Expanding Indications of Endoscopic Submucosal Dissection for Early Gastric Cancer: Hope or Hype?

which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Endoscopic submucosal dissection (ESD) has been established as one of the treatment options for selected cases of early gastric cancer (EGC). It is generally agreed that lesions within absolute indications (AI)—so-called " conventional indications " in Korea and " guideline indications " in Japan—can be safely resected by ESD, and the long-term outcome is comparable with surgery. Some lesions beyond AIs also can be histologically completely resected by endoscopy, so many researchers are trying to develop wider indications of endoscopic treatment of EGC. There are some literatures suggesting that ESD may be appropriate not only for AI but also for expanded indication (EI). However, due to the limitations of the study design, there are concerns on the EI of ESD. Some examples are (1) unclear definition of EI and handling of undifferentiated type cancer, (2) diagnostic discrepancies in pre-and post-endoscopic resections, (3) selection bias of retrospective analyses, and (4) scanty data on the long-term outcomes. First of all, a standard definition of EI is urgently needed. By the recently published clinical practice guideline for gastric cancer in Korea, expanded indications include (1) well or moderately differentiated adenocarcinoma in the mucosal layer without an ulcer regardless of the size, (2) well or moderately differentiated adenocarcinoma measuring less than 3 cm in the mucosal layer with ulcer, (3) small (less than 2 cm) intramucosal cancer with undifferentiated histology, and (4) well or moderately differentiated adenocarcinoma with minute submucosal invasion (500 or less micrometer, SM1). 1 However, there is no consensus whether undifferentiated type EGCs (i.e., poorly differentiated adenocarcinomas and signet-ring cell carcinomas) should be included in EI of ESD. Data on clinical outcomes of ESD for undifferentiated type EGCs indicate that optimal cura-tive resection would be difficult to guarantee, given the overall unpredictability of tumor depth and extent. In addition, there is little long-term outcome data to support endoscopic treatment of undifferentiated type EGC at this time. 2-4 There are some cases with histological heterogeneity. In order to avoid confusions regarding histological type, we propose that the long-term outcome of ESD for differentiated type EGCs, undifferentiated type EGCs, and EGCs with mixed histology need to be separately reported. The second limitation can be named as " indication/criteria issue. " We choose ESD candidates using some kind of indications. After ESD, we evaluate the resected …