Rituximab, Fludarabine, Cyclophosphamide, and Mitoxantrone: A New, Highly Active Chemoimmunotherapy Regimen for Chronic Lymphocytic Leukemia

Abstract

Purpose: The addition of monoclonal antibodies to chemotherapy has significantly improved treatment of chronic lymphocytic leukemia (CLL). Based on excellent results with the chemotherapy-only regimen fludarabine, cyclophosphamide, and mitoxantrone (FCM), we built a new chemoimmunotherapy combination—rituximab plus FCM (R-FCM). We report a phase II clinical trial consisting of an initial treatment with R-FCM followed by rituximab maintenance. Patients and Methods: Seventy-two untreated CLL patients age 70 years or younger received rituximab 500 mg/m² on day 1 (375 mg/m² the first cycle), fludarabine 25 mg/m² IV on days 1 to 3, cyclophosphamide 200 mg/m² on days 1 to 3, and mitoxantrone 6 mg/m² IV on day 1, given at 4-week intervals with up to six cycles supported with colony-stimulating factor. Patients achieving response received maintenance with rituximab 375 mg/m² every 3 months for 2 years. Results: The overall response, minimal residual disease (MRD) –negative complete response (CR), MRD-positive CR, and partial response rates were 93%, 46%, 36%, and 11%, respectively. Severe neutropenia developed in 13% of patients. Major and minor infections were reported in 8% and 5% of cycles, respectively. Advanced clinical stage, del(17p), or increased serum β2-microglobulin levels correlated with a lower CR rate. Conclusion: R-FCM is highly effective in previously untreated CLL, with an 82% CR rate and a high proportion of MRD-negative CRs (46%). Treatment toxicity is acceptable. Parameters correlating with a lower response rate were advanced clinical stage, high serum β2-microglobulin levels, and del(17p). Based on these results, R-FCM warrants further investigation in randomized clinical trials.