PATIENT CHARACTERISTICS: Age: 3 and over Performance status: Karnofsky 60-100% (age 10 and over) OR Lansky 60-100% (age under 10) Life expectancy: At least 8 weeks Hematopoietic: Absolute neutrophil count greater than 1,000/mm3* Platelet count greater than 100,000/mm3* * Lower values allowed with approval of the investigator Hepatic: Bilirubin less than 3.0 mg/dL Renal: Creatinine less than 2 mg/dL Blood urea nitrogen less than 30 mg/dL Electrolytes (including calcium, magnesium, phosphate) normal Other: No active infection Negative pregnancy test Fertile patients must use effective contraception