High-Dose Methotrexate and Leucovorin in Treating Patients With Newly Diagnosed Glioblastoma Multiforme

DISEASE CHARACTERISTICS: * Histologically confirmed glioblastoma multiforme (GBM) * Supratentorial grade IV disease * Measurable and contrast-enhancing disease ≥ 1 cm by CT scan or MRI * No radiographic evidence of ascites or pleural effusion PATIENT CHARACTERISTICS: Age * 18 and over Performance status * ECOG 0-2 Life expectancy * Not specified Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * SGOT ≤ 4.0 times upper limit of normal * Bilirubin ≤ 2.0 mg/dL Renal * Creatinine ≤ 2.0 mg/dL * Creatinine clearance ≥ 50 mL/min Cardiovascular * No uncontrolled hypertension * No unstable angina * No symptomatic congestive heart failure * No uncontrolled cardiac arrhythmia * No myocardial infarction within the past 6 months Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * Able to achieve hydration * No diabetes insipidus * No known hypersensitivity to methotrexate or leucovorin calcium * No concurrent serious infection or medical illness that would preclude study participation * No other malignancy within the past 2 years except basal cell or squamous cell skin cancer or carcinoma in situ of the cervix PRIOR CONCURRENT THERAPY: Biologic therapy * No prior immunotherapy for GBM * No prior administration of any of the following biologic agents for GBM: * Immunotoxins * Immunoconjugates * Antisense therapy * Peptide receptor antagonists * Interferons * Interleukins * Tumor-infiltrating lymphocytes * Lymphokine-activated killer cells * Gene therapy * No concurrent prophylactic growth factors (e.g., filgrastim \[G-CSF\] or sargramostim \[GM-CSF\]) Chemotherapy * No prior chemotherapy for GBM * No other concurrent chemotherapy Endocrine therapy * Prior glucocorticoid therapy allowed * No prior hormonal therapy for GBM * Patients must be maintained on a stable corticosteroid regimen for at least 1 week Radiotherapy * No prior cranial irradiation * No prior radiotherapy for GBM Surgery * Recovered from prior surgery Other * At least 1 week since prior treatment with any of the following: * Salicylates * Non-steroidal anti-inflammatory drugs * Sulfonamide medications * Vitamin C * No other concurrent investigational agents