Study supports value of sigmoidoscopy, an alternative to colonoscopy

Having the procedure lowered the risk of getting a colon cancer diagnosis by 21 percent and the chances of dying from the disease by 26 percent, the researchers reported.

Many doctors no longer offer sigmoidoscopies, but an editorial accompanying the study pointed out that sigmoidoscopies are still a good option for some patients.

"Physicians need to find out which colorectal cancer screening test the patient sitting in front of them will do, and recommend that test," said editorial author Dr. John Inadomi, a professor of medicine at the University of Washington School of Medicine in Seattle. "It's the test the patient wants to do -- not the test the doctor wants them to do -- that is important."

Colon and rectal cancers kill more than 51,000 people a year in the United States, according to the National Cancer Institute. Colonoscopies allow doctors to view the lining of the entire colon as they engage in search-and-destroy missions against polyps that could develop into cancer.

Sigmoidoscopies use a smaller scope that searches only the lower colon, potentially missing some precancerous polyps. Patients can return to home or work right after the procedure because they are not sedated.

Both kinds of screening require a notoriously unpleasant cleansing of the colon via a liquid laxative. However, sigmoidoscopies require less laxative consumption than colonoscopies, Inadomi said.

But there is a hitch to sigmoidoscopies: If the procedure turns up potentially dangerous polyps, they need to be removed during a subsequent colonoscopy.

In the new study, researchers randomly assigned half of 154,900 people aged 55 to 74 to sigmoidoscopies -- 84 percent actually got them -- and tried to get those patients to return for a second sigmoidoscopy three to five years later. The study lasted from 1993 to 2001.

The risk of colon cancer deaths in the patients overall was small -- 593 occurred over an average of 12 years of follow-up. But the risk fell by 26 percent in those who had the procedures compared to people in the usual care group, who only got colonoscopies or sigmoidoscopies if they asked for one or their doctor recommended one. The researchers estimated that if they had used colonoscopies rather than sigmoidoscopies in their study, they would have spotted 16 percent more cancers.

However, the researchers discovered that even colonoscopies sometimes failed to find precancerous polyps.

When it comes to the ability of regular colonoscopies to detect polyps, "we may have to do better," said study author Dr. Robert Schoen, a professor of medicine and epidemiology at the University of Pittsburgh School of Medicine. "Or maybe we can't do better."

The study appears online May 21 in the New England Journal of Medicine, to coincide with a presentation at the annual Digestive Diseases Week meeting in Chicago.

More information: For more about colon cancer, try the U.S. National Library of Medicine.

Journal reference: New England Journal of Medicine

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