Maintenance Rituximab after CVP Results in Superior Clinical Outcome in Advanced Follicular Lymphoma (FL): Results of the E1496 Phase III Trial from the Eastern Cooperative Oncology Group and the Cancer and Leukemia Group B.

Abstract

Abstract E1496 is a phase III trial designed to evaluate the ability of 2 years (yr) of maintenance rituximab (MR) to prolong progression-free survival (PFS) after CVP (cyclophosphamide 1 G/m2 day [d] 1, vincristine 1.4 mg/m2 [max = 2 mg] d 1, prednisone 100 mg/m2 d 1–5) chemotherapy in stage III–IV follicular grade 1 and 2 and small lymphocytic lymphoma. After CVP treatment to maximum response, (6–8 cycles), stable and responding patients (pt) were randomized to MR (375 mg/m2 weekly x 4) every 6 months x 4 or observation (OBS). Stratification factors included histology, response and residual disease after CVP. With 3-yr median follow-up, survivals (from time of randomization, one-sided logrank p values) for all pt (n=304) favored MR for PFS (p = 3 x 10–8; hazard rate {HR} = 0.38 [0.28;0.54, 95% confidence intervals]) and OS (p = 0.09; HR = 0.66 [0.36–1.22]). Because the large majority of pt have FL and because rituximab efficacy is notably greater in FL, we focused in this report on the 237 FL pt. Median age was 58 yr, 65% were stage IV, 64% had marrow disease, 64% had high tumor burden and 37% had high-risk disease by the follicular lymphoma prognostic index. PFS after randomization was significantly longer for MR vs OBS (p = 3 x 10-7; HR = 0.39 [0.27;0.57]). The estimated PFS at 4 yr (~4.5 yr after start of treatment) was 56% for MR vs 33% for OBS. Differences in PFS were significant within the predefined strata and the differences were most significant in favor of MR for pt with high initial tumor burden and minimal residual disease after CVP. Overall survival was superior for MR (p = 0.03; HR = 0.51 [0.25;1.04]. Estimated OS at 4 yr (~4.5 years after start of treatment) was 88% for MR vs 72% for OBS. Of 33 deaths, 21 occurred on the OBS arm. These data demonstrate that maintenance rituximab not only significantly delays disease progression in FL compared with OBS but that a substantial proportion of patients treated with MR remain disease-free at 4 years after the completion of CVP. These are the first data to strongly suggest a survival benefit with a therapy that includes rituximab and CVP and the first to strongly suggest a survival benefit with maintenance rituximab in FL.