Peroral endoscopic myotomy: ready for prime time in all achalasia patients?

 

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It was 10 years ago that the first endoscopic myotomies, performed in four pigs, were described by Pasricha et al. [1]. Inoue refined the technique, and in 2010 he described in this journal the excellent results of the procedure in the first 17 patients with achalasia; it was the first time the abbreviation POEM was used for peroral endoscopic myotomy [2]. His enthusiasm, the elegance of the technique, and the excellent results have led to a rapid uptake of the technique worldwide. POEM is the first natural orifice transluminal endoscopic surgery technique with the potential to become a routine treatment, albeit for a rare disease.

The paper by Akintoye et al. published in this issue of Endoscopy describes the pooled results of 2373 patients from 36 case series, and makes clear that the technique is indeed encouraging and safe [3]. The analysis showed that, without exception, POEM was extremely successful. Short-term clinical success, defined in nearly all studies as having an Eckardt score of 3 or less, was obtained in 98 % of the patients. There were also significant reductions seen in objective outcomes, such as lower esophageal sphincter pressures on manometry and stasis on timed barium esophagogram.

The analysis also showed that POEM is safe and that severe complications are rare. Perforation and major bleeding were both encountered in 0.2 % of cases. Mucosal injury was seen in 4.8 %, pneumoperitoneum in 6.8 %, and subcutaneous emphysema in 7.5 %, but these were generally without consequences. POEM thus seems very safe despite the fact that it is a new technique and most cases described were among the first cases performed by individual endoscopists. Nevertheless, it should be borne in mind that these case series are generally the result of pioneering centers with expert endoscopists performing these procedures, who are, perhaps, less likely to produce complications [4].

One of the concerns of POEM is reflux. After successful treatment of achalasia, regardless of the technique that was used, the high-pressure zone at the esophagogastic junction (EGJ) is diminished so that swallowed foods can traverse the aperistaltic esophagus and reach the stomach; gravity is the only driving force. It may be no surprise, therefore, that the condition of the EGJ after transection or dilation of the lower esophageal sphincter is a serious risk factor for the development of reflux disease. Reflux of gastric content can occur freely as the EGJ is no longer an effective antireflux barrier. Indeed Akintoye et al. describe abnormally high acid exposure in 47 % of patients. Although in achalasia, acid exposure is not always caused by reflux but can also indicate stasis and the subsequent acidification of stagnant food in the esophagus, the high prevalence of pathological acid exposure will definitely lead to frequent reflux esophagitis and reflux symptoms in the longer term, particularly when patients regain weight, as this will increase the gastroesophageal pressure gradient and drive reflux even more. The risk of reflux symptoms should however be seen in the context of the condition patients were in before treatment. Most patients are delighted that they can eat again after treatment, and they often regard reflux symptoms as a minor problem that is usually treated easily with oral acid suppressants.

Is POEM thus ready for prime time in all patients with achalasia? POEM has been shown to be effective in achalasia patients who have never been treated before, but also in patients in whom previous botox injection therapy and pneumodilation have failed. POEM is also feasible and safe in children, and there are even small series describing good results of POEM performed after failed laparoscopic Heller myotomy [5] [6].

When comparing POEM with current treatments, there are several advantages of this new technique. It seems more effective in the short term than pneumodilation, and the risk of severe complications is definitely not higher in POEM compared with pneumodilation. Compared with laparoscopic Heller myotomy, there is less dissection around the esophagus and abdominal fat is not a complicating factor during the procedure. Furthermore POEM does not leave scars on the skin.

Conversely, POEM is definitely more invasive than pneumodilation, postoperative pain is more severe, and the technique requires advanced endoscopic skills and more expensive equipment than pneumodilation. POEM does not seem to be much less invasive than laparoscopic Heller myotomy, and the latter is usually combined with an anterior Dor fundoplication in order to reduce the risk of developing reflux disease, something that is not possible to perform during POEM.

Laparoscopic Heller myotomy, POEM, and pneumodilation thus have theoretical advantages and disadvantages, and uncontrolled series will never be sufficient to determine the optimal treatment. High-quality, randomized controlled trials (RCTs) with significant sample sizes have been performed in the past to compare pneumodilation and Heller myotomy [7] [8] [9]. These studies have highlighted the differences between these treatments and have made decision making in achalasia treatment easier by generating solid comparative data. These RCTs also showed that the results of each treatment were definitely not as good as those observed in previous uncontrolled series. Therefore, before we can decide on the place of POEM in achalasia treatment, we need more robust studies such as RCTs on which to base our treatment decisions; more uncontrolled series will only be of limited additional value.

Furthermore, Akintoye et al. pointed out that the efficacy of POEM in the short term is very high and reaches 98 %. However, a recent study suggested that after a median follow-up of 29 months, the efficacy of POEM dropped substantially from 96.3 % initially to about 78.5 %, which is certainly not better than the efficacy rates of pneumodilation and laparoscopic Heller myotomy that were reached in the randomized European Achalasia Trial (86 % and 90 % after 2 years, and 82 % and 84 % after 5 years) [7] [10] [11]. Achalasia is a chronic disease and treatment should therefore offer a long-term solution. Whether this is offered by POEM will need to be determined by prospective, long-term, follow-up studies, ideally with a comparative treatment included in the trial.

In conclusion, the results described by Akintoye et al. in this issue of Endoscopy confirm that POEM is promising as a new treatment for achalasia. Whether it deserves to be the new treatment of choice in achalasia will need to be determined by RCTs comparing POEM with the current standard treatments of pneumodilation and laparoscopic Heller myotomy.

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