As the technology continues to evolve, endoscopy has become not only an imaging modality but also a therapeutic instrument as one of the minimally invasive treatment options. Since late 1960s, when gastric polyps were first removed with endoscopy using an electrocautery snare, the indications have been expanded parallel with improvements in endoscopic techniques as well as the development of new endoscopic devices. In this chapter, we outline the indications for endoscopic resection of early gastric cancer, describe three major endoscopic techniques, and the outcomes of endoscopic treatment including major complications are summarized, followed by our view of the future perspective of endoscopic minimally invasive treatment.
INDICATIONS FOR ENDOSCOPIC RESECTION FOR EARLY GASTRIC CANCER
The indications for endoscopic local resection are determined by technical and theoretical conditions. The principles of surgical treatment for cancer are to obtain a margin-free, en bloc resection in order to achieve complete resection of the primary lesion without residual disease and to fully evaluate the tumor by histopathology. The ability to achieve reliable margin-free resection is completely different depending on each resection technique. Therefore, the indication for endoscopic resection should be based on the ability of each resection technique to yield a negative margin. For example, endoscopic resection using a snare for polypectomy or endoscopic mucosal resection (EMR), to remove a small, pedunculated lesion is appropriate to obtain a clear margin as described below. However, en bloc resection for larger lesions or lesions is hardly achievable by these methods.1-4 In this situation, snare resection must be limited to lesions 2 cm or less in size and without scar formation in order to achieve complete resection.5 Endoscopic submucosal dissection (ESD), which is mainly composed of circumferential mucosal incision and subumucosal dissection, has broken new ground in achieving R0 resection of larger lesions via an endoscopic approach.6-9 There is no limitation in size or location of the tumor amenable to ESD for an experienced operator since the targeted area can be freely incised by electrosurgical knives in ESD. Furthermore, the submucosal layer beneath the lesion can be dissected under direct visualization, which enables en bloc resection even for a lesion with severe fibrosis within the submucosal layer.
Endoscopic submucosal dissection, however, is endoluminal surgery that cannot resect extraluminal lymph nodes. Therefore, the indication of ESD is theoretically limited to node-negative cancers. By investigating a large amount of surgically resected cases (more than 5000 cases), the conditions that predict node-negative early gastric cancer were elucidated as follows:10 (1) intestinal-type mucosal cancer without ulcer findings, irrespective of size; (2) intestinal-type mucosal cancer with ulcer findings, 3 cm or less in size; (3) intestinal-type cancer invading superficial submucosa up to 500 µm (SM1), 3 cm or less in size; or (4) diffuse-type mucosal cancer without scarring formation, 2 cm or less in size.11 Early gastric cancer fulfilling one of these four conditions is expected to be node-negative, ...