Lung cancer screening using low dose CT: screening population and positive results definition.

Lung cancer is the leading cause of cancer-related death worldwide. The morbidity and mortality increase steadily in the near future. The 5-year survival rate of IA, IB, IIA, IIB, IIIA, IIIB and IV stage lung cancer decreased with the progression of disease, which was 50%, 43%, 36%, 25%, 19%, 7% and 2%, respectively (1). Therefore, early detection, early diagnosis and early therapy play great roles in decreasing the mortality and improving the life quality of patients. Among the current imaging modalities, CT is the most effective technique for lung cancer screening due to high detection rate and detailed anatomic structures. Sone and his colleagues reported the mass screening for lung cancer using mobile spiral CT in 1998, which was the first mass screening (5,483 participants) using CT (2). In the following about 20 years, many screening programs were performed, such as National Lung Screening Trial (NLST), International Early Lung Cancer Action Project (I-ELCAP), Nederlands-Leuvens Longkanker Screenings Onderzoek (NELSON) and Italian Lung (ITALUNG) (3-6).