Primary Prevention – Secondary prevention or preclinical prevention, “three early” prevention. The goal is to prevent the development of incipient disease. Its task includes taking “three early” (early detection, early diagnosis, early treatment) measures against potential or hidden diseases before the appearance of cancer symptoms. In order to stop or slow down the development of the disease, reverse to stage 0 as early as possible and restore health. (A) Pay attention to the ten danger signals of cancer Gradual increase in the size of palpable lumps on the surface of the body or superficially. Persistent digestive abnormalities, or a feeling of fullness in the upper abdomen after eating. Sternal discomfort or even choking sensation when swallowing food. Persistent cough with blood in the sputum. Tinnitus, hearing loss, epistaxis, nasopharyngeal discharge with blood. Irregular vaginal bleeding outside the menstrual period or after menopause, especially contact bleeding. Fecal occult blood, blood in stool, hematuria. Long-standing ulcers. Observations of moles and warts that increase in size and color in a short period of time, hair loss, itchiness, and ulceration. Unexplained weight loss. (ii) Universal screening of certain groups of people. (C) Treatment of precancerous lesions such as severe 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 groups, such as those with genetic susceptibility to cancer and family history of cancer are susceptible to cancer. They must be monitored regularly. (e) Self-examination of tumors Regular self-examination of palpable and visible parts of the body surface is also possible. For example, self-breast examination for women. Long-standing ulcers. Moles and warts that increase in size, deepen in color, lose hair, itch and break down in a short period of time. Unexplained weight loss.