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How do I keep from getting colon cancer?

Several options exist to help keep you safe from colon cancer. The recommended choices are colonoscopy, the fecal occult blood test and flexible sigmoidoscopy.

Colonoscopy may be the best test for you. It reduces the risk of death from left-sided cancer by 60-70%. It also protects the right side of the colon. It is the "preferred" screening test for colorectal cancer prevention according to the American College of Gastroenterology. The benefits of colonoscopy are that it is widely available, it examines the entire colon, it allows for single-session diagnosis and treatment, and it need not be uncomfortable when sedation is used.

The stool for blood test (also called the FOBT test) requires that several stool samples be sent for analysis to determine if blood is in the stool. In a study in the New England Journal of Medicine, the FOBT test identified only 23.9% of patients who had an advanced pre-cancerous lesion or cancer as determined by a colonoscopy performed right after the FOBT test. This test needs to be repeated every one or two years. It reduces death from colon cancer by 15-33% and is better than no screening at all. It is cheap and safe and easy to do. Colonoscopy is better at preventing colon cancer. The Asia Pacific consensus recommendations for colorectal cancer screening suggest that this test is appropriate for use in resource-limited countries.

Other options include flexible sigmoidoscopy, which is a colonoscopy that stops half-way through the colon. In combination with the FOBT test, it overlooks advanced colonic neoplasia (lesions at risk for colon cancer) in 24% of people. Colon cancers are distributed about equally throughout the entire colon. Flexible sigmoidoscopy + FOBT is an improvement over FOBT alone and over flexible sigmoidoscopy alone. Colon cancer rates are increasing in the right colon, a region seen by colonoscopy but not by flexible sigmoidoscopy.

CT colonography involves taking images of the colon with a series of x-rays. It compares favorably to colonoscopy and is an accepted screening option for colon cancer. Funding for it is somewhat limited and other options such as colonoscopy or stool testing are more commonly used.   This test requires a bowel preparation and if lesions suspicious for polyps are found, it may result in a recommendation for a follow-up colonoscopy. This test is suggested to be performed every five years for screening and it is an important option for patients who decline colonoscopy.

For further reading, the American College of Surgeons provides a patient information brochure that compares and contrasts available screening options. The Ontario Association of Gastroenterology comments on the Canadian Task Force on Preventative Care recommendations for colon cancer screening, saying "Colonoscopy is probably the best colon cancer screening test".