Multi-center phase II trial of bortezomib and rituximab maintenance combination therapy in patients with mantle cell lymphoma after consolidative autologous stem cell transplantation

Background: Mantle cell lymphoma (MCL) is an aggressive and incurable lymphoma. Standard of care for younger patients with MCL is induction chemotherapy followed by autologous stem cell transplantation (auto-HCT). Rituximab maintenance after auto-HCT has been shown to improve progression-free survival (PFS) and overall survival (OS) in MCL. Bortezomib maintenance therapy has also been shown to be tolerable and feasible in this setting. However, the combination of bortezomib and rituximab as maintenance therapy post-auto-HCT has not been studied. Methods: We conducted a multicenter, phase II trial of bortezomib given in combination with rituximab as maintenance in MCL patients after consolidative auto-HCT. Enrolled patients (n = 23) received bortezomib 1.3 mg/m(2) subcutaneously weekly for 4 weeks every 3 months (up to 24 months) and rituximab 375 mg/m2 intravenously weekly for 4 weeks every 6 months (up to 24 months) for a total duration of 2 years. The primary study endpoint was disease-free survival (DFS). Results: With a median follow-up of 35.9 months, the 2-year DFS probability was 90.2% (95% CI 66-97), and 2-year OS was 94.7% (95% CI 68-99). The most frequent grade 3/4 toxic events were neutropenia (in 74% of patients) and lymphopenia (in 35%). The incidence of peripheral neuropathy was 48% for grade 1, 9% for grade 2, and 0% for grade 3/4. We also examined the role of quantitative cyclin D1 (CCND1) mRNA in monitoring minimal residual disease. Conclusion: Combined bortezomib and rituximab as maintenance therapy in MCL patients following auto-HCT is an active and well-tolerated regimen.