Epidemiology, characteristics and survival of post‐colonoscopy colorectal cancer in Asia: a population‐based study

Abstract

BACKGROUND AND AIMS: Population-based studies on post-colonoscopy colorectal cancer (CRC) from Asia are sparse. We aimed to determine the characteristics and predictive factors and survival of post-colonoscopy CRC in Hong Kong. METHODS: This is a territory-wide retrospective cohort study. Patients aged ≥40 years with colonoscopies performed between 2005 and 2013 without history of CRCs, inflammatory bowel disease and prior colectomy were included. Post-colonoscopy colorectal cancer for an interval of 3 years (PCCRC-3y) was defined as CRC diagnosed between 6 and 36 months after index colonoscopy, whereas CRC diagnosed within 6 months of index colonoscopy was regarded as 'detected CRC'. We used multivariable logistic regression to derive adjusted odds ratio (aOR) of PCCRC-3y, and Cox model for adjusted hazard ratio (aHR) of cancer-specific mortality after CRC diagnosis. RESULTS: Of the 197,902 eligible patients, 10,005 (92.1%) were detected CRC and 854 (7.9%) PCCRC-3y. The median age at PCCRC-3y diagnosis was 75.9 years (IQR: 65.5-83.8) - a delay of 1.2 years (IQR:0.8-1.9) from index colonoscopy, and 60.1% were male. Predictive factors for PCCRC-3y included older age (aOR:1.07), male sex (aOR:1.45), history of colonic polyps (aOR:1.31), polypectomy/biopsy at index colonoscopy (aOR:3.97), surgical endoscopists (aOR:1.53) and a higher center annual endoscopy volume. Independent predictive factors for cancer-specific mortality after CRC diagnosis included PCCRC-3y (aHR:1.32), proximal cancer location (aHR:1.80) and certain patient factors. CONCLUSION: The PCCRC-3y rate was 7.9% in Hong Kong, with a high proportion (>80%) of distal cancers and a higher cancer-specific mortality compared to detected CRC.