One of the earliest proposed training algorithms by Yamamoto et al. in 2009 puts emphasis on the initial pre-procedural phase of the training [26]. Thus, the endoscopists who intended to start ESD must attend pre- and post-treatment conferences including gastroenterologists, surgeons, and pathologists, in order to learn how to diagnose the extent and depth of the tumor, establish the optimum treatment strategy, and manage the patients appropriately through the pathological staging. To improve R0 resection rates, that is by making marking dots correctly around the tumor boarder, the pre-procedural training to master detailed preoperative examination by magnifying endoscopy with narrow band imaging (NBI) is clinically essential [27]. A similar approach is proposed by Kaltenbach et al., where the trainees are assisted in developing crucial diagnostic skills to select appropriate lesions and in practicing specific management strategies for ESD cases [23].

The next phase is for trainees to observe various ESD procedures performed by expert endoscopists [29]. ESD is a technically demanding procedure, requiring a high level of endoscopic skill. Also, the trainees take part in actual ESD procedures for at least 1 year before beginning to do ESD. Trainees acquire the skills needed to troubleshoot various situations. Obtaining expertise in endoscopic hemostasis is especially key, since most of the difficulties surrounding the procedure are related to uncontrollable hemorrhage [26].

Consequently, in the second stage of training, the trainees start by assisting experts in performing ESD procedures. Next, the trainees are exposed to animal models to enhance their technical skills. Hands-on experience with ESD in the isolated porcine stomach or live porcine facilitates familiarity with the devices and techniques of ESD procedure. Trainees can appreciate the differences in technique depending on lesion size and location. Then, trainees typically start performing ESD in patients, initially removing small gastric lesions in the antrum (maybe on anterior wall or greater curve) or body (especially on lesser curve), under the supervision of experienced endoscopists who both offers suitable and valid advice and may have to rescue the remaining procedure, like a “closer,” if necessary [23, 29]. Yamamoto et al. propose a system where the trainees do not use animal models but start as assistants in live patient cases and then continue with performing ESD on patients under expert supervision [26]. For this reason, they recommend that in this “supervision-only” training algorithm, one should start with small lesions in the lower third of the stomach (antrum). These lesions are relatively easy and less time-consuming to remove, so the trainees have the opportunity to learn the entire ESD procedure.

Ohata et al. propose a 7-step training system for learning colorectal ESD, which is very similar to the training algorithms used for gastric ESD, however impose complicated manipulations by performing the procedure in a narrower space and thinner wall [47]. One of the mandatory enrollment criteria is performance of at least 30 gastric ESDs. The results suggest that trainees with relatively little prior experience with gastric ESD could reach a stable level of technical competency in colorectal ESD after an average of 30 cases of the latter procedure. The study also found that, regardless of the gastric ESD experience, the mean procedure time of each trainee became less than 80 min after performing more than 30 cases.

The essential step of the training can be accomplished through independent effort, using printed and video materials to learn about the procedure, indication, and diagnosis. Then, the endoscopists attend live presentations and enroll in hands-on training courses to learn about the use of various devices and to practice on animal models. After accumulation of this theoretical and practical fund of knowledge, a visit to an expert center to observe the experts’ technique is recommended. Most of these centers are, unfortunately, located in Japan. There are very few cases of early gastric cancer in other countries, therefore little opportunity for the trainee to start their training in locations that are considered easier, such as the gastric antrum. [26, 48, 49]. In addition, the choice of devices, endoscopes, and ancillary equipment for ESD that is available in the West is different compared with those available in Japan [50]. However, with more endoscopists learning this technique, it is anticipated that new training centers are already and will be conducted throughout the world. It is understood that not all endoscopists can spend long periods of time outside their practice; however, trainees are encouraged to spend at least 2–3 weeks visiting a high volume center, maybe in Japan. Upon return to their center, when working on human patients, the lesions located in the distal stomach or rectum, as these are relatively easier to remove and have a lower complication rate, might be good candidates. During the initial human cases, expert supervision by means of videoconference is encouraged if direct supervision is not possible. Then, gradually, the endoscopists can expand to cases of increasing difficulty, such as treating larger lesions, or lesions located in the cardia, fundus, colon, or esophagus. Finally, as in any other field, we recommend continuous training, with attending/presenting at conferences, re-visiting expert centers, reviewing literature, and participating in courses and live demonstrations.

In summary, in Japan, a consensus exists on the following issues: (phase 1) need for solid cognitive background regarding lesion evaluation, indications, contraindications, and technical aspects of ESD; (phase 2) need for observation of ESD as done by experts; (phase 3) need to assist experts and operate the ESD devices; (phase 4) need for hands-on training in humans under direct expert supervision; and (phase 5) starting hands-on training with easier lesions before progressing to more difficult ones.