Temozolomide and Radiation Therapy in Treating Patients With Brain Metastasis Secondary to Non-Small Cell Lung Cancer

Inclusion Criteria: * Histologically confirmed non-small cell lung cancer (NSCLC), including the following histologies: * Squamous cell carcinoma * Adenocarcinoma * Large cell carcinoma * Bronchoalveolar carcinoma * All variants of NSCLC * At least 1 bidimensionally measurable brain metastasis * Confirmed by MRI within the past two weeks, and computed tomography (CT) scan is not acceptable * Biopsy is not required * Not eligible for surgical resection or radiosurgery of brain metastasis * Systemic disease not in immediate need of chemotherapy * Age\>=18 years * ECOG Performance status of 0-1 * More than 12 weeks of life expectancy * Adequate hematologic, renal, and liver function as demonstrated by laboratory values performed within two weeks, inclusive, prior to administration of study drug or registration * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 10 g/dL * Bilirubin ≤ 2 times upper limit of normal (ULN) * Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) ≤ 2 times upper limit of normal (5 times ULN if liver metastases are present) * Alkaline phosphatase ≤ 2 times ULN (5 times ULN if liver metastases are present) * Creatinine ≤ 1.6 mg/dL * Fertile patients must use effective contraception * Prior biologic therapy allowed * More than 4 weeks since prior chemotherapy * Prior radiotherapy for local control or palliative therapy for painful bony lesions allowed * Prior surgery for brain metastasis allowed * At least 4 weeks since prior radiotherapy to ≥ 15% of bone marrow (2 weeks for \< 15% of bone marrow) and recovered * No prior radiotherapy to ≥ 50% of bone marrow * Concurrent radiotherapy to painful bony lesions allowed provided no more than 15% of bone marrow is irradiated Exclusion Criteria: * HIV positive * AIDS-related illness * Poor medical risks due to active nonmalignant systemic disease * Frequent vomiting * There is medical condition that would interfere with oral medication intake (e.g., partial bowel obstruction) * Pregnant or nursing * Prior temozolomide * Prior radiotherapy to the brain, including stereotactic radiosurgery to a different lesion * Concurrent intensity modulated radiotherapy or 3-D cranial radiotherapy * Other concurrent investigational agents * Other concurrent treatment for brain metastasis * Other concurrent chemotherapy during study radiotherapy * Concurrent growth factors to induce elevations in blood counts for the purposes of administration of study drug at scheduled dosing interval or to allow treatment with study drug at a higher dose