Sessile Serrated Adenoma Detection Rate and Serrated Polyposis Syndrome in a Faecal Immunochemical Test (FIT) Positive Screening Population in the New Zealand Bowel Screening Pilot

Authors List

Byun, U., Auckland City Hospital, Auckland, New Zealand Bissett, I., Auckland City Hospital, Auckland, New Zealand Kramer, N., North Shore Hospital, Auckland, New Zealand Frankish, P., North Shore Hospital, Auckland, New Zealand

Introduction: Colorectal cancer is the second common cause of cancer deaths in New Zealand. Sessile serrated polyps (SSP) are becoming increasingly important with regards to detection and hence quality of screening. Currently, adenoma detection rates (ADR) are better described for faecal immunochemical test (FIT) positive screening populations. More data for SSP detection rate (SSP-DR) and the prevalence of serrated polyposis syndrome (SPS) is needed to set quality indicators for FIT based screening programs.

Aims
: Present ADR and SSP-DR and SPS detected in an asymptomatic, average risk population from the New Zealand Bowel Screening Pilot (BSP) from Rounds one and two; determine correlation between ADR and SSP-DR for individual endoscopists; present pathology.

Methods
: This was a retrospective study of those aged 50 to 75 undergoing FIT (75 ngHb/mL sensitivity) as part of the BSP from January 2012 to December 2015. Participants with positive tests were offered colonoscopy, carried out at a single centre by 29 endoscopists. Each resected polyp was sent in a single pot for histopathological analysis by gastrointestinal pathologists trained to the current WHO classifications of gastrointestinal tumours. Patient demographics and polyp size, location, histopathological type, level of dysplasia were extracted.

Results
: A total of 16397 polyps were resected and analysed from 7467 colonoscopies. ADR was 55.3% and SSL-DR was 11.4%. The adenoma per colonoscopy was 1.33, and SSP per colonoscopy was 0.23. 21 participants fit the criteria for SPS (0.3%). There was poor correlation between an individual’s ADR and SSP-DR.

Conclusions
: While ADR is within international benchmarks and guidelines, our SSP-DR is higher than most of the published SSP-DR in other FIT screening programs. The rate of SPS is similar to international figures. The poor correlation between an individual’s ADR and SSP-DR support the benefit of further training in the detection of sessile lesions which may present differently.

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