Background: A small