Significant Missed Polyps in the UK Bowel Cancer Screening Programme (BCSP): A Retrospective Analysis of Prevalence and Contributing Factors

Background Colorectal cancer (CRC) remains a significant public health challenge. Patients having abnormal faecal immunochemical test (FIT) results are offered a colonoscopy. The effectiveness of colonoscopies can, however, often be challenged by the occurrence of missed polyps. This study aims to assess the rate of significant missed polyps in the Bowel Cancer Screening Programme (BCSP) in the UK. Methods A retrospective analysis of BSCP screening data in the Cheshire region in the UK from 2020 to March 2023 was conducted. A significant polyp was defined as a polyp ≥ 10mm. The inclusion criteria included patients (age range: 54-74 years) who had had an index colonoscopy followed by site checks, repeats, or planned polypectomies. Results Out of 2,759 index colonoscopies, 261 (9.5%) met our criteria, and 23 (8.8%) of these had significant polyps. Of the 261, the missed polyp rate was 30% (453/1531 polyps). The overall significant missed polyp rate was 1.6% (24/1531). Of the missed polyps, 5% (24/453) were significant polyps. The majority (71%) of the significant polyps were found on the left of the colon. Men had a higher missed polyp rate (22%) compared to women (7%) (relative risk (RR) = 2.56, 95% CI: 2.1-3.13, p<0.0001). They also had a higher significant missed polyp rate (1.1%) compared to women (0.4%) (RR = 2.41, 95% CI: 1-5.8, p<0.05). A total of 50% of the bowel prep at index colonoscopy was rated as 'adequate/fair' and 79% of the bowel prep at the discovery of the significant polyp was rated as either 'excellent' or 'good' (odds ratio (OR) = 3.8, 95% CI: 1.07-13.5, p<0.05); 92% (22/24) of the significant polyps found were either tubular adenoma (TA) low-grade dysplasia (LGD) or tubular villous adenoma (TVA) LGD, and none were found to be cancerous. Conclusions Almost a third of all polyps detected were missed, and one in 20 of these were significant polyps, putting these patients in the high-risk group for CRC. Improving bowel preparation and monitoring patients with multiple polyps could reduce the rate of missed polyps.