S0001 RT and Carmustine With or Without O6BG in Patients With New Glioblastoma Multiforme or Gliosarcoma

DISEASE CHARACTERISTICS: * Histologically confirmed glioblastoma multiforme or gliosarcoma * Biopsy or surgical resection within the past 28 days * MRI\* with gadolinium performed before registration * Patients who undergo a simple biopsy only require preoperative MRI\* with gadolinium * No more than 2 noncontiguous tumor sites based on T2-weighted MRI (in 3 dimensions)\* * No prior radiotherapy-delivered cephalad to the interspace between the seventh cervical and the first thoracic vertebral body NOTE: \*If an MRI is not medically feasible, patients may have a CT scan with contrast PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Zubrod 0-2 Life expectancy: * Not specified Hematopoietic: * Absolute neutrophil count at least 3,000/mm\^3 * Platelet count at least 100,000/mm\^3 * Hemoglobin at least 8 g/dL Hepatic: * Bilirubin no greater than 2 times upper limit of normal (ULN) * SGOT/SGPT no greater than 2 times ULN * Alkaline phosphatase no greater than 2 times ULN * PT/PTT no greater than 1.2 times ULN Renal: * Not specified Cardiac: * No severe cardiac disease, including any of the following: * Uncontrolled arrhythmias or conduction defects * Major problems with edema (e.g., residual swelling in the legs from deep vein thrombosis) * Recent coronary artery disease * Poorly controlled hypertension (i.e., diastolic blood pressure greater than 110 mm Hg and/or systolic blood pressure greater than 180 mm Hg) Pulmonary: * DLCO at least 70% of predicted * No severe pulmonary disease Other: * HIV negative * No severe Cushing's syndrome * No known allergies to any of the study drugs * No major psychiatric illness * No poorly controlled diabetes complicated by steroid treatment * No other medical illness that cannot be adequately controlled or that would preclude study participation * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or adequately treated stage I or II cancer currently in complete remission * Not pregnant or nursing * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * No prior chemotherapy * No other concurrent antitumor chemotherapy Endocrine therapy: * No concurrent hormonal therapy except postmenopausal estrogen replacement therapy * Corticosteroids at stable or decreasing dose for tumor edema allowed Radiotherapy: * See Disease Characteristics * No prior radiotherapy * No other concurrent radiotherapy (including intensity-modulated radiotherapy) to the index lesion(s) Surgery: * See Disease Characteristics * No concurrent antitumor surgery Other: * No other concurrent investigational drugs * No other concurrent antineoplastic drugs or therapy