Rituximab, Pentostatin, Cyclophosphamide, and Lenalidomide in Treating Patients With Previously Untreated B-Cell Chronic Lymphocytic Leukemia or Small Lymphocytic Lymphoma

DISEASE CHARACTERISTICS: * Diagnosis of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL), meeting the following criteria: * Biopsy-proven SLL according to WHO criteria * CLL diagnosis\* according to NCI working group criteria as evidenced by all of the following: * Peripheral blood lymphocyte count of \> 5,000/mm³ * Small to moderate peripheral blood lymphocyte with \< 55% prolymphocytes * Immunophenotyping consistent with CLL defined as: * B-cell markers with CD5 antigen in the absence of other pan-T-cell markers (e.g., CD3, CD2) * CD19, CD20, or CD23 * Dim surface immunoglobulin expression * Exclusively kappa or lambda light chains * Diagnosis of mantle cell lymphoma must be excluded by negative FISH analysis for t(11;14)(IgH/CCND1) on peripheral blood or tissue biopsy or negative immunohistochemical stains for cyclin D1 on involved tissue biopsy NOTE: \*Splenomegaly, hepatomegaly, or lymphadenopathy are not required for the diagnosis of CLL * Previously untreated disease and meets ≥ 1 of the following criteria\*: * At least 1 or more of the following disease-related symptoms: * Weight loss \> 10% within the previous 6 months * Extreme fatigue attributed to CLL * Fevers \> 100.5º F for 2 weeks without evidence of infection * Night sweats without evidence of infection * Evidence of progressive marrow failure as manifested by the development of or worsening anemia (i.e., hemoglobin ≤ 11 g/dL) and/or thrombocytopenia (i.e., platelet count ≤ 100,000/mm³) not due to autoimmune disease * Symptomatic or progressive lymphadenopathy, splenomegaly, or hepatomegaly * Progressive lymphocytosis due to CLL with an increase of \> 50% over a 2-month period or an anticipated doubling time \< 6 months NOTE: \*Marked hypogammaglobulinemia or the development of a monoclonal protein in the absence of any of the above criteria for active disease are not sufficient for protocol therapy PATIENT CHARACTERISTICS: * ECOG performance status 0-3 * Serum creatinine ≤ 1.5 times upper limit of normal (ULN) * Total bilirubin ≤ 3.0 times ULN (unless due to Gilbert disease) * Direct bilirubin \< 1.5 mg/dL for Gilbert disease to be diagnosed if total bilirubin \> 3.0 times ULN * AST and ALT ≤ 3.0 times ULN (unless due to hemolysis or CLL) * Willing to provide blood samples * Able to take acetylsalicylic acid (ASA) (81 or 325 mg) daily as prophylactic anticoagulation (patients intolerant to ASA may use low molecular weight heparin) * Not pregnant or nursing * Negative pregnancy test * Female patients must use effective double-method contraception beginning 1 month prior to, during, and for 4 weeks after completion of study treatment * Male patients must use effective contraception during and for 4 weeks after completion of study treatment * No comorbid conditions, including any of the following: * New York Heart Association class III or IV heart disease * Recent myocardial infarction (\< 1 month) * Uncontrolled infection * Infection with HIV/AIDS * No other active primary malignancy requiring treatment or that limits survival to ≤ 2 years * No history of deep venous thrombosis or pulmonary embolism ≤ 12 months prior to study registration * No active hemolytic anemia requiring immunosuppressive or other pharmacologic therapy PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior chemotherapy or monoclonal antibody-based therapy for treatment of CLL * Nutraceutical treatments with no established benefit in CLL (e.g., epigallocatechin gallate or other herbal treatments) are not considered prior therapy * More than 4 weeks since prior radiotherapy * At least 4 weeks since prior major surgery * No concurrent corticosteroids * Concurrent low doses of steroids (e.g., \< 10 mg of prednisone or equivalent dose of other steroid) used for treatment of non-hematologic medical conditions allowed * Prior use of corticosteroids allowed * No prior thalidomide or lenalidomide * No concurrent therapeutic doses of coumadin-derivative anticoagulants (e.g., warfarin) * Doses of ≤ 2 mg daily allowed for thrombosis prophylaxis * Prophylactic doses of low molecular weight heparin allowed