PATIENT CHARACTERISTICS: Age: 21 and under at diagnosis Performance status: Karnofsky 50%-100% Life expectancy: More than 4 weeks Hematopoietic: (unless extensive bone marrow involvement) ANC greater than 750 Platelets greater than 75,000 Hepatic: Not specified Renal: Creatinine normal for age OR Glomerular filtration rate at least 50 mL/min per 1.73 square meters Other: Adequate nutritional status No serious uncontrolled infection No pregnant or nursing women