Virtual Colonoscopy Effective for Average Risk People

Sept. 18 -- WEDNESDAY, Sept. 17 (HealthDay News) -- For people with an average risk of colon cancer, two new studies offer good news on the colon cancer screening front.

First, one study found that virtual colonoscopy -- or CT colonography -- was effective in detecting 90 percent of precancerous lesions larger than 10 millimeters. And, the second study found that five years after having an initial standard colonoscopy, no cancers were found in people who repeated the test.

"CT colonography is a reasonable option for colon cancer screening," said Dr. Durado Brooks, director of prostate and colorectal cancer for the American Cancer Society. "It will miss some abnormalities, but even colonoscopy is not a perfect tool. Studies of back-to-back colonoscopy show miss rates of between 2 and 11 percent."

The second study, Brooks said, "reinforces the fact that colonoscopy screening does not need to be taking place at an every five-year interval." He said that, although the current cancer society recommendations for people with an average colon cancer risk are to have a colonoscopy every 10 years, some doctors feel that interval is too long and advise their patients to have a colonoscopy every three to five years. Since this new study found no cancers at all after five years, Brooks said this should "provide an additional level of comfort" to those who were concerned that the screening interval was too long.

Results of both studies are published in the Sept. 18 issue of the New England Journal of Medicine.

The first study included 2,531 people from 15 centers across the United States. All were over age 50 and had no known significant risk factors for colon cancer.

The study participants underwent CT colonography (virtual colonoscopy) and then a follow-up colonoscopy on the same day to verify the CT colonography findings. The preparation for CT colonography is the same as it is for colonoscopy and includes a limited diet the day before the test and the use of purging laxatives. (Brooks said there is ongoing research trying to devise a prep-less CT colonography, since the preparation for the test is what people often find most objectionable.)