A twelve-year study of the prevalence, risk factors and characteristics of interval colorectal cancers after negative colonoscopy

INTRODUCTION

The objective of our study was to describe and analyse the Post-Colonoscopy Colorectal Cancers (PCCRCs) and endoscopist performance-related risk factors in the Isère regional screening programme.

METHOD

This was a population-based retrospective cohort study between 2002-2013, where Post-Colonoscopy Colorectal Cancers (PCCRCs) were defined as colorectal adenocarcinoma diagnosed between six and sixty months post-colonoscopy following a positive gFOBT. We analysed the endoscopist performance-related risk factors of the 62 gastroenterologists who had carried out at least 30 colonoscopies during this period.

RESULTS

During the period reviewed, there were 10,557 negative colonoscopies performed. Fifteen post-colonoscopy colorectal cancers were diagnosed from 2002-2013 with an average patient age of 67.1 years. Men comprised 73% of the cases and 53% of all the cases were found in the distal colon. These 15 cases comprised 1.1% of all Colorectal Cancers (CRCs) diagnosed in the screening programme, with an incidence rate of 0.42 (0.21-0.77) per 1,000 person-years. The aetiological breakdown was as follows: 47% related to missed cancers, 27% were new cancers, 20% were failed biopsy detection, and 6% related to incomplete removal. The Adenoma Detection Rate (ADR) among gastroenterologists was an average of 30%, but large heterogeneity was present within this number, ranging from 11% to 49%.

CONCLUSION

The post-colonoscopy colorectal cancer prevalence and incident rate were low relative to the literature. However, significant heterogeneity was present in the adenoma detection rate. Decreasing this heterogeneity by establishing a national benchmark, regular performance feedback and training modules should homogenise adenoma detection rates and decrease the number of interval cancers in the region.