Doubts Remain About Usefulness in Patients at High Risk of Colorectal Cancer
WebMD Health News
Reviewed By Louise Chang, MD
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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."
Medicare Won't Cover Virtual Colonoscopy
More than 14 million traditional colonoscopies are performed in the United States every year, but millions more people who could benefit from colorectal cancer screening are not getting it.
The American Cancer Society estimates that only about 40% of people over the age of 50 are getting any kind of screening for colon cancer.
Supporters of virtual colonoscopy say the noninvasive test could convince many of these people to get screened.
But those supporters were dealt a blow last month when it was announced that Medicare would no longer pay for the procedure.
Federal policy makers concluded that the evidence was not sufficient to prove that virtual colonoscopy "improves health benefits for asymptomatic, average risk Medicare beneficiaries."
American Cancer Society Chief Medical Officer Otis W. Brawley, MD, expressed disappointment in a written statement released soon after the decision was announced.
The American Cancer Society "still believes that a battery of different tests for colorectal cancer screening should be available to the American people," he writes.
Hated Bowel Prep Still Needed
In an editorial published with the study, Finlayson writes that it remains to be seen if clinicians are willing to accept the downsides of virtual colonoscopy if it means that more people will get screened.
But Rex says there is little evidence that patients would be more willing to have a virtual colonoscopy than a traditional one.
Both procedures require the same daylong, intensive bowel prep, which is what patients complain about most.
"The procedure itself is not what people hate. It's the prep," Rex says.
SOURCES: Regge, D. Journal of the American Medical Association, June 17, 2009; vol 301: pp 2453-2461. Daniel Regge, MD, Institute for Cancer Research and Treatment, Turin, Italy. Emily Finlayson, MD, MS, Michigan Surgical Collaborative for Outcomes Research and Evaluation, University of Michigan, Ann Arbor. Douglas Rex, MD, FACP, professor of medicine, Indiana University School of Medicine; director of endoscopy, Indiana University Hospital; past president, American College of Gastrointerology. ACS response to Medicare decision on CT Colonography, May 12, 2009.
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