Pentostatin Combined with Cyclophosphamide, and Rituximab Induces High Response Rates in Patients with Untreated Indolent B-Cell Lymphoma.

The addition of rituximab to combination chemotherapy has improved treatment outcomes of indolent lymphomas. Combination therapy with purine analogs, akylating agents, and monoclonal antibodies is a promising approach for treating indolent B-cell lymphoma. Nucleoside analog-based regimens selectively target lymphoid cells, making them attractive drugs for lymphoid cancers. Pentostatin is a nucleoside analog that compared with other nucleoside analogs appears to have less bone marrow cell toxicity. The combination of pentostatin, cyclophosphamide, and rituximab (PCR) is an effective regimen for relapsed chronic lymphocytic leukemia and relapsed indolent B-cell lymphoma. In this study, we examined the efficacy of pentostatin, cyclophosphamide, and rituximab for the treatment of B-cell lymphoma. Pentostatin (4 mg/m²), cyclophosphamide (600 mg/m²), and rituximab (375 mg/m²) were given on day 1 of a 21-day cycle with restaging after every 3 cycles. Patients received prophylaxis with acyclovir 400 mg/po bid and trimethoprim-sulfamethoxazole 3 times per week. Small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL), was stained for ZAP70 staining and immunoglobulin heavy chain gene mutations. At the time of abstract submission, 29 patients are eligible for response and toxicity. There were 12 patients with follicular lymphoma, 13 with SLL/CLL, and 4 with mucosa-associated lymphoid tissue (MALT), and the median age was 63 years. This regimen was used as first-line therapy for 26 patients and second-line therapy in 3 patients. We observed an overall response of 27 out of 29 (93%), CR/CRu in 19 out of 29 (65%), PR in 8 out of 29 (27%), and mixed response in 2 out of 29 (7%). The main toxicities were nausea and vomiting. No prolonged pancytopenia or myelodysplasia were observed. The correlation of ZAP70 and immunoglobulin heavy chain gene mutations with response is ongoing. Our preliminary data demonstrate that PCR therapy is an effective regimen in previously untreated indolent lymphoma.