Phase II study of bendamustine combined with rituximab in relapsed/refractory mantle cell lymphoma: efficacy, tolerability, and safety findings

In most cases of relapsed/refractory mantle cell lymphoma (MCL), patients respond to salvage therapy, though typically responses are partial and/or transient followed by disease progression, even with newer agents (e.g., ibrutinib). In this multicenter, open-label, single-arm, phase II study, patients with relapsed/refractory non-blastoid MCL received bendamustine 90 mg/m2 (days 1 and 2) and rituximab 375 mg/m2 (day 1) for 6 planned 28-day cycles. Functional imaging with 18-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) was conducted at baseline and after cycle 6. Forty-five patients were enrolled (median age, 70 years; 82 % stage IV disease; median number of prior chemotherapies, 2 [range, 1–4]), showing an overall response rate (ORR; primary efficacy measure) of 82 % (complete response [CR], 40 %; partial response, 42 %). In the 32 patients with complete 18F-FDG PET/CT data, 75 % achieved a complete metabolic response. Median duration of response was 1.6 years, 1-year progression-free survival was 67 %, and 3-year overall survival was 55 %. Main non-hematologic adverse events were nausea (69 %), fatigue (56 %), decreased appetite (42 %), constipation (38 %), diarrhea (36 %), vomiting (36 %), and decreased weight (31 %). Grade 3/4 neutropenia and lymphopenia occurred in 44 and 89 % of patients, respectively. ORR and CR rate compared favorably with single-agent ibrutinib (ORR, 67 %; CR, 23 %); bendamustine-rituximab is an effective therapy with manageable toxicity in relapsed/refractory MCL.