Pentostatin and cyclophosphamide compared to pentostatin, cyclophosphamide, and rituximab as salvage therapy for patients with chronic lymphocytic leukemia

6568 Background: Combination therapy with purine analogs, alkylators, and/or monoclonal antibodies represents a promising new approach to treatment of patients with chronic lymphocytic leukemia (CLL). Most regimens have utilized fludarabine as the purine analog but the severe myelosuppression and immunosuppression of these combinations requires careful attention to dosing and schedule to minimize these toxic complications. Of the purine analogs active in CLL, pentostatin appears to be least myelosuppressive. Methods: We have treated sequential cohorts of patients first with pentostatin and cyclophosphamide (PC regimen) and more recently with the 3 drug combination pentostatin, cyclophosphamide, and rituximab (PCR regimen). We now report on 45 patients with CLL treated with these regimens. The PC regimen (21 patients) consists of pentostatin 4mg/m2 and cyclophosphamide 600mg/m2 administered on the same day every 3 weeks for 6 treatments. The PCR regimen (24 patients) is identical to PC but with rituximab 3...