On January 28, 2011, the U.S. Food and Drug Administration approved rituximab (Rituxan, Genentech, Inc) for maintenance therapy for patients with previously untreated follicular, CD-20 positive, B-cell non-Hodgkin lymphoma who achieve a response to rituximab in combination with chemotherapy.
The approval was based on the PRIMA study, an open-label, multinational, randomized Phase 3 study evaluating the benefit of rituximab maintenance therapy. Patients with previously untreated follicular lymphoma with high tumor burden were randomized to receive either rituximab maintenance therapy or no maintenance therapy after achieving a response to a chemotherapy regimen including rituximab.
After achieving a complete or partial response to a rituximab-chemotherapy induction regimen, 1018 patients were randomized (1:1) to receive either rituximab 375 mg/m2 , intravenously, every 8 weeks (maximum 12 doses) or observation. Forty percent of patients were > 60 years, 70% had stage IV disease, 96% had ECOG PS 0-1 and 42% had FLIPI (follicular lymphoma international prognostic index) scores of 3-5. Induction therapy consisted of R-CHOP in 75% of patients, R-CVP in 22%, and R-FCM in 3%.
Progression-free survival, evaluated by an independent review committee, was the trial’s primary endpoint. Maintenance rituximab reduced the risk of a PFS event by 46% (stratified HR: 0.54, 95% CI: 0.42, 0.70, stratified log-rank test p <0.0001). Results for OS remain immature at this time
Safety data collection was limited to grade ≥ 2 infections, and grade ≥ 3 adverse reactions. In 501 patients who received at least one dose of rituximab maintenance therapy, infections were reported more frequently compared to the observation arm (37 vs. 22%). Grade 3-4 adverse reactions occurring at a higher incidence (≥ 2%) in the rituximab group were infections (4 vs. 1%) and neutropenia (4 vs. <1%).
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