DISEASE CHARACTERISTICS: Diagnosis of one of the following: Acute myelogenous leukemia (M0-M7) M3 must have received tretinoin as part of induction or salvage chemotherapy No greater than 2 prior intensive induction regimens Acute lymphocytic leukemia (L1 or L2) in first or second relapse Circulating blasts in blood or greater than 5% blasts in bone marrow No greater than 2 prior intensive induction regimens Chronic myelogenous leukemia in myeloid or lymphoid blast crisis Initial diagnosis OR No greater than 2 prior intensive induction regimens Acute myelogenous leukemia secondary to prior myelodysplastic syndrome or prior cytotoxic therapy No greater than 2 prior intensive induction regimens Myelodysplastic syndrome (must be neutropenic (absolute neutrophil count less than 500/mm3) or platelet or red cell transfusion dependent) Refractory anemia with excess blasts (RAEB) OR RAEB in transformation OR Chronic myelomonocytic leukemia Relapse after greater than 3 months since prior autologous stem cell transplant allowed No relapse after allogeneic bone marrow transplant No active CNS leukemia

PATIENT CHARACTERISTICS: Age: 12 and over Performance status: ECOG 0-3 Life expectancy: At least 4 weeks Hematopoietic: See Disease Characteristics Hepatic: Bilirubin no greater than 2.0 mg/dL AST and ALT less than 3 times upper limit of normal Renal: Creatinine clearance at least 50 mL/min Cardiovascular: No symptomatic cardiac disease No active ischemic heart disease No poorly controlled congestive heart failure No myocardial infarction within past 6 months Cardiac ejection fraction at least 40% Pulmonary: No symptomatic pulmonary disease No symptomatic restrictive or obstructive lung disease Other: Not pregnant or nursing Fertile patients must use effective contraception No active infections, unless receiving antibiotics and clinically stable Fever caused by tumor allowed HIV negative No other active malignant disease Curatively treated prior malignancies allowed No severe neurologic disease

PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics At least 5 days since prior hematopoietic growth factors Chemotherapy: See Disease Characteristics At least 24 hours since prior hydroxyurea At least 2 weeks since other prior cytotoxic anticancer therapy Prior carboplatin, fludarabine, or topotecan allowed Endocrine therapy: Concurrent corticosteroids allowed Radiotherapy: Not specified Surgery: Not specified