Objective: Post-colonoscopy colorectal cancer (PCCRC), a cancer occurring within a short interval of a colonoscopy, might be partly explained as missed or incompletely resected lesions. Associated risk factors are age, sex, comorbidity, cancer location, and colonoscopy volume. There is a gap in the knowledge of prevalence of PCCRC and the impact of different risk factors in Sweden.
Methods: This is a retrospective population-based observational cohort study of the colonoscopies performed on adults during the years 2001-2010 that were identified from Swedish health registers. The rate of PCCRC (diagnosed 6-36 months after the first colonoscopy) was defined as the number of PCCRCs divided by the number of colorectal cancers (CRC) in the interval of 0-36 months. Univariate and multivariate Poisson regression analyses examined associations with PCCRC.
Results: There were 289 729 colonoscopies performed on 249 079 individuals included in the study. There were 16 319 individuals with a colorectal cancer diagnosis 0-36 months after a colonoscopy. Of these, 1286 (7.9%) were PCCRCs. In the multivariate analysis, young age (18-30 years) and former polyp diagnosis had the highest risks [relative risk (RR)=3.3; 95% confidence interval: 2.1-5.2 and RR=3.1; 95% confidence interval: 2.7-3.6]. The impact of other risk factors, such as female sex, comorbidity, right sided colorectal cancer location, and time period, was consistent with the finding in other studies.
Conclusion: The prevalence of PCCRC in Sweden seems to be relatively high, indicating that there is room for improvement in colonoscopy quality. The high RR of PCCRC in the youngest age group, even though there were only a few cases, has not been described in other studies.