DISEASE CHARACTERISTICS:

• Histologically confirmed malignant glioma

  • Glioblastoma
  • Gliosarcoma
  • High-grade glioma
  • Anaplastic astrocytoma
  • Anaplastic mixed oligoastrocytoma
  • Anaplastic oligodendroglioma
  • Anaplastic ependymoma
• Must have completed radiotherapy

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• More than 3 months

Hematopoietic:

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10 g/dL

Hepatic:

• Bilirubin less than 1.5 times upper limit of normal (ULN)
• SGOT/SGPT less than 3 times ULN
• Alkaline phosphatase less than 2 times ULN

Renal:

• BUN less than 1.5 times ULN
• Creatinine less than 1.5 times ULN

Pulmonary:

• Pulmonary function test with diffusion greater than 50 OR
• Clearance by the pulmonary service

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• HIV negative
• No AIDS-related illness
• No nonmalignant systemic disease that would preclude study
• No acute infection requiring IV antibiotics
• No psychiatric condition that would preclude study compliance
• No frequent vomiting or medical condition that would interfere with oral medication intake (e.g., partial bowel obstruction)
• No other prior or concurrent malignancy except surgically cured carcinoma in situ of the cervix or basal cell or squamous cell skin cancer

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No prior immunotherapy
• No prior biologic therapy

Chemotherapy:

• No prior chemotherapy

Endocrine therapy:

• Not specified

Radiotherapy:

• See Disease Characteristics
• At least 2 weeks since prior radiotherapy

Surgery:

• Not specified