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Sigmoidoscopy and stool blood tests are the most cost-effective screening tests for colon cancer

Flexible sigmoidoscopy, a screening technique to examine the lining of the last part of the colon, performed every 5 years and the annual stool blood test are the two most cost-effective strategies for colon cancer screening in asymptomatic adults aged 50-85 years. In a study funded by the Agency for Healthcare Research and Quality, Rezaul K. Khandker, Ph.D., and colleagues compared the cost-effectiveness of eight screening strategies based on guidelines published in 1997 by the American Gastroenterological Association.

The cost-effectiveness analysis measured the costs arising from screening against the gains that it yielded, compared with doing no screening. Flexible sigmoidoscopy conducted every 5 years ranked lowest in terms of cost per life-year saved at $12,636 in 1994 dollars, followed by the annual stool test—a technique to detect blood leaking from a polyp or tumor in the colon—at $14,394.

Colonoscopy, a costly procedure that directly examines the entire colon and permits immediate removal of precancerous polyps, is inherently the most effective strategy. The study found that reducing the cost of colonoscopy by 50 percent would make performing this test the second most cost-effective choice if performed every 10 years. The study showed that the appeal of alternative screening strategies was dependent on how many years it took for a polyp in the colon to undergo the genetic changes that transform the growth into cancer.

After sigmoidoscopy every 5 years and the annual stool blood testing, the other strategies, in the order of declining cost-effectiveness under the likeliest assumptions, were sigmoidoscopy every 3 years, double-contrast barium enema every 5 years, colonoscopy every 10 years, annual stool blood testing plus sigmoidoscopy every 5 years, annual stool blood testing plus sigmoidoscopy every 3 years, and colonoscopy every 5 years.

These cost-effectiveness ratios compared favorably with other types of screening. For example, mammography screening for women between the ages of 50 and 69 years had a cost-effectiveness ratio of $21,400 in 1995 dollars. The Pap smear with AutoPap—a computer-assisted rescreening technology—conducted every 2 and 3 years for women aged 20 to 65 years yielded ratios of $42,666 and $16,259, respectively, using 1996 dollars.

For more details, see "A decision model and cost-effectiveness analysis of colorectal cancer screening and surveillance guidelines for average-risk adults," by Dr. Khandker, Jane Dulski, M.P.H., Jeffrey B. Kilpatrick, B.A., and others in the Summer 2000 International Journal of Technology Assessment in Health Care 16, pp. 799-810.

The full report from this study, Cost-Effectiveness Analysis of Colorectal Cancer Screening and Surveillance Guidelines (AHRQ Publication No. 00-R051), is available from the AHRQ Publications Clearinghouse.

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