Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically proven recurrent or progressive malignant glioma of one of the
following types:

- Anaplastic oligodendroglioma or oligoastrocytoma

- Anaplastic astrocytoma

- Glioblastoma multiforme (stratum closed to accrual 11/30/01)

- Patients who have failed radiotherapy are eligible

- Measurable disease by CT scan or MRI

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- Karnofsky 70-100%

Life expectancy:

- At least 12 weeks

Hematopoietic:

- Absolute neutrophil count greater than 1,500/mm^3

- Platelet count greater than 100,000/mm^3

- Hemoglobin greater than 10 g/dL

Hepatic:

- SGOT or SGPT less than 3 times upper limit of normal (ULN)

- Alkaline phosphatase less than 2 times ULN (if greater than 2 times ULN then a gamma
glutamyl transferase test must be performed)

Renal:

- BUN less than 1.5 times ULN

- Creatinine less than 1.5 times ULN

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective barrier contraception

- No other serious concurrent infection or other medical illness that would preclude
study entry

- No frequent vomiting or partial bowel obstruction

- HIV negative

- No AIDS-related illness

- No other concurrent malignancy except carcinoma in situ of the cervix or basal cell
skin cancer

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No concurrent epoetin alfa

Chemotherapy:

- At least 6 weeks since other prior chemotherapy

Endocrine therapy:

- Not specified

Radiotherapy:

- See Disease Characteristics

- At least 3 months since prior radiotherapy (exceptions allowed for
recurrent/progressive disease at discretion of primary investigator)

Surgery:

- Recovered from prior surgery

Other:

- No other concurrent investigational agents

- Concurrent anticonvulsant therapy allowed