Post-colonoscopy colorectal cancers identified by probabilistic and deterministic linkage: Results in an Australian prospective cohort

Objective Post-colonoscopy colorectal cancers (PCCRCs) are recognised as a critical quality indicator. Benchmarking of PCCRC rate has been hampered by the strong influence of different definitions and methodologies. We adopted a rigorous methodology with high-detail individual data to determine PCCRC rates in a prospective cohort representing a single jurisdiction. Setting We performed a cohort study of individuals who underwent colonoscopy between 2001 and 2008 at a single centre serving Australian Capital Territory (ACT) and enclaving New South Wales (NSW) region. These individuals were linked to subsequent colorectal cancer (CRC) diagnosis, within 5 years of a negative colonoscopy, through regional cancer registries and hospital records using probabilistic and deterministic record linkage. All cases were verified by pathology review. Predictors of PCCRCs were extracted. Participants 7818 individuals had a colonoscopy in the cohort. Linkage to cancer registries detected 384 and 98 CRCs for notification dates of 2001-2013 (ACT) and 2001-2010 (NSW). A further 55 CRCs were identified from a search of electronic medical records using International Classification of Diseases-10 diagnosis codes. After verification and exclusions, 385/537 CRCs (58% male) were included. Primary outcome measure PCCRC rates. Results There were 15 PCCRCs in our cohort. The PCCRC incidence rate was 0.384/1000 person-years and the 5-year PCCRC risk was estimated as 0.192% (95% CI 0.095 to 0.289). The index colonoscopy prior to PCCRC was more likely to show diverticulosis (p=0.017 for association, OR 3.56, p=0.014) and have poor bowel preparation (p=0.017 for association, OR 4.19, p=0.009). Conclusion In this population-based cohort study, the PCCRC incidence rate was 0.384/1000 person-years and the 5-year PCCRC risk was 0.192%. These data show the a € real world' accuracy of colonoscopy for CRC exclusion.