Inclusion Criteria

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