Essential Updates 2018/2019: Essential Updates for esophageal cancer surgery

Abstract Key papers to treatment of esophageal cancer surgery and reduction of postoperative complications after esophagectomy published between 2018 and 2019 were reviewed. Within this review there was a focus on minimally invasive esophagectomy (MIE), robot‐assisted MIE (RAMIE), and centralization to high‐volume center. Advantages of MIE, irrespectively of hybrid or total MIE, to prevent postoperative complications, especially pneumonia, were shown in comparison to open procedure. However, whether total MIE has evident effects or not, as compared to hybrid MIEs, still remains unclear. Differences between RAMIE and MIE were reported to be marginal, though the advantage of lymphadenectomy, especially along recurrent laryngeal nerve, has been suggested. Centralization to high‐volume center evidently benefits esophageal cancer patients by improving short‐term outcomes. The definition of high‐volume center has not been established yet, though institutional structure and quality are thought to be important. Transmediastinal esophagectomy, currently developed, has a potential to be one radical option of MIE for esophageal cancer.


| INTRODUC TI ON
Surgery remains a mainstay of treatment for esophageal cancer worldwide. It is, however, one of the most invasive procedures and is associated with high morbidity. Postoperative complications, especially pulmonary complications such as pneumonia, were reported to reduce the survival rate. 1-3 Therefore, the prevention of postoperative complications is the urgent and most important issue. The key papers to treatment of esophageal cancer surgery and reduction of the postoperative complications published worldwide in the period between 2018 and 2019 were reviewed. With a focus on minimally invasive esophagectomy (MIE), robot-assisted procedure, and the centralization to high-volume center, this review evaluates their effects and significance to reducing morbidity, especially pulmonary complications.

| MINIMALLY INVA S IVE E SOPHAG ECOMY (MIE )
The first MIE was reported in 1992 by Cuschieri et al. 4 In those five patients, video-assisted thoracoscopic surgery for esophagectomy and laparotomy were used. The combinations of thoracoscopy and laparotomy, such as in the report by Cushcieri, are regarded as hybrid MIE. Total MIE, i.e., the procedures performed by the combination of thoracoscopy and laparoscopy, was first reported by Luketish et al. 5   to the open esophagectomy group. 9 These two studies were retrospective, but it is important to consider that they were based on a large cohort, and no useful randomized controlled trial has reported on this topic to date. Two propensity score-matched analyses from a single institution study also showed less respiratory complications 10 16 In a short summary, the above-mentioned papers suggested the advantages of MIE, irrespectively of hybrid or total MIE, to prevent postoperative complications, especially pneumonia; however, some disadvantages, such as longer operation time, [9][10][11]14 were also re- As Gottlieb-Vedi's definition included mediastinoscopic procedure, 6 recently, the usefulness of transmediastinal approach using mediastinoscopy, i.e., less pulmonary complications and better QOL, was recently introduced. 18 Transhiatal esophagectomy has been performed as a less invasive procedure, though it is regarded as less radical because of insufficient lymphadenectomy.
Transmediastinal esophagectomy consists of the combination of the transhiatal and transcervical approaches, and was shown to enable the similar mediastinal lymphadenectomy to transthoracic approach. 19 In that radical procedure, neither transthoracic approach nor one-lung ventilation anesthesia are necessary. This approach has the potential to be one option as a radical surgical procedure.

| ROBOT-A SS IS TED PRO CEDURE
Robot-assisted esophagectomy was firstly reported by Horgan et al. 20 In that case, transhiatal approach was applied, in which the procedure of lymphadenectomy was thought to be insufficient as from NSQIP database analysis and concluded that RAMIE might be a feasible but non-superior option. 25 . Four propensity score-matched studies [26][27][28][29] and one prospective study from a single center 30 also reported similar results. As for lymphadenectomies, two papers reported no significant difference of the number of dissected lymph nodes, 26,27 though many papers showed the advantage of RAMIE on lymphadenectomy as compared to MIE. [28][29][30][31][32] Especially, usefulness of the dissection along recurrent laryngeal nerve was reported to be yielded by RAMIE. [29][30][31][32] Yang et al noted a higher incidence of nerve injury as well as more harvested lymph nodes. 31

| CENTR ALIZ ATI ON TO HI G H -VOLUME CENTER
Since hospital volume is the greatest effect to reduce operative mortality in esophagectomy among various procedures was observed by Birkmeyer et al, 42 centralization of esophageal cancer surgery has been advancing. 43,44 Many papers published to date have also supported that effect worldwide. 8,43-47 Furthermore, postoperative complication rate 44,45 and operation time 44 were reported to be reduced by centralization. However, what a high-volume center is, remains unsolved. The number of esophagectomies per year is likely to define the high-volume, though it was reported to vary from five to 20. 8,43,44,46 A population-based, nationwide Swedish cohort study showed the superiority of university hospital to nonuniversity hospital status. 48 49 Another question, whether hospital or surgeon volume is more important, 50 is also difficult to answer. Kaupplia et al reported that individual surgeon volume had a tendency to reduce mortality, but this was not showed as statistically significance. 48 The aim of centralization is undoubtedly to offer its benefit to patients.
Riele et al pointed out that institutional characteristics had a stronger influence on mortality than volume. 51 Cooke, also, presented important consideration. The quote is as follows; to improve the outcomes, we either must develop methods to facilitate access to centralized, high-volume centers, or we translate the institutional knowledge, best practice and recovery and rescue pathways from our centralized programs to the communities. 52 In a short summary, centralization to high-volume centers evidently benefits esophageal cancer patients by improving short-term outcomes. However, the definition of a high-volume center has not yet been established. Regardless, the system's clinical resources and support, including manpower, are essential to aid patients, irrespectively of hospital volume, when critically adverse events occurs.
Considering patient access to high-volume centers, and sharing the knowledge and practice between high-and not-high-volume centers, is also imperative.

D I SCLOS U R E
Conflict of interest: The author declares no conflict of interest for this article.