Fludarabine in Treating Patients With Chronic Lymphocytic Leukemia

DISEASE CHARACTERISTICS: Confirmed diagnosis of B-cell chronic lymphocytic leukemia (CLL) Previously untreated Rai stage I, II, III, or IV Requiring systemic therapy Persistent lymphocytosis of greater than 5,000/mm^3 Morphologically mature lymphocytes Monoclonal B-cell population CD19/CD5/CD23 positive with kappa or lambda light chain restriction by immunophenotyping No other lymphoproliferative disorders including prolymphocytic leukemia, mantle cell lymphoma, progression to aggressive B-cell lymphoma, or Richter's syndrome No clinical autoimmune hematologic complication of CLL including Coomb's-positive hemolytic anemia or immune thrombocytopenia Positive Coomb's test allowed if no clinical hemolysis PATIENT CHARACTERISTICS: Age 16 and over Performance status ECOG 0-2 Life expectancy At least 6 months Hematopoietic See Disease Characteristics Hepatic Bilirubin no greater than 2 times upper limit of normal (ULN) AST and/or ALT no greater than 2 times ULN Renal Creatinine no greater than 2 times ULN Other Accessible for treatment and follow-up No known HIV infection No active bacterial, viral, or fungal infection requiring systemic antibiotics No conditions requiring corticosteroid therapy No history of other malignancies except for the following: Adequately treated nonmelanoma skin cancer Curatively treated carcinoma in situ of the cervix Other solid tumors curatively treated with no evidence of disease within the past 5 years No other major medical illness that would preclude study No known hypersensitivity to fludarabine or its components Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for at least 6 months after study PRIOR CONCURRENT THERAPY: Biologic therapy No concurrent immunotherapy including monoclonal antibody therapy No concurrent autologous or allogeneic stem cell or bone marrow transplantation Chemotherapy No other concurrent cytotoxic drugs Endocrine therapy No concurrent corticosteroids except inhaled or topical corticosteroids No concurrent corticosteroids for nausea prophylaxis Radiotherapy No prior radiotherapy affecting more than 25% of bone marrow and/or involving the pelvic area No concurrent radiotherapy Surgery Not specified Other At least 4 weeks since prior investigational agents No other concurrent investigational agents