Depth of the cutting plane with underwater and conventional endoscopic mucosal resection: Post-hoc analysis of a randomized study

BACKGROUND AND AIM

A multicenter randomized controlled trial reported a better R0 resection rate for intermediate-sized (10-20 mm) colorectal polyps with underwater endoscopic mucosal resection (UEMR) than conventional endoscopic mucosal resection (CEMR). To clarify whether UEMR removes enough submucosal tissue in the removal of unpredictable invasive cancers, we investigated the cutting plane depth with UEMR versus CEMR.

METHODS

This was a post-hoc analysis of a randomized controlled trial in which 210 intermediate-sized colorectal polyps were removed in five Japanese hospitals. One pathologist and two gastroenterologists independently reviewed all resected specimens and measured the cutting plane depth. The cutting plane depth was evaluated as (i) maximum depth of submucosal layer and (ii) mean depth of submucosal layer, calculated using a virtual pathology system.

RESULTS

We identified 168 appropriate specimens for the evaluation of the cutting plane depth, resected by UEMR (n = 88) and CEMR (n = 80). The median resection depth was not significantly different between UEMR and CEMR specimens, regardless of the measurement method ([i] 1317 vs 1290 μm, P = 0.52; [ii] 619 vs 545 μm, P = 0.32). All specimens in the UEMR and CEMR groups contained substantial submucosa and no muscularis propria.

CONCLUSIONS

The cutting plane depth with UEMR was comparable with that with CEMR. UEMR can be a viable alternative method that adequately resects the submucosal layer for the histopathological assessment of unpredictable submucosal invasive cancers.

Resection depth and layer of cold snare polypectomy versus endoscopic mucosal resection

BACKGROUND

Cold snare polypectomy (CSP) has not undergone sufficient histopathological evaluation. This study aimed to clarify the histopathological features of CSP specimens, including resection depth and layer, as compared with endoscopic mucosal resection (EMR).

METHODS

Polyps were recruited retrospectively. Sessile, semi-pedunculated, and 0-IIa polyps of ≤ 9 mm were selected by propensity score matching and classified as either a complete resection or one with an unevaluable/positive (X/+) margin. Resection depth and layer were estimated and the risk factors for an X/+ margin were evaluated.

RESULTS

A total of 1072 polyps were enrolled. After matching, 184 polyp pairs were selected. An X/+ margin was seen in 105/184 (57%) vs. 70/184 (38%) CSP vs. EMR specimens (p < 0.001): specimen damage was 53/184 (29%) vs. 30/184 (16%) (p < 0.01) and vertical margin (VM) X/+ was 11/184 (6%) vs. 2/184 (1%) (p < 0.05). Among 193 completely resected specimens, resection depth from the muscularis mucosae in CSP vs. EMR was 76 vs. 338 µm (p < 0.001) and resection layer was the submucosa in 7/79 (9%) vs. 105/114 (92%) (p < 0.001). In multivariate analysis, CSP was a risk factor for procedure-associated VMX/+ [odds ratio (OR) 6.80, 95% confidence interval (CI) 1.33-34.69, p < 0.05]. Sessile serrated adenoma/polyp (SSA/P) was a risk factor for VMX/+ margin in CSP specimens (OR 58.36, 95% CI 7.45-456.96, p < 0.001).

CONCLUSIONS

SSA/P and colorectal cancer may not be suitable for CSP adoption.