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In Canada colorectal cancer is the third most common cancer, accounting for more than 12% of cases of cancer in both sexes. It was estimated that there would be 17 000 new cases and 6500 deaths from colorectal cancer in Canada in 2000.1 These rates, particularly among men, are among the highest in the world. People in kindreds with familial adenomatous polyposis or hereditary nonpolyposis colon cancer have close to a 50% chance of acquiring colorectal cancer because of the autosomal dominant mode of inheritance of these syndromes. Similarly, people with a family history of colorectal cancer who do not meet the criteria for hereditary nonpolyposis colon cancer or familial adenomatous polyposis may be at increased risk, but that risk is less well defined.
People at normal risk
· Multiphasic screening with fecal occult blood test as first phase
· Multiphase screening with sigmoidoscopy
· Uniphase screening with colonoscopy
People at above-average risk
· Flexible sigmoidoscopy or genetic testing for people in kindreds with familial adenomatous polyposis
· Colonoscopy for people in kindreds with hereditary nonpolyposis colon cancer
· Colonoscopy for people with a family history (first-degree relative) of polyps or colorectal cancer
· Reduction in mortality from colorectal cancer
· Sequelae of false-positive or false-negative results from fecal occult blood tests (e.g., unnecessary investigations and false reassurance)
· Perforation (sigmoidoscopy 1.4 per 10 000 procedures; colonoscopy 10 per 10 000 procedures); bleeding
· Anxiety, poor compliance
The Ontario Expert Panel on Colorectal Cancer recommends a multiphasic screening program, beginning with fecal occult blood testing, for people at normal risk between the ages of 50 and 75 years.2 The US Preventive Services Task Force recommends screening with either annual fecal occult blood testing or sigmoidoscopy (interval unspecified) or both for people over 50 years.3 A number of groups in the United States, including the American Cancer Society, the American College of Gastroenterology, the Crohn's and Colitis Foundation of America and the Oncology Nursing Society, recommend screening with fecal occult blood testing annually, flexible sigmoidoscopy every 5 years, combined fecal occult blood testing and flexible sigmoidoscopy, double-contrast barium enema every 5–10 years or colonoscopy every 10 years for people aged 50 or older with no other risk factors.4 These groups also made recommendations for people with additional risk factors: genetic counselling and possible genetic testing for those at risk of familial adenomatous polyposis and, for people with positive genetic test results, flexible sigmoidoscopy beginning at puberty. For people in kindreds with hereditary nonpolyposis colon cancer, annual colonoscopy beginning between 20 and 30 years of age is recommended. These groups made screening recommendations for people with a family history of polyps or colon cancer similar to those for people at normal risk but beginning at age 40 rather than 50.
The Canadian Task Force on Preventive Health Care is an independent panel funded through a partnership of the federal and provincial/territorial governments of Canada.
This statement is based on the technical report “Preventive health care, 2001 update: screening strategies for colorectal cancer,” by Robin S. McLeod, with the Canadian Task Force on Preventive Health Care. The full technical report is available from the task force office (gro.chpftc@ftc).