Trends in pathology diagnoses during 10 years of a colorectal cancer screening programme

Aims: We report pathology findings from the first 10 years of the faecal-occult blood-based Northern Ireland Bowel Cancer Screening Programme, presenting summary data and trends in pathology diagnoses and clinicopathological features of screen-detected cancers.

Methods and results: Data were analysed from a comprehensive polyp-level pathology database representing all endoscopy specimens from programme inception in 2010 until 2021. A total of 9800 individuals underwent 13 472 endoscopy procedures, yielding 25 967 pathology specimens and 32 119 diagnoses. Index specimen diagnoses (4.1%) and index colonoscopies (10.4%) yielded a diagnosis of colorectal cancer, representing 1045 cancers from 1020 individuals (25 with synchronous cancers). A further 13 index cancers were identified via computed tomography colonography; 65.3% of cancer diagnoses were in males; 41.7% were stage I, 23.1% stage II, 25.8% stage III and 1.8% stage IV (7.6% unstaged). Of 233 pT1 cancers diagnosed within local excision specimens, 79 (33.9%) had completion surgery. Ten-year trends showed a steady decline in the proportion of index colonoscopies that yielded a diagnosis of cancer (14.7% in year 1; 4.8% in year 11) or advanced colorectal polyp. There was a strong upward trend in diagnoses of sessile serrated lesions, which overtook hyperplastic polyps in proportions of total index diagnoses by the end of the study time-frame (8.7% compared to 8.5%).

Conclusions: Over the first 10 years of a population colorectal cancer screening programme, 'real world' pathology data demonstrate success in the form of reduced diagnoses of cancer and advanced colorectal polyp with passage of successive screening rounds. Interesting trends with respect to serrated polyp diagnoses are also evident, probably related to pathologist and endoscopist behaviour.