The Combination of Weekly Infusion of Rituximab and Bortezomib Is Effective in Relapsed or Refractory Indolent and Mantle Cell Lymphoma: Long-Term Results of Phase II BRIL06 Study of the Fondazione Italiana Linfomi (FIL)

Background. Bortezomib, an inhibitor of the proteasome, is effective in relapsed mantle cell lymphoma (MCL) and indolent lymphomas and it is synergistic with Rituximab to enhance apoptosis and NFkB depletion. On these basis, the FIL conducted a phase II multicenter study aimed to evaluate safety and efficacy of Bortezomib in association with Rituximab in relapsed/refractory non-follicular Lymphoma (Linfocytic, LL and Marginal Zone Lymphoma, MZL) and MCL, not eligible to high dose chemotherapy with stem cell transplantation. Patients and methods. The study was a prospective single arm phase II trial, designed on Simon two-stage Optimal Design. Primary end-point was to obtain an Overall Response Rate (ORR) > 40%. The aim of this analysis is to evaluate long term follow-up of Bortezomib and Rituximab combination. A central histological revision was planned in all the patients at the enrollment. Inclusion criteria were: 18-75 years, relapsed/refractory LL, MZL, MCL after 1-4 lines. Treatment schedule was: one course of 1.6 mg/sqm Bortezomib weekly in combination with standard 375 mg/sqm Rituximab on days 1, 8, 15, 22 followed by two courses of four weekly intravenous bolus of Bortezomib alone; patients with complete (CR), partial remission and stable disease at the intermediate evaluation were planned to be given three further courses with the same schedule. Results. From September 2006 to March 2008, 55 patients were enrolled and six were excluded at central histological revision. Clinical characteristics were: median age 68 (50-74); 16 (33%) LL, 8 (16%) MZL, 25 (51%) MCL; 42 (86%) stage III/IV; 33 (67%) bone marrow involvement. Median number of previous treatments was 2 (range 1-7); 34 (69%) were Rituximab pretreated; 21 (43%) had refractory disease. Thirty (61%) patients completed the treatment and 233 courses were delivered (median: 4.7 courses/patient); 19 (39%) patients did not because of no response in 13, adverse events in five, with only one toxic death due to interstitial pneumonia. ORR was 53% (CR 26.5%); no response was seen in 43% and 4% were not evaluable for response. ORRs by clinical subgroup were: LL 37%, MZL 50%, MCL 64%; Rituximab pretreated 62%, Rituximab naïve 33%; relapsed 64% and refractory 38%. With a median follow-up of 85 months, median Overall Survival (OS) was 61.5 months (95%CI: 35.0-81.5), with 5-years OS 51% (95% CI: 36-65) and median Progression Free Survival (PFS) was 8.9 months (95%CI: 5.3-18.3), with 5-years PFS 16% (95% CI: 7-28%). Five-years PFS by histology was: 12% (95% CI: 2-31) for LL, 17% (95% CI: 5-34) for MCL and 19% (95% CI: 11-53) for MZL. PFS rates were not different between Rituximab pretreated versus naïve nor international prognostic index 1-2 versus 3-4-5 nor refractory versus relapsed. By number of previous therapies, 5-years PFS for 1 previous therapy versus 2 versus 3 or more was: 24%, 14% and 13%, respectively, p=0.36. Conclusions. Weekly infusion of Bortezomib in combination with Rituximab is effective in relapsed/refractory indolent and MCL and represents a treatment option in this setting of patients. Disclosures No relevant conflicts of interest to declare.