinical parameters and the duration of the previous remission. If the initial remission was longer than 65 months and the patient is eligible to receive chemotherapy, re-treatment with initial therapy is recommended. For a remission between 24 and 65 months, re-treatment with a purine analog combined with an anti-CD20 monoclonal antibody may be considered.³⁴ If the first remission is shorter than 24 months, confirmation of the original diagnosis as well as consideration for testing for additional mutations with therapeutic targets (BRAF V600E, MAP2K1) should be considered before a treatment decision is made. For these patients, alternative therapies, including investigational agents, should be considered.²⁴

Monoclonal antibody therapy has been studied in both the up-front setting and in relapsed or refractory HCL.³⁵ An initial study of 15 patients with relapsed HCL found an overall response rate of 80%, with 8 patients achieving a complete response. A subsequent study of 26 patients who relapsed after cladribine therapy found an overall response rate of 80%, with a complete response rate of 32%. Median relapse-free survival was 27 months.³⁶ Ravandi and others studied rituximab in the up-front setting in combination with cladribine, and found an overall response rate of 100%, including in patients with vHCL. At the time of publication of the study results, the median survival had not been reached.³⁷ As has been seen with other lymphoid malignancies, concurrent therapy with rituximab appears to enhance the activity of the agent with which it is combined. While its use in the up-front setting remains an area of active investigation, there is a clear role for chemo-immunotherapy in the relapsed setting.

 

In patients with cHCL, excellent results including complete remissions have been reported with the use of BRAF inhibitors, both as a single agent and when combined with anti-CD20 therapy. The 2 commercially available BRAF inhibitors are vemurafenib and dabrafenib, and both have been tested in relapsed cHCL.^38,39 The first study of vemurafenib was reported by Tiacci and colleagues, who found an overall response rate of 96% after a median of 8 weeks and a 100% response rate after a median of 12 weeks, with complete response rates up to 42%.³⁸ The median relapse-free survival was 23 months (decreasing to only 6 months in patients who achieved only a partial remission), indicating that these agents will likely need to be administered in combination with other effective therapies with non-overlapping toxicities. Vemurafenib has been administered concurrently with rituximab, and preliminary results of this combination therapy showed early rates of complete responses.⁴⁰ Dabrafenib has been reported for use as a single agent in cHCL and clinical trials are underway evaluating its efficacy when administered with trametinib, a MEK inhibitor.^39,41 Of note, patients receiving BRAF inhibitors frequently develop cutaneous complications of RAF inhibition including cutaneous squamous cell carcinomas and keratoacanthomas, and close dermatologic surveillance is required.

Variant HCL does not harbor the BRAF V600E mutation, but up to half of patients have been found to have mutations of MAP2K1, which upregulates MEK1 expression.⁴² Trametinib is approved by the US Food and Drug Administration for the treatment of patients with melanoma at a dose of 2 mg orally daily, and has been successfully used to treat 1 patient with vHCL.⁴³ Further evaluation of this targeted therapy is underway.

Ibrutinib, a Bruton tyrosine kinase inhibitor, and moxetumomab pasudotox, an immunotoxin conjugate, are currently being studied in National Institutes of Health–sponsored multi-institutional trials for patients with HCL. Ibrutinib is administered orally at 420 mg per day until relapse.⁴⁴ Moxetumomab pasudotox was tested at different doses between 5 and 50 μg/kg intravenously every other day for 3 doses for up to 16 cycles unless they experienced disease progression or developed neutralizing antibodies.⁴⁵ Both agents have been shown to have significant activity in cHCL and vHCL and will likely be included in the treatment armamentarium once trials are completed. Second-line therapy options are summarized in Table 4.

 

 

Complications and Supportive Care

The complications of HCL may be separated into the pre-, intra-, and post-treatment periods. At the time of diagnosis and prior to the initiation of therapy, marrow infiltration by HCL frequently leads to cytopenias which cause symptomatic anemia, infection, and/or bleeding complications. Many patients develop splenomegaly, which may further lower the blood counts and which is experienced as abdominal fullness or distention, with early satiety leading to weight loss. Patients may also experience constitutional symptoms with fatigue, fevers in the absence of infection, and unintentional weight loss even without splenomegaly.

