As mankind’s understanding of cancer as a persistent disease continues to deepen, it is gradually realized that prevention is the most effective weapon in the fight against cancer. According to current research, 1/3 of cancers can be prevented; 1/3 of cancers can be cured if diagnosed early; and 1/3 of cancer patients can be relieved of pain, improve their quality of life and prolong their lives through reasonable and effective treatment. Cancer prevention is one of the most important aspects of cancer prevention and fight against cancer. The ultimate goal of cancer prevention is to reduce the incidence and mortality of cancer, and in order to achieve this goal, it can be prevented through the following three levels of preventive measures. Primary prevention Ⅰ prevention – The first level of prevention, or etiologic prevention, aims at preventing the occurrence of cancer. Its tasks include researching the causes and risk factors of various cancers, taking preventive measures against specific cancer-causing and cancer-promoting factors such as chemical, physical and biological factors as well as internal and external disease-causing conditions, and taking measures against the healthy organism by strengthening environmental protection, suitable diet and suitable sports to promote physical and mental health. (a) Avoiding smoking: Smoking has been a clear and well-known cancer-causing factor, which is related to 30% of cancers. Smoke tar contains many kinds of carcinogenic substances and cancer-promoting substances, such as benzo(a)pyrene, polycyclic aromatic hydrocarbons, phenols, nitrosamines, etc. When the smoke of tobacco burning is inhaled, the tar particles will be adhered to the mucous membrane of the bronchial tubes, and after long-term chronic stimulation, it can induce cancerous changes. Smoking mainly causes cancer in lung, pharynx, larynx and esophagus, and in many other parts of the body, it can also increase the risk of tumor. (ii) Dietary structure: Colon, breast, esophageal, stomach and lung cancers are the most likely to be prevented by changing dietary habits. As a matter of fact, a reasonable diet may have a preventive effect on most cancers, especially the existence of a variety of anti-cancer components in plant-type foods, which are effective in the prevention of almost all cancers. 8 dietary guidelines published by the Chinese Nutritional Society in 1997 are as follows: 1) Variety of foods, cereal-based. Diversified foods should include grains and potatoes, animal foods, beans and their products, vegetables and fruits, and pure calorie foods. 2, eat more vegetables, fruits and potatoes, maintain cardiovascular health, increase resistance to disease, cancer prevention, prevention of eye disease. 3, eat milk, beans and their products every day. Our dietary calcium is generally lacking, only half of the recommended supply. And dairy foods contain high calcium, and with legumes, is an excellent source of protein. 4, often eat the right amount of fish, poultry, eggs, lean meat, less fat and meat oil. The amino acid composition of animal protein is comprehensive, with high lysine content; and the unsaturated fatty acids of fish have the effect of lowering blood lipids and preventing thrombosis. 5.Balance diet and physical activity to maintain proper body weight. The calories for breakfast, lunch and dinner should be 30%, 40% and 30% respectively. 6, eat light meals with less salt. The average salt intake of our residents is about 15 grams per day, which is more than twice the recommended value by the World Health Organization, so we should reduce the amount of salt intake. 7, alcohol consumption should be moderated. 8, eat clean and hygienic, non-perishable food. This includes shopping for food that meets hygiene standards, especially green food. (iii) The top 25 preventable risk factors that predispose to cancer are: 1. Hepatitis B virus infection – liver cancer; 2. Smoking (10 years of smoking, 2 packs or more per day) – lung cancer; 3. Human papillomavirus (HPV -16 or HPV-18) – cervical cancer; 4. Dietary intake high in saturated fat – colon, pancreatic, lung cancer; 5. Dietary intake low in folic acid -cervical cancer; 6, excessive alcohol consumption (any alcohol) – oropharyngeal cancer; 7, DDT in pesticides – breast cancer; 8, frequent consumption of beef and lamb — colon cancer; 9, Helicobacter infection — stomach cancer; 10, highly stressful life experiences (lasting more than 2 years) — various cancers; 11, low vitamin E dietary intake -colon cancer; 12, low vitamin C dietary intake -cervical cancer; 13, oral contraceptives (at age 40-44) – Breast cancer; 14, Long-term use of black hair beamer – Lymphoma; 15, Lack of dietary intake