Screening is the key to curb colorectal cancer Screening for people with high risk of colorectal cancer includes: 1. If one of parents, siblings and children has colorectal cancer, the risk of the disease increases, and the standard screening test of colonoscopy, fecal occult blood or both should be performed at the age of 40. 2.For those who have undergone radical colorectal cancer surgery, the risk of recurrent or new cancer increases. If the CEA does not decrease continuously or decreases for a short time and then increases again, the possibility of incomplete resection or recurrence should be considered, and colonoscopy should be performed in time to detect the presence of tumor. If the person who performs resection of colorectal cancer does not have thorough examination before surgery, colonoscopy is recommended within 1 year after surgery. 3. Familial adenomatous polyposis is caused by a congenital or acquired defect in the adenomatous polyposis of the colon (APC) gene. Mutations in this gene occur mostly at the age of 20 to 30 years and can lead to hundreds of adenomas in the colon, and after the age of 40 years, almost 100% of those with this gene develop cancer. For such family members, they should receive genetic counseling and undergo regular colonoscopy from adolescence. 4. The cancer rate of adenomatous polyps is related to the size of the polyps. The larger the polyp, the greater the chance of cancer. If adenoma is found at the first examination, all of them will be biopsied electrically, and those who are confirmed to be adenoma will be reviewed regularly. 5. Hereditary non-polyposis colon cancer and rectal cancer is an autosomal dominant disease in which several people in the same family suffer from colon cancer and rectal cancer. Individuals suspected of the disease should undergo colonoscopy every one to two years from the age of 20 to 30 years, and once a year after the age of 40. 6. Patients with ulcerative colitis have an increased risk of developing colorectal cancer. This risk starts 8 years after the disease and continues to increase steadily thereafter. Patients with total colitis should undergo colonoscopy every 1 to 2 years after 8 years of illness, and patients with left colitis after 15 years of illness. 7.In the past, it was thought that the polyps of patients with melanotic polyposis would not become cancerous. However, in recent years, medical research has found that patients with melanotic polyposis have a much higher chance of developing cancer than normal people, and a survey shows that the incidence of malignant tumors in patients with melanotic polyposis is 20% to 23%. Therefore, patients with melanotic polyposis should be actively followed up and examined for treatment. For patients over 10 years old, whole gastrointestinal tract imaging is routinely performed every two years; patients over 20 years old should also receive colonoscopy every two years. 8. For those who have alarm symptoms recently, patients with blood in stool, change in stool habit, deformation of stool and wasting should undergo colonoscopy.