Characteristics of the colonoscopy rather than those of the adenomas removed during this procedure may be the most important aspects of stratifying a person’s risk for colorectal cancer.

Researchers in Germany reached this conclusion in Annals of Internal Medicine (2012;157[4]:225-232) after conducting a population-based case-control study designed to assess the roles of colonoscopy-related factors and polyp characteristics in the risk for colorectal cancer after colonoscopic polyp detection. Colonoscopy-related factors included incompleteness, poor bowel preparation, incomplete removal of all polyps, and no surveillance colonoscopy within 5 years. Polyp characteristics included polyp size of at least 1 cm, villous components or high-grade dysplasia, the presence of three or more polyps, and the presence of one or more proximal polyps.

A total of 155 of the 3,148 case participants and 260 of the 3,274 control participants had physician-validated polyp detection (other than hyperplastic polyps) at a prior colonoscopy performed in the previous 10 years. Overall, 41.1% of cancer cases were statistically attributable to colonoscopy-related factors and 21.7% to polyp characteristics.


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The following characteristics were significantly more common among case participants than among control participants:

  • Not all polyps were completely removed (29% vs 9.6%).
  • The patient had no surveillance colonoscopy within 5 years (26.5% vs 11.5%).
  • Three or more polyps were detected (14.2% vs 7.3%).