Colonoscopy screening would avert cancer.

Of all malignancies, colon cancer seems the most avoidable. By inserting a flexible scope into a person's colon via the rectum, a physician can detect precancerous growths called polyps. A device attached to the scope can snip them off--all during the same outpatient visit. But the procedure, called colonoscopy, is expensive and uncomfortable. So, many people avoid it.

Colorectal cancer, meanwhile, kills more than 50,000 people every year in the United States. Among malignancies, only lung cancer kills more. Two studies now bolster the case for more-frequent colonoscopy screening.

Colonoscopy screening that would test people over 50 once a decade could cut colorectal cancer deaths by half, researchers from Duke University Medical Center in Durham, N.C., reported last month in New York at the 65th Annual Scientific Meeting of the American College of Gastroenterology.

Another team finds that colonoscopy once per decade would be as cost-effective in the long run as less expensive, less invasive colorectal screening tests that must be administered more frequently. The report of that finding by Amnon Sonnenberg and his colleagues at the Department of Veterans Affairs Medical Center and the University of New Mexico in Albuquerque appears in the Oct. 17 ANNALS OF INTERNAL MEDICINE.

The two statistical analyses compared colonoscopy for people over age 50 with a combination of laboratory examination of stool samples (see p. 311) and a procedure called sigmoidoscopy, which reveals the lower third of the colon.

A stool examination costs about $33, a sigmoidoscopy runs roughly $250, and a colonoscopy can be priced anywhere from $700 to $1,000. Insurance companies and Medicare have only recently begun paying for these tests, and only in certain cases, says Sonnenberg. To avoid colon cancer, "the down payment for colonoscopy is larger," he says.

The studies complement earlier reports showing colonoscopy reveals up to twice as many polyps as sigmoidoscopy.

A polyp takes about 20 years on average to become cancerous, says A. Lindsay Frazier of Harvard Medical School in Boston. A single colonoscopy at age 55 could catch a third of all polyps before they become malignant, she and her colleagues estimate in a report in the Oct. 18 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION.

"Everyone over 50 should be screened," Frazier says, either by colonoscopy or a combination of the other tests. As of 1997, less than a third of people in the United States over age 50 had had a sigmoidoscopy in the preceding 5 years.

Whether these reports ultimately will lead to routine colonoscopy screening may depend more on economic issues than medical ones. "The question is," says Sonnenberg, "are we willing to invest resources in the prevention of colorectal cancer?"

--N.S.