PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 6 weeks Hematopoietic: Not specified Hepatic: Bilirubin no greater than 2.0 mg/dL (except for leukemic infiltration dysfunction) Alkaline phosphatase less than 2 times upper limit of normal (except for leukemic infiltration dysfunction) Renal: Creatinine no greater than 2.0 mg/dL Other: No active infection Not pregnant Fertile patients must use effective contraception No history of seizure disorders