Cancer Biology or Ineffective Surveillance? A multicentre retrospective analysis of colitis-associated post-colonoscopy colorectal cancers.

BACKGROUND AND AIMS: Inflammatory bowel disease (IBD) is associated with high rates of post-colonoscopy colorectal cancer (PCCRC), but further in-depth qualitative analyses are required to determine whether they result from inadequate surveillance or aggressive IBD cancer evolution. METHODS: All IBD patients who had a colorectal cancer (CRC) diagnosed between January 2015 to July 2019 and a recent (<4 years) surveillance colonoscopy at one of four English hospital trusts underwent root cause analyses as recommended by the World Endoscopy Organisation to identify plausible PCCRC causative factors. RESULTS: 61% (n=22/36) of the included IBD CRCs were PCCRCs. They developed in patients with high cancer risk factors (77.8%; n=28/36) requiring annual surveillance, yet 57.1% (n=20/35) had inappropriately delayed surveillance. Most PCCRCs developed in situations where (i) an endoscopically unresectable lesion was detected (40.9%; n=9/22), (ii) there was a deviation from the planned management pathway (40.9%; n=9/22) e.g. service, clinician or patient-related delays in acting on a detected lesion, or (iii) lesions were potentially missed as they were typically located within areas of active inflammation or post-inflammatory change (36.4%; n=8/22). CONCLUSIONS: IBD PCCRC prevention will require more proactive strategies to reduce endoscopic inflammatory burden, improve lesion optical characterisation, adherence to recommended surveillance intervals and patient acceptance of prophylactic colectomy. However, the significant proportion appearing to originate from non-adenomatous-looking mucosa which fail to yield neoplasia on biopsy yet display aggressive cancer evolution highlight the limitations of current surveillance. Emerging molecular biomarkers may play a role in enhancing cancer risk stratification in future clinical practice.