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