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Colorectal Cancer Health Center

New Evidence on Benefits of Colonoscopies

Study Shows Colonoscopy Exam Can Prevent Colorectal Cancer Throughout Colon
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Reduction in Right-Side Cancers continued...

Study participants were asked whether they had had a colonoscopy during the previous 10 years, and patient medical records were analyzed.

After taking into account known colorectal cancer risk factors, colonoscopy screening within the previous decade was associated with a 77% overall reduction in colorectal cancer risk.

The risk reduction was 84% and 56%, respectively, for left-sided and right-sided cancers. In patients younger than age 60, however, screening was associated with a 26% reduction in risk in right-sided cancer, which was not statistically significant.

The reduction in risk was seen for all cancer stages and for both men and women.

Second Opinion

In an editorial published with the study, Weinberg writes that while it is not entirely clear why colonoscopy is not as effective in the right colon, it would be a mistake to conclude that it is ineffective.

He tells WebMD that the newest findings do not necessarily contradict those of the Canadian studies because those studies also showed protection against right-sided cancers when colonoscopies were performed by doctors who had a high polyp detection rate.

Douglas K. Rex, MD, agrees, noting that the Canadian findings may reflect the fact that a large proportion of colonoscopies in that country are performed by surgeons and primary care doctors and not gastroenterologists who specialize in the exam.

A gastroenterologist himself, Rex is a distinguished professor of medicine at Indiana University School of Medicine and he is the co-author of the American College of Gastroenterology’s screening guidelines for colorectal cancer.

“This is a procedure that requires a certain amount of skill,” he says. “But that doesn’t mean that every gastroenterologist does this exam well.”

Two Key Questions Every Patient Should Ask

In the U.S., screening for colorectal cancer is recommended to start at age 50 for people at average risk and at a younger age for those who have an increased or high risk for the cancer.

But Rex says doctors who perform colonoscopies in the U.S. are not required to document the thoroughness of the exam.

This is not the case in Germany, where quality assurance measures have been introduced nationwide.

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