Endoscopic Resection of Undifferentiated Early Gastric Cancer

Abstract

Endoscopic resection (ER) is widely performed for early gastric cancer (EGC) with a negligible risk of lymph node metastasis (LNM) in Eastern Asian countries. In particular, endoscopic submucosal dissection (ESD) leads to a high en bloc resection rate, enabling accurate pathological evaluation. As undifferentiated EGC (UD-EGC) is known to result in a higher incidence of LNM and infiltrative growth than differentiated EGC (D-EGC), the indications for ER are limited compared with those for D-EGC. Previously, clinical staging as intramucosal UD-EGC ≤2 cm, without ulceration, was presented as 'weakly recommended' or 'expanded indications' for ER in the guidelines of the United States, Europe, Korea, and Japan. Based on promising long-term outcomes from a prospective multicenter study by the Japan Clinical Oncology Group (JCOG) 1009/1010, the status of this indication has expanded and is now considered 'absolute indications' in the latest Japanese guidelines published in 2021. In this study, which comprised 275 patients with UD-EGC (cT1a, ≤2 cm, without ulceration) treated with ESD, the 5-year overall survival (OS) was 99.3% (95% confidence interval, 97.1%-99.8%), which was higher than the threshold 5-year OS (89.9%). Currently, the levels of evidence grades and recommendations for ER of UD-EGC differ among Japan, Korea, and Western countries. Therefore, a further discussion is warranted to generalize the indications for ER of UD-EGC in countries besides Japan.

Keywords: Endoscopic submucosal dissection; Endoscopy; Gastric cancer; Neoplasms; Stomach.

Fig. 1. Criteria of the indication for ER of EGC in the JGCA guidelines (6th edition) and JGES guidelines (2nd edition).

ER = endoscopic resection; EGC = early gastric cancer; JGCA = Japanese Gastric Cancer Association; JGES = Japanese Gastroenterological Endoscopy Society; M = cancer confined to the mucosa; UL0 = without ulceration; UL1 = ulceration; SM = cancer invading the submucosa.

Fig. 2. Flowchart for the curability evaluation and therapeutic approach after ER of EGC in the JGCA guidelines (6th edition) and JGES guidelines (2nd edition).

ER = endoscopic resection; EGC = early gastric cancer; JGCA = Japanese Gastric Cancer Association; JGES = Japanese Gastroenterological Endoscopy Society; M = cancer confined to mucosa; UL0 = without ulceration; UL1 = ulceration; SM1 = cancer with submucosal invasion depth <500 μm; HM0 = negative horizontal margin; HM1 = positive horizontal margin; HMX = unevaluable horizontal margin; VM0 = negative vertical margin; Ly0 = no lymphatic invasion; V0 = no vascular invasion; eCura = endoscopic curability; ESD = endoscopic submucosal dissection.