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