Combination Chemotherapy Plus PSC-833 in Treating Children With Refractory or Relapsed Acute Leukemia

DISEASE CHARACTERISTICS: * Acute myeloid leukemia (AML) in one of the following categories: * First relapse if initial CR less than 6 months * Refractory to first or second induction with daunomycin, cytarabine, and thioguanine (DAT) or other anthracycline-containing regimens * Relapse following bone marrow transplantation provided good trilineage engraftment followed transplant and greater than 6 months since transplant * Presentation with secondary AML or AML evolving from myelodysplastic syndrome --Acute lymphocytic leukemia in one of the following categories: * In second or subsequent relapse or failed second or later induction attempts regardless of prior remissions * Relapsed following bone marrow transplantation provided good trilineage engraftment followed transplant and greater than 6 months since transplant * No isolated CNS or extramedullary relapse PATIENT CHARACTERISTICS: * Age: Under 22 at diagnosis * Performance status: Karnofsky 50-100% (ECOG 0-2) * Lansky 40-100% (in patients under 12 years of age) * Life expectancy: At least 8 weeks * Bilirubin less than 1.5 mg/dL * ALT less than twice normal * Creatinine normal for age (within 2 standard deviations) OR glomular filtration rate at least 70 mL/min * Albumin at least 3 g/dL * Ejection fraction greater than 50% at rest or with 5% increase with exercise OR shortening fraction greater than 27% by echocardiogram * No history of clinical heart failure * No uncontrolled infection * No anticonvulsant therapy * No history of allergic reactions or anaphylaxis to etoposide not remediable by premedication * Not pregnant or nursing * Fertile patients must use effective contraception * Third percentile weight for height PRIOR CONCURRENT THERAPY: * At least 4 weeks since chemotherapy and recovered * Prior cumulative anthracycline dose no greater than 360 mg per square meter * Hydroxyurea therapy allowed just prior to study for rapidly rising blast count