'Virtual colonoscopy' techniques and training need to be improved before widespread clinical use

April 13, 2004

The accuracy of computed tomographic colonography ("virtual colonoscopy") for the detection of colorectal cancer is lower than that for conventional colonoscopy, suggesting that use of "virtual" colonoscopy should be limited until techniques and training can be improved, according to a study in the April 14 issue of The Journal of the American Medical Association (JAMA).

According to background information in the article, conventional colonoscopy is the best available method for detection of colorectal cancer and its precursors. However, it is invasive and not without risk, so a simpler alternative would be welcome. Computed tomographic colonography (CTC) has been reported to be reasonably accurate in the diagnosis of colorectal tumors in studies performed at expert centers. CTC involves the examination of computer-generated images of the colon constructed from data obtained from an abdominal computed tomographic examination.

Peter B. Cotton, M.D., of the Digestive Disease Center at the Medical University of South Carolina, Charleston, S.C., and colleagues assessed the accuracy of CTC in a large number of participants from multiple centers. The study included 615 patients aged 50 years or older who were referred for routine, clinically indicated colonoscopy at nine major hospital centers between April 17, 2000 and October 3, 2001. The CTC was performed before the standard colonoscopy and results were compared.

The researchers found that the sensitivity of CTC for detecting participants with one or more lesions sized at least 6 mm was only 39 percent and for lesions sized at least 10 mm, it was only 55 percent. These results were significantly lower than those for conventional colonoscopy, with sensitivities of 99 percent and 100 percent, respectively. The accuracy of CTC varied considerably between centers and did not improve as the study progressed.

"Our results indicate that CTC using these techniques is not ready for routine use at this time, as many others have concluded. There is an obvious need for continuing collaboration between radiologists and gastroenterologists in further evaluation of this exciting new technology. If and when results do justify widespread introduction, similar multidisciplinary collaboration will be needed to ensure its efficient application," the authors write.
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(JAMA. 2004;291:1713-1719. Available post-embargo at JAMA.com)

Editor's Note: This study was supported by a grant from the Office of Naval Research of the U.S. Department of Defense. Co-authors Dr. Pineau is a minor stockholder and Dr. Vining is a major stockholder in PointDX, a radiology structured reporting company.

EDITORIAL: VIRTUAL COLONOSCOPY - WHAT IT CAN DO VS. WHAT IT WILL DO

In an accompanying editorial, David F. Ransohoff, M.D., of the University of North Carolina, Chapel Hill, writes that "as the study by Cotton et al suggests, the biggest near-term problem for virtual colonoscopy is that it may be implemented too widely without sufficient regard for current technological problems that affect sensitivity.

"The level of sensitivity and specificity that virtual colonoscopy can achieve, in some specialized situations, is known. Yet the differences between what virtual colonoscopy can do and what it will do if applied in ordinary practice circumstances are so great that physicians must be cautious. There are many important steps yet to be taken in learning how to implement this new technology appropriately," he writes.

(JAMA. 2004;291:1772-1774. Available post-embargo at JAMA.com)

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