Lung cancer is the most common cancer worldwide. In the United States, it causes more cancer-related deaths than the next four causes (breast cancer, prostate cancer, colon cancer, and pancreatic cancer) of cancer-related mortality combined (1). About 30% of people have already progressed to stage III lung cancer and 40% to stage IV at the time they are diagnosed (2). Although chest X-ray and sputum cytology, when applied in health check-ups, can identify some relatively small tumors, they are not able to lower the overall mortality (3). More recently, the low-dose spiral CT scanning reduces the mortality of lung cancer when applied for lung cancer screening (4,5).