Radiation Therapy With or Without Temozolomide in Treating Older Patients With Newly Diagnosed Glioblastoma Multiforme

DISEASE CHARACTERISTICS: * Histopathologically confirmed glioblastoma multiforme * Grade IV disease by WHO classification * Newly diagnosed disease * Initial diagnostic surgery or biopsy performed within the past 4 weeks * Not a candidate for standard radiotherapy (60Gy/30 fractions over 6 weeks) in combination with temozolomide PATIENT CHARACTERISTICS: * ECOG performance status 0-2 * Absolute granulocyte count ≥ 1,500/mm³ * Platelet count ≥ 100,000/mm³ * Creatinine ≤ 1.5 times upper limit of normal (ULN) * Bilirubin ≤ 1.5 times ULN * ALT and AST \< 2.5 times ULN * No known hypersensitivity to temozolomide or compounds with similar chemical composition to temozolomide * No history of other malignancies except adequately treated nonmelanoma skin cancer, curatively treated in situ cancer of the cervix, or other curatively treated solid tumors with no evidence of disease for at least 5 years * No serious active infection (e.g., wound infection requiring parenteral antibiotics) or other serious underlying medical conditions that would preclude study treatment * No other condition (e.g., psychological or geographical) that would preclude study compliance PRIOR CONCURRENT THERAPY: * No prior chemotherapy * No prior radiotherapy * No prior or concurrent investigational therapy * No concurrent surgical procedures for tumor debulking * No concurrent stereotactic boost radiotherapy * No other concurrent chemotherapy, immunotherapy, or biological therapy * No concurrent epoeti…