PATIENT CHARACTERISTICS: Age: 21 and under Performance status: Not specified Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Bilirubin no greater than 3 times upper limit of normal Renal: Creatinine no greater than 1.5 mg/dL Uric acid no greater than 8.0 mg/dL Cardiovascular: Cardiac function normal by echocardiogram Pulmonary: No uncontrolled, life threatening pneumonia Other: No uncontrolled, life threatening sepsis or meningitis Not pregnant Fertile patients must use effective contraception