DISEASE CHARACTERISTICS:

• Pathologically confirmed recurrent malignant glioma for which surgery is indicated
• Unilateral, supratentorial, solitary lesion at least 1.0 cm in diameter on contrast-enhanced CT or MRI

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• At least 8 weeks

Hematopoietic:

• WBC at least 3,500/mm^3
• Platelet count at least 100,000/mm^3

Hepatic:

• Bilirubin, AST, ALT, and alkaline phosphatase less than 2.5 times normal

Renal:

• Creatinine less than 1.5 times normal
• BUN less than 2.5 times normal
• Protein no greater than 3 g/dL
• No gross hematuria

Other:

• No hypersensitivity to nitrosoureas
• Not pregnant
• Fertile patients must use effective contraception
• No concurrent life threatening disease

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No concurrent immunotherapy during first 8 weeks of study

Chemotherapy:

• At least 4 weeks since chemotherapy (6 weeks since nitrosoureas)
• No concurrent chemotherapy during first 8 weeks of study

Endocrine therapy:

• Not specified

Radiotherapy:

• Prior definitive external-beam radiotherapy (i.e., at least 5,000 cGy) required
• No concurrent radiotherapy or brachytherapy during first 4 weeks of study

Surgery:

• Prior cytoreductive surgery for supratentorial brain tumor required
• Biopsy alone not sufficient

Other:

• No concurrent investigational therapy during first 8 weeks of study