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An image from a "virtual" colonoscopy. Image credit: National Cancer Institute
CHAPEL HILL, NC — A UNC physician authored an editorial in the July 27 online issue of the Journal of the National Cancer Institute (JNCI) commenting on results of an analysis of the cost effectiveness of colonoscopy versus computed tomographic colonography (CTC).
The cost effectiveness analysis concluded that CTC or “virtual” colonoscopy is not cost effective compared with colonoscopy if reimbursed at the same rate as colonoscopy.
Both CT colonography and colonoscopy examine the inside of the colon (the large intestine) for either cancer or large polyps (growths that could become cancer). CTC colonography does this examination indirectly, using a CT scan (a type of x-ray). Colonoscopy does this examination directly, using a camera on the end of a tube inserted into the colon.
Unfortunately, there has been no “comparative effectiveness” study to compare the benefits and harms of CTC with colonoscopy. So the researchers in the JNCI article used simulation models to compare the two tests in an unscreened population of Medicare beneficiaries ages 65 to 80 years. These models use mathematics to estimate what would happen if one used one test compared with the other.
In his editorial, Harris notes that cost-effectiveness analyses are useful, but that they often cannot include some important considerations. In this case, Harris shows how the cost-effectiveness analysis could not include some of the potential harms of both CTC and colonoscopy. For example, CTC often leads to finding abnormalities outside the colon (such as in the kidneys or adrenal glands) that require further testing and even surgery, yet finding these abnormalities usually does not help people live longer.
Colonoscopy often leads to removing small polyps that do not need to be removed, yet their removal may lead to complications such as excessive bleeding.
In the end, Harris suggests that neither CTC nor colonoscopy are ideal screening tests. He concludes: “Wouldn’t it be interesting if we ended up, a few years from now, with neither CTC nor colonoscopy as the primary screening test, but rather an improved fecal test as our gold standard.”
Harris is a national expert on cancer screening issues. He has served on the U.S. Preventive Services Task Force, a group that conducts scientific evidence reviews of a broad range of clinical preventive health care services and develops recommendations for primary care clinicians and health systems.
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