DISEASE CHARACTERISTICS: Histologically confirmed recurrent or progressive glioblastoma multiforme, anaplastic astrocytoma, or gliosarcoma Resistant to nitrosourea (defined as progressive or recurrent disease within 8 weeks of receiving nitrosourea) Measurable residual disease by MRI or CT scan

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: Not specified Hematopoietic: Absolute granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin greater than 10 g/dL Hepatic: Bilirubin normal SGOT no greater than 2.5 times upper limit of normal Renal: Creatinine no greater than 1.5 mg/dL BUN no greater than 25 mg/dL Pulmonary: DLCO greater than 80% predicted Other: Not pregnant or nursing Fertile patients must use effective contraception during and for 2 months after study

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy At least 6 weeks since prior nitrosourea, procarbazine, or mitomycin and recovered No prior nitrosourea greater than 1,200 mg/m2 Endocrine therapy: Concurrent stable dose corticosteroids allowed if on for at least two weeks prior to study Radiotherapy: At least 4 weeks since prior radiotherapy Surgery: Not specified