Optical assessment of scars after endoscopic mucosal resection of large colorectal polyps in a multicenter, community hospital setting: is routine biopsy still necessary?

Background:  Piecemeal endoscopic mucosal resection (EMR) of large (≥ 20 mm) nonpedunculated colorectal polyps (LNPCPs) is succeeded by a 6-month surveillance endoscopy to evaluate the post-EMR scar for recurrence. Data from expert centers suggest that routine tattoo placement and scar biopsies can be omitted, but data from community hospitals are lacking.

Methods:  The agreement between optical assessment and histological confirmation by routine biopsies was evaluated in a post-hoc analysis of the STAR-LNPCP study (NTR7477), containing prospective data on 6-month post-EMR scar assessments in 30 Dutch community hospitals (October 2019 to May 2022). A standardized protocol was followed for documentation of optical characteristics, imaging, and biopsy of the post-EMR scar. RESULTS : In 1277 post-EMR scar assessments, identification of the scar was achieved in 1215/1277 (95 %). Tattoo placement did not influence scar identification. Scar biopsy was performed in 1050/1215 cases (86 %). Recurrences were seen in 200/1050 cases (19 %). There was good agreement between optical assessment of recurrence and histological confirmation (Cohen's kappa 0.78 [95 %CI 0.73-0.83]). The negative and positive predictive values were 98 % (95 %CI 97 %-99 %) and 74 % (95 %CI 68 %-80 %), respectively. A higher false-positive rate was seen after prior use of clips (11 % vs. 5 %; P = 0.02). Dedicated endoscopists identified the scar more often (96 % vs. 88 %; P < 0.001), and showed a lower optical recurrence miss rate (1 % vs. 3 %; P = 0.11) compared with nondedicated endoscopists. CONCLUSION : Based on this multicenter community hospital study, routine tattoo placement and scar biopsies of the post-EMR scar can be omitted. Assessment of post-EMR scars by dedicated endoscopists is advised.