Patients with mantle cell lymphoma (MCL) have increased odds of achieving complete remission after being treated with a combination regimen, according to research presented at the 2017 ASCO Annual Meeting (June 2-6, 2017; Chicago, IL).
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Relapsed or refractory MCL is difficult to treat and often offers a poor prognosis. The chemotherapy agents ibrutinib and venetoclax both have proven activity in relapsed or refractory disease. However, complete remission is achieved in fewer than 25% of cases treated with either agent alone, and limited research exists involving the treatments in combination.
Constantine Si Lun Tam, MD, Peter MacCallum Cancer Centre, and colleagues conducted a phase II study to assess the activity of ibrutinib and venetoclax in combination for relapsed or refractory MCL. A total of 24 patients with relapsed, refractory, or frontline disease received ibrutinib (560 mg, daily) for 4 weeks, followed by introduction of venetoclax in increasing doses until the target (400 mg, daily). Primary endpoint was complete remission after 16 weeks.
Results were assessed by positron emission tomography (PET) and computed tomography (CT) scans, but responses to treatment were calculated separately from PET results by IWG criteria in order to compare with previously reported studies.
Researchers acknowledged that at the cutoff date, 6 patients discontinued therapy due to progressive disease (n = 4), treatment-related adverse events (n = 1), or unrelated death (n = 1).
After the 16-week trial period, researchers reported that the objective response rate was 71%, 63% of which consisted of complete remission. Eighty percent of complete responders were flow-cytometry negative in the marrow.
Using CT without PET results, the objective response rate was 78%, 42% of which consisted of complete remission.
After a median follow-up of 8.3 months, progression-free survival and overall survival estimates for 8 months were estimated at 74% and 81%, respectively.
Most common grade 1-2 adverse events as a result of the combination therapy included fatigue (71%), diarrhea (67%), nausea (50%), and gastro-esophageal reflux (33%). The only reported grade 3-4 adverse event was neutropenia (25%).
Researchers concluded that combination therapy of ibrutinib plus venetoclax were tolerable and significantly aided complete remission in patients with relapsed or refractory MCL. Further phase III studies are needed to confirm the results of this investigation.—Zachary Bessette
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