Luminary Learning Gastrointestinal Disorder- Issue 1

Current Guidelines for Colonoscopy •  33 that the first colonoscopy was associated with the overall greatest benefit in risk reduction, and that an earlier start of general screening (e.g., at age 40) was of only limited value. However, it has been postulated by some of the professional societies to start routine screen- ing earlier in some subgroups and ethnicities that were associated with an overall increased risk or have shown no or an insufficient decrease of CRC incidence rates over the past decades. Among these groups are African-Americans who are recommended to start screening at the age of 45 years [4]. Moreover, if there is a positive family history involving, in particular, first-degree rela- tives, and no known genetic mutation is identifiable, the first screening colonoscopy should be recommended to start at age of 40 or 10–15 years before the age at diagnosis of the youngest family member with CRC or advanced adenoma (whichever comes first). Recommendations for high-risk categories include not only a much earlier start, but due to the accelerated adenoma-carcinoma sequence, much shorter intervals, more frequent repeat exams, and potentially screening for extra-colonic pathology. The specifics are also outlined in Table 3 and depend on the nature of the risk (e.g., genetic syndrome versus IBD) [12]. Preferably, the gene carrier status in families with known genetic syndromes (FAP, Lynch, MAP) should be established by genetic testing rather than “screening” for the presence of polyps. Patients with established clinical or genetic diagnosis of FAP have traditionally been recommended to start Table 2: Risk categories for the development of colorectal cancer. Category Fraction of population (%) Lifetime risk of CRC Details Average risk 65–75 4.5% • No personal risk factors • Negative family history Increased risk 20–30 10–20% (?) • CRC or advanced adenoma in one first-degree relative with age ≤ 60 years or ≥ two first- degree relatives of any ages • Personal history of curative resection of CRC • Personal history of large adenomatous polyp (> 1 cm) or multiple colorectal polyps of any size • Personal history of sessile serrated adenomas (proximal to sigmoid colon) • African-American ethnicity, Ashkenazi Jews High risk 6–8 Nearly 100% by age 45 • FAP 70% • Attenuated FAP (AFAP) 60–80% • Lynch syndrome (HNPCC) Nearly 100% by age 65 • MUTYH-associated polyposis (MAP) 10–20% • IBD CRC colorectal cancer, FAP  familial adenomatous polyposis,  IBD  inflammatory bowel disease, HNPCC hereditary nonpolyposis colorectal cancer, MUTYH  ( aka MYH ) MutY Homolog of E.coli gene