Other tests may be effective for rescreening after initial colonoscopy is negative

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A new modeling study has found that people who undergo colonoscopy at age 50 years in which no precancerous polyps are found can be rescreened at age 60 years with one of three alternative methods, rather than undergoing colonoscopy every 10 years, without affecting their life expectancy. The alternative screening methods are highly sensitive fecal occult blood testing (HSFOBT), fecal immunochemical testing (FIT), or computed tomographic colonography (CTC, also known as virtual colonoscopy). Using these alternative methods would also cause fewer complications and cost less.

Most current guidelines recommend rescreening with colonoscopy 10 years after an initial negative colonoscopy. However, those recommendations are not based on reports from randomized trials. “There are ongoing trials of colonoscopy, but none of them have reported results yet,” said lead author Amy Knudsen, PhD, of Massachusetts General Hospital.

The researchers used a model called SimCRC, which was the model used to inform the 2008 update of the United States Preventive Services Task Force guidelines on colorectal cancer screening. The investigators used the model to simulate five different rescreening strategies:  no further screening, colonoscopy every 10 years, HSFOBT every year, FIT every year, or CTC every 5 years.

Two adherence scenarios were evaluated: one in which people received the tests as scheduled (perfect adherence) and one that mimicked real-life adherence, as recorded in several published studies (imperfect adherence).

The results were the same in both scenarios: all four rescreening methods reduced the number of deaths from colorectal cancer compared with no rescreening, and the difference among the four methods was small. For example, the imperfect-adherence scenario yielded between 6.1 and 6.7 deaths per 1,000 persons for all four screening methods.

Rescreening with colonoscopy produced the highest rates of perforation, meaning tears in the colon, along with other complications, and it was also the most expensive strategy. Rescreening with one of the other three screening methods produced lifetime savings of up to $495 per person, compared with imperfect adherence with colonoscopy. At a population level, these savings could add up to nearly $3 billion for HSFOBT or FIT, and $0.6 billion for CTC, over the lifetimes of the estimated 6.5 million people who had negative colonoscopy results in 2008.

“Models can be helpful to inform [population] guidelines overall. On an individual level, decisions should be made in consultation with one's doctor," concluded Knudsen.

This study was published in the Annals of Internal Medicine (2012;157(9):611-620).
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