Multi-center trial compares virtual colonoscopy with standard colonoscopy

Thursday, September 18, 2008

SCOTTSDALE, Ariz. – Virtual colonoscopy is comparable to standard colonoscopy, according to results of a large, multi-center trial that are published in the Sept. 18, 2008, issue of the New England Journal of Medicine.

The results address the question many people over age 50 have asked in reflecting on their need to plan for a colonoscopy: Is virtual colonography as good as the standard colonoscopy?

Colonoscopy is a strongly recommended screening test for early detection of colon cancer, and in the standard procedure, a long, flexible tube is used to view the lining of the colon. After prepping to cleanse the colon, the patient is sedated for the procedure and then generally goes home to rest for the remainder of the day.

Virtual colonoscopy, known more formally as computerized tomography (CT) colonography, employs virtual reality technology to produce a three-dimensional view of the entire colon and rectum. The clinical trial, sponsored by the National Cancer Institute (NCI), part of the National Institutes of Health (NIH), enrolled 2,600 patients at 15 sites nationwide. It is the largest study of its kind to compare the accuracy of virtual colonoscopy to the gold standard of conventional colonoscopy.

The virtual colonoscopy procedure involves insertion of a small enema tip into the rectum, accompanied by carbon dioxide gas to inflate the colon. No sedation is required other than a muscle relaxer.

Principal investigator of the American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial is C. Daniel Johnson, M.D., chair of the Department of Radiology at Mayo Clinic in Arizona.

"We hope that this additional, less-invasive option for cancer screening will lead more people to get screened and will ultimately result in fewer deaths from colorectal cancer," says Dr. Johnson.

Despite the known benefits of colorectal screening, studies indicate that the majority of Americans age 50 and older are not being screened for the disease.

In the ACRIN trial, the virtual colonoscopy findings were evaluated using colonoscopy as the standard. Virtual colonoscopy was found to be highly accurate for detection of intermediate and large polyps. Ninety percent of polyps 1 centimeter or larger were detected by the CT colonography. Polyps as small as one-half centimeter were detected with a high degree of accuracy as well. Most colon cancers develop from polyps.

"The most important advice we can give patients is to get screened," says gastroenterologist and study author Paul Limburg, M.D., Mayo Clinic in Rochester, Minn. "How they get screened should be an individual decision based on discussions between patients and their medical providers."

Those in the study had to be at least 50 years old, scheduled for a colonoscopy and must not have received a colonoscopy in the past five years. Each participant underwent the virtual (CT) colonography, followed by the standard colonoscopy, with 99 percent of both exams accomplished on the same day.

For both procedures, the usual preparation is required – taking laxative solution to clear and cleanse the colon.

Colorectal cancer is the third most frequently diagnosed cancer and the second-leading cause of cancer death in the U.S.

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