For patients who initiate therapy with purine nucleoside analogs, the early part of treatment is associated with the greatest risk of morbidity and mortality. Chemotherapy leads to both immunosuppression (altered cellular immunity) as well as myelosuppression. Thus, patients who are already in need of treatment because of disease-related cytopenias will experience an abrupt and sometimes significant decline in the peripheral blood counts. The treatment period prior to recovery of neutrophils requires the greatest vigilance. Because patients are profoundly immunocompromised, febrile neutropenia is a common complication leading to hospital admission and the cause is often difficult to identify. Treatment with broad-spectrum antibiotics, investigation for opportunistic and viral infections, and considerations for antifungal prophylaxis or therapy are required in this setting. It is recommended that all patients treated with purine nucleoside analogs receive prophylactic antimicrobials for herpes simplex virus and varicella zoster virus, as well as prophylaxis against Pneumocystis jirovecii. Unfortunately, growth factor support has not proven successful in this patient population but is not contraindicated.⁴⁶

Following successful completion of therapy, patients may remain functionally immunocompromised for a significant period of time even with a normal neutrophil count. Monitoring of the CD4 count may help to determine when prophylactic antimicrobials may be discontinued. A CD4 count greater than 200 cells/µL is generally considered to be adequate for prevention of opportunistic infections. Although immunizations have not been well studied in HCL, it is recommended that patients receive annual influenza immunizations as well as age-appropriate immunizations against Streptococcus pneumoniae and other infectious illnesses as indicated. Live viral vaccines such as the currently available herpes zoster vaccine can lead to infections in this patient population and are not recommended.

 

Like many hematologic malignancies, HCL may be associated with comorbid conditions related to immune dysfunction. There is a known association with an increased risk of second primary malignancies, which may predate the diagnosis of HCL.⁴⁷ Therefore, it is recommended that patients continue annual cancer screenings as well as undergo prompt evaluation for potential symptoms of second malignancies. In addition, it is thought that there may be an increased risk for autoimmune disorders such as inflammatory arthritis or immune-mediated cytopenias. One case-control study found a possible association between autoimmune diseases and HCL, noting that at times these diseases are diagnosed concurrently.⁴⁸ However, because of the rarity of the disease it has been difficult to quantify these associated conditions in a systematic way. There is currently an international patient data registry under development for the systematic study of HCL and its complications which may answer many of these questions.

Survivorship and quality of life are important considerations in chronic diseases. It is not uncommon for patients to develop anxiety related to the trauma of diagnosis and treatment, especially when intensive care has been required. Patients may have lingering fears regarding concerns of developing infections due to exposure to ill persons or fears regarding risk of relapse and need for re-treatment. A proactive approach with partnership with psychosocial oncology may be of benefit, especially when symptoms of post-traumatic stress disorder are evident.

Conclusion

HCL is a rare, chronic lymphoid malignancy that is now subclassified into classic and variant HCL. Further investigations into the disease subtypes will allow more precise disease definitions, and these studies are underway. Renewed efforts toward updated risk stratification and clinical staging systems will be important aspects of these investigations. Refinements in treatment and supportive care have resulted in greatly improved overall survival, which has translated into larger numbers of people living with HCL. However, new treatment paradigms for vHCL are needed as the progression-free survival in this disease remains significantly lower than that of cHCL. Future efforts toward understanding survivorship issues and management of long-term treatment and disease-related complications will be critical for ensuring good quality of life for patients living with HCL.

Introduction

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder, with only approximately 2000 new cases diagnosed in the United States each year.¹ It is now recognized that there are 2 distinct categories of HCL, classic HCL (cHCL) and variant HCL (vHCL), with vHCL now classified as a separate entity under the World Health Organization Classification of Hematopoietic Tumors.² For this reason, the 2 diseases will be discussed separately. However, they do bear many clinical and microscopic similarities and because of this were originally indistinguishable using diagnostic techniques previously available. Even in the modern era using immunophenotypic, molecular, and genetic testing, differentiating between the classic and variant disease subtypes is sometimes difficult.

For cHCL the median age of diagnosis is 55 years, with vHCL occurring in patients who are somewhat older; HCL has been described only in the adult population, with 1 exception.^3,4 There is a 4:1 male predominance, and Caucasians are more frequently affected than other ethnic groups. While the cause of the disease remains largely unknown, it has been observed to occur more frequently in farmers and in persons exposed to pesticides and/or herbicides, petroleum products, and ionizing radiation.⁴ The Institute of Medicine recently updated their position regarding veterans and Agent Orange, stating that there is sufficient evidence of an association between herbicides and chronic lymphoid leukemias (including HCL) to consider these diseases linked to exposure.⁵ Familial forms have also been described that are associated with specific HLA haplotypes, indicating a possible hereditary component.⁶ Most likely, a combination of environmental and genetic factors ultimately contributes to the development of HCL.

