Anchoring endoscopic mucosal resection for colorectal polyps – keep this weapon in mind

It has been a long time since conventional endoscopic mucosal resection (C-EMR) was launched as a procedure of choice for the treatment of nonpedunculated colorectal polyps; however, for lesions of > 20 mm, piecemeal EMR has been associated with significant incomplete resection rates. The sequence from incomplete resection to colon cancer is well documented in the literature. Therefore, techniques that increase the rate of en bloc R0 resection with EMR are of the utmost importance. To this end, modified EMR techniques such as precutting EMR or anchoring EMR (A-EMR) have been proposed. A-EMR was first described in the last decade [1] [2], but what is this technique and what is its merit? A small incision is created with the tip of the snare in the submucosa of the mucosal area surrounding the polyp. Subsequently, the snare tip is anchored in the defect, with the aim of both preventing slippage of the snare and widening the diameter of the open snare.

So, what is already known about this technique? A multicenter French retrospective study [3] evaluating 141 sessile or flat lesions of 10–30 mm showed that the A-EMR technique was very effective for lesions of 10–20 mm. For lesions of < 20 mm specifically, the en bloc R0 resection was 82.8 %; however, the proportions of en bloc R0 resection were lower for larger lesions, reaching only 50 % for lesions of > 30 mm. Complete transmural perforation was observed in three out of 141 cases, all of which were treated endoscopically. It is worth noting that no perforations occurred with lesions of < 20 mm. Data arising from this study are promising, indicating that A-EMR might be considered as a valuable alternative to endoscopic submucosal dissection (ESD).

“The superiority of anchoring EMR over conventional EMR was even more clear for colorectal lesions of > 15 mm and those located in the right colon.”

Two comparative retrospective studies between A-EMR and C-EMR, one from Korea [4] and another from Japan [5], showed that A-EMR was superior to C-EMR in terms of en bloc R0 resection.

In 2021, a Japanese single-center randomized controlled trial (RCT) [6] was published, showing that A-EMR increased the rate of en bloc resection compared with C-EMR, without increasing the rates of complications. More specifically, 82 patients with noninvasive superficial colorectal neoplasms of 15–25 mm were allocated to the A-EMR or C-EMR groups. The en bloc resection rate was superior in the A-EMR group compared with the C-EMR group (90.2 % vs. 73.1 %; P = 0.04). In terms of R0 resection, no significant differences were observed between A-EMR and C-EMR (73.2 % vs. 58.5 %, respectively; P = 0.19). Furthermore, the final cumulative recurrence rates (2.8 % vs. 5.2 %, respectively) and the rates of adverse events were not significantly different between the two groups.

ESD has been associated with high en bloc R0 resection rates and lower local recurrence rates for large colorectal sessile lesions; however, its technical difficulty, the risk of adverse events, and the prolonged procedural time have discouraged endoscopists worldwide from adopting it as an everyday procedure. Indeed, it would be interesting to investigate a comparison between A-EMR and ESD. For now, this gap is covered by one retrospective study evaluating A-EMR and ESD for 20–30-mm nonpedunculated colorectal neoplasms [7]. As expected, ESD was superior to A-EMR as far as the en bloc (99.3 % vs. 85 %) and R0 resection rates (90.7 % vs. 62.9 %) were concerned, and inferior in terms of the procedural time (60 vs. 8 minutes). Of note, R0 failure in the A-EMR group was mainly due to an indeterminable horizontal margin, which, unlike the vertical margin, has not been associated with local recurrence. Therefore, A-EMR seems to be a promising alternative to ESD for 20–30-mm nonpedunculated colorectal neoplasms.

In this issue of Endoscopy, Oh et al. [8] present valuable data from an RCT of A-EMR vs. C-EMR for 10–25 mm nonpedunculated colorectal polyps. This RCT includes more cases than the previous one [6], with a total of 105 and 106 polyps allocated to the A-EMR and C-EMR groups, respectively. The en bloc resection rate for the A-EMR group was 92.4 % vs. 76.4 % for the C-EMR group (relative risk [RR] 1.21, 95 %CI 1.06–1.37; P = 0.005] and the R0 resection rates were 77.1 % and 64.2 %, respectively (RR 1.18, 95 %CI 0.98–1.42; P = 0.07). In per-protocol analysis, the difference in the R0 removal rate became significant. The superiority of A-EMR was even more clear for colorectal lesions of > 15 mm and those located in the right colon. The difference in the R0 excision rate in this study reached statistical significance in the per-protocol analysis, clearly owing to the larger sample size compared with the previous RCT [6]. No significant differences were observed in terms of complications, and the difference in the procedural times between the two groups was not clinically meaningful. The recurrence rate was not evaluated.

Notably, the perforation rate in the present study was very low (one case in the C-EMR group). Nowadays, many endoscopists, and in particular ESD endoscopists, work more efficiently and safely in the submucosal layer than endoscopists in previous decades. Caution should however be advised in the use of this technique, particularly by less experienced endoscopists. Avoidance of a perforation event is considered critical, even if, in most cases, it is effectively treated endoscopically.

To summarize the advantages of the A-EMR technique, we have to mention its simplicity, high efficacy for lesions of 10–25 mm, lower procedural time compared with ESD, and its low rate of side effects. Additionally, in the days of expensive medicine, it is of vital importance to consider also the low cost of A-EMR in current times. Against this, its disadvantage is mainly its rather low efficacy for sessile polyps of > 30 mm.

For many years, the endoscopy world has been focusing on reducing post-colonoscopy colorectal cancer by improving the colonoscopy procedure and the techniques of colonoscopic polypectomy. Obviously, this cornerstone issue is multifactorial and there is still room for improvement. A-EMR, a simple modification of C-EMR, is another step forward, which increases rather easily the effectiveness of polypectomy for nonpedunculated polyps sized 10–30 mm.

Publication History

Article published online:
08 November 2022

• References

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