Temozolomide in Treating Patients With Low-Grade Glioma

DISEASE CHARACTERISTICS: Histologically proven supratentorial low-grade (grade II) glioma of any of the following histologic subtypes: Oligodendroglioma Astrocytoma Oligoastrocytoma Has undergone surgical resection or biopsy within 35 days after diagnosis of low-grade glioma Study treatment must begin between 14 days and 4 months after surgical resection or biopsy Evaluable disease by gadolinium-MRI PATIENT CHARACTERISTICS: Karnofsky performance status 60-100% Absolute neutrophil count ≥ 1,500/mm^3 Platelet count ≥ 100,000/mm^3 Hemoglobin ≥ 10 g/dL Creatinine < 1.5 times upper limit of normal (ULN) BUN < 1.5 times ULN Bilirubin < 1.5 times ULN SGOT < 2.5 times ULN Alkaline phosphatase < 2 times ULN Life expectancy > 12 weeks No nonmalignant systemic disease resulting in the patient being a poor medical risk No acute infection requiring intravenous antibiotics No frequent vomiting or medical condition that would interfere with oral medication intake (e.g., partial bowel obstruction) No other concurrent malignancies except surgically cured carcinoma in situ of the cervix or basal cell or squamous cell carcinoma of the skin Prior malignancies must be in remission for ≥ 5 years No known HIV positivity No AIDS-related illness Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: See Disease Characteristics No prior radiotherapy, interstitial brachytherapy, or radiosurgery for low-grade glioma No prior biological therapy or chemotherapy for low-grade glioma No other concurrent chemotherapy No concurrent radiotherapy or biological therapy No concurrent prophylactic growth factors No concurrent epoetin alfa No other concurrent investigational drugs