In recent years enormous progress has been made with respect to new insights into the biology of cHCL and vHCL, with significant refinement of diagnostic criteria. In addition, tremendous advances have occurred in both treatment and supportive care regimens, which have resulted in a dramatically increased overall life expectancy as well as decreased disease-related morbidity. This has meant that more patients are affected by HCL over time and are more likely to require care for relapsed HCL or associated comorbidities. Although no curative treatment options exist outside of allogeneic transplantation, therapeutic improvements have resulted in patients with cHCL having a life expectancy similar to that of unaffected patients, increasing the need for vigilance to prevent foreseeable complications.

Biology and Patheogenisis

The family of HCLs are chronic B-cell malignancies that account for approximately 2% of all diagnosed leukemias.⁷ The first detailed characterization of HCL as a distinct clinical entity was performed by Dr. Bouroncle and colleagues at the Ohio State University in 1958.⁸ Originally called leukemic reticuloendotheliosis, it was renamed HCL following more detailed description of the unique morphology of these malignant cells.⁹ Significant advances have recently been made in identifying distinctive genetic, immunophenotypic, and morphologic features that distinguish HCL from other B-cell malignancies.

HCL B cells tend to accumulate in the bone marrow, splenic red pulp, and (in some cases) peripheral blood. Unlike other lymphoproliferative disorders, HCL only rarely results in lymphadenopathy. HCL derives its name from the distinct appearance of the malignant hairy cells (Figure). Morphologically, HCL cells are mature, small lymphoid B-cells with a round or oval nucleus and abundant pale blue cytoplasm. Irregular projections of cytoplasm and microvilli give the cells a serrated, “hairy” appearance.¹⁰ The biological significance of these fine hair-like projections remains unknown and is an area of ongoing investigation. Gene expression profiling has revealed that HCL B cells are most similar to splenic marginal zone B cells and memory B cells.^11–13 A recent analysis of common genetic alterations in HCL suggests that the cell of origin is in fact the hematopoietic stem cell.¹⁴

Compared to other hematologic malignancies, the genomic profile of HCL is relatively stable, with few chromosomal defects or translocations observed. A seminal study by Tiacci and colleagues revealed that the BRAF V600E mutation was present in 47 out of 47 cHCL cases examined, results that have since been replicated by other groups, confirming that BRAF V600E is a hallmark mutation in cHCL.¹⁵ The BRAF V600E gain-of-function mutation results in constitutive activation of the serine-threonine protein kinase B-Raf, which regulates the mitogen-activated protein kinase (MAPK)/RAF-MEK-ERK pathway. Indeed, cHCL B cells have elevated MAPK signaling, leading to enhancement of growth and survival.¹⁶ This specific mutation in the BRAF gene is also seen in a number of solid tumor malignancies including melanoma and thyroid cancer, and represents a therapeutic target using BRAF inhibitors already developed to treat these malignancies.¹⁷ Testing for BRAF V600E by polymerase chain reaction or immunohistochemical staining is now routinely performed when HCL is suspected.

 

While BRAF V600E is identified in nearly all cases of cHCL, it is rare in vHCL.¹⁸ The variant type of HCL was classified as a distinct clinical entity in 2008 and can now often be distinguished from cHCL on the basis of BRAF mutational status, among other differences. Interestingly, in the rare cases of BRAF V600E–negative cHCL, other mutations in BRAF or downstream targets as well as aberrant activation of the RAF-MEK-ERK signaling cascade are observed, indicating that this pathway is critical in HCL and may still represent a viable therapeutic target. Expression of the IGHV4-34 immunoglobulin rearrangement, while more common in vHCL, has also been identified in 10% of cHCL cases and appears to confer poor prognosis.¹⁹ Other mutated genes that have been identified in HCL include CDKN1B, TP53, U2AF1, ARID1A, EZH2, and KDM6A.²⁰

