Phase II Trial of Weekly Bortezomib in Combination With Rituximab in Relapsed or Relapsed and Refractory Waldenstrom Macroglobulinemia

Purpose This study aimed to determine activity and safety of weekly bortezomib and rituximab in patients with relapsed/refractory Waldenstrom macroglobulinemia (WM). Patients and Methods Patients who had at least one previous therapy were eligible. All patients received bortezomib intravenously weekly at 1.6 mg/m(2) on days 1, 8, and 15, every 28 days for six cycles and rituximab 375 mg/m(2) weekly on cycles 1 and 4. The primary end point was the percentage of patients with at least a minor response. Results Thirty-seven patients were treated. The majority of patients (78%) completed treatment per protocol. At least minimal response (MR) or better was observed in 81% (95% Cl, 65% to 92%), with two patients (5%) in complete remission (CR)/near CR, 17 patients (46%) in partial response, and 11 patients (30%) in MR. The median time to progression was 16.4 months (95% Cl, 11.4 to 21.1 months). Death occurred in one patient due to viral pneumonia. The most common grade 3 and 4 therapy-related adverse events included reversible neutropenia in 16%, anemia in 11%, and thrombocytopenia in 14%. Grade 3 peripheral neuropathy occurred in only two patients (5%). The median progression-free (PFS) is 15.6 months (95% Cl, 11 to 21 months), with estimated 12-month and 18-month PFS of 57% (95% Cl, 39% to 75%) and 45% (95% Cl, 27% to 63%), respectively. The median overall survival has not been reached. Conclusion The combination of weekly bortezomib and rituximab showed significant activity and minimal neurologic toxicity in patients with relapsed WM.