of fresh fruits and vegetables – Lung cancer; 16, Chronic obesity – Colon cancer; 17, low carbohydrate intake – colorectal cancer; 18, passive smoking (more than 22 years) – lung cancer; 19, high total calorie intake – prostate cancer; 20, low activity (less than 1,000 calories per week) – colorectal cancer; 21, low dietary intake of selenium – lung cancer; 22, low dietary intake of fiber – colorectal cancer; 23, not having had children – breast cancer; 24, low dietary intake of legumes – lung cancer; 25, having your first child after age 30 – breast cancer. In addition to some cancers being related to family genetic factors, about 84% are related to lifestyle, such as dietary habits, smoking, and reduced intake of fresh fruits and vegetables. Many cancers can be prevented if people know more about the top 25 risk factors that can cause cancer and take precautions. In order to reduce your cancer risk, people should try their best to change their bad lifestyle and develop good living habits. Secondary prevention Level II prevention – Secondary prevention or preclinical prevention, also known as “three early” prevention (early detection, early diagnosis and early treatment) measures. The goal is to prevent the development of incipient diseases. (a) Pay attention to the ten major danger signs of cancer: 1. Gradual increase in the size of palpable lumps on the surface of the body or superficially. 2. 2. Persistent digestive abnormalities, or a feeling of fullness in the upper abdomen after eating. Sternal discomfort or even choking sensation when swallowing food. 4.Persistent cough with blood in sputum. 5, Tinnitus, hearing loss, epistaxis, nasopharyngeal secretion with blood. 6, Irregular vaginal bleeding outside menstruation or after menopause, especially contact bleeding. 7, fecal occult blood, blood in stool, hematuria. 8, Long-standing ulcers. 9, nevus, warts within a short period of time, increase in size, deepening of color, hair loss, itching, ulceration and other observations. (10) Unexplained weight loss. (ii) Universal examination of certain groups of people. (iii) Treatment of precancerous lesions: e.g. heavy hyperplasia of esophageal epithelium, atypical hyperplasia, chemosis and atrophic gastritis of gastric mucosa, chronic hepatitis and cirrhosis of the liver, colon polyps, hyperplasia and chemosis of bronchial epithelium. (d) Strengthening the monitoring of susceptible people: people with genetic susceptibility to cancer and family history of cancer are susceptible to cancer. They must be monitored regularly. (e) Tumor self-examination: Regular self-examination can be carried out for the palpable and visible parts of the body surface. For example, self-breast examination for women. Tertiary prevention Tertiary prevention – the third level of prevention, clinical (stage) prevention or rehabilitative prevention. Its task is to adopt multidisciplinary comprehensive diagnosis and treatment, and correctly select reasonable and effective diagnosis and treatment programs in order to cure cancer as early as possible, try to restore function, reduce death, promote rehabilitation, improve quality of life, and even return to society. The main treatments for cancer are: surgery, radiotherapy, chemotherapy, bio-immunotherapy, traditional Chinese medicine and other treatments (e.g. interventional therapy, ultrasonic knife therapy). Early detection and early treatment is the key to cure, but most of the cases are found in the middle or late stage, and it is often difficult to cure by single means of treatment. Comprehensive treatment is the best way to increase the rate of cure. Comprehensive treatment is not an accumulation of several treatment methods, but a planned, timely and reasonable arrangement of using existing means of treatment according to different patients, pathological types, biological behaviors, stages of disease and organ functions, so as to achieve the purpose of improving the cure and recovery rate, prolonging the survival period and improving the quality of life. Preoperative radiotherapy and chemotherapy can shrink the tumor, improve the surgical resection rate, reduce the scope of surgical resection, and preserve the function of important organs. Postoperative radiotherapy and chemotherapy are conducive to the complete elimination of potential cancer cells and prevention of recurrence and metastasis. For those who are not suitable for surgery, local arterial perfusion chemotherapy and radiotherapy after chemotherapy to control extensive lesions can further treat the primary foci. Biological immunotherapy can eliminate potential metastatic foci without causing damage to the patient’s body and achieve the goal of cure and improvement.