Classic HCL is characterized by the immunophenotypic expression of CD11c, CD25, CD103, and CD123, with kappa or lambda light chain restriction indicating clonality; HCL B cells are generally negative for CD5, CD10, CD23, CD27, and CD79b. In contrast, vHCL often lacks expression of CD25 and CD123.¹⁸ The B-cell receptor (BCR) is expressed on hairy cells and its activation promotes proliferation and survival in vitro.²¹ The role of BCR signaling in B-cell malignancies is increasingly recognized, and therapies that target the BCR and associated signaling molecules offer an attractive treatment strategy.²² HCL B cells also typically express CD19, CD20, CD22, CD79a, CD200, CD1d, and annexin A1. Tartrate-resistant acid phosphatase (TRAP) positivity by immunohistochemistry is a hallmark of cHCL. Interestingly, changes to the patient’s original immunophenotype have been observed following treatment and upon disease recurrence, highlighting the importance of tracking immunophenotype throughout the course of disease.

Diagnosis

Prior to the advent of annual screening evaluations with routine examination of complete blood counts (CBC), patients were most often diagnosed with HCL when they presented with symptoms of the disease such as splenomegaly, infections, or complications of anemia or thrombocytopenia.²³ In the current era, patients are more likely to be incidentally diagnosed when they are found to have an abnormal value on a CBC. Any blood lineage may be affected and patients may have pancytopenia or isolated cytopenias. Of note, monocytopenia is a common finding in cHCL that is not entirely understood. The cells typical of cHCL do not usually circulate in the peripheral blood, but if present would appear as mature lymphocytes with villous cytoplasmic projections, pale blue cytoplasm, and reniform nuclei with open chromatin (Figure).⁹ Even if the morphologic examination is highly suggestive of HCL, additional testing is required to differentiate between cHCL, vHCL, and other hematologic malignancies which may also have cytoplasmic projections. A complete assessment of the immunophenotype, molecular profile, and cytogenetic features is required to arrive at this diagnosis.

The international Hairy Cell Leukemia Foundation recently published consensus guidelines for the diagnosis and treatment of HCL.²⁴ These guidelines recommend that patients undergo examination of the peripheral blood for morphology and immunophenotyping and further recommend obtaining bone marrow core and aspirate biopsy samples for immunophenotyping via immunohistochemical staining and flow cytometry. The characteristic immunophenotype of cHCL is a population of monoclonal B lymphocytes which co-express CD19, CD20, CD11c, CD25, CD103, and CD123. Variant HCL is characterized by a very similar immunophenotype but is usually negative for CD25 and CD123. It is notable that CD25 positivity may be lost following treatment, and the absence of this marker should not be used as the sole basis of a cHCL versus vHCL diagnosis. Because marrow fibrosis in HCL may prevent a marrow aspirate from being obtained, many of the key diagnostic studies are performed on the core biopsy, including morphological evaluation and immunohistochemical stains such as CD20 (a pan-B cell antigen), annexin-1 (an anti-inflammatory protein expressed only in cHCL), and VE1 (a BRAF V600E stain).

As noted above, recurrent cytogenetic abnormalities have now been identified that may inform the diagnosis or prognosis of HCL. Next-generation sequencing and other testing of the genetic landscape are taking on a larger role in subtype differentiation, and it is likely that future guidelines will recommend evaluation for significant mutations. Given that BRAF V600E mutation status is a key feature of cHCL and is absent in vHCL, it is important to perform this testing at the time of diagnosis whenever possible. The mutation may be detected via VE1 immunohistochemical staining, allele-specific polymerase chain reaction, or next-generation sequencing. Other less sensitive tests exist but are utilized less frequently.

 

Minimal Residual Disease

There is currently no accepted standard for minimal residual disease (MRD) monitoring in HCL. While detection of MRD has been clearly associated with increased risk of disease progression, cHCL cells typically do not circulate in the peripheral blood, limiting the use of peripheral blood immunophenotyping for quantitative MRD assessment. For quantitative monitoring of marrow involvement by HCL, immunohistochemical staining of the bone marrow core biopsy is usually required. Staining may be performed for CD20, or, in patients who have received anti-CD20 therapy, DBA.44, VE-1, or CD79a. There is currently not a consensus regarding what level of disease involvement constitutes MRD. One group studied this issue and found that relapse could be predicted by evaluating MRD by percentage of positive cells in the marrow by immunohistochemical staining, with less than 1% involvement having the lowest risk for disease relapse and greater than 5% having the highest risk for disease relapse.²⁵ A recent study evaluated MRD patterns in the peripheral blood of 32 cHCL patients who had completed frontline therapy. This group performed flow cytometry on the peripheral blood of patients at 1, 3, 6, and 12 months following therapy. All patients had achieved a complete response with initial therapy and peripheral blood MRD negativity at the completion of therapy. At a median follow-up of 100 months post therapy, 5 patients converted from peripheral blood–MRD negative to peripheral blood–MRD positive, and 6 patients developed overt disease progression. In all patients who progressed, progression was preceded by an increase in detectable peripheral blood MRD cells.²⁶ Although larger studies are needed, peripheral blood flow cytometric monitoring for MRD may be a useful adjunct to predict ongoing response or impending relapse. In addition, newer, more sensitive methods of disease monitoring may ultimately supplant flow cytometry.

