OBJECTIVES: Primary * Compare the complete response rate in patients with refractory or relapsed B-cell chronic lymphocytic leukemia treated with fludarabine and alemtuzumab vs fludarabine and rituximab. Secondary * Compare the overall response rate in patients treated with these regimens. * Compare 1-year survival of patients treated with these regimens. * Compare time to progression in patients treated with these regimens. * Compare duration of response in patients treated with these regimens. * Compare the adverse event profile of these regimens in these patients. * Compare the molecular response rate in patients treated with these regimens. * Compare lymphocyte and lymphocyte subset recovery (CD3, CD3/CD4, CD3/CD8, CD20) in patients treated with these regimens. * Compare the time to complete response in patients treated with these regimens. * Compare the rate of cytomegalovirus reactivation and time to reactivation in patients treated with these regimens. OUTLINE: This is a randomized, open-label, multicenter study. Patients are stratified according to prior treatment with fludarabine (yes vs no). Patients are randomized to 1 of 2 treatment arms. * Arm I: Patients receive fludarabine IV over 30 minutes on days 1-5. At least 30 minutes before fludarabine administration, patients receive alemtuzumab subcutaneously (SC) on days 1-5. * Arm II: Patients receive fludarabine as in arm I. At least 30 minutes before fludarabine administration, patients receive rituximab IV on days 1 and 4 of course 1 and on day 1 only in subsequent courses. In both arms, treatment repeats every 28 days for 4-6 courses in the absence of disease progression or unacceptable toxicity. An interim assessment is performed during course 4. Patients achieving a partial response or stable disease receive 2 additional courses of therapy (for a total of 6 courses). Patients achieving a complete response (CR) do not receive further treatment beyond CR. Patients are followed weekly for 2 months, monthly for 6 months, every 2 months for 6 months, and then every 6 months for 1 year. PROJECTED ACCRUAL: A total of 150 patients (75 per treatment arm) will be accrued for this study.
DISEASE CHARACTERISTICS: * Diagnosis of B-cell chronic lymphocytic leukemia (CLL), defined as: * Peripheral lymphocyte count \> 5,000/mm\^3 * Clonal CD5-, CD19-, and CD23-positive lymphocytes * Refractory to OR relapsed after prior first-line therapy * No CNS involvement with CLL PATIENT CHARACTERISTICS: Age * 18 and over Performance status * ECOG 0-2 Life expectancy * Not specified Hematopoietic * See Disease Characteristics Hepatic * Bilirubin ≤ 1.5 times upper limit of normal (ULN) * Hepatitis B surface antigen negative * Hepatitis C antibody negative Renal * Creatinine ≤ 1.5 times ULN Immunologic * No active cytomegalovirus * No prior fludarabine-associated autoimmune hemolytic anemia or immune thrombocytopenic purpura * No active infection requiring treatment with antibiotic, antiviral, or antifungal agents * No prior significant allergic reaction to antibody therapies that required therapy to be discontinued * HIV negative Other * No active secondary malignancy * No other concurrent severe diseases or mental disorders * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy * More than 4 weeks since prior alemtuzumab and/or rituximab * No prior bone marrow transplantation * No concurrent thrombopoietin or pegfilgrastim Chemotherapy * More than 3 weeks since prior fludarabine Endocrine therapy * Not specified Radiotherapy * Not specified Surgery * Not specified Other * More than 3 months since prior investigational drugs * No other concurrent cytotoxic therapy