DISEASE CHARACTERISTICS: Histologically confirmed myelodysplatic syndrome (MDS), diagnosed at least 3 months prior to study enrollment, with one of the following subtypes: Refractory anemia with excess blasts (RAEB) RAEB in transformation (RAEB-T) Chronic myelomonocytic leukemia (CMML) CMML with leukocytosis not controlled by hydroxyurea eligible in absence of neutropenia No treatment- or mutagen-related MDS One or more cytopenias required: Untransfused hemoglobin less than 10 g/dL and/or transfusion-dependent (requiring at least four units of red blood cells in prior 12 weeks) Platelet count no greater than 50,000/mm3 or absolute neutrophil count less than 1,000/mm3 No myelosclerosis occupying more than 30% of marrow

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: At least 3 months Hematopoietic: See Disease Characteristics No hereditary hemolytic disorders Transferrin saturation greater than 20% Ferritin at least 50 ng/mL Hepatic: Bilirubin less than 3 mg/dL AST/ALT and LDH less than 2 times upper limit of normal Renal: Creatinine less than 2 mg/dL Cardiovascular: No significant cardiovascular disorders (unrelated to MDS) No uncontrolled hypertension Pulmonary: No significant pulmonary disorders (unrelated to MDS) Neurologic: No significant neurologic disorders (unrelated to MDS) No history of epilepsy Metabolic: No significant endocrine disorders (unrelated to MDS) Other: Not pregnant or nursing No significant gastrointestinal diseases (unrelated to MDS) or GI blood loss No significant genitourinary system diseases (unrelated to MDS) No active infection requiring IV antibiotic therapy No other serious illness or medical condition Not HIV positive Not hepatitis B surface antigen positive No iron, vitamin B12, or folate deficiencies No autoimmune disease No prior or concurrent malignancy within 2 years except in situ carcinoma of the cervix or basal cell or squamous cell carcinoma of the skin

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent hematopoietic stimulants Chemotherapy: See Disease Characteristics At least 35 days since prior chemotherapy Endocrine therapy: No concurrent androgen therapy No concurrent corticosteroids Radiotherapy: Not specified Surgery: Not specified Other: At least 35 days since any previous therapy for MDS (other than transfusion) No participation in any other experimental clinical trial within 35 days of entry into current trial