The addition of monoclonal antibodies to chemotherapy has significantly improved treatment of patients with CLL. Based upon the excellent results obtained with our chemotherapy-only regimen fludarabine, cyclophosphamide and mitoxantrone (FCM) (Bosch et al. Clin Cancer Res, 2008) we have build up a new chemoimunotherapy combination, R-FCM (rituximab plus FCM). In November 2005 we initiated a multicentric phase II clinical trial that includes R-FCM as initial treatment followed by a maintenance therapy phase consisting of rituximab (375 mg/m2 every there months for 2 years). We report here the final results of the initial phase of this study, namely R-FCM treatment. From November 2005 to November 2007, 72 patients under the age of 70 with active CLL according the NCI and IWCLL criteria (Cheson et al. Blood, 1996; Hallek et al. Blood, 2008) were treated. Patients received rituximab 500 mg/m2 on day 1 (375 mg/ m2 in the first cycle), fludarabine 25 mg/ m2 i.v. on days 1 to 3, cyclophosphamide 200 mg/ m2 on days 1 to 3, and mitoxantrone 6 mg/ m2 i.v. on day 1, given at 4-week intervals up to six cycles. Treatment outcome was correlated with clinical and biological parameters. Minimal residual disease (MRD) was evaluated by four-color flow cytometry (Rawstron et al. Leukemia, 2007). Median cycles of R-FCM administered were 5 (range, 3–6), with 91% of patients completing all planed treatment. Response was evaluated three months after finishing therapy. Altogether, the overall response, MRD-negative CR, MRD-positive CR, and PR rates were 93%, 46%, 36%, and 10%, respectively. Variables correlated with a lower CR rate were del(17p) (25% CR) and increased β2-M serum levels (72% CR). No differences in response were observed according to the age of the patients. Severe neutropenia developed in 13% of patients. Major and minor infections were reported in 8% and 5% of cycles, respectively. Treatment-related mortality was 1%. With a median follow up of 24 months no cases of secondary MDS/AML have been observed.. Although based in two different phase II studies that preclude a completely valid statistical comparison, the CR rate obtained with R-FCM (82%, of which 46% MRD-negative CRs) favorably compares with that achieved with FCM (CR 64%, MRD-negative CRs 38%). In summary the 82% CR rate obtained with R-FCM is among the highest ever reported for any form of therapy for CLL. Both high β2-M serum levels and del(17p) predicted lower CR rate. Treatment toxicity was acceptable and manageable. Based on these results, R-FCM warrants further investigation, particularly in randomized clinical trials.

Disclosures: No relevant conflicts of interest to declare.

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