Disruption in colonic polypectomy: rocking the trendReferring to Yoshida N et al. p. 871–876
28. August 2019 (online)
Endoscopic resection is well established as first-line management of benign colorectal polyps. Even though a “complete cut” and a “safe cut” are cornerstones of colonoscopic resection, the risk of incomplete resection of large flat polyps is as high as 31 % . Unless we assure high rates of complete (R0) endoscopic resection, patients may continue to be referred to surgery for fear of recurrence and cancer development .
Obtaining an R0 resection is important for many reasons . Beyond the esthetic elegance of presenting a grateful patient with a photo of an en bloc specimen, R0 resection reduces the risk of polyp recurrence, number of surveillance examinations, and progression to cancer. Although recurrence can be managed, endoscopic treatment of recurrent lesions can be technically challenging or end in failure as a result of submucosal fibrosis.
Standard endoscopic mucosal resection (EMR) is readily able to achieve an en bloc resection for colon lesions of < 20 mm in size, whereas larger lesions (> 20 mm) often require piecemeal EMR. Hybrid endoscopic submucosal dissection (ESD) and precutting EMR (EMR-P) could be utilized for en bloc resection of colon lesions of 20 – 30 mm. Hybrid ESD involves a circumferential mucosal incision followed by a limited submucosal dissection and snare resection, whereas EMR-P involves a mucosal incision followed by snare resection. Both procedures are especially relevant in the management of polyps sized 20 – 30 mm, for which standard EMR is unlikely to result in a histologically complete (R0) resection, but for which ESD may be unnecessary from the standpoint of procedural risk and time.
“Hybrid ESD and precutting EMR (EMR-P) make sense from a training standpoint, as a “gateway” toward training in ESD for endoscopists and trainees experienced in EMR.”
We therefore read with interest the study by Yoshida et al., which describes the efficacy of EMR-P on benign colorectal lesions 20 – 30 mm in size, or lesions 10 – 19 mm in size for which standard EMR was difficult (lesions in challenging locations [i. e. right colon or behind folds], flat morphology, poor submucosal lifting, or poor endoscope access) . Either a full or partial circumferential incision was made using the snare tip, although a full circumferential incision was made in the vast majority of the lesions. Using this technique, significant differences were seen in both en bloc and R0 resection rates. Comparing EMR-P vs. standard EMR among “difficult” lesions 10 – 19 mm in size, en bloc and R0 resection rates were 98.0 % vs. 85.7 % and 87.8 % vs. 67.3 %, respectively. Comparing EMR-P vs. standard EMR among lesions 20 – 30 mm in size, en bloc and R0 resection rates were 88.6 % vs. 48.5 % and 71.4 % vs. 42.9 %, respectively. No differences were seen in perforation or post-polypectomy hemorrhage.
EMR-P using the snare tip fundamentally makes sense for polyps of 20 – 30 mm. The endoscopic snare is an instrument that is universally familiar to endoscopists and does not require any additional formal training in its use. Additionally, a full circumferential incision is not necessary for EMR-P to be successful. By guaranteeing the lateral margin, recurrence can be minimized even if the EMR ends up becoming piecemeal.
There are several important points worth highlighting. First, clear delineation of the margins of the lesion, including recognition of a subtle “skirt” around the obvious lesion is critical for en bloc resection, irrespective of the endoscopic resection technique utilized. A study demonstrated that laterally spreading lesions (LSTs) with a skirt were associated with a significantly higher local recurrence rate compared with LSTs without a skirt (11.4 % vs. 2.0 %), especially with piecemeal EMR (66.7 % recurrence with a skirt vs. 14.0 % without a skirt) . On multivariate analysis, the presence of a skirt (odds ratio [OR] 8.29) and piecemeal resection (OR 43.48) were significant predictors of local recurrence. The presence of a skirt may potentially account for high recurrence rates observed after surgical transanal treatment such as transanal resection and transanal endoscopic microsurgery. These findings emphasize the importance of accurate assessment of the margins of the lesion.
Second, studies have demonstrated the benefit of ablating the margins of the resection defect using either argon plasma coagulation or with snare tip soft coagulation, especially when en bloc resection is not achieved . In the event of a partial precut, we recommend ablating the margins, and perhaps additionally marking the uncut borders of the lesion before resecting so that a “skirt” is not inadvertently left behind.
Novel endoscopic tools may also facilitate greater adoption of EMR-P. EMR-P is currently typically performed using a snare or with a standard needle-type ESD knife. However, the snare tip is large and is not easy to manipulate for a full circumferential incision. ESD knives are advantageous in their ability to stabilize and place tension on the mucosal surface during circumferential incision; however, this requires the use of an additional instrument, with associated cost and learning curve. Recently, a novel multifunctional snare (Souten; Kaneka Medics, Tokyo, Japan), was introduced into the Japanese market . The multifunctional snare combines a 1.5 mm needle-knife and knob-shaped tip, attached to the top of an 18.5 mm snare loop, and therefore facilitates EMR-P or hybrid ESD. The gradual dissemination of such devices is likely to allow greater adoption of EMR-P.
Finally, EMR-P makes sense from a training standpoint, as a “gateway” toward training in ESD for endoscopists and trainees experienced in EMR. Current advanced endoscopy fellowships in the United States do not routinely offer exposure or formal training in ESD, although opportunities may exist in selected circumstances . However, advanced endoscopy fellows are routinely involved with EMR. The gradual introduction of EMR-P into the advanced endoscopy fellowship curriculum will enhance the ability of fellows to pursue additional postgraduate training in complex endoscopic resection, including hybrid ESD followed by full ESD.
The bottom line is that EMR-P is disruptive in the current endoscopic resection paradigm for multiple reasons. In addition to the ability to reliably and safely resect lesions of 20 – 30 mm with lower risk of recurrence and higher rate of R0 resection and clean margins, EMR-P serves as a useful gateway into ESD training. However, EMR-P requires the endoscopist to be well trained in optical diagnosis and accurate identification of lesion borders, as there are currently no endoscopic resection techniques that will salvage inadequate endoscopic assessment. EMR-P also requires the endoscopist to understand adjunctive techniques for hemostasis, and ablation of resection margins to reduce recurrence risk. Finally, the introduction of novel devices such as multifunction snares will help facilitate greater adoption of the technique.
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