DISEASE CHARACTERISTICS:

• Histologically confirmed glioblastoma multiforme
• Measurable disease
• No CNS metastases or carcinomatous meningitis

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• ECOG 0-2 OR
• Karnofsky 70-100%

Life expectancy:

• At least 12 weeks

Hematopoietic:

• Granulocyte count greater than 1,500/mm^3
• Platelet count greater than 100,000/mm^3
• Hemoglobin at least 9.0 g/dL

Hepatic:

• Bilirubin no greater than 1.5 mg/dL
• SGOT no greater than 3 times upper limit of normal (ULN) (5 times ULN if liver involvement)
• No known Gilbert's syndrome

Renal:

• Creatinine no greater than 1.5 mg/dL

Cardiovascular:

• No myocardial infarction within the past 6 months
• No congestive heart failure requiring therapy

Other:

• HIV negative
• No active or uncontrolled infection
• No psychiatric disorder that would preclude study
• No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix
• No uncontrolled diabetes mellitus (i.e., random blood sugar of 200 mg or more)
• No other severe disease that would preclude study
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No prior immunotherapy or biologic therapy
• No concurrent sargramostim (GM-CSF)
• No concurrent filgrastim (G-CSF) with course 1
• No concurrent immunotherapy

Chemotherapy:

• No prior chemotherapy
• No other concurrent chemotherapy

Endocrine therapy:

• Must have maintained a stable or decreasing dose of corticosteroids for 2 weeks prior to study
• Concurrent corticosteroids for cerebral edema allowed
• No concurrent anticancer hormonal therapy

Radiotherapy:

• No prior radiotherapy
• No concurrent radiotherapy

Surgery:

• At least 2 weeks since prior surgery

Other:

• No other concurrent investigational agent or participation on any other clinical study
• No concurrent immunosuppressive drugs
• No concurrent phenobarbital or valproic acid
• No concurrent anticonvulsants except carbamazepine or gabapentin
• No concurrent prochlorperazine on day of irinotecan treatment