Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed supratentorial malignant glioma, including any of the
following:

- Glioblastoma multiforme

- Gliosarcoma

- Anaplastic astrocytoma

- Anaplastic oligodendroglioma

- Anaplastic mixed oligoastrocytoma

- Malignant glioma/astrocytoma not otherwise specified OR

- Clinical and radiographic diagnosis of progressive low-grade glioma

- Radiographically diagnosed infiltrating brain stem gliomas not amenable to biopsy
allowed

- Recurrent or progressive disease as determined by 1 of the following:

- CT scan or MRI within the past 21 days

- Biopsy within the past 12 weeks

- Failed prior radiotherapy

PATIENT CHARACTERISTICS:

Age

- 18 and over

Performance status

- Karnofsky 60-100%

Life expectancy

- More than 8 weeks

Hematopoietic

- Granulocyte count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3 (transfusion independent)

- Hemoglobin at least 8 g/dL (transfusion allowed)

Hepatic

- Bilirubin no greater than 1.5 mg/dL

- AST and ALT no greater than 2 times upper limit of normal

- No significant active hepatic disease that would preclude study participation

Renal

- Creatinine no greater than 1.5 mg/dL OR

- Creatinine clearance at least 60 mL/min

- No significant active renal disease that would preclude study participation

Cardiovascular

- No significant active cardiac disease that would preclude study participation

Other

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 2 months after study
participation

- No other malignancy within the past 3 years except nonmelanoma skin cancer or
carcinoma in situ of the cervix

- No significant active psychiatric disease that would preclude study participation

- No other condition or laboratory abnormality that would preclude study participation

- Able to swallow capsules whole

PRIOR CONCURRENT THERAPY:

Biologic therapy

- At least 2 weeks since prior interferon

- No concurrent immunotherapy

Chemotherapy

- At least 2 weeks since prior vincristine

- At least 3 weeks since prior procarbazine

- At least 4 weeks since prior temozolomide or carboplatin

- At least 6 weeks since prior nitrosoureas

- No other concurrent anticancer chemotherapy

Endocrine therapy

- At least 2 weeks since prior tamoxifen

- Concurrent steroids allowed provided dose has been stable for at least 5 days prior
to study enrollment

Radiotherapy

- See Disease Characteristics

- At least 2 weeks since prior radiotherapy

- No concurrent radiotherapy

Surgery

- At least 2 weeks since prior resection of a recurrent or progressive tumor

Other

- At least 2 weeks since other prior non-cytotoxic therapy

- At least 4 weeks since other prior cytotoxic therapies

- More than 28 days since prior experimental study drugs

- No other concurrent investigational agents