Radiation Therapy to Prevent Brain Metastases in Patients With Previously Treated Extensive-Stage Small Cell Lung Cancer

RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Radiation therapy to the brain may be effective in preventing brain metastases. It is not yet known if radiation therapy is effective following chemotherapy in preventing brain metastases. PURPOSE: Randomized phase III trial to determine the effectiveness of radiation therapy in preventing brain metastases in patients who have received chemotherapy for extensive-stage small cell lung cancer.