The efforts of many researchers and technological developers have made ESD both safer and easier, and as a result the ESD technique is now widely practiced in Japan as a first-line therapeutic option for early gastrointestinal neoplasms. The indications of ER could be expanded for larger lesions by ESD. In the extended indications for gastric cancer, there is no limitation on tumor size for differentiated (intestinal type) mucosal cancers without ulceration. An enormous amount of data has been obtained from meticulous histological analysis of ESD specimens following a strict, standardized pathological protocol. These results have indicated that the therapeutic outcomes of ESD for the extended indications of purely differentiated lesions are comparable with those of surgical resection [15, 37]. However, ESD is not yet the global method of choice for ER techniques. The social acceptance of ESD is geographically diverse, and the technique is predominantly practiced in East Asia. ESD requires specialized skills to intuitively manipulate flexible endoscopes and needle knives with unique designs that result in longer operation times. As a result, ESD requires optimal training in selected relatively easy cases to gradually obtain a high level of skill that will permit the safe completion of the procedure for challenging cases such as Barrett’s and colonic neoplasms, which are the main indications of ER in the West. In fact, the safety of ESD in Western countries that have a lower prevalence of early gastric cancers and lack the appropriate cases for training is not equivalent to the published data for ESD in Eastern countries [12, 38, 39]. It is difficult to establish the knowledge and skill bases for adequate preoperative assessment of the precise delineation of lesions. These basic attributes are mandatory to achieve a satisfactory outcome from ESD due to the absence of opportunities for screening endoscopies to detect asymptomatic, early cancers in Western countries. Other therapeutic options, including piecemeal resection and even surgical resection, should be considered if overwhelming challenges are encountered during ER.

Various novel, multi-degree-of-freedom therapeutic endoscopes have been developed to enable intuitive performance of complicated surgical procedures with the flexible endoscopic platform. Therapeutic scopes with water-jet capabilities and multi-bending portions are recognized as standard equipment for ESD. The triangulation platform is considered an eventual design of the therapeutic endoscope, which has dual mobile instrumental channels or articulated manipulators at the tip of an endoscope (Fig. 1.3) [40, 41]. These systems provide an operative environment more like laparoscopic surgery rather than ordinary endoscopic intervention. They have been tested with ESD for deflecting the diseased mucosa away from the dissection plane and horizontally swinging a needle knife parallel to the muscularis propria. Ho and colleagues have applied robotics to the triangulation platform and successfully introduced their original master–slave type endoscopic robot to gastric ESD in human patients [42, 43]. At present, all triangulation platforms are still too cumbersome in their current form and need to be miniaturized for use within a narrow GI lumen.