Risk Stratification

Although much progress has been made in the risk stratification profiling of hematologic malignancies in general, HCL has unfortunately lagged behind in this effort. The most recent risk stratification analysis was performed in 1982 by Jansen and colleagues.²⁷ This group of researchers performed a retrospective analysis of 391 HCL patients treated at 22 centers. One of the central questions in their analysis was survival time from diagnosis in patients who had not yet undergone splenectomy (a standard treatment at the time). This group consisted of a total of 154 patients. As this study predated modern pathological and molecular testing, clinical and laboratory features were examined, and these mostly consisted of physical exam findings and analysis of the peripheral blood. This group found that several factors influenced the survival of these patients, including duration of symptoms prior to diagnosis, the degree of splenomegaly, hemoglobin level, and number of hairy cells in the peripheral blood. However, because of interobserver variation for the majority of these variables, only hemoglobin and spleen size were included in the proportional hazard model. Using only these 2 variables, the authors were able to determine 3 clinical stages for HCL (Table 1). The stages were found to correlate with median survival: patients with stage 1 disease had a median survival not reached at 72 months, but patients with stage 2 disease had a median survival of 18 months, which decreased to only 12 months in patients with stage 3 disease.

Because the majority of patients with HCL in the modern era will be diagnosed prior to reaching stage 3, a risk stratification system incorporating clinical features, laboratory parameters, and molecular and genetic testing is of considerable interest and is a subject of ongoing research. Ultimately, the goal will be to identify patients at higher risk of early relapse so that more intensive therapies can be applied to initial treatment that will result in longer treatment-free intervals.

Treatment

Because there is no curative treatment for either cHCL or vHCL outside allogeneic transplantation, and it is not clear that early treatment leads to better outcomes in HCL, patients do not always receive treatment at the time of diagnosis or relapse. The general consensus is that patients should be treated if there is a declining trend in hematologic parameters or they experience symptoms from the disease.²⁴ Current consensus guidelines recommend treatment when any of the following hematologic parameters are met: hemoglobin less than 11 g/dL, platelet count less than 100 × 10³/µL, or absolute neutrophil count less than 1000/µL.²⁴ These parameters are surrogate markers that indicate compromised bone marrow function. Cytopenias may also be caused by splenomegaly, and symptomatic splenomegaly with or without cytopenias is an indication for treatment. A small number of patients with HCL (approximately 10%) do not require immediate therapy after diagnosis and are monitored by their provider until treatment is indicated.

 

First-Line Therapy

Despite advances in targeted therapies for HCL, because no treatment has been shown to extend the treatment-free interval longer than chemotherapy, treatment with a purine nucleoside analog is usually the recommended first-line therapy. This includes either cladribine or pentostatin. Both agents appear to be equally effective, and the choice of therapy is determined by the treating physician based on his or her experience. Cladribine administration has been studied using a number of different schedules and routes: intravenous continuous infusion (0.1 mg/kg) for 7 days, intravenous infusion (0.14 mg/kg/day) over 2 hours on a 5-day regimen, or alternatively subcutaneously (0.1–0.14 mg/kg/day) on a once-per-day or once-per-week regimen (Table 2).^28,29

Pentostatin is administered intravenously (4 mg/m²) in an outpatient setting once every other week.³⁰ Patients should be followed closely for evidence of fever or active infection, and routine blood counts should be obtained weekly until recovery. Both drugs cause myelosuppression, and titration of both dose and frequency of administration may be required if complications such as life-threatening infection or renal insufficiency arise (Table 2).³⁰ Note that chemotherapy is not recommended for patients with active infections, and an alternative agent may need to be selected in these cases.

