Approach to Management of Giant Basal Cell Carcinomas

Comment

Typical BCC lesions are indolent and small, occurring primarily on the head and neck.^5,11,12,17 We report the case of a locally advanced, extremely large and penetrating lesion located on the trunk. This relatively unique case provides for an interesting comparison between available treatments for BCC as well as several of the generally accepted principles of management previously described in the literature.

Treatment Considerations

The approach to management of BCC considers factors related to the tumor and those related to the patient and practitioner. Telfer et al⁶ recommended that tumors be categorized as relatively low or high risk based on prognostic factors including size, site, histologic subtype and growth pattern; definition of margins; and presence or absence of prior treatment. Characteristics of high-risk tumors include size greater than 2.5 to 3 cm in diameter; location on the midface, nose, or ears; aggressive histologic subtype including morpheic, infiltrating, and metatypical; deep extension; perineural invasion; neglected or long-standing lesions; incomplete SE or Mohs micrographic surgery (MMS); and recurrence of tumor after prior treatment.^13,14,18 Although rare, tumors of the metatypical subtype are particularly important to identify, as they are known to be more aggressive and prone to spread than other forms of BCC.^19,20 The clinical appearance of metatypical BCCs often is identical to lower-risk subtypes, reinforcing the importance of careful histologic examination of an adequately deep biopsy, given that metatypical features often are present only in the deep tissue planes.¹⁹

The practitioner also must consider patient-related factors such as age, general health, immunocompromised states, coexisting medical conditions, and current medications. The skills, experience, and recommendations of the physician also are expected to influence treatment selection.^6,21

Surgical Versus Nonsurgical Treatment Approaches

Treatment of large, locally advanced, primary BCCs can be divided into surgical and nonsurgical approaches.^5,6 Surgical approaches include MMS and SE. Mohs micrographic surgery, electrodesiccation and curettage, and cryosurgery may achieve high cure rates in lesions that are low risk but generally are not recommended for use with recurrent or high-risk large and aggressive tumors.^5,6 Nonsurgical approaches include radiotherapy; chemotherapy; and vismodegib, an oral inhibitor of the hedgehog pathway involved in the development of many BCCs.^5,6,22 Topical photodynamic therapy with 5-aminolevulinic acid, topical imiquimod (immune-response modulator) and 5-fluorouracil, and intralesional interferon are other nonsurgical options that are primarily effective for small superficial BCCs. These modalities are not indicated for high-risk tumors.^5,6,23

For small tumors, MMS is regarded by most practitioners as the gold standard due to the high cure rate and cosmetic results it provides.^5,6,18,24 This procedure allows for precise mapping of tumor location on frozen sections and, unlike surgical excision, examination of close to 100% of the deep and peripheral margins.¹⁸ Excision and evaluation of thin horizontal sections for tumor extension also allows for a greater degree of tissue conservation than other modalities.^6,25 Mohs micrographic surgery is particularly useful for tumors of the midface, aggressive histologic subtype (eg, morpheic, infiltrating, basosquamous, micronodular), deep invasion, and perineural spread.^6,8,18,25 In a large review of 3 studies including a total of 7670 patients with primary BCC treated by MMS, Rowe et al²⁶ reported a 5-year recurrence rate of 1.0%, which was 8.7 times less than the weighted average of all non-MMS modalities. Similarly, in a large prospective review by Leibovitch et al,¹⁸ the 5-year recurrence rate of BCC treated with MMS was 1.4% in primary cases and 4.0% in previously recurrent cases.¹⁸ They reported that the main predictors of recurrence included longer tumor duration, more levels of excision required to obtain clear margins, notable subclinical extension, and prior recurrence. Interestingly, tumor and postexcision defect size did not predict recurrence.¹⁸ Margin-controlled excision with MMS was associated with higher success rates than modalities based on clinical margins without histologic control (eg, surgical excision, electrocautery, curettage) and potentially incomplete excision.^12,18

Although MMS has been demonstrated to have a high success rate, it has relative disadvantages. Tumors that are multicentric or have indistinct borders are more difficult to treat with MMS, and cure rates with MMS have been shown to decrease with increasing tumor diameter.^13,25 For example, reported cure rates are greater than 99% for MMS in BCCs less than 2 cm in diameter compared to 98.6% for those between 2 and 3 cm, and only 90.5% for those greater than 3 cm.²⁷ Mohs micrographic surgery requires a highly trained surgeon and can be extremely time consuming and labor intensive, particularly with large and locally aggressive tumors.^6,25 Tumors that involve fat and cartilage require modifications to standardized processing techniques, and deep wounds involving muscle and bone create technical challenges in maintaining orientation.²⁵ In the past, MMS was more expensive than other treatment modalities; however, cost analyses have demonstrated a near-equal cost of MMS compared to surgical excision with permanent section control and lower cost as compared to radiation therapy for selected cases.²⁸

