Radiation Therapy, Arsenic Trioxide, and Temozolomide in Treating Patients With Newly Diagnosed High-Grade Glioma

DISEASE CHARACTERISTICS: * Newly diagnosed grade III or IV glioma including any of the following: * Glioblastoma * Anaplastic astrocytoma * Gliosarcoma * Anaplastic oligodendroglioma * Anaplastic oligoastrocytoma * Measurable or nonmeasurable disease * No more than 5 weeks since prior brain surgery * Recovered from surgery, post- operative infection, and other complications * Preoperatively and postoperatively diagnostic contrast-enhanced MRI or CT scan of the brain performed prior to radiation therapy * Patients diagnosed by stereotactic biopsy do not require the postoperative scan PATIENT CHARACTERISTICS: * Karnofsky performance status ≥ 60% * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Serum creatinine ≤ 1.5 times upper limit of normal (ULN) * Total bilirubin ≤ 2.0 mg/dL * AST ≤ 4.0 times ULN * No prolonged QT interval \> 460 milliseconds on baseline electrocardiogram in the presence of normal serum potassium and magnesium * No uncontrolled electrolyte imbalance (i.e., sodium \< 132 mmol/L, potassium \< 3.5 mEq/dL, magnesium \< 1.7 mg/dL) * No history of torsades de pointes type of ventricular arrhythmia * Negative pregnancy test * Not pregnant or nursing * Fertile patients must use effective contraception * No medical or psychiatric illness that, in the investigator's opinion, could potentially preclude the completion of study therapy * No HIV positivity * No active connective tissue disorders (e.g., lupus or scleroderma) that, in the investigator's opinion, may put the patient at high risk for radiation toxicity PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior brain radiotherapy or chemotherapy for brain tumor * Concurrent corticosteroids to control cerebral edema allowed provided dose is stable or decreasing for the past 5 days * No concurrent or plan to receive drugs that are known to prolong the QT interval * No prior radiation to the head or neck (except for T1 glottic cancer) resulting in overlap of radiation fields