Characteristics of post-polypectomy colorectal cancer events and deaths

Post-polypectomy colorectal cancers (PPCRCs) are diagnosed after a cancer-negative colonoscopy with polypectomy. Analyzing PPCRC characteristics informs prevention and early detection strategies. We investigated interval types and etiologies of PPCRCs using World Endoscopy Organization (WEO) guidelines. PPCRCs were identified in a retrospective cohort of U.S. Veterans who underwent colonoscopy with polypectomy 1999-2016. We classified PPCRCs into interval, non-interval type A, non-interval type B, defined as cancers diagnosed before, at, and after next recommended surveillance exam, respectively. A root cause analysis was conducted to determine the most plausible etiology. We identified 396 PPCRC events and 90 PPCRC deaths over a median follow-up of 3.9 and 4.2 years, respectively. Among PPCRC events, 55% (95% CI: 50%, 60%) were interval, 12% (CI: 9%, 15%) non-interval type A and 33% (CI: 29%, 38%) non-interval type B. Interval cancers were more likely to be diagnosed at stage 4 than non-interval cancers (16% interval vs 2.1% non-interval A, 8.3% non-interval B, p = 0.003). Most interval cancers were due to possible missed lesions with adequate examinations (60%, CI: 53%, 66%), while most non-interval cancers were likely new CRCs (type A: 48%, CI: 34%, 62%; type B: 84%, CI: 77%, 90%). Similar results were found for PPCRC deaths. Most PPCRC events and deaths were diagnosed before the next recommended exam, largely due to procedural factors, underscoring the need to optimize quality of baseline colonoscopy and polypectomy. Many PPCRCs were diagnosed after recommended exam, suggesting the need to improve patient adherence to recommended surveillance intervals.