Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed supratentorial grade IV astrocytoma (glioblastoma
multiforme)

- Newly diagnosed disease

- Patients enrolled in the phase I initial safety portion of the study must meet the
following additional criteria:

- Received 90% of planned radiotherapy and ≥ 80% of planned concurrent
temozolomide within the past 28-49 days

- No grade 3-4 toxicity attributed to temozolomide

- Has undergone gadolinium MRI or contrast CT scan within the past 28 days

- Patients enrolled in the phase I dose-escalation/phase II portion of the study must
meet the following additional criteria:

- Recovered from immediate post-operative period and maintained on a stable
corticosteroid regimen (no increase in 5 days) prior to starting study treatment

- Has undergone gadolinium MRI or contrast CT scan within the past 14 days

PATIENT CHARACTERISTICS:

- Karnofsky performance status 60-100%

- Life expectancy ≥ 3 months

- ANC ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- Hemoglobin ≥ 9.0 g/dL

- Creatinine ≤ 2.0 mg/dL OR creatinine clearance ≥ 60 mL/min

- Total bilirubin ≤ 1.5 mg/dL

- Transaminases ≤ 2.5 times upper limit of normal

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception prior to, during, and for 3 months
after completion of study therapy

- Mini Mental State Exam score ≥ 15

- Able to swallow and retain oral medications

- No concurrent serious infection or medical illness that would jeopardize the ability
of the patient to receive study treatment with reasonable safety

- No other malignancy within the past 5 years except for curatively treated carcinoma
in situ or basal cell carcinoma of the skin

- No known uncontrolled seizure disorder (i.e., status epilepticus) or seizures
occurring ≥ 3 times per week over the past month

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- More than 10 days since prior cytochrome P450-inducing anticonvulsants (e.g.,
phenytoin, carbamazepine, phenobarbital, primidone, or oxcarbazepine)

- At least 1 week since prior biopsy or resection of tumor (for patients enrolled in
the phase I dose-escalation/phase II portion of the study)

- No prior radiotherapy, chemotherapy, immunotherapy, hormonal therapy, or biological
therapy (including immunotoxins, immunoconjugates, antisense therapy, peptide
receptor antagonists, interferons, interleukins, tumor-infiltrating lymphocytes,
lymphokine-activated killer cells, or gene therapy) for treatment of brain tumor (for
patients enrolled in the phase I dose-escalation/phase II portion of the study)

- Prior glucocorticoid therapy allowed

- No other prior chemotherapy or investigational agents (for patients enrolled in the
phase I initial safety portion of the study)

- Prior Gliadel wafers allowed (for patients enrolled in the phase I portion of the
study)

- No prior Gliadel wafers (for patients enrolled in the phase II portion of the study)