Predictive factors of residual tumor for the patients with non-curative resection after endoscopic submucosal dissection for early gastric cancer.

32 Background: Endoscopic submucosal dissection (ESD) is commonly performed for the patients who diagnosed with early gastric cancer. Although additional gastrectomy is recommended for the patients with non-curative ESD in the points of potential risk of residual tumor, many cases have neither lymph node (LN) metastasis nor local residual tumor in surgical specimens. Clinically, it can be difficult to decide whether to perform additional surgery according to patients’ conditions. This study aimed to analyze the clinicopathological features of patients who underwent additional gastrectomy as well as to detect the predictive factors for residual tumor after non-curative ESD. Methods: The patients who underwent additional gastrectomy after non-curative ESD in our institution from January 2005 to August 2016 were retrospectively reviewed. The incidence rates of LN metastasis or local residual tumor were calculated, and furthermore the predictive factors for these outcomes were estimated. Results: 211 patients were enrolled in this study. Pathological examination after additional surgery revealed LN metastasis in 18 patients (8.5%) and local residual tumor in 26 patients (12.3%). Multivariable analysis revealed that lymphatic invasion ( p< 0.0001, odds ratio = 15.6), vascular invasion ( p= 0.042, odds ratio = 3.92) and macroscopic findings (flat/elevated type) ( p= 0.03, odds ratio = 3.53) are predictors for lymph node metastasis. All of the patients without LN metastasis revealed no lymphovascular invasion. Positive vertical margin ( p= 0.0045, odds ratio = 4.17) and horizontal margin ( p= 0.0002, odds ratio = 6.6) were predictors for local residual tumor. Conclusions: The risk of residual tumor can be estimated based on histopathology of ESD. Patients without lymphovascular invasion appear to be a low risk subpopulation for LN metastasis.