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 who have undergone gross total resection and have no detectable residual disease are eligible
* No pilocytic astrocytoma, ganglioglioma, pleomorphic xanthoastrocytoma, or dysembryoplastic neuroepithelial tumors

PATIENT CHARACTERISTICS:

* Karnofsky performance status 60-100%
* WBC ≥ 3,000/mm\^3
* ANC ≥ 1,500/mm\^3
* Platelet count ≥ 100,000/mm\^3
* Hematocrit ≥ 30%
* Bilirubin ≤ 2 times upper limit of normal (ULN)
* AST and ALT ≤ 3 times ULN
* Creatinine ≤ 2.0 times ULN
* Not pregnant or nursing
* Negative pregnancy test
* Able to undergo MRI with and without contrast
* No other malignancy within the past 5 years, except for nonmelanoma skin cancer or cervical carcinoma in situ
* No uncontrolled infection
* No known HIV positivity
* No medical disorder that would increase risks associated with radiotherapy and temozolomide
* No other disorder that would limit life expectancy to \< 5 years

PRIOR CONCURRENT THERAPY:

* No prior radiotherapy, cytotoxic chemotherapy, radiosurgery, or investigational therapy directed at the brain tumor

  * Any number of prior surgical procedures for the brain tumor allowed
* No prior radiotherapy to the head unless the radiotherapy ports entirely excluded the brain
* At least 2 weeks since any prior brain surgery (e.g., stereotatic biopsy, open biopsy, or resection)
* At least 6 weeks since prior MRI and chest x-ray

  * If resection is performed, an MRI after surgery is required