Editorial: Learning Curve for ESD and Other Advanced Endoscopy Procedures

Endoscopy training has evolved over time, with the current emphasis on structured training programs and focus on the level of competency achieved, and not just numbers of procedures performed. Nonetheless, the concept of threshold numbers, although not absolute, remains important, as trainees progress from novice phase to a level of competency and eventual mastery [1]. Globally, formal programs are available and well established for basic endoscopy [2, 3] and advanced procedures such as endoscopic retrograde cholangiopancreatography (ERCP) and endosonography (EUS) [4]. Although endoscopic submucosal dissection (ESD) was introduced into clinical practice more than two decades ago, outside of East Asia, formal training programs are limited, due to lack of suitable case volume and expertise despite the clinical needs. While it may be possible to undergo a hands-on training fellowship if a temporary medical license is obtained, it may not be logistically feasible or practical for senior advanced endoscopists to spend an entire year or more abroad for further formal fellowship training. Multipronged stepwise strategies have been explored to meet this need [5].

In this issue of Journal of Gastroenterology and Hepatology, Pattarajierapan et al. reported on the learning curve of a single endoscopist for colorectal ESD, using cumulative sum analysis (CUSUM) of the resection speed as the primary outcome [6]. The endoscopist had prior extensive experience in colonoscopy and endoscopic mucosal resection (EMR). He underwent supervised training in 30 cases of colorectal ESD in Thailand, then went to Japan for 4 months, where he had further cognitive training and hands-on training in four colonic and one gastric ESD. On return to Thailand, he performed a further 70 cases of colorectal ESD. CUSUM of the resection speed revealed that proficiency was achieved after 36 cases. This study demonstrated that such customized training can help attain competency to provide clinical service that can be benchmarked to international standards. The weakness is that this only reflected the experience of a single endoscopist with prior extensive experience in endoscopy and may not be generalizable to less experienced endoscopists who would require a closer level of supervision. Nonetheless, this adds to our knowledge base that more than one playbook is possible for the acquisition of complex skills with a steep learning curve. A study from Japan reported that for Japanese trainees who perform ESD under expert supervision, 30 cases were required to attain competency in gastric ESD [7], while other Japanese studies that evaluated colorectal ESD without prior gastric ESD experience reported that a higher level of competency was achieved after 21 [8] to 40 cases [8]. A study from the United States examined the learning curve of ESD with an untutored prevalence-based approach and reported that competency was achieved at 250 cases [9]. Conversely, a German study reported that in the context of highly experienced endoscopists who had previously only observed ESD procedures and participated in ex vivo courses, in the absence of supervised training, competence levels for esophageal and gastric ESD were achieved within 80 cases while most benchmarks for proficiency was achieved within 120 cases [10]. Such a wide range in case volume needed to achieve competency is reflective of the value of supervised training to overcome the steep learning curve for ESD. The fact that the inflection point in this study is only 36 cases, much less than the reported Western data, affirmed the importance of guidance by a local expert, even if the expertise may not be at the same level as that of the Japanese endoscopist, such that when in a higher level training environment, skills acquisition can be accelerated. Another important point to note is the cognitive training that was highlighted by the author. ESD training is not solely about mastering resection techniques. It also requires expertise in pre-ESD endoscopic diagnosis, especially for lesions suspected to be T1 colorectal cancer (CRC). The ability to accurately predict invasion depth is crucial, as it significantly impacts the risk of recurrence and the long-term outcomes for patients. Competency in colorectal ESD should be defined by both proficiency in diagnosing T1 CRC and in resection technique.

A dedicated trainer with sufficient expertise, well-designed training curricula and training resources, sufficient case volume and training intensity, and the innate aptitude and foundational skills of the trainee are all important factors for successful endoscopy training. The flipped classroom concept further enhanced the process. The ideal framework is continuous supervised training until proficiency is achieved. Mastery would happen with continued dedication to further skill upgrading. The availability of web-based educational resources, ex vivo training models, and focused short courses provides an opportunity for endoscopists with sufficient foundational skills to advance their skills in advanced procedures in absence of continuous supervised training. Although not as ideal, and requiring a longer training period, a comparable level of competency can eventually be achieved, without compromising safety and efficacy. A similar approach is used for learning other advanced endoscopic procedures such as per-oral endoscopic myotomy, endoscopic full thickness resection, Level 4 ERCP procedures, and therapeutic EUS procedures as advanced endoscopists seek to upgrade their skillsets to improve patient care. For this approach to work, the endoscopist must have sufficient foundation to proceed to the next level, and there is a need to ensure that the key patient outcome measures such as success rate and safety are not compromised and benchmarked against accepted standards. In this era of increased medicolegal pressure, appropriate patient disclosure about the level of experience of the endoscopist should be considered. Procedural time would only be a secondary consideration and would naturally improve as proficiency is enhanced. It is crucial that in the context of nonsupervised procedures even as competency is being established, the endoscopist does not embark on a procedure in a cavalier manner until there is sufficient confidence, based on observations and ex vivo model training, that the same standard of safety and a reasonable success can be achieved, even if it may take comparatively more time in the beginning.

There are unmet patient needs due to lack of trained advanced endoscopists, and in some less developed counties, even basic endoscopists. It is important to provide equitable access to healthcare, but referrals to international centers of excellence may not be practical. Patients would then be subjected to more invasive treatment options or even no treatment. Such focused training opportunities must continue to be encouraged and supported, until a point within the local context when sufficient expertise has developed for a formal training program. The endoscopists and training centers who dedicate themselves to disseminate knowledge and techniques are to be commended for their selfless service.

Tiing Leong Ang and Han-Mo Chiu are Editorial Board members of JGH and co-authors of this article. To minimize bias, they were excluded from all editorial decision-making related to the acceptance of this article for publication.