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Am Fam Physician. 2010;81(9):1073-1076

Original Article: Colorectal Cancer: A Summary of the Evidence for Screening and Prevention

Issue Date: December 15, 2008

to the editor: The article on colorectal cancer confirms the validity of annual fecal occult blood testing (FOBT) as an effective colon cancer screening method. This is important because there is powerful pressure, aimed at family physicians and the population at large, advocating colonoscopy as the only valid means of colorectal cancer screening. Indeed, local gastroenterologists have accused me of negligence for encouraging patients to consider having yearly FOBT instead of colonoscopy for routine screening.

In addition to the difference in cost, convenience, and comfort between the two forms of testing, another issue was not addressed in the article. Although the official recommendation for screening colonoscopy is every 10 years starting at 50 years of age, many gastroenterologists do not follow this guideline. In fact, it is much more common that colonoscopies are performed every three to five years.1 Clearly, there are some indications for shorter screening intervals. However, in comparing the cost as well as the risks of screening, it is important to consider the official recommendations and how colonoscopy is practiced in real life. If the test is inappropriately performed every three to five years, then the cost and risks (including bowel perforation) of screening colonoscopy are doubled or tripled.

to the editor: In this article on colorectal cancer, I question the following statement from the authors: “Office testing of stool samples obtained by digital rectal examination has not been shown to reduce mortality. A single FOBT [fecal occult blood test] performed by digital rectal examination will miss 95 percent of colorectal cancer.” I have always performed a rectal examination and I have found many rectal cancers that were not suspected. I also have had positive FOBT on many occasions that were followed by colonoscopy or, years ago, by barium enema. A rectal examination is easy to do and is more thorough. Moreover, I have found many cancers of the prostate.

I believe it was Sir William Osler who said that the difference between a specialist and an ordinary doctor is that the specialist does a rectal routinely at the time of a thorough examination.

in reply: In 2009, the American Cancer Society estimated 146,970 new cases of and 49,920 deaths from colorectal cancer.1 Of greatest importance, the morbidity and mortality from colorectal cancer could be significantly reduced in the United States from a successful national colorectal cancer screening program. We agree with Dr. Fried that annual fecal occult blood testing (FOBT) is an effective, convenient option for colorectal cancer screening.2 Other recommended screening tests include fecal immunochemical test every year, flexible sigmoidoscopy every five years, colonoscopy every 10 years, or fecal DNA testing (no recommended interval).3

We also agree with Dr. Fried that endoscopists often recommend repeat colonoscopy at shorter intervals than recommended by national guidelines, and this is well supported in the literature.46 This situation complicates analysis of the cost effectiveness of colorectal cancer screening and may raise costs without improving outcomes.7

In regards to Dr. Andersen's comments about rectal examination, available evidence shows that a single FOBT obtained during digital rectal examination is less able to prevent death from colorectal cancer than a series of three FOBTs performed at home by the patient,2 and a negative office test may provide false reassurance. If a physician and patient agree on FOBT for colorectal cancer screening, then the patient should be sent home with FOBT cards and instructions to complete them. No guidelines recommend FOBT obtained by digital rectal examination as an adequate colorectal cancer screening test.2

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This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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