PATIENT CHARACTERISTICS: Age: 3 to 21 Performance status: Karnofsky or Lansky 50-100% Life expectancy: At least 6 weeks Hematopoietic: Absolute neutrophil count at least 1,000/mm3 Platelet count at least 75,000/mm3 Hepatic: SGPT less than 2 times normal Renal: Creatinine normal for age OR Creatinine clearance greater than 70 mL/min