Colorectal cancer screening is of great importance in the prevention and treatment of colorectal cancer, but people without symptoms are usually reluctant to go to their doctors for colorectal cancer screening such as anal finger examination, anoscopy and colonoscopy; at present, many units in China do not have a physical examination program involving specific colorectal cancer screening, yet these examinations play a key role in the prevention, successful diagnosis and treatment of colorectal cancer. The longer colorectal cancer screening is delayed, the larger the small polyps that are easily removed in the early stages will grow and may turn into cancer. Screening for colorectal cancer is already a very important task in the West and in some countries such as Japan and Korea. Since 1990, the American Cancer Society has proposed a screening protocol for colorectal cancer, which has been modified to divide patients into three groups: average, moderate and high risk. Screening consists of fecal occult blood tests, sigmoidoscopy and colonoscopy. The choice of screening method depends on the patient’s high or low risk of colorectal cancer development. Patients at average risk are those with no family history of colorectal cancer, no history of colonic polyps and no clinical signs of familial polyposis, hereditary non-polyposis colon cancer or inflammatory bowel disease. Patients at intermediate – high risk are those who have appeal risk factors. 1. Colorectal cancer screening program for people with average risk Most people fall into the category of average risk. For these people, colorectal cancer screening should start at the age of 40, and the screening is usually recommended by annual anal finger examination and fecal occult blood test, and colonoscopy every 2-3 years. Those with abnormal fecal occult blood tests should undergo colonoscopy of the entire colon. Recent studies have shown that colonoscopy is more effective in screening for colorectal cancer because it can visualize the right half of the colon, which cannot be reached by sigmoidoscopy. If you find colon polyps during a colonoscopy, you are at increased risk for colorectal cancer and therefore need more screening. 2. Colorectal cancer screening program for people with adenomatous polyps in the colon People with adenomatous polyps in the colon have an increased likelihood of developing multiple colon polyps and colorectal cancer, and thus these people need more screening. Studies have shown that colonoscopy is effective in preventing the development of tumors in patients with a history of colon polyps. By performing repeated colonoscopies on these patients, the incidence of colon cancer was reduced by 90% compared to those who did not undergo colonoscopy. In addition, despite the high accuracy of colonoscopy in the diagnosis of polyps, approximately 10-15% of small polyps are missed at the first examination. Therefore, patients diagnosed with large adenomatous polyps or multiple polyps need to undergo colonoscopy once a year, and if no abnormality is found on re-examination, it can be changed to once every 2 years. 3.Colorectal cancer screening program for people with family history of colorectal cancer The risk of colorectal cancer for people with colorectal cancer or colorectal adenoma in their immediate family is more than six times higher than those without family history, thus requiring more vigorous screening. Screening should begin at 35-40 years of age, or 10 years or more earlier than the minimum age of cancer diagnosis for their family members. The frequency of screening can be referred to the screening of the general population. If there are multiple immediate family members with colorectal cancer, and some had colorectal cancer at a very early age, there is a possibility of having an inherited non-polyposis colorectal syndrome, thus requiring counseling for the relevant genes at a specialized institution. 4. Colorectal cancer screening program for people with inflammatory bowel disease Patients with inflammatory bowel disease need to start colonoscopy 8 years after the definite diagnosis, and then need to have a new colonoscopy every 1 to 2 years. During the examination, multiple biopsies of colon mucosal biopsies should be performed every 10 cm to look for possible tumor formation. Developmental abnormalities of low or high differentiation should be resected from the colon and rectum because of the high cancer rate. 5. Genetic colorectal cancer screening program for family members with genetic colorectal cancer Patients or families with a history of familial polyps should be followed up by an institution that can provide appropriate genetic counseling and management. When genetic testing is not available, sigmoidoscopy should be performed every 1-2 years starting at age 12 until age 40. Once polyps are detected by sigmoidoscopy and diagnosed in patients with familial polyposis, total colorectal resection should be considered. In addition, patients with familial polyposis are at increased risk for duodenal polyps and should therefore undergo upper gastroscopy every 1-3 years. For patients suspected of having hereditary nonpolyposis colon cancer, a total colonoscopy is required starting at age 21. and every 2 years until age 40 and annually thereafter. Genetic screening can help identify patients with hereditary nonpolyposis colon cancer who have a genetic mutation and should be screened for other related tumors. 6. Colorectal cancer screening program for postoperative colorectal cancer patients Postoperative colorectal cancer patients need to undergo colonoscopy once a year after surgery. After one examination is normal, the examination should be repeated once every 2 years. The frequency of anoscopy or sigmoidoscopy should be increased for patients with rectal cancer undergoing low anterior resection. The combination of fecal occult blood test and screening colonoscopy is the key to early diagnosis of colorectal cancer, and based on recent studies, colonoscopy is more effective in early and follow-up screening of patients at average risk, thus prompt colonoscopy should be performed in average risk patients over 40 years of age.