Temozolomide During and After Radiation Therapy in Treating Patients Who Have Undergone Previous Surgery and Placement of Gliadel Wafers for Newly Diagnosed Glioblastoma Multiforme

DISEASE CHARACTERISTICS: Histologically confirmed supratentorial grade IV astrocytoma (glioblastoma multiforme) Underwent gross total resection within the past 6 weeks Postoperative contrast-enhancing tumor extends ≤ 1 cm from the margin of the surgical cavity 6-8 polifeprosan 20 with carmustine implants (Gliadel® wafers) were placed in the surgical resection cavity at time of surgery PATIENT CHARACTERISTICS: Age 18 and over Performance status Karnofsky 60-100% Life expectancy Not specified Hematopoietic Absolute neutrophil count ≥ 1,500/mm^3 Platelet count ≥ 100,000/mm^3 Hepatic Bilirubin ≤ 1.5 mg/dL Transaminases ≤ 4 times upper limit of normal Renal Creatinine ≤ 1.7 mg/dL Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No known hypersensitivity reaction to temozolomide No other malignancy within the past 5 years except curatively treated carcinoma in situ or basal cell skin cancer PRIOR CONCURRENT THERAPY: Biologic therapy No prior immunotherapy for the brain tumor No prior biologic agents (e.g., immunotoxins, immunoconjugates, antisense agents, peptide-receptor agonists, interferons, interleukins, tumor-infiltrating lymphocyte therapy, lymphokine-activated killer cell therapy, or gene therapy) for the brain tumor Chemotherapy See Disease Characteristics No other prior chemotherapy for the brain tumor Endocrine therapy No prior hormonal therapy for the brain tumor Prior glucocorticoid therapy allowed Radiotherapy No prior radiotherapy for the brain tumor Surgery See Disease Characteristics