NEW YORK – New, targeted treatments, especially ibrutinib (Imbruvica), have sharply shifted prognosis for patients with chronic lymphocytic leukemia (CLL) and raised new issues for managing these patients now that they survive years longer.
“Ibrutinib has produced a profound change in survival” of patients with CLL, Timothy G. Call, MD, a hematologist/oncologist at the Mayo Clinic in Rochester, Minn., said at a conference held by Imedex. It “has changed the playing field.” No other new agent so far “has produced the same level of progression-free survival in CLL.”
Mitchel L. Zoler/Frontline Medical News
Dr. Timothy G. Call
An analysis published in early 2017 projected a greater than 50% jump in U.S. patients living with CLL from 2011, before the advent of targeted oral drugs, to 2025, when the study predicted that there will be nearly 200,000 U.S. patients living with CLL (J Clin Oncol. 2017 January;35[2]:166-74). With targeted drugs like ibrutinib and idelalisib (Zydelig) costing about $130,000 per patient each year, the projected cost for managing the U.S. CLL population is on track to rise to more than $5 billion by 2025, a nearly sixfold increase, compared with CLL patient expenditures in 2011, according to this analysis.
The impact of the higher cost of treatment is already being felt more acutely by many patients because of recent cuts in assistance from the Patient Access Network, which helps patients with copays but recently had to put a lid on CLL assistance availability when its funding availability hit a wall, Dr. Call said.
On the clinical side, there are new considerations triggered by greater patient longevity. “As we make patients live longer with CLL, we need to double down on the diagnosis and treatment of its complications,” such as watching for development of secondary cancers, Dr. Call said in an interview. This stems from the reduced immunosurveillance in patients with CLL and their resulting increased susceptibility to developing environmentally-triggered malignancies like lung and skin cancers. Other long-term implications of impaired immunosurveillance include increased infection susceptibility, an ongoing risk for Richter’s or Hodgkin lymphoma transformation, and a risk for autoimmune complications, such as red blood cell aplasia and transfusion-associated graft versus host disease.
Patients with CLL can also be susceptible to complications from long-term use of the targeted drug they’re on. The new targeted agents can trigger bruising and bleeding, diarrhea, rash, fatigue, muscle and joint aches, and arrhythmia, he noted.
Potential adverse effects, specifically from ibrutinib, include a 3% risk for a major bleed, a 10% rate of new-onset atrial fibrillation, and a 20% risk for new hypertension, Dr. Call said. Before starting ibrutinib, patients should undergo screening for hepatitis B virus infection and receive prophylaxis against herpes zoster activation with acyclovir or valacyclovir. If the patient starts with a CD4 cell count below 200 cells/mm3, it might be prudent to prophylax the patient against Pneumocystis jirovecii pneumonia.
However, even if a toxicity develops on ibrutinib, Dr. Call recommended reducing the dosage rather than discontinuing the drug. “I rarely see a loss in response from a reduced dosage of ibrutinib,” he said.
Because ibrutinib is primarily metabolized via the liver enzyme cytochrome P450 3A (CYP3A), other drugs that enhance or reduce the activity of this enzyme produce significant changes in ibrutinib levels. The Food and Drug Administration considers ibrutinib a “sensitive substrate” for fluctuations in CYP3A activity. Strong CYP3A inhibitors include clarithromycin, ketoconazole, and various anti-HIV medications; moderate CYP3A4 inhibitors include ciprofloxacin, and verapamil; and inducers of CYP3A include phenytoin and rifampin. A more complete list of the drugs that inhibit or induce CYP3A activity can be found at the FDA website: https://www.fda.gov/Drugs/DevelopmentApprovalProcess/DevelopmentResources/DrugInteractionsLabeling/ucm093664.htm#table2-2.
Dr. Call presented the combined experience from several U.S. Mayo Clinic centers for 118 patients treated with ibrutinib after the drug received FDA marketing approval in November 2013. The clinicians identified 75 patients (64%) who were on a concurrent medication that could potentially increase the risk for ibrutinib toxicity and 4 patients (3%) who were on a concurrent drug with the potential to reduce ibrutinib efficacy (Leukemia Lymphoma, 2017;58[6]:1376-83).
“We don’t change the dosage of ibrutinib when the patient is on a CYP3A inducer, but, if the patient is getting a CYP3A inhibitor, we change that to another drug or reduce the ibrutinib dosage,” Dr. Call said.
Dr. Call had no disclosures.
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