Compared with conventional EMR, ESD has a high complete resection rate and high curability . For this reason, it has been performed not only in the stomach [15, 16], esophagus, and colon, but also in various organs such as the pharynx and duodenum in recent years. ESD is also useful for cancer that develops in the gastrointestinal tract after surgery. Lesions in the postoperative gastrointestinal tract are often particularly difficult to resect using conventional EMR due to the anastomosis and subsequently narrow lumen . However, with ESD, incision and dissection can be performed under direct vision, and the complete resection rate is high even for lesions that occur in the postoperative gastrointestinal tract.
Most cancers in the remnant esophagus after esophagectomy are located in the cervical esophagus, where endoscopic observation is difficult due to the pharyngeal reflex and the contraction or bending of the digestive tract . General anesthesia may be required to adequately observe the target lesion . In fact, in this study about 90% of treatment procedures were performed under general anesthesia. The remaining 10% were treated with conscious sedation, but in all these cases the distance from the esophageal entrance to the lesion was maintained. If it is difficult to observe the target lesion adequately at the time of endoscopic examination, treatment under general anesthesia should be considered necessary . In addition, the postoperative gastrointestinal tract has a reduced peristaltic function, so the possibility of food retention is higher than that of the normal gastrointestinal tract. In this study, food intake was stopped 2 days before treatment for all cases. Therefore, no residual food contents were observed in any case at the time of treatment. It was considered important to set an appropriate fasting period before the endoscopy. In our hospital, after esophagectomy, regular postoperative surveillance is performed. Endoscopic and CT surveillance is performed by every six months. Many cases of ESCC are detected in relatively early stage, probably because the observation range is short. Esophageal cancer in the remnant esophagus is difficult in terms of diagnosis as well as treatment. In diagnosis, both detection and diagnosis of invasion depth may be challenging. In this study, the average period from esophagectomy to ESD was 2800 days, and cancer may develop even a long time after surgery. Endoscopic follow-up after surgery for esophageal cancer should therefore be performed carefully even after a long time.
In this study, the diagnostic accuracy of tumor depth was as high as 87%. For all cases, diagnosis was by using NBI magnification during the detection and diagnosis of tumor depth. Iodine staining is sometimes difficult to use because the remnant esophagus is close to the larynx and in such cases, NBI magnification may be useful for the diagnosis  in the remnant esophagus. In our hospital, there are little cases of using EUS, because patients with the remnant esophagus after esophagectomy have high risk of aspiration. In this study, the complete resection rate was about 80%. Although there were no cases of tumor-positive vertical margins, in 6 cases the lateral margin was positive or unclear. Compared with other reports of esophageal ESD, the resection rate with tumor-negative margins was considered to be low, possibly attributable to two reasons. First, it was considered that scar or fibrosis was present at the anastomosis site, making it difficult to resect with negative margins. Second, because the cervical esophagus has a high incidence of post-ESD stenosis, it was considered to have a low negative margin rate because it was resected close to the lesion. However, no local recurrence was observed in the average observation period of 2033 ± 1146 days, and thus local control by ESD was considered good. ESD for cervical esophageal lesions has been reported to have a higher likelihood of postoperative stenosis than other sites. However, in this study the mean tumor diameter was found at a relatively small stage of 17.8 mm, and stenosis was prevented, for example, by steroid therapy. Systemic steroid administration  and intralesional steroid injection [22, 23] obstructs esophageal stricture after ESD . Unlike ESD of cervical ESCC, ESD of remnant esophagus requires treatment of the anastomotic site. It is the factor of technical difficulty. One of the three lesions with positive lateral margins, which the specimen size is 30 mm x 30 mm, invaded the anastomosis. There was only one case of stenosis. In this one case, stenosis was improved with 5 dilatations, but stenosis of the cervical esophagus was difficult to control, thus suggesting that stenosis prevention should be implemented as much as possible.
There are several limitations to this study. It is the retrospective study design with a small number of single-center facilities. In addition, it is a study of a single group of ESD in the remnant esophagus. In the future, we would like to search usefulness for ESD in the remnant esophagus by comparison study.
This study is based on procedures performed by a skilled endoscopist. Although the technical difficulty of ESD in the remnant esophagus is thought to be high, it was considered necessary to verify what skill level of endoscopist will be required to perform this procedure in the future. Second, it is not clear whether the lesion site is the cervical or upper thoracic esophagus. The definition of cervical esophagus thus needs to be unified.
In this study, ESD for superficial cancer of the remnant esophagus often required general anesthesia, the en bloc resection rate was high, and no serious complications were observed, indicating that the technique is feasible. Pathologically, the rate of tumor-positive lateral margins was relatively high, but no residual or local recurrence was observed and local control was good. Thus, ESD is a safe and useful treatment for superficial cancer of the remnant esophagus after esophagectomy.