DISEASE CHARACTERISTICS: Histologically or cytologically confirmed glioblastoma multiforme Recurrent disease by CT scan or MRI At least 1 bidimensionally measurable target lesion at least 2 cm in the largest diameter

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 3 months Hematopoietic: Neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin less than 1.5 times upper limit of normal (ULN) Alkaline phosphatase no greater than 2.5 times ULN AST and ALT no greater than 2.5 times ULN Renal: Creatinine no greater than 1.5 mg/dL Creatinine clearance at least 60 mL/min Cardiovascular: Cardiac function normal No history of ischemic heart disease within the past 6 months 12 lead ECG normal Other: No other prior or concurrent malignancy except cone biopsied cervical cancer or adequately treated basal cell or squamous cell skin cancer No unstable systemic disease No active uncontrolled infection No psychological, familial, sociological, or geographical condition that would preclude study Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent prophylactic growth factors (e.g., filgrastim (G-CSF)) Chemotherapy: No more than 1 prior chemotherapy regimen as adjuvant therapy or for recurrent disease At least 6 weeks since prior chemotherapy Endocrine therapy: Stable or decreasing dose of corticosteroids for at least 1 week prior to study Radiotherapy: At least 3 months since prior radiotherapy to the brain No prior high-dose radiotherapy (more than 65 Gy), stereotactic radiosurgery, or internal radiotherapy unless the disease recurrence is histologically confirmed Surgery: No prior surgery (except biopsy) for recurrent brain tumor At least 3 months since prior surgery for primary brain tumor Other: No other concurrent anticancer agents No other concurrent investigational agents