The majority of patients with small cell lung cancer have incurable extensive stage disease. The usual initial treatment for this condition is chemotherapy which produces responses in about 50-80% of patients. Despite this, the cancer usually returns. Once common body region where it re-grows is in the chest, which can cause symptoms such as shortness of breath, cough, difficulty swallowing, pain and bleeding. These symptoms can worsen a patient's quality of life and in some situation be life-threatening. In this study , we propose to give patients who have extensive stage small cell lung cancer which responds to chemotherapy radiotherapy treatments to the chest. By giving this type of radiation before the cancer has a chance to re-grow, we hope to control the disease within the chest and prevent future symptoms that it may cause if the cancer were to re-grow in the chest. Patients treated on the protocol will be checked regularly for disease control, quality of life and radiation side effects, if any.

Inclusion Criteria:

• Histologic or cytologic confirmation of small cell lung cancer
• extensive stage disease
• adequate pulmonary function tests (FEV-1>1.0, DLCO>50%)
• patients of childbearing potential must practice adequate contraception
• age ≧ 18 years
• Karnofsky performance status ≧ 70
• documented objective response to initial chemotherapy
• signed study-specific informed consent form

Exclusion Criteria:

• complete or subtotal tumor resection
• non-small cell histology
• prior or concurrent malignancy except non-melanoma skin cancer unless disease-free for at least 5 years
• prior chest or neck RT
• inadequate pulmonary function tests (FEV-1<1.0 OR DLCO<50%)
• pregnant