Colorectal Cancer Screening and Prevention.

Colorectal cancer is a common cause of morbidity and mortality in the United States. Most colorectal cancers arise from preexisting adenomatous or serrated polyps. The incidence and mortality of colorectal cancer can be reduced with screening of average-risk adults 50 to 75 years of age. Randomized controlled trials show evidence of reduced colorectal cancer-specific mortality with guaiac-based fecal occult blood tests and flexible sigmoidoscopy. There are no randomized controlled trials on the effectiveness of colonoscopy to reduce colorectal cancer-specific mortality; however, several randomized controlled trials comparing colonoscopy with other strategies are in progress. The best available evidence supporting colonoscopy is from prospective cohort studies that demonstrate decreased incidence of colorectal cancer and colorectal cancer-related mortality in individuals undergoing colonoscopy. Other screening options include fecal immunochemical testing, computed tomographic colonography, and multitargeted stool DNA testing combined with fecal immunochemical testing. There is good evidence that aspirin, nonsteroidal anti-inflammatory drugs, cyclooxygenase-2 inhibitors, and hormone therapy decrease the risk of colorectal cancer and adenomatous polyps, but potential harms limit their usefulness. There is good evidence that calcium supplementation, moderate dairy consumption, reduced red meat consumption, increased physical activity, decreased body mass index, and statin use decrease the risk of colorectal cancer and adenomatous polyps. Although increased alcohol intake and tobacco use are associated with an increased risk of colorectal cancer, there is no direct evidence that reducing alcohol consumption or smoking cessation decreases the risk.

Colorectal Cancer Screening and Surveillance in Individuals at Increased Risk.

Individuals at increased risk of developing colorectal cancer include those with a personal or family history of advanced adenomas or colorectal cancer, a personal history of inflammatory bowel disease, or genetic polyposis syndromes. In general, these persons should undergo more frequent or earlier testing than individuals at average risk. Individuals who have a first-degree relative with colorectal cancer or advanced adenoma diagnosed before 60 years of age or two first-degree relatives diagnosed at any age should be advised to start screening colonoscopy at 40 years of age or 10 years younger than the earliest diagnosis in their family, whichever comes first. In individuals with ulcerative colitis or Crohn disease with colonic involvement, colonoscopy should begin eight to 10 years after the onset of symptoms and be repeated every one to three years. Individuals who have a first-degree relative with hereditary nonpolyposis colorectal cancer should begin colonoscopy at 25 years of age and repeat colonoscopy every one to two years. In persons with a family history of adenomatous polyposis syndromes, screening should begin at 10 years of age or in a person's mid-20s, depending on the syndrome; repeat colonoscopy is typically required every one to two years. Screening colonoscopy should begin at eight years of age in individuals with Peutz-Jeghers syndrome. If results are normal, colonoscopy can be repeated at 18 years of age and then every three years. Persons with sessile serrated adenomatous polyposis should begin annual colonoscopy as soon as the diagnosis is established.