LAUSR

BACKGROUND Pre-resection biopsy (PRB) of large non-pedunculated colorectal polyps (LNPCPs, ≥20mm) is often performed before referral for endoscopic mucosal resection (EMR). How this affects the EMR procedure is unknown. METHODS Retrospective analysis of a prospectively collected cohort of patients with LNPCPs referred for EMR between 2013 to 2016 at an Australian tertiary centre. Outcomes were differences in PRB and EMR histology and effects of PRB on the EMR. RESULTS Amongst 586 LNPCPs, lesions having PRB were larger (median 35mm vs 30mm, P <0.001), and more likely morphologically flat or slightly elevated (P = 0.014). PRB histology was upstaged in 26.1%, down-staged in 13.8% and unchanged in 60.1% after EMR. Sensitivity of PRB was 77.2% (95% CI 71.1-82.4) for low grade dysplasia (LGD) and 21.2% (95% CI 11.5-35.1) for high grade dysplasia (HGD). Where EMR specimen showed HGD, PRB detected LGD in 76.9%. Where EMR specimen showed cancer, PRB detected dysplasia only. PRB was associated with more submucosal fibrosis (P = 0.001) and intra-procedural bleeding (P = 0.033). EMR success or recurrence was not affected. CONCLUSIONS Routine PRB of LNPCP does not reliably detect advanced histology, and may affect EMR complexity. PRB should be utilised with caution in guiding endoscopic management of LNPCPs.