Surgical excision also is considered a highly effective treatment of primary BCC and is the most commonly used treatment modality for BCC.^5,18,29 In this procedure, the peripheral and deep margins of excised tissue can be examined by a pathologist.⁶ Telfer et al⁶ recommended SE as the preferable treatment of choice for both large and small tumors in low-risk sites (ie, those that do not include the face) with nodular histology, tumors with morpheic histology in low-risk sites, and small (<2 cm) superficial tumors in high-risk sites. It is recommended that the size of surgical margins correlate with the likelihood of the presence of subclinical tumor extensions. Larger and morpheic-type BCCs require wider margins to achieve complete excision. In these cases, a 3-mm margin yields only a 66% cure rate, while 5-mm margins yield an 82% cure rate and 13- to 15-mm margins yield cure rates higher than 95%.^6,29,30 In a series examining recurrence rates of primary BCC, Rowe et al²⁶ reviewed 10 studies (2606 patients treated by SE) and calculated a 5-year recurrence rate of 10.1%. Silverman et al³¹ reviewed 5-year recurrence rates in 588 cases of BCC treated with SE. They concluded that BCC on the neck, trunk, arms, and legs of any size may be effectively treated with this modality, with 1 case of recurrence among 187 cases (0.5% recurrence rate). Multivariate analysis identified 2 independent risk factors for recurrence: anatomic site (head) and patient sex (male). Analysis of BCCs on the head distinct from other body sites demonstrated a moderately significant trend (P=.196) of increasing diameter with increasing recurrence rates. Age at treatment, duration of lesion, and length of treatment were not significantly associated with an increased risk of recurrence.³¹ Similarly, a review of 1417 cases of BCC by Dubin and Kopf²¹ demonstrated an increased risk with tumors located on the head and larger lesions.

RELATED ARTICLE: Basal Cell Carcinoma: Analysis of Factors Associated With Incomplete Excision

Radiotherapy (RT) is a commonly employed nonsurgical approach to management. Its use has been declining in recent years due to relative disadvantages and side effects. Similar to MMS, it can be extremely effective for carefully selected patients.^11,31 Radiotherapy is most effective for use with aggressive, rapidly growing BCC subtypes that are more sensitive to radiation, as replicating cells undergo mitotic death when radiation is applied.¹⁵ Radiotherapy is considered a viable option for patients who are not candidates for surgery, tumors in locations difficult to access for SE, and for rare unresectable tumors as a primary therapy.^5,11 In a randomized comparison between RT and SE approaches to the treatment of primary BCCs on the face, RT was found to be inferior to SE both in efficacy (4-year recurrence rate, 7.5% vs 0.7%) and cosmesis (rate of good results, 69% vs 87%).³²

The major disadvantages of RT as compared to other treatment modalities such as MMS or SE are the lack of control at margins and compromised inferior cosmetic outcomes. Hair loss, hyperpigmentation or hypopigmentation, telangiectasia, keloids, cutaneous necrosis, and RT-induced dermatitis have been reported as side effects of RT.^6,11,32-34 Other disadvantages of RT include the inconvenience of multiple visits to the hospital for treatment, and high cost as compared to other modalities such as MMS.³⁵ Finally, use of RT even for relatively benign disease has been linked to an increased risk for both squamous cell carcinoma, BCC, and sarcomas.^15,36

Vismodegib is an oral drug approved by the US Food and Drug Administration in 2012 for the treatment of locally advanced BCC. It is a first-in-class small-molecule systemic inhibitor of the intracellular hedgehog signaling pathway, which has been implicated in the growth and development of several types of cancer, including BCC.^36-38 Most patients with BCC carry loss-of-function mutations that affect PTCH1 and result in unregulated reactivation of the hedgehog pathway and uncontrolled cell growth.^38-40 Vismodegib is a small molecule that selectively deactivates the hedgehog pathway. It currently is indicated for the treatment of metastatic BCC or patients with locally advanced BCCs who are not candidates for SE or RT.^38-41 An open-label nonrandomized phase 2 study by Sekulic et al⁴² evaluated the effectiveness of vismodegib for treatment of metastatic or inoperable BCCs. In 33 patients with metastatic BCCs, the response rate was 30% (10/33) with a 9.5-month median progression-free survival. All responses were partial, with 73% (24/33) showing tumor shrinkage. In 63 patients with locally advanced BCCs, the response rate was 43% (27/63). Most patients demonstrated visible reductions in tumor size and improvement in appearance, but 13 patients (21%) in this group were noted to have a complete response (ie, absence of residual BCC on biopsy). Both cohorts had a median response time of 7.6 months.⁴²