PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: At least 60 days Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL Transaminases no greater than 4 times upper limit of normal Renal: Creatinine no greater than 1.7 mg/dL Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception for 1 year after surgery No other concurrent significant life threatening disease No known hypersensitivity to nitrosoureas No other malignancy in past five years except curatively treated carcinoma in situ of the cervix or basal cell carcinoma of the skin