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Virtual Colonoscopy: Who Should Get It?

Doubts Remain About Usefulness in Patients at High Risk of Colorectal Cancer
By
WebMD Health News
Reviewed by Louise Chang, MD

June 16, 2009 -- Virtual colonoscopy may be an acceptable screening alternative to traditional colonoscopy for some, but not all, patients with a higher-than-normal risk for colorectal cancer, new research suggests.

The noninvasive screening method, which uses X-rays and computers to produce 3-D images of the colon, identified 85% of suspicious growths in people who had elevated risks for colorectal cancer in the newly published study conducted in Italy.

But despite the positive results, critics contend that virtual colonoscopy, known medically as computed tomographic (CT) colonography, makes little sense for those at high risk for developing colorectal cancer.

"This is not the right population to be doing CT colonography in," Indiana University Hospital Director of Endoscopy Douglas Rex, MD, FACP, tells WebMD.

One big drawback is that virtual colonoscopy can only detect growths, requiring another procedure to remove them. Traditional colonoscopy can detect and remove them in the same procedure.

High-risk populations are far more likely to have suspicious growths that need to be removed, Rex points out.

"I don't see how a diagnosis-only strategy like CT colonography makes sense," he says.

Virtual Colonoscopy Not for Everyone

The Italian and Belgian study included 937 participants who had an increased risk of colorectal cancer because of either a close family history of colorectal cancer, a personal history of polyps that had been removed, or a positive fecal occult blood test (FOBT) that detected blood in the stool.

Overall, virtual colonoscopy identified 151 of 177 people with growths that were 6 millimeters or larger and correctly identified 667 of 760 people who did not have suspicious lesions.

Half of the participants with a recent positive fecal occult blood test had serious growths that required removal, compared to 7.5% of people with a positive family history and 11% of people with previous polyps.

The study, which appears in this week's Journal of the American Medical Association, makes it clear that people with a positive FOBT are not appropriate candidates for virtual colonoscopy, colorectal surgeon Emily Finlayson, MD, tells WebMD.

The test is also not for patients with inflammatory bowel disease or those with a history of flat polyps, which are often missed with virtual colonoscopy, she says. "In my opinion, CT colonography is a pretty good test, but it is not for everyone."

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