Temozolomide in Treating Patients With Progressive Low-Grade Glioma

DISEASE CHARACTERISTICS: Histologically confirmed progressive, primary, intracranial, supratentorial, low-grade glioma including: Astrocytoma Oligodendroglioma Mixed glioma Optic pathway glioma* Pontine glioma* NOTE: *Biopsy not required Patients with optic pathway glioma must also meet the following criteria: Progressive loss of vision as defined by doubling of octaves Visual acuity loss not explained by other causes Increase in proptosis of greater than 3 mm Increase in diameter of optic nerve of at least 2 mm on neuroimaging Increase in distribution of tumor involving optic tracts or optic radiations as indicated by CT scan or MRI PATIENT CHARACTERISTICS: Age: 4 and over Performance status: Karnofsky 70-100% Life expectancy: More than 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/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: Creatinine less than 1.5 times ULN BUN less than 1.5 times ULN Other: Must be neurologically stable No systemic disease No acute infection requiring IV antibiotics No frequent vomiting No other medical condition that would interfere with oral medication (e.g., partial bowel obstruction) No other prior or concurrent malignancies except: Surgically cured carcinoma in situ of the cervix Basal or squamous cell skin cancer HIV negative No AIDS-related illness Not pregnant or nursing Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy (growth factors or epoetin alfa) Chemotherapy: At least 6 weeks since prior chemotherapy unless evidence of disease progression No other concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: At least 6 weeks since prior radiotherapy unless evidence of disease progression No concurrent radiotherapy Surgery: At least 3 weeks since prior surgery unless evidence of disease progression Recovered from all prior surgery Other: No other concurrent investigational drugs