Rectal cancer is similar to colon cancer, and the medical community refers to colon cancer and rectal cancer collectively as colorectal cancer, and the screening methods are as follows: 1. For people in the age group of 50-74 years old, they can do high-risk questionnaire survey or stool occult blood test by immunoassay, and if either of them is determined to be positive, the patient should be recommended to do colonoscopy, and if the patient has colon cancer or rectal cancer, it can be detected early; 2. Nowadays, the industry Many doctors sometimes add tumor markers, such as CEA (carcinoembryonic antigen) and CA19-9, to assist in the screening process. If a patient reaches the age range of 50-74 years old, it means that he or she has already entered the high-risk age group for colon cancer development. It is recommended to go to the hospital for an effective colonoscopy in time, so that if there is to be early cancer or precancerous lesions, they can be detected in time.