Post written by Theodore A. Tollivoro, MD, from the Division of Research, Kaiser Permanente Northern California, Oakland, California, USA.

Over the last 20 years, we have realized the importance of quality metrics as they apply to colonoscopic exam. We track physician adenoma detection rates, cecal intubation rates, and ensure our patients undergo exams with optimal bowel preparations. However, despite these advances, we remain plagued and paranoid by the patient who develops colon cancer after an index colonoscopy. In this study, we sought to identify index colonoscopy-related risk factors associated with the development of postcolonoscopy colorectal cancers (PCCRCs), which we defined as any cancer that developed >1 year and up to 10 years following a colonoscopy negative for such.

Working in a large community-based integrated health system provided us the benefit of capturing over 1200 PCCRCs and comparing them to matched cancer-free controls. By identifying potentially modifiable risk factors related to colonoscopy surveillance, exam completeness, and polyp resection, we hope to highlight targets for increasing the effectiveness of colonoscopy screening.

We found that the 3significant index exam-related risk factors for PCCRC were detection of a polyp ≥10 mm, incomplete colonoscopy, and detection of an adenoma regardless of size. In a secondary analysis, we stratified PCCRCs as early if the cancer was diagnosed within 12-36 months of the index exam. Early PCCRCs were associated with incomplete excision of a polyp in the segment in which the subsequent cancer was diagnosed, failure to examine the segment in which the cancer was diagnosed, and a ≥10-mm polyp in the colon segment in which the cancer was diagnosed. Remarkably, almost half of the cases (559) had 1 or more risk factors significant for PCCRC. Our data suggest that improvements in colonoscopy quality, particularly as related to complete examinations and excision of polyps, may substantially reduce the burden of PCCRC.

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