Effect of pre-resection biopsy on detection of advanced dysplasia in large nonpedunculated colorectal polyps undergoing endoscopic mucosal resection.

BACKGROUND : Pre-resection biopsy (PRB) of large nonpedunculated colorectal polyps (LNPCPs, ≥ 20 mm) is often performed before referral for endoscopic mucosal resection (EMR). How this affects the EMR procedure is unknown. METHODS : This was a retrospective analysis of a prospectively collected cohort of patients with LNPCPs referred for EMR between 2013 to 2016 at an Australian tertiary center. Outcomes were differences between PRB and EMR histology, and effects of PRB on the EMR procedure. RESULTS:  Among 586 LNPCPs, lesions that underwent PRB were larger (median 35 vs. 30 mm;  < 0.007), and more commonly morphologically flat or slightly elevated ( = 0.01) compared with lesions without PRB. PRB histology was upstaged in 26.1 %, downstaged 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 had detected LGD in 76.9 %. Where EMR specimen showed cancer, PRB had detected dysplasia only. PRB was associated with more submucosal fibrosis ( = 0.001) and intraprocedural bleeding ( = 0.03). EMR success or recurrence was not affected. CONCLUSIONS:  Routine PRB of LNPCP did not reliably detect advanced histology and may have affected EMR complexity. PRB should be utilized with caution in guiding endoscopic management of LNPCPs.