Endoscopic submucosal dissection: can it safely expand indications for a minimally invasive approach to patients with early gastric cancer?

Abstract

In contrast to Western countries, Asian countries such as Japan and Korea diagnose gastric cancers at an early stage, confronting the disease with screening programs and perhaps a different cancer biology. This early detection allows a minimally invasive treatment approach, substantially improving quality of life (QOL) for patients with early gastric cancer (EGC). In these Asian countries, conventional open gastrectomy and minimally invasive interventions including endoscopic mucosal resection (EMR) and laparoscopic gastrectomy have been established as standard treatment when specific criteria are met. For example, EMR is recommended by Japanese guidelines for small tumors confined to the mucosal layer of the intestinal type [1]. However, many patients do not meet these criteria. In an effort for these patients to improve both curability (by deeper gastric wall resection) and QOL (by avoiding open gastrectomy), endoscopic submucosal dissection (ESD) has been developed. To assess whether ESD is a safe procedure for undifferentiated early gastric cancer, Kang et al. [2] reported on ESD in a recent issue of Surgical Endoscopy. They performed a retrospective study of patients with early gastric cancer treated at the Seoul National University Hospital, Seoul, Korea. Of the 456 patients with early gastric cancer treated by ESD between 2005 and 2008, 60 lesions (13.2%) were diagnosed as undifferentiated gastric cancer adenocarcinoma or signet ring cell carcinoma. The complete resection (R0) rate was significantly lower for undifferentiated EGC (55%) cases than for differentiated EGC cases (84.1%; P \ 0.001). Tumor size larger than 20 mm, submucosal invasion, and ulceration were associated with increased risk of incomplete resection (R1). During a mean follow-up period of 16 months, no recurrence was experienced by any of the patients with undifferentiated EGCs thought to be completely resected by ESD. The authors conclude that ESD may be considered for carefully selected patients with undifferentiated EGC. This large series of ESD for EGC has contributed data that are very important clinically for specialized institutions performing ESD. However, these findings warn concerning the risk of an R1 resection of undifferentiated carcinoma. The incomplete resection rate in this series was very high (45%), a finding that is not surprising given the widely spread submucosal invasion of this histologic type. Indeed, this type of gastric cancer, which corresponds to the diffuse type of cancer in Lauren classification usually used in the Western world, is characterized by diffuse spread beyond the tumor. Therefore, much larger resection margins are required than with intestinal type cancer. A follow-up period longer than the 16 months in this study is required for two reasons: to assess local recurrence and to evaluate the risk of nodal recurrence. Indeed, expanding the indications for ESD to include diffuse cancers, larger tumors, and ulcerations, there is evidence of increased risk to found positive lymph nodes. These metastatic lymph nodes are left behind after ESD with substantial risk of residual nodal disease and recurrence. A recent study has demonstrated a nodal metastasis rate for EGC that may reach 23% for certain aforementioned risk groups [3]. Early gastric cancer has an excellent prognosis, with high cure rates even in the West by appropriate R0 E. Fatourou Department of Hepatology, Ippokrateio Hospital, University of Athens, Athens, Greece