(I) Overview No matter in developed or developing countries, the harm of malignant tumors cannot be ignored. Due to the aging of population and other reasons, the trend of malignant tumor growth is unabated, and the prevention and control of malignant tumors has become a public health problem that cannot be avoided by all countries in the world. After the theory of environmental factors causing cancer was proposed, it was found that 80-90% of tumors are caused by environmental factors, including lifestyle, diet, socio-economic and culture. Therefore, theoretically most human tumors are avoidable. It has been shown that 1/3 of cancer deaths are related to smoking, 1/3 to irrational diet, the remaining 1/3 to infections, occupational exposure and environmental pollution, etc., and only 1-3% are due to genetic factors. This quantitative estimation provides a clear idea for the prevention and control of cancer. The WHO proposed that “1/3 of tumor patients can be prevented, 1/3 of tumor patients can be cured, 1/3 of tumor patients can prolong their lives and improve the quality of survival” is a high summary of tumor prevention and control work, which is also the goal for tumor prevention and control work. (2) Tertiary prevention measures of malignant tumors 1. Primary prevention of tumors (i.e. etiological prevention) refers to the preventive measures to eliminate or reduce cancer-causing factors for the general population, to promote health and to prevent the disease before it happens. Effective preventive measures include the following: (1) Smoking cessation: The causal relationship between smoking and lung cancer and other cancers has been established by many global epidemiological studies, providing the best opportunity for cancer prevention so far, and has been confirmed by the practice of several developed countries. The declining trend in lung cancer incidence and mortality among men in the United States in the 1990s led to a declining trend in total cancer incidence and mortality in the United States in the 1990s, which was attributed to massive smoking cessation. (2) Proper diet: The role of diet is universal, and research has focused on the intake of fat and vitamins in the diet. The consumption of large amounts of vegetables and fruits will reduce the incidence of certain tumors. (3) Moderation of alcohol consumption: Alcohol consumption induces many tumors, mainly in the pharynx, oral cavity and esophagus, and has a synergistic effect with smoking. (4) Immunization: Human papilloma virus (HPV) has been clearly demonstrated to be associated with the development of cancer of the female cervix, and hepatitis B virus (HBV) increases the risk of primary liver cancer. A WHO-funded trial of vaccination against HBV infection to prevent hepatitis B in newborns and thereby reduce the incidence of liver cancer has been conducted in Qidong, China, for 18 years, and the HPV vaccine to prevent cervical cancer has entered phase III clinical trials. (5) Prevention of occupational cancer: such as prevention of ionizing radiation and asbestos in the working environment. (6) Health education and health promotion: to inform the general public of the known risk factors and protective factors of tumors through various forms and ways, so that they can establish reasonable dietary habits and healthy lifestyles, etc. 2.Tumor secondary prevention (i.e. pathogenesis prevention) refers to the screening of precancerous lesions or early tumor cases for specific high-risk groups, so as to carry out early detection, early prevention and early treatment, and its measures include screening and intervention experiments. (1) Cervical cancer screening Cervical smears have gained wide acceptance as the method of choice for reducing cervical cancer mortality. High-risk HPV testing is now being used in many countries for screening of high-risk populations. (2) Breast cancer screening Breast smear under the condition of relatively high technology of smear can reduce the mortality rate of breast cancer; teaching breast self-examination to the public. (3) Colorectal cancer screening: screening for early colorectal cancer by fecal occult blood (FOB); sigmoidoscopy screening can significantly reduce mortality. (4) Screening of gastric cancer: endoscopic screening of gastric cancer has been successful in Japan, resulting in a detection rate of over 40% for early gastric cancer. (5) Early diagnosis and treatment of esophageal cancer: endoscopic iodine staining + indicative biopsy screening of esophageal cancer carried out in Lin County, China, has achieved good results. The esophageal epithelial severe atypical hyperplasia/carcinoma in situ detected by the examination can be treated with minimally invasive treatment such as endoscopic mucosal resection and argon ion coagulation therapy with good effect. 3.Tertiary prevention of tumor refers to measures to prevent recurrence, reduce its complications, prevent disability, improve survival and recovery rate, and reduce pain caused by tumor, such as three-step pain relief, hospice care, etc. for patients with existing tumor.