DISEASE CHARACTERISTICS:

• Histologically confirmed recurrent primary low grade glioma including:

  • Fibrillary astrocytoma
  • Oligodendroglioma
  • Mixed glioma
• Evidence of measurable enhancing or non-enhancing CNS neoplasm on MRI

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• Not specified

Hematopoietic:

• Hematocrit greater than 29%
• Absolute neutrophil count greater than 1500/mm^3
• Platelet count greater than 125,000/mm^3

Hepatic:

• SGOT less than 1.5 times upper limit of normal (ULN)
• Bilirubin less than 1.5 times ULN

Renal:

• Creatinine less than 1.5 mg/dL
• BUN less than 25 mg/dL

Other:

• Not pregnant or nursing
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• Not specified

Chemotherapy:

• At least 4 weeks since prior chemotherapy unless disease progression

Endocrine therapy:

• Concurrent corticosteroids allowed (must be on stable dose for 1 week prior to study)
• No concurrent immunosuppressive agents

Radiotherapy:

• At least 4 weeks since prior radiotherapy unless disease progression

Surgery:

• Not specified

Other:

• No other concurrent medication that may interfere with study