Indication for endoscopic treatment based on the risk of lymph node metastasis in patients with undifferentiated early gastric cancer.

Background: Despite the risk of lymph node metastasis (LNM), the indications of endoscopic submucosal dissection (ESD) has expanded to undifferentiated type (UD-type) early gastric cancer (EGC). There is debate as to whether the endoscopic resection can be used. This study was conducted to evaluate risk factors for LNM in undifferentiated early gastric cancer, implications for the indication of the ESD so as to providing evidence for proper clinical management for UD-type EGC.

Method: We retrospectively analyzed 203 patients with UD-type EGC who underwent gastrectomy for primary gastric adenocarcinoma between 2012 and 2017. We evaluated the relationship between the clinicopathological factors and the presence of LNM using univariable and multivariable logistic regression analyses.

Results: A total of 203 UD-type EGC patients were enrolled, and LNM was positive in 40 cases (19.7%). Multivariable logistic regression analysis identified three independent risk factors for LNM, the tumor size (≥2.0 cm, P < 0.001), depth of invasion (P < 0.001), and lymphatic vessel involvement (LVI, P < 0.001). LNM was observed in 5.9% patients without the three predictive factors in UD-type EGC, whereas 7.7% and 37.7% of patients with one and two risk factors had LNM, respectively. In contrast, the LNM rate was up to be 66.7% in patients with three factors. Of 41 patients satisfying the expanded indication of ESD, 3 patients (7.3%) showed LNM. LNM was not found in any of 12 patients with small intramucosal lesions (<1.0 cm) without LVI.

Conclusions: LNM-related risk factors were tumor larger than 2.0 cm, submucosal invasion, and the presence of LVI in UD-type EGC. ESD alone may be sufficient treatment for the intramucosal UD-type EGC that is smaller than 1.0 cm in size. When endoscopically resected specimens show unexpectedly larger tumor size, unexpected submucosal and LVI than that determined at pre-ESD endoscopic diagnosis, an additional gastrectomy with lymphadenectomy should be considered.