Colonoscopy saves lives, but proves to be one-sided

December 16, 2008

(ChattahBox) — A colonoscopy is still a very effective procedure for combating colorectal cancer, but it may not be quite as good as previously thought, a new study suggests. The procedure does a good job of detecting early signs of disease on the left side of the colon, or large intestine, but is not as effective at spotting potential problems of the right side of the organ. This means a colonoscopy’s success at preventing colorectal cancer deaths seems to lie with its ability to uncover so-called “left-sided” problems.A complete colonoscopy is a procedure where a physician inserts a long, flexible tube called a colonoscope up into the patient’s rectum to scan the entire colon for potentially cancerous growths. If a polyp or lesion is detected, it can often be removed during the colonoscopy so that no additional procedures or surgery are needed.

According to the study, colonoscopy shows almost no mortality prevention benefit for cancer that develops in the right side of the colon. Colorectal cancer is the second-leading cause of cancer death in North America. The study appears today on the Annals of Internal Medicine Web site (www.annals.org) and will be printed in the January 6, 2009, issue.

Researchers reviewed health records for persons aged 52 to 90 who received a colorectal cancer diagnosis between 1996 and 2001 and died of colorectal cancer by 2003. These patients were compared to a control group who were selected from the population of Ontario and had not died of colorectal cancer.

According to the researchers, complete colonoscopy was strongly associated with fewer deaths from left-sided colorectal cancer. Conversely, the data showed that colonoscopy seemed to have almost no mortality prevention benefit for right-sided colorectal cancer.

The researchers suggest several reasons why colonoscopy may be less effective in preventing death from right-sided colorectal cancer. First, some colonoscopies considered “complete” may not evaluate the entire right colon. Second, bowel preparation may be worse in the right colon. Third, right and left colonic cancers and polyps may differ biologically. Right-sided growths may be less likely to have a fleshy stalk and are occasionally flat, which makes them harder to identify and remove, or they may grow more rapidly.

“Colonoscopy is an effective intervention,” said David F. Ransohoff, MD, author of an accompanying editorial. “The study results, however, should caution physicians about saying that colonoscopy will reduce the risk of dying from colorectal cancer by 90 percent. A 60 to 70 percent risk-reduction rate seems more reasonable.”

Reported by: BreakThroughDigest Medical News


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