Japanese phase II study of rituximab maintenance for untreated indolent B-cell non-Hodgkin lymphoma with high tumor burden

Recent large-scale randomized clinical trials in Europe and the US demonstrated that maintenance therapy with rituximab significantly improved the progression-free survival (PFS) in indolent B-cell non-Hodgkin lymphoma (B-NHL) patients, especially those with follicular lymphoma (FL). However, rituximab maintenance has not been approved in Japan, because there are no clinical data supporting the benefit of rituximab maintenance in Japanese patients. Therefore, we conducted a single-arm, multicenter bridging study in previously untreated indolent B-NHL patients with high tumor burden. The primary endpoint was 4-year PFS and was expected to be 70 % based on previous studies. Sixty-two patients, including 55 FL patients, were enrolled and received induction therapy with CHOP combined with rituximab (R-CHOP). Fifty-eight patients responding to R-CHOP induction received rituximab at 375 mg/m² every 8 weeks for 2 years as for the rituximab maintenance arm in the PRIMA study. A 4-year PFS of 69.8 % was obtained (95 % confidence interval 55.9–80.0 %). Rituximab maintenance was well tolerated and common adverse events were infections, neutropenia, and/or leukopenia that were manageable with conventional supportive care. No patients died. These data were compatible with the PRIMA data. R-CHOP induction followed by rituximab is useful in Japanese patients with untreated indolent B-NHL having high tumor burden.