Unlike cHCL, vHCL remains difficult to treat and early disease progression is common. The best outcomes have been seen in patients who have received combination chemo-immunotherapy such as purine nucleoside analog therapy plus rituximab or bendamustine plus rituximab.³¹ One pilot study of bendamustine plus rituximab in 12 patients found an overall response rate of 100%, with the majority of patients achieving a complete response.³¹ For patients who achieved a complete response, the median duration of response had not been reached, but patients achieving only a partial response had a median duration of response of only 20 months, indicating there is a subgroup of patients who will require a different treatment approach.³² A randomized phase 2 trial of rituximab with either pentostatin or bendamustine is ongoing.³³

Assessment of Response

Response assessment involves physical examination for estimation of spleen size, assessment of hematologic parameters, and a bone marrow biopsy for evaluation of marrow response. It is recommended that the bone marrow biopsy be performed 4 to 6 months following cladribine administration, or after completion of 12 doses of pentostatin. Detailed response assessment criteria are shown in Table 3.

 

 

Second-Line Therapy

Although the majority of patients treated with purine analogs will achieve durable remissions, approximately 40% of patients will eventually require second-line therapy. Criteria for treatment at relapse are the same as the criteria for initial therapy, including symptomatic disease or progressive anemia, thrombocytopenia, or neutropenia. The choice of treatment is based on clinical parameters and the duration of the previous remission. If the initial remission was longer than 65 months and the patient is eligible to receive chemotherapy, re-treatment with initial therapy is recommended. For a remission between 24 and 65 months, re-treatment with a purine analog combined with an anti-CD20 monoclonal antibody may be considered.³⁴ If the first remission is shorter than 24 months, confirmation of the original diagnosis as well as consideration for testing for additional mutations with therapeutic targets (BRAF V600E, MAP2K1) should be considered before a treatment decision is made. For these patients, alternative therapies, including investigational agents, should be considered.²⁴

Monoclonal antibody therapy has been studied in both the up-front setting and in relapsed or refractory HCL.³⁵ An initial study of 15 patients with relapsed HCL found an overall response rate of 80%, with 8 patients achieving a complete response. A subsequent study of 26 patients who relapsed after cladribine therapy found an overall response rate of 80%, with a complete response rate of 32%. Median relapse-free survival was 27 months.³⁶ Ravandi and others studied rituximab in the up-front setting in combination with cladribine, and found an overall response rate of 100%, including in patients with vHCL. At the time of publication of the study results, the median survival had not been reached.³⁷ As has been seen with other lymphoid malignancies, concurrent therapy with rituximab appears to enhance the activity of the agent with which it is combined. While its use in the up-front setting remains an area of active investigation, there is a clear role for chemo-immunotherapy in the relapsed setting.

 

In patients with cHCL, excellent results including complete remissions have been reported with the use of BRAF inhibitors, both as a single agent and when combined with anti-CD20 therapy. The 2 commercially available BRAF inhibitors are vemurafenib and dabrafenib, and both have been tested in relapsed cHCL.^38,39 The first study of vemurafenib was reported by Tiacci and colleagues, who found an overall response rate of 96% after a median of 8 weeks and a 100% response rate after a median of 12 weeks, with complete response rates up to 42%.³⁸ The median relapse-free survival was 23 months (decreasing to only 6 months in patients who achieved only a partial remission), indicating that these agents will likely need to be administered in combination with other effective therapies with non-overlapping toxicities. Vemurafenib has been administered concurrently with rituximab, and preliminary results of this combination therapy showed early rates of complete responses.⁴⁰ Dabrafenib has been reported for use as a single agent in cHCL and clinical trials are underway evaluating its efficacy when administered with trametinib, a MEK inhibitor.^39,41 Of note, patients receiving BRAF inhibitors frequently develop cutaneous complications of RAF inhibition including cutaneous squamous cell carcinomas and keratoacanthomas, and close dermatologic surveillance is required.

Variant HCL does not harbor the BRAF V600E mutation, but up to half of patients have been found to have mutations of MAP2K1, which upregulates MEK1 expression.⁴² Trametinib is approved by the US Food and Drug Administration for the treatment of patients with melanoma at a dose of 2 mg orally daily, and has been successfully used to treat 1 patient with vHCL.⁴³ Further evaluation of this targeted therapy is underway.

