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Colonoscopy Crowned Best for Detecting Colon Cancer

WebMD Health News

July 19, 2000 -- Colorectal cancer is a killer. It attacks silently, usually making its presence known only when it cannot be stopped. But colorectal cancer doesn't start out deadly. It develops from growths in the rectum and colon called polyps, which aren't yet cancerous. If detected early, the growths are removed and cancer will most likely be prevented.

Many leading experts say the best way to find and remove those growths is to examine the whole length of the colon using a tiny scope that allows the doctor to carefully view the inside walls. Called colonoscopy, this procedure recently gained additional prominence when TV personality Katie Couric underwent one on TV. Now two studies in the July 18 issue of The New England Journal of Medicine offer more proof that colonoscopy may be the most effective way to screen for colon cancer.

Some background: The best technique for screening the colon is a controversial subject. Some doctors advocate the use of flexible sigmoidoscopy, a procedure that looks at just the lower part of the colon and can be performed in the doctor's office. Colonoscopy, on the other hand, can look for cancers throughout the whole colon but requires anesthesia. To further confuse the issue, many doctors recommend yearly testing of the stool for blood, sometimes an early sign of cancer. This test is also very controversial.

In one study, a group of researchers used colonoscopy to screen more than 3,000 healthy male volunteers aged 55 to 75. They found early cancers in almost 10% of those screened. David A. Lieberman, MD, lead author of the study, tells WebMD that these men had no symptoms, and adds that colonoscopy is probably the only tool that could have located the cancers due to their location. Lieberman is a professor of medicine and chief of the division of gastroenterology at the Oregon Health Sciences University in Portland.

Lieberman concludes that colorectal cancer screening using colonoscopy is the way to go "because most lesions begin as precancerous growths that we can detect and remove and thus prevent cancer." That possibility makes a compelling case for use of the most effective screening tool, he says.

The second study in the journal attempted to determine whether the presence of polyps in the lower area of the colon is a marker for cancers higher in the colon. The researchers thought that if a lower polyp predicts the presence of a cancer higher up, then flexible sigmoidoscopy may be an adequate screening tool. The scientists analyzed almost 2,000 patients with no symptoms over the age of 50 who underwent initial colonoscopy. Twelve cancers -- eight in men -- were detected by the screening.

The scientists found that the presence of a polyp in the lower colon does increase the likelihood that the person has a colon cancer farther up. However, one of the study's authors, Thomas F. Imperiale, MD, tells WebMD that more than half of the people with cancer high in the colon -- beyond the range of the flexible sigmoidoscope -- had no polyps close to the rectum.

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