PATIENT CHARACTERISTICS: Age: 17 and over Performance status: ECOG 0-2 Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Bilirubin no greater than 2.5 mg/dL Renal: Creatinine no greater than 2.5 mg/dL Other: Not pregnant or nursing Fertile patients must use effective contraception during and for at least 4 months after study No history of grand mal seizures (other than infantile febrile seizures) No active serious infections that are not controlled by antibiotics