Primary lung cancer (hereafter referred to as lung cancer) is one of the most common malignant tumors in China. Data released by the National Tumor Registry in 2014 showed that in 2010, there were 605,900 new cases of lung cancer in China (416,300 men and 189,600 women), ranking first in malignant tumors (first in men and second in women) and accounting for 19.59% of new cases of malignant tumors (23.03% in men and 14.75% in women). The incidence rate of lung cancer is 35.23/100,000 (49.27/100,000 for men and 21.66/100,000 for women). During the same period, the number of lung cancer deaths in China was 486,600 (336,800 for men and 166,200 for women), accounting for 24.87% (26.85% for men and 21.32% for women) of the causes of death from malignant tumors. The mortality rate of lung cancer was 27.93/100,000 (39.79/100,000 for men and 16.62/100,000 for women). Screening for lung cancer Screening for lung cancer in high-risk groups is beneficial for early detection of early lung cancer and improves the cure rate. Low-dose CT (LDCT) is 4-10 times more sensitive than conventional chest radiography in detecting early lung cancer, and can detect early peripheral lung cancer early. Data from the International Early Lung Cancer Action Plan show that annual screening with LDCT can detect 85% of stage I peripheral lung cancers, with an expected survival rate of 92% at 10 years after surgery. The U.S. National Lung Cancer Screening Trial demonstrated that LDCT screening can reduce lung cancer mortality by 20%, making it the most effective lung cancer screening tool available. In China, LDCT is recommended for lung cancer screening in high-risk groups in the pilot technical guidelines for cancer screening and early diagnosis and treatment currently conducted in a few regions. Risk assessment factors for lung cancer screening proposed in the National Comprehensive Cancer Network guidelines: include history of smoking (current and past), history of radon exposure, occupational history, history of cancer, family history of lung cancer, history of disease (chronic obstructive pulmonary disease or tuberculosis), and history of smoke exposure (passive smoking exposure). Risk status was divided into 3 groups: (1) High-risk group: age 55-74 years, history of smoking ≥ 30 pack-years (example 1 pack/day * 30 years = 30 pack-years), history of smoking cessation < 15 years (category 1); or age ≥ 50 years, history of smoking ≥ 20 pack-years, and additionally with one risk factor other than passive smoking (category 2B). (2) Intermediate risk group: age ≥ 50 years, history of smoking or passive smoking exposure ≥ 20 pack years, and no other risk factors. (3) Low-risk group: age <50 years, history of smoking <20 pack-years. The NCCN guidelines recommend lung cancer screening for the high-risk group and not for the low- and intermediate-risk groups.