Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically proven malignant high-grade glioma that is progressive or recurrent
after radiotherapy and/or chemotherapy

- Anaplastic astrocytoma

- Anaplastic oligodendroglioma

- Glioblastoma multiforme

- Prior low-grade glioma that has progressed to high-grade glioma after radiotherapy
and/or chemotherapy allowed

- Measurable disease by MRI or CT scan

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- Karnofsky 60-100%

Life expectancy:

- Not specified

Hematopoietic:

- Absolute neutrophil count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

Hepatic:

- Bilirubin no greater than 1.5 mg/dL

- Transaminases no greater than 2.5 times upper limit of normal

Renal:

- Creatinine no greater than 1.5 mg/dL

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

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

- No other prior malignancy within the past 5 years except curatively treated basal
cell or squamous cell skin cancer or carcinoma in situ of the cervix or breast

- Mini mental score at least 15

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- See Disease Characteristics

- No more than 2 prior chemotherapy regimens

- At least 3 weeks since prior chemotherapy (6 weeks for nitrosoureas) and recovered

Endocrine therapy:

- Maintained on a stable corticosteroid regimen for at least 5 days before and during
study

Radiotherapy:

- See Disease Characteristics

- At least 3 months since prior radiotherapy and recovered

Surgery:

- Recovered from prior surgery

Other:

- No other concurrent investigational agents