Pentostatin, Cyclophosphamide, and Rituximab in Treating Patients With Chronic Lymphocytic Leukemia or Other B-cell Cancers

DISEASE CHARACTERISTICS: Intermediate- or high-risk chronic lymphocytic leukemia (CLL) as defined by the three-stage Rai system Rai intermediate disease must be active disease (including weight loss, fatigue, fevers, evidence of progressive marrow failure, splenomegaly, progressive lymphadenopathy, and progressive lymphocytosis with a rapid doubling time) Other low-grade B-cell neoplasms, including small lymphocytic lymphoma (and its variants), Waldenstrom's macroglobulinemia, and follicular lymphoma allowed Autoimmune hemolytic anemia or autoimmune thrombocytopenia allowed regardless of disease stage B-cells demonstrated by immunophenotypic (or immunohistochemical) analysis of the malignant lymphocytes Must be previously treated For CLL, absolute lymphocytosis in the blood at least 5,000 lymphocytes/mm^3 OR Bone marrow lymphocytosis at least 30% of all nucleated cells No Rai intermediate-risk disease that meets the criteria of Montserrat "smoldering leukemia" NOTE: A new classification scheme for adult non-Hodgkin's lymphoma has been adopted by PDQ. The terminology of "indolent" or "aggressive" lymphoma will replace the former terminology of "low", "intermediate", or "high" grade lymphoma. However, this protocol uses the former terminology. PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: More than 4 weeks Hematopoietic: See Disease Characteristics Hepatic: Bilirubin no greater than 2.0 mg/dL Renal: Creatinine no greater than 2.0 mg/dL Other: No active infections requiring systemic antibiotics Not pregnant or nursing Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior biologic therapy Concurrent intravenous immunoglobulin allowed Concurrent epoetin alfa allowed Chemotherapy: At least 4 weeks since prior chemotherapy No other concurrent chemotherapy Endocrine therapy: Concurrent prednisone therapy allowed as long as dose is stable or decreasing over the past 4 weeks No increase in prednisone therapy while on study Radiotherapy: At least 4 weeks since prior radiotherapy No concurrent radiotherapy Surgery: Not specified