POEM : Latest Updates

The first esophageal peroral endoscopic myotomy (POEM) series was reported in 2010 by Professor Harohiro Inoue. Seven years later, more than 7,000 procedures have been performed worldwide culminating in a recent AGA Clinical Practice Update stating, “if the expertise is available, POEM should be considered as a treatment option comparable with laparoscopic Heller myotomy for any of the achalasia syndromes,” and “POEM should be considered as primary therapy for type III achalasia.” POEM is currently performed world-wide by gastroenterologists and surgical endoscopists with reliable and consistent outcomes in terms of clinical efficacy and safety. Overall, studies have reported success in 80 to 100 percent of patients in the short term. An emerging body of literature suggests that the medium-term (greater than two to five years) efficacy is maintained in the majority of patients (about 80 to 85 percent). Long-term efficacy (greater than five to 10 years) is not yet known. Retrospective and cohort studies have also suggested that efficacy and safety is comparable to Heller myotomy with better perioperative outcomes in terms of post-operative pain and return to activities of daily living. Abnormal esophageal acid exposure occurs in up to 60 percent of patients after POEM.

The results from the first randomized trial of POEM versus pneumatic dilation were reported during Digestive Disease Week® (DDW) 2017 in Chicago. A total of 133 patients with treatment-naïve achalasia were randomized to either POEM (n=67) or pneumatic dilation (n=66). At one-year follow-up, clinical response was significantly higher in the POEM group (92.2 percent vs. 70 percent, p<0.01). One perforation occurred in the pneumatic dilation group and was treated with endoscopic suturing, while there were no severe adverse events in the POEM group. Endoscopy performed off proton pump inhibitors (PPIs) revealed significantly higher incidence of esophagitis in the POEM group (40 percent grade A/B, 8.3 percent grade C/D vs. 13.1 percent grade A/B, 0 percent grade C/D, p=0.02). Results from other randomized trials are awaited, including a comparative trial of POEM vs. Heller myotomy and our trial of POEM using anterior approach versus posterior approach.

The positive outcomes of esophageal POEM have resulted in a new application of the procedure (performed in the stomach) for the treatment of some patients with gastroparesis with symptoms refractory to dietary and medical therapy.

The largest report on POEM was recently published and aimed to study (1) the prevalence of adverse events and (2) factors associated with occurrence of adverse events in patients undergoing POEM.1 A total of 1,826 patients underwent POEM. Overall, 156 adverse events occurred in 137 patients (7.5 percent). A total of 51 (2.8 percent) inadvertent mucosotomies occurred. Mild, moderate and severe adverse events had a frequency of 116 (6.4 percent), 31 (1.7 percent) and nine (0.5 percent), respectively. Multivariable analysis demonstrated that sigmoid-type esophagus (odds ratio (OR) 2.28, P=0.05), endoscopist experience less than 20 cases (OR 1.98, P=0.04), use of a triangular tip knife (OR 3.22, P=0.05) and use of an electrosurgical current different than spray coagulation (OR 3.09, P=0.02) were significantly associated with the occurrence of adverse events. This large study comprehensively assessed the safety of POEM and highly suggests POEM as a relatively safe procedure when performed by experts at tertiary centers.

The positive outcomes of esophageal POEM have resulted in a new application of the procedure (performed in the stomach) for the treatment of some patients with gastroparesis with symptoms refractory to dietary and medical therapy. The first gastric POEM (G-POEM), or endoscopic pyloromyotomy, was reported by us in 2013. The procedure is also based on principles of submucosal endoscopy and follows the same steps as with esophageal POEM: mucosal incision, submucosal tunneling, myotomy and mucosal closure. A multicenter study that included 30 gastroparetic patients was reported by Khashab et al. with a technical success of 100 percent and minimal adverse events, and an 86 percent clinical response.2 In addition, there was improvement in the majority of the gastric emptying studies with complete normalization in 47 percent of the patients. The only prospective study to date was recently reported by Gonzalez et al.3 A total of 29 patients underwent G-POEM with 100 percent technical success and clinical success of 79 percent at three months and 69 percent at six months. Gastric emptying normalized in 70 percent of the cases.

These early results suggest that G-POEM may play a role in a subset of patients with difficult-to-treat gastroparesis. It is believed that gastroparetic patients with pylorospasm will be mostly appropriate for G-POEM and, as such, the most pressing current need is the accurate identification of such patients. Emerging data on the role of impedance planimetry using Flip® (functional lumen imaging probe) (Crospon, Ireland) suggests its potential in the identification of a distinct subset of patients with decreased pyloric distensibility. Whether this information will lead to more tailored therapy and selection of a clinical subset that may more readily benefit from G-POEM remains to be seen and further investigation is ongoing.

Dr. Khashab is a consultant and serves on the medical advisory board for Boston Scientific and Olympus.

1. Haito-Chavez, Y., Inoue, H., Beard, K.W. et al, Comprehensive Analysis of Adverse Events Associated With Per Oral Endoscopic Myotomy in 1826 Patients: An International Multicenter Study. Am J Gastroenterol. 2017;112:1267-1276.
2. Khashab, M.A., Ngamruengphong, S., Carr-Locke, D. et al, Gastric per-oral endoscopic myotomy for refractory gastroparesis: results from the first multicenter study on endoscopic pyloromyotomy (with video). AGastrointest Endosc. 2017;85:123-128.
3. Gonzalez, J.M., Benezech, A., Vitton, V. et al, G-POEM with antro-pyloromyotomy for the treatment of refractory gastroparesis: mid-term follow-up and factors predicting outcome. Aliment Pharmacol Ther. 2017;46:364-370.
4. Kumbhari, V., Familiari, P., Bjerregaard, N.C. et al, Gastroesophageal reflux after peroral endoscopic myotomy: a multicenter casecontrol study. Endoscopy. 2017;49:634-642.

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