Temozolomide in Treating Adults With Newly Diagnosed Primary Malignant Glioblastoma Multiforme

DISEASE CHARACTERISTICS: Histologically proven, newly diagnosed, supratentorial malignant glioblastoma multiforme not requiring immediate radiation therapy At least 1 bidimensionally measurable lesion PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: Greater than 12 weeks Hematopoietic: Absolute neutrophil count at least 1500/mm^3 Platelet count at least 100,000/mm^3 Hemoglobin at least 10 g/dL Hepatic: Bilirubin less than 1.5 times upper limit of normal (ULN) SGOT and SGPT less than 2.5 times ULN Alkaline phosphatase less than 2 times ULN Renal: BUN less than 1.5 times ULN Creatinine less than 1.5 times ULN Other: Must be neurologically stable No systemic disease No acute infection requiring intravenous antibiotics No frequent vomiting No other medical condition that would interfere with oral medication intake such as partial bowel obstruction No prior or concurrent malignancies except: Surgically cured carcinoma in situ of the cervix Basal or squamous cell carcinoma of the skin HIV negative No AIDS-related illness Not pregnant or nursing Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: No prior biologic therapy No concurrent biologic therapy (growth factors or erythropoietin) Chemotherapy: No prior chemotherapy No other concurrent chemotherapy Endocrine therapy: Concurrent steroid allowed (must be on stable dose for at least 1 week prior to study) Radiotherapy: No prior radiation therapy No prior interstitial brachytherapy No prior radiosurgery to the brain Not requiring immediate radiation therapy No concurrent radiotherapy Surgery: Recovered from any effects of prior surgery At least 2 weeks since prior surgical resection Other: No other concurrent investigational drugs