The advancements in endoscopic resection techniques have resulted in the shift from radical surgery to minimally invasive and organ-sparing endoscopic resection techniques, such as ESD and EMR, for the treatment of colorectal lesions. With reference to 2015 ESGE guidelines, ESD should be considered for colorectal lesions larger than 20mm, with high suspicion of submucosal invasion, or those where en bloc resection by EMR are not feasible.6 Previous meta-analyses comparing ESD and EMR for colorectal polyps primarily reported data from Asian countries, with 72.7% of the published studies from Japan.7 Since then, several retrospective and prospective studies comparing ESD and EMR for the treatment of colorectal polyps have been published outside of Japan. The present study is the most extensive meta-analysis evaluating the surgical, histological, and oncological outcomes of ESD in comparison to EMR in the treatment of colorectal polyps. Nine out of 21 studies (42.9%) on colorectal polyps included in this meta-analysis were conducted in countries outside of Japan. While ESD has been known to provide significantly better resection outcomes and lower recurrence rate, our analysis found that polyp size and depth of invasion did not significantly influence the en bloc and complete resection rate, bleeding and perforation risk, and recurrence rate in colorectal polyps that was not previously reported. Additionally, previous reviews were confined only to sessile lesions larger than 20mm.7, 8 Our analysis also showed the increased proficiency in performing ESD and EMR in Japan as compared to the rest of the world.
Consistent with previous studies, ESD showed benefits in the technical, histological, and oncological outcomes. Pooled analysis showed higher rates of en bloc resection and complete resection in ESD than in EMR albeit significant publication bias (p=0.0025). En bloc resection offers the technical advantage of removing the entire pathologic specimen, thus allowing for detailed histologic evaluation. This results in an increase in the complete resection rate which in turn reduces the recurrence rate. Therefore, en bloc resection with ESD is favored as it provides curative treatment without the need for surgery for lesions with significant likelihood of submucosal invasion.39 However, the advantages of ESD come at the expense of longer procedural time, additional surgical operations, and increased perforation risk compared to EMR.7 The high rate of additional surgical operations for ESD is presumed to be due to the aggressive selection of ESD for T1 lesions. Although the perforation risk was higher with ESD, most perforations in the studies included were treated conservatively or endoscopically using endoclips.10, 13, 32, 34, 35, 38
Meta-regression was performed to assess the risk factors that affect surgical, histological, and oncological outcomes. Our present analysis showed that polyp size did not affect the risk of perforation, which was reported otherwise in studies by Kim et al and Hong et al.40, 41 Polyp size and depth of invasion were also not associated with significant change in en bloc and complete resection rate, risk of bleeding, and recurrence between ESD and EMR. Furthermore, the en bloc resection rate (before RR=1.837, 95% CI 1.464 to 2.305, p< 0.001; after RR=1.932, 95% CI 1.389 to 2.688, p<0.001) and recurrence rate (before RR=0.269, 95% CI 0.112 to 0.648, p=0.003; after RR=0.191, 95% CI 0.085 to 0.431; p<0.001) appeared comparable before and after the sensitivity analysis to ≥20mm polyps. Instead, the risk of perforation was increased in patients with right colonic polyps and this was consistent with previous study which identified the technical difficulty and proficient endoscopic skills required to remove polyps from right colon safely.42 As such, training should ensure endoscopists achieve procedural proficiency in left sided lesions before proceeding to attempt right sided lesions. Other factors including polyp size and depth of invasion are less important criteria when deciding between EMR and ESD in skilled tertiary centers.
Despite the advantages of ESD, the data regarding the efficacy of colorectal ESD have been inconsistent and vary between Japan and the rest of the world. One of the reasons is the limitations to the implementation of ESD in other countries, which are in part due to the lack of expertise and training centers. To date, no meta-analysis comparing ESD and EMR between Japan and the rest of the world have been performed. Our single arm meta-analysis found that Japan performed better than the rest of the world in ESD and EMR. Significantly, perforation is a major concern in ESD. The perforation risk of ESD and EMR was 4% and 0.0002%, respectively in Japan, and 8% and 1%, respectively in the rest of the world. While there is an observed increase risk of perforation from Japan only studies (RR=9.586) compared to the rest of the world (RR=4.602), even after sensitivity analysis, the risk of perforation for ESD was only statistically higher in Japan only studies due to the very low risk of perforation in EMR in Japan. In addition, the challenges of doing ESD in difficult could have resulted in the higher perforation rate in ESD compared with EMR in Japan. Another important factor to consider is the recurrence rate of ESD and EMR which was 1% and 7%, respectively in Japan and 3% and 27%, respectively in the rest of the world following sensitivity analysis. The observed increase in recurrence rate from Japan only studies (RR=0.204) compared to the rest of the world (RR=0.179) was due to the much lower recurrence rate of EMR in Japan as compared to the rest of the world. Overall, our results seem to favor studies from Japan and are in tandem with a single arm analysis of ESD only procedures with subgroup on region efficacy43. However, most of the studies originating from the rest of the world should be interpreted with the understanding that these studies are mainly from tertiary centers and the results may not be generalized to non-tertiary centers.
The potential of ESD resection is limited by the difficulty in conducting the procedure as the length of procedure for ESD even when performed by experienced endoscopists can be three times longer than that for EMR.44 However, the advancement in endoscopic resection equipment has been shown to shorten the procedure time despite a relatively short training duration.45 Using the cumulative sum (CUSUM) method, Miyakawa et al recently reported the use of Stag-Beetle Knife Jr for ESD in a Japan single-center study generated good learning curve to achieve satisfactory resection speed (min/cm2), which allowed the acquisition of proficient and safe skills within 120 cases.45 Other alternatives to ESD do exist, such as hybrid ESD and pre-cut EMR. This hybrid approach has been shown to have lower en bloc resection rate (68.4% vs 91.0%) and complete resection rate (60.6% vs 82.9%) than conventional ESD.43 Currently, underwater EMR has been thought to be a safe and effective method with higher rate of en bloc resection and lower rate of recurrence,46 but no head-to-head comparisons have been done between UMER and ESD.
Strengths and Limitations
The inclusion of 21 studies with a total of 281,344 polyps based on our search strategy and inclusion criteria represents the most extensive meta-analysis on this issue. However, as no randomized controlled trials comparing the performance between EMR and ESD have yet been conducted, this highlights the need for a randomized study to better understand the efficacy and safety of these techniques in the management of colorectal polyps. The evaluation of heterogeneity allowed us to compare the significant differences in the performance of ESD and EMR between Japan and the rest of the world.
Our meta-analysis has some limitations. While we aimed to decrease heterogeneity, the included articles used a variety of EMR techniques including standard EMR, piecemeal EMR (EPMR), EMR with small incision, EMR-precutting (EMR-P) and EMR-circumferential incision (EMR-CI). This, however, was an acceptable confounding factor in previous meta-analysis analysis. Also, a major factor that we were unable to regress for was the procedural skills of each centers. ESD and EMR are largely operator dependent and we were only able to account for it in a subgroup analysis comparing between studies conducted in Japan and the rest of the world.