Causes of lung cancer

The exact cause of lung cancer is still unknown. After years of extensive investigation and research, it is now generally recognized that the following factors are closely related to the cause of lung cancer.

1. Smoking

According to a large number of survey data from various countries, the cause of lung cancer is closely related to smoking. The increase in the incidence of lung cancer is parallel to the increase in cigarette sales. Cigarettes are rich in benzopyrene and other carcinogens. Experimental animals that inhale cigarette smoke or apply tar can induce respiratory and skin cancer. The incidence rate is higher for those who smoke more. Data show that the incidence rate of lung cancer for those who smoke more than 25 cigarettes a day is 2.27/1,000 person-years, 15-24 cigarettes is 1.39/1,000 person-years, and 1-14 cigarettes is 0.57/1,000 person-years. At the end of the last century, with the increasing number of female smokers in Western European countries, the incidence rate of lung cancer in female patients also increased significantly. Among the clinically diagnosed lung cancer cases, those who smoke more than 20 cigarettes a day for more than 30 years account for more than 80%. In the past 20 to 30 years, the smoking situation in my country has been very serious, and nearly 300 million people have the habit of smoking. The smoking rate of male adults in large cities such as Beijing, Tianjin, and Shanghai is nearly 50%, and that of females is nearly 5%. There are also many smokers among young people. Long-term smoking can cause bronchial mucosal epithelial cell hyperplasia, squamous metaplasia, and induce squamous cell carcinoma or undifferentiated small cell carcinoma. Although non-smokers can also develop lung cancer, adenocarcinoma is more common.

2. Air pollution

The incidence of lung cancer is high in industrially developed countries, higher in cities than in rural areas, and higher in factory and mining areas than in residential areas. The main reason is that the atmosphere is polluted by harmful substances such as benzopyrene carcinogenic hydrocarbons produced by the combustion of oil and coal and asphalt road dust in industrial and transportation-developed areas. Survey materials show that the incidence of lung cancer is also higher in areas with high concentrations of benzopyrene in the atmosphere. Air pollution and smoking may promote each other and play a synergistic role in the incidence of lung cancer.

3. Occupational factors

In the 1930s, there were reports in the literature that the incidence of lung cancer was high in the Schneeberg mining area in Europe. After years of investigation and research, it is now recognized that long-term exposure to radioactive substances such as uranium, radium and their derivatives, carcinogenic hydrocarbons, arsenic, chromium, nickel, copper, tin, iron, coal tar, asphalt, petroleum, asbestos, mustard gas and other substances can induce lung cancer.

4. Chronic lung diseases

For example, tuberculosis, silicosis, and pneumoconiosis can coexist with lung cancer, and the incidence of cancer in these cases is higher than that of normal people. In addition, chronic inflammation of the lung bronchus and pulmonary fibrosis scar lesions may cause squamous metaplasia or hyperplasia during the healing process, and on this basis, some cases may develop into cancer.

5. Others

Internal factors of the human body, such as family inheritance, reduced immune function, metabolic activity, endocrine dysfunction, etc., may also play a certain role in promoting the onset of swelling and pain. If there is a lack of retinoids in the food, the sensitivity of experimental animals to carcinogens will increase. A large number of experimental and clinical studies have shown that C-myc, L-myc, N-myc and RaF genes are overexpressed in small cell lung cancer.