O(6)-Benzylguanine in Treating Patients With Malignant Glioma

DISEASE CHARACTERISTICS: * Must be undergoing a diagnostic/therapeutic craniotomy for biopsy/resection of recurrent or newly diagnosed (or presumed) cerebral anaplastic astrocytoma or glioblastoma multiforme * Patients undergoing stereotactic biopsy or partial resection are eligible PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * SWOG 0-2 OR * Karnofsky 60-100% Hematopoietic: * WBC at least 3,500/mm3 * Absolute neutrophil count at least 1,800/mm3 * Platelet count at least 125,000/mm3 * Hemoglobin at least 9 g/dL Hepatic: * Bilirubin less than 1.5 mg/dL * SGOT less than 2 times upper limit of normal Renal: * Creatinine less than 1.5 mg/dL OR * Creatinine clearance greater than 70 mL/min Cardiovascular: * No cardiovascular illnesses that cannot be adequately controlled with * appropriate therapy or would increase risk, e.g.: * Severe cardiac disease such as uncontrolled arrhythmias or conduction * defects * Major problems with edema (e.g., residual leg swelling from deep venous * thrombosis) * Recent coronary artery disease * Poorly controlled hypertension (systolic pressure greater than 180 mm Hg, * diastolic pressure greater than 110 mm Hg) Other: * No other medical illnesses that cannot be adequately controlled with * appropriate therapy or would increase risk, e.g.: * Major problems with edema (e.g., Cushing's syndrome) * Major psychiatric illness * No other malignancy requiring active therapy * Not pregnant or nursing * Fertile patients must us effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * Must have failed or received no prior treatment with a nitrosourea, * procarbazine, or temozolomide * No prior O6-benzylguanine * At least 4 weeks since prior chemotherapy and recovered Endocrine therapy: * Not specified Radiotherapy: * At least 6 weeks since prior radiotherapy * No prior radiotherapy to greater than 10-20% of bone marrow Other: * No concurrent therapy for any other malignancy * At least 2 weeks since other prior investigational drug