More selective colon cancer screening urged

Updated guidance from a US task force stresses the need for targeted, high-quality follow-up screening in patients who have undergone colonoscopy or polyp removal, in an effort to cut down on unnecessary repeat procedures.

The new guidelines from the US Multi-Society Task Force (MSTF) on Colorectal Cancer, published in Gastroenterology, reflect evidence that has emerged since the MSTF's previous report in 2006. In particular, the authors hope they will give doctors confidence to lengthen surveillance intervals in low-risk patients, something that until now they seem reluctant to do.

"During the past 6 years, new evidence has emerged that endorses and strengthens the 2006 recommendations. We believe that a stronger evidence base will improve adherence to the guidelines," say David Lieberman (Oregon Health and Science University, Portland, USA) and colleagues.

The report provides an assessment of the evidence and recommendations for screening based on the number, size, and histology of polyps.

Studies published since 2006 support 10-year screening in patients who have had no adenomas or polyps or those with only distal hyperplastic polyps at baseline, which are considered low-risk adenomas. Contrary to the guidelines, however, a recent survey found that 25% of patients with no adenomas at baseline had undergone a repeat colonoscopy within 5 years, while over 40% with small adenomas had undergone one or more.

The study also supported previous recommendations for high-risk adenomas, for example, those with multiple lesions and those with villous histology, which require shorter screening intervals.

The authors note the need to balance overscreening with underscreening: "Overutilization exposes patients to the cost and risk of unnecessary procedures. Underutilization could result in higher-risk patients developing cancer."

For the first time, the task force provides guidance on screening after detection of serrated polyps, which are precursors to hypermethylated cancers. Sessile serrated polyps of at least 10 mm in size or with cytologic dysplasia should be managed as a high-risk adenoma. However, the evidence for this is still limited and of low quality, highlighting a need for further research.

The report also highlights the limitations of colonoscopy. Most importantly, the authors insist upon the need for high-quality screening and routine assessment of quality in practice. They point to evidence that most interval cancers are due to missed lesions at baseline colonoscopy and of a clear relationship between quality indicators and the risk of interval cancer after colonoscopy.

Lieberman et al. recommend: "All endoscopists monitor key quality indicators as part of a colonoscopy screening and surveillance program."

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