Radiation Therapy With or Without Temozolomide in Treating Patients With Low-Grade Glioma

DISEASE CHARACTERISTICS: * Histologically confirmed\* supratentorial low-grade glioma, including 1 of the following: * Grade 2 astrocytoma * Grade 2 oligodendroglioma * Grade 2 oligoastrocytoma (mixed glioma containing astrocytoma and oligodendroglioma) * NOTE: \*If the pathology from multiple procedures supports the diagnosis of a brain tumor, the qualifying pathology of grade 2 astrocytoma, oligodendroglioma, or oligoastrocytoma must be the most recent pathological diagnosis; no pathological diagnosis of grade 3 or 4 glioma at any time * Paraffin-embedded tumor specimen available for submission for confirmation of pathological review and determination of 1p and 19q deletion status * Patients must currently meet ≥ 1 of the following criteria\*: * Uncontrolled symptoms, defined as any of the following: * Headaches associated with mass effect * Uncontrolled seizures despite two different antiepileptic drug regimens (i.e., two antiepileptic drugs tested either sequentially or in combination) * Focal neurological symptoms * Cognitive symptoms or deficits * Tumor progression by serial MRIs, defined as any of the following: * New or progressive enhancement * New or progressive T2 or FLAIR signal abnormality * Age ≥ 40 years * NOTE: \*Patients \< 40 years of age whose only symptom of low-grade glioma is seizures that are well-controlled on antiepileptic drugs AND who have no evidence of radiographic progression are not eligible. * Patients w…