Ibrutinib, a Bruton tyrosine kinase inhibitor, and moxetumomab pasudotox, an immunotoxin conjugate, are currently being studied in National Institutes of Health–sponsored multi-institutional trials for patients with HCL. Ibrutinib is administered orally at 420 mg per day until relapse.⁴⁴ Moxetumomab pasudotox was tested at different doses between 5 and 50 μg/kg intravenously every other day for 3 doses for up to 16 cycles unless they experienced disease progression or developed neutralizing antibodies.⁴⁵ Both agents have been shown to have significant activity in cHCL and vHCL and will likely be included in the treatment armamentarium once trials are completed. Second-line therapy options are summarized in Table 4.

 

 

Complications and Supportive Care

The complications of HCL may be separated into the pre-, intra-, and post-treatment periods. At the time of diagnosis and prior to the initiation of therapy, marrow infiltration by HCL frequently leads to cytopenias which cause symptomatic anemia, infection, and/or bleeding complications. Many patients develop splenomegaly, which may further lower the blood counts and which is experienced as abdominal fullness or distention, with early satiety leading to weight loss. Patients may also experience constitutional symptoms with fatigue, fevers in the absence of infection, and unintentional weight loss even without splenomegaly.

For patients who initiate therapy with purine nucleoside analogs, the early part of treatment is associated with the greatest risk of morbidity and mortality. Chemotherapy leads to both immunosuppression (altered cellular immunity) as well as myelosuppression. Thus, patients who are already in need of treatment because of disease-related cytopenias will experience an abrupt and sometimes significant decline in the peripheral blood counts. The treatment period prior to recovery of neutrophils requires the greatest vigilance. Because patients are profoundly immunocompromised, febrile neutropenia is a common complication leading to hospital admission and the cause is often difficult to identify. Treatment with broad-spectrum antibiotics, investigation for opportunistic and viral infections, and considerations for antifungal prophylaxis or therapy are required in this setting. It is recommended that all patients treated with purine nucleoside analogs receive prophylactic antimicrobials for herpes simplex virus and varicella zoster virus, as well as prophylaxis against Pneumocystis jirovecii. Unfortunately, growth factor support has not proven successful in this patient population but is not contraindicated.⁴⁶

Following successful completion of therapy, patients may remain functionally immunocompromised for a significant period of time even with a normal neutrophil count. Monitoring of the CD4 count may help to determine when prophylactic antimicrobials may be discontinued. A CD4 count greater than 200 cells/µL is generally considered to be adequate for prevention of opportunistic infections. Although immunizations have not been well studied in HCL, it is recommended that patients receive annual influenza immunizations as well as age-appropriate immunizations against Streptococcus pneumoniae and other infectious illnesses as indicated. Live viral vaccines such as the currently available herpes zoster vaccine can lead to infections in this patient population and are not recommended.

 

Like many hematologic malignancies, HCL may be associated with comorbid conditions related to immune dysfunction. There is a known association with an increased risk of second primary malignancies, which may predate the diagnosis of HCL.⁴⁷ Therefore, it is recommended that patients continue annual cancer screenings as well as undergo prompt evaluation for potential symptoms of second malignancies. In addition, it is thought that there may be an increased risk for autoimmune disorders such as inflammatory arthritis or immune-mediated cytopenias. One case-control study found a possible association between autoimmune diseases and HCL, noting that at times these diseases are diagnosed concurrently.⁴⁸ However, because of the rarity of the disease it has been difficult to quantify these associated conditions in a systematic way. There is currently an international patient data registry under development for the systematic study of HCL and its complications which may answer many of these questions.

Survivorship and quality of life are important considerations in chronic diseases. It is not uncommon for patients to develop anxiety related to the trauma of diagnosis and treatment, especially when intensive care has been required. Patients may have lingering fears regarding concerns of developing infections due to exposure to ill persons or fears regarding risk of relapse and need for re-treatment. A proactive approach with partnership with psychosocial oncology may be of benefit, especially when symptoms of post-traumatic stress disorder are evident.

Conclusion

HCL is a rare, chronic lymphoid malignancy that is now subclassified into classic and variant HCL. Further investigations into the disease subtypes will allow more precise disease definitions, and these studies are underway. Renewed efforts toward updated risk stratification and clinical staging systems will be important aspects of these investigations. Refinements in treatment and supportive care have resulted in greatly improved overall survival, which has translated into larger numbers of people living with HCL. However, new treatment paradigms for vHCL are needed as the progression-free survival in this disease remains significantly lower than that of cHCL. Future efforts toward understanding survivorship issues and management of long-term treatment and disease-related complications will be critical for ensuring good quality of life for patients living with HCL.