Phase I trial of weekly and twice-weekly bortezomib with rituximab, cyclophosphamide, and prednisone in relapsed or refractory non-hodgkin lymphoma

Purpose: To determine the safety and efficacy of substituting weekly or twice-weekly bortezomib for vincristine in the R-CVP (rituximab, cyclophosphamide, vincristine, and prednisone) regimen in patients with relapsed/refractory indolent and mantle cell lymphoma (MCL). Experimental Design: Of the 57 patients in this phase I trial, 55 participated in 1 of 2 dosing schedules that included rituximab (375 mg/m²) and cyclophosphamide (750 or 1,000 mg/m²) administered on day 1 of each 21-day cycle and prednisone (100 mg orally) days 2 to 6. In the once-weekly schedule, bortezomib was administered on days 2 and 8; on the twice-weekly schedule, bortezomib was given on days 2, 5, 9, and 12. Bortezomib and cyclophosphamide were alternately escalated. A separate cohort of 10 patients in the twice-weekly schedule received concurrent pegfilgrastim (PegG) on day 2. Results: Both schedules of R-CBorP (rituximab, cyclophosphamide, bortezomib, and prednisone) were well tolerated. Most toxicities across all dose levels and cycles were grade 1 or 2. The overall response rates for patients on the weekly (n= 13) and twice-weekly (n = 33) schedules were 46% [23% complete response/complete response unconfirmed (CR/CRu)] and 64% (36% CR/CRu), respectively. Concurrent PegG did not increase hematologic toxicities in this regimen. A randomized phase II study is under way to further compare toxicity and efficacy of the 2 dosing schedules. Conclusions: R-CBorP is a safe and effective regimen in patients with relapsed/refractory indolent and MCLs. Most toxicities were grade 1 or 2, and a promising response rate was seen in this phase I study.