How often to screen for colon cancer? NEJM study finds 5-year risk extremely low

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Regenstrief Institute, Inc.

How frequently should symptom-free individuals at average risk for colon cancer undergo screening with colonoscopy? In a study published in the Sept. 18, 2008, New England Journal of Medicine, researchers led by Thomas F. Imperiale, M.D., of the Indiana University School of Medicine and the Regenstrief Institute, report that while there still is no definitive answer to the question, they now know the procedure need not be performed any sooner than every five years. This is the first large study to systematically rescreen a group of average risk individuals who had normal findings from an initial colonoscopy. The rescreening showed that after five years they remained cancer free.

All 1,256 participants in the study were 50 years or older, had undergone a first-time screening with no cancer or pre-cancerous findings, and had no symptoms of colon cancer such as rectal bleeding, change of bowel habits or unexplained weight loss during the 5 year interval between screenings.

"The American Cancer Society and other guideline organizations call for colonoscopic screenings every 10 years but these recommendations are based on extrapolated, indirect data. No study has rescreened a large number of individuals ten years after a normal initial colonoscopy. Our study didn't assess whether the recommendation of 10-year screening interval for colonoscopy is 'right on' but we did determine that the appropriate screening interval can be more than 5 years for average risk individuals. Frankly, we don't know the optimal time interval between screenings," said Dr. Imperiale, who is a gastroenterologist and begins to discuss rescreening with his own patients 7 to 8 years after a previous normal exam unless they develop symptoms or have a family history of colon cancer in a first-degree relative.

The risk of colon cancer increases with age. Changes in lifestyle behaviors such as smoking, alcohol consumption and physical activity also can affect risk.

"I try to tailor my rescreening recommendation to the individual patient. The interval and what rescreening method to use – colonoscopy, virtual colonoscopy, fecal occult blood testing -- are all factors we discuss, said Dr. Imperiale, who is a professor of medicine at the IU School of Medicine and a member of the Indiana University Melvin and Bren Simon Cancer Center.

"Determination of the appropriate frequency of rescreening for persons with normal findings on initial screening colonoscopy could have a substantial effect on the cost of colonoscopy and the capacity to provide it," the study notes. And, adds Dr. Imperiale, who is a clinical epidemiologist and an affiliate investigator of the Center on Implementing Evidence-based Practices at the Roudebush VA Medical Center, it may impact the likelihood that individuals will return for rescreening.

According to the American Cancer Society, "colorectal cancer is the third leading cause of cancer-related deaths in the United States when men and women are considered separately, and the second leading cause when both sexes are combined. It is expected to cause about 49,960 deaths (24,260 men and 25,700 women) during 2008."

Source: Indiana University