The current internationally accepted treatment method for familial adenomatous polyposis is prophylactic total colorectal resection combined with endoscopic follow-up. However, total colorectal resection will bring a sharp decline in the quality of life of patients. Therefore, how to improve treatment methods and improve the quality of life for such patients under the premise of medical quality is the current medical focus. This study intends to establish three parallel observation cohorts, namely the surgical treatment group, the intensive colonoscopy treatment group, and the autonomous monitoring group. During the three-year study period, the investigators observed changes in the number of adenomas, carcinogenesis, and medical expenses in each group during the 3-year study period, and compared the groups to determine whether the intensive colonoscopy therapy has the possibility of delaying or replacing preventive surgery.

Familial adenomatous polyposis is a kind of colorectal cancer syndrome, which belongs to rare diseases. It is estimated that the number of patients in China is about 100,000, accounting for about 1% of all colorectal cancer patients. This type of patients onset between the ages of ten and thirty years old. The typical manifestation is the growth of tens to thousands of colorectal adenomas, and the lifetime risk of colorectal cancer is close to 100%, accompanied by multiple extraintestinal manifestations . Without treatment, the average life span is 40-50 years. The current internationally accepted treatment method is prophylactic total colorectal resection combined with endoscopic follow-up. This program has a significant effect and can extend life expectancy by 10-20 years. However, total colorectal resection will bring a sharp decline in the quality of life of patients. The patients will lose many abilities (working ability, social ability, fertility, etc.) from the age of 20, and the prolonged survival period also brings more misery. This, in turn, also reduces the compliance of treatment. Many patients refuse to accept surgery and turn to endoscopic treatment or even give up treatment. However, there is currently no evidence that methods other than prophylactic surgery can effectively control the risk of colorectal cancer in such patients. Therefore, how to improve treatment methods and improve the quality of life for such patients under the premise of medical quality is the current medical focus. This study intends to establish three parallel observation cohorts, namely the surgical treatment group, the intensive colonoscopy treatment group, and the autonomous monitoring group. Among them, the intensive colonoscopy treatment group will be treated with colonoscopy intensive treatment (that is, colonoscopy treatment is performed every 3 months, Carry out colorectal tumor reduction in segments, and continue to control the growth of adenomas several times) for patients who refuse surgery. During the three-year study period, the investigators observed changes in the number of adenomas, carcinogenesis, and medical expenses in each group during the 3-year study period, and compared the groups to determine whether the intensive colonoscopy therapy has the possibility of delaying or replacing preventive surgery, so as to explore ways to improve the quality of life of such patients.

Inclusion Criteria:

• The initial number of polyps is between 100-1000 visually;
• Pathological diagnosis of multiple lesions confirmed colorectal adenoma;
• Germline mutation detection is clearly a point mutation or large deletion of APC gene;
• No cancer or distant metastasis.

Exclusion Criteria:

• Age <18, or >40 years old;
• The initial number of polyps is <100, or >1000;
• The polyp has become cancerous or has suspected distant metastasis;
• Patients with intestinal obstruction, intestinal perforation, intestinal bleeding and other patients who need emergency surgical resection;
• Past history of colorectal surgery;
• Suffering from malignant tumors in other parts and requiring treatment or using chemotherapy drugs or NSAIDs;
• The patient has contraindications to colonoscopy;
• Patients or family members cannot understand the conditions and goals of this study;
• The patient plans to receive surgical treatment of preventive colorectal resection;
• Other reasons considered by the study doctor to be inappropriate for inclusion in the study.

The anticipants will be allocated in one of the three groups, and accept the corresponding intervention and at least 3 year follow up.