Clinical Outcomes of Endoscopic Submucosal Dissection for Undifferentiated or Submucosal Invasive Early Gastric Cancer

Background/Aims: Early gastric cancer (EGC) that is undifferentiated or shows submucosal invasion has not been generally accepted as an indication for endoscopic treatment. But recently, experiences with endoscopic submucosal dissection (ESD) for undifferentiated EGC or submucosal invasive (SM) EGC have increased. The aim of this study was to evaluate clinical outcomes of ESD for EGC with undifferentiation or submucosal invasion. Methods: Between August 2005 and August 2009, among 210 EGCs treated using ESD at our hospital, 18 lesions were diagnosed as undifferentiated gastric cancer and 41 as SM gastric cancer. A retrospective analysis was done on the medical records of these patients. Results: Mean follow-up periods were 19.39${\pm}$11.2 months. During the follow-up period, local recurrence was noted in 4 lesions. Local recurrence rates of the EGC groups (group 1, mucosal cancer with undifferentiation; group 2, SM cancer with differentiation; group 3, SM cancer with undifferentiation) were 10%, 4.5%, and 50%, respectively. Groups 1 and 2 were not significantly different in local recurrence rates compared to the mucosal cancer with differentiation group (p=0.061, p=0.125, respectively). The undifferentiated EGC group was significantly lower in curability using ESD than the differentiated EGC group (55.6% vs. 89.6%, p=0.000). The curability of the SM EGC group was lower than the mucosal EGC group (36.6% vs. 98.9%). Conclusions: Complete resection using ESD is difficult in undifferentiated and SM gastric cancers. SM cancer with undifferentiation should be treated immediately by salvage operation. For mucosal cancer with undifferentiation or SM cancer with differentiation, one should consider careful short-term follow-up.