Bethesda, Maryland (July 1, 2005) The risk of developing cancer as a result of being exposed to X-rays during computed tomography colonography (also known as "virtual colonoscopy" or CT colonography) is considerably less than 1 percent, according to an article published today in the American Gastroenterological Association (AGA) journal Gastroenterology. Researchers say the radiation risk can be further reduced by creating optimized protocols for performing this screening test.

"It's good news that the radiation risk is low with CT colonography, but many practical issues need to be addressed before the test can be recommended to patients for routine colorectal cancer screening," said AGA President David A. Peura, MD. "Evaluating issues of standardization and accuracy of test results and addressing disparities in consistent and uniform training of professionals performing the test should be the focus of future studies. In addition, the procedure still requires a great amount of bowel preparation and causes discomfort--both issues largely affect the current state of patient compliance in colorectal cancer screening."

Researchers from the Center for Radiological Research at Columbia University Medical Center estimated the radiation dose to different organs from adult CT colonography scans. Dose-, organ- and gender-specific excess relative risks for cancer incidence in Japanese A-bomb survivors were used as a basis to generate risk estimates for the U.S. population. This study found the estimated lifetime risk of cancer as a result of radiation from CT colonography in a 50-year-old subject is about 0.14 percent and 0.022 percent for a 70-year-old patient. The main organs found to be at risk for cancer are the colon, stomach and bladder.

"Our study shows that radiation risks associated with virtual colonoscopy are relatively small--much smaller, for example, than for CT-based lung cancer screening," said David J. Brenner, PhD, lead st
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Contact: Kimberly Wise
media@gastro.org
301-941-2620
American Gastroenterological Association
1-Jul-2005

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