Rates and Risk Factors of Post-Colonoscopy Colorectal Cancer in a Large, United States Population-based Cohort Study

Colorectal cancer (CRC) is the third leading cause of cancer death in the United States. Colonoscopy can reduce CRC incidence and deaths through removal of precancerous adenomatous polyps (adenomas) and detection of cancer at an earlier, more treatable stage. However, some patients develop CRC after a colonoscopy in which no cancer is diagnosed. The World Endoscopy Organization (WEO) defines post-colonoscopy colorectal cancers (PCCRCs) as CRC diagnosed 6 months after a colonoscopy that did not detect cancer. PCCRC is poorly understood as there is uncertainty about how often these cancers occur, their likely etiologies, the risk factors for these cancers, and whether they are more lethal than detected CRCs. To address these uncertainties, the WEO published a consensus statement to provide comprehensive guidance for the investigation of PCCRC cases. Their recommendations include a standardized definition for PCCRC, a defined method for calculating PCCRC rates, and standardized methods for performing qualitative reviews of cases to determine their likely etiology. The primary goal of the proposed study is to use recently published WEO methods to determine PCCRC rates, the likely etiologies for these cancers, their risk factors, and prognoses for PCCRC in the large integrated healthcare setting of Kaiser Permanente Northern California (KPNC).

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