Combination Chemotherapy Plus Radiation Therapy in Treating Patients With Small Cell Lung Cancer

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Radiation therapy uses high-energy x-rays to damage tumor cells. Combining more than one chemotherapy drug with radiation therapy may kill more tumor cells. It is not yet known which treatment regimen is more effective for small cell lung cancer. PURPOSE: Randomized phase III trial to study the effectiveness of combination chemotherapy using two different doses of cyclophosphamide followed by alternating chemotherapy and radiation therapy in treating patients with small cell lung cancer.