In recent decades, the incidence rate of lung cancer in China has increased alarmingly. In Shanghai, for example, the incidence rate of lung cancer was 5.25/100,000 in 1960, and 75.6/100,000 from 1993 to 1997, an increase of 14.4 times in 35 years. It jumped from the 6th to the 1st place in the ranking of malignant tumor incidence rate. The exact cause of lung cancer is still unclear, but it is recognized to be related to the following factors: 1. smoking: tobacco contains more than 10 carcinogenic substances such as tobacco tar, 3,4-benzopyrene and nitrosamines. The incidence of lung cancer is proportional to the fourth power of the number of years of smoking. That means the longer you smoke, the more likely you are to develop lung cancer. The risk of lung cancer is reduced by 50% after 5 years of stopping smoking, 80% after 10 years, and is similar to that of nonsmokers after 15 years. Passive smoking also increases the risk of lung cancer, with a relative risk of 1.3. Tobacco control can reduce lung cancer by about 80% or more and total cancer deaths by 30%. 2.Atmospheric pollution: In industrial and transportation areas, the burning of oil, coal and internal combustion engines and asphalt highway dust produce harmful gases such as sulfur dioxide, coal tar, and especially 3,4-benzopyrene, which can cause cancer. The distribution pattern of lung cancer is as follows: areas with developed industries and serious air pollution are higher than those with less developed industries, urban residents are higher than farmers, and suburbs are higher than distant suburbs. Occupational factors: Occupational exposure to certain carcinogens, such as asbestos, radon, dichloromethyl ether, polycyclic aromatic hydrocarbon compounds, chromium, nickel and inorganic arsenic compounds can increase the risk of lung cancer. 4, lung diseases: such as tuberculosis, silicosis, pneumoconiosis, etc., the incidence rate of lung cancer is higher than that of normal people. Chronic bronchial fibrous scar lesions can cause squamous epithelial metaplasia and hyperplasia during the healing process, which can develop into cancer in some cases. The combined lung cancer rate of pneumoconiosis, silicosis and asbestosis can reach 15%, and the combined lung cancer of tuberculosis can reach 2-4%. 5, dietary factors: smokers who consume more fruits and vegetables have a lower risk of lung cancer. The protective effect of vegetables and fruits may originate from their high content of carotenoids. Carotenoids are able to neutralize a large number of singlet oxygen radicals, thus reducing the effects of certain harmful biochemical reactions, including lipid peroxidation. 6. Individualized differences: such as genetic factors, reduced immune function, metabolic activity, endocrine dysfunction, etc. The results of family lineage studies show that non-smokers with a family history have a higher risk of lung cancer than those without a family history. 7, non-smoking female lung cancer high incidence factors : small indoor environmental pollution, high sodium intake, low intake of vitamin C and E, etc. Coal stove in the bedroom can increase the relative risk of lung cancer in women by 53.8%, and cooking with coal for more than 15 years can increase the relative risk of lung cancer by 125%, while using gas as fuel can reduce the relative risk of lung cancer by 70%. Other unknown factors are still more numerous. Metastatic lung cancer is the metastasis of other cancers to the lungs and falls under the category of metastatic lung cancer. It is important to manage both the primary tumor and the metastases.