Endoscopic Resection for Early Gastric Cancer: What is the Limit?

Abstract

Majority of the gastric cancers in the world occurred in Asia, especially in Japan and Korea. The prevalence of early gastric cancer (EGC) is up to 60 % of all gastric cancers detected in these two countries, where their governments have adopted a screening program for gastric cancer. Pioneered by Japanese endoscopists, endoscopic submucosal dissection (ESD) has become the current standard of treatment for early gastric cancer. Prospective large-scale clinical studies with 500–1,000 cases showed that the average operative time of ESD ranged from 60 to 80 min, with en bloc resection rate of more than 90 %. Three retrospective cohort studies comparing conventional endoscopic mucosal resection (EMR) against ESD for treatment of early gastric cancer showed that ESD achieved a higher en bloc resection rate and lower local recurrence rate compared with EMR. Although ESD is highly effective for treatment of intramucosal gastric cancer, those with high risk of nodal metastasis cannot be adequately cured by endoscopic resection alone. Japanese Gastric Cancer Association has developed guidelines for treatment of gastric cancer. In the past, only early differentiated intramucosal gastric cancer with size of less than 20 mm was indicated for endoscopic treatment. Gotoda et al. reviewed the histopathology of 5,625 patients with EGC who underwent radical gastrectomy and lymph node dissection. The study confirmed that none of 1,230 differentiated carcinomas less than 30 mm had nodal metastasis, and no nodal metastasis was found in 929 of these without ulceration regardless of tumor size. For tumors of SM1 invasion and less than 30 mm in size, none was shown to have nodal metastasis. Shimada et al. reviewed 1,051 patients with EGC who underwent radical gastrectomy, and the nodal metastasis rate for intramucosal tumors was 2.3 %. For those with submucosal invasion, there was a significant rate of nodal metastasis of 19.8 %. The recommended indication for endoscopic resection of EGC was expanded, especially when techniques of ESD became available. Submucosal infiltration by gastric cancer has been a known risk factor to nodal metastasis. Ahn et al. compared the outcomes of early gastric cancer in 1,370 patients who received endoscopic resection under both absolute indication and expanded indication. Among these, 119 patients had superficial submucosal invasive gastric cancer with a size of less than 30 mm treated by endoscopic resection. These cases would be considered as curative in the expanded criteria. However, 34 patients subsequently received surgery and 1 patient who had no residue cancer in the stomach was found to have a metastatic perigastric lymph node. Therefore, even with the expanded criteria for endoscopic resection, caution should be exercised in choosing the appropriate treatments for superficial submucosal early gastric cancer. In this issue, Eom et al. examined the optimal submucosal invasive of early gastric cancer suitable for endoscopic resection in 1,322 patients who received radical gastrectomy. Among the 1,322 patients who received curative gastrectomy with standard nodal dissection for submucosal gastric cancer, 18.8 % was found to have a positive lymph node. This study showed that a cutoff point of 300 lm of submucosal infiltration achieved the highest negative predictive value of 98 % for predicting lymph node metastasis. The authors proposed for large-scale study to validate the cutoff value. Son et al. examined the risk factors for lymph node metastasis in early gastric cancers treated by endoscopic resection. The important risk factors for nodal metastasis included submucosal invasion, Society of Surgical Oncology 2015