Colon and rectal cancer, also called colorectal cancer, ranks in top 3 among Chinese people in respect of the incidence rate, and holds the largest share in the hereditary tumor, approximate 25% of which is caused by the hereditary factors. Hereditary colon and rectal cancer is seriously concerned in the world for its high incidence rate, NCCN guidelines-the most authoritative oncology clinical practice guidelines in the world also definitely pointed out the recommended content on diagnosis, screening and risk management and so on of hereditary colon and rectal cancer.
The most prevalent hereditary colon and rectal cancer types
Lynch syndrome is caused by an occurrence of mutations in the gene family called MMR. MMR gene family member include multiple genes such as MLH1, MSH6 and PMS2, which all play an important role in repairing of DNA mismatch and can ensure accurate duplication and transmitting of hereditary information by DNA. If mutations in these genes result in functional gene deficiency, then DNA will become unstable in human body, some error will be present in gene group leading to the development of disease.
The National Comprehensive Cancer Network (NCCN) recommends that the patients with colon and rectal cancer should accept the Lynch syndrome gene detection. Similarly, American Joint Committee on Cancer (AJCC) suggests that all patients with colorectal cancer should receive the Lynch syndrome gene detection after admitted to hospital, and recommends that the relatives of the patients detected positive should also accept the Lynch syndrome gene detection.
2. Familial adenomatous polyposis (FAP) is characterized by intestinal multiple polyposis, which has very high risk of canceration in colon and rectal even reaching 90%. FAP is induced for the reason that its normal function cannot be performed due to the mutation in a gene called APC. The offspring of the hereditary mutation carrier has 50% probability of carrying the same mutation, and other immediate relatives also have high risk of carrying the same mutation.