Whole-Brain Radiation Therapy and Pemetrexed in Treating Patients With Brain Metastases From Non-Small Cell Lung Cancer

OBJECTIVES: Primary * Estimate the response in patients with intracranial brain metastases from non-small cell lung cancer treated with whole-brain radiotherapy and pemetrexed disodium. Secondary * Determine the toxicity of this regimen in these patients. * Estimate the overall survival of patients treated with this regimen. * Evaluate the functional status of patients treated with this regimen. * Assess neurological function and progression in patients treated with this regimen. * Determine the response of patients with extracranial disease treated with pemetrexed disodium. OUTLINE: Patients undergo whole-brain radiotherapy 5 days a week for 3 weeks beginning on day 1. Patients also receive pemetrexed disodium IV on day 1, 2, or 3 and day 28 of course 1, and on day 1 of each subsequent course. Treatment with pemetrexed disodium repeats every 21 days for a total of 4 courses in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed at 30 days and then every 2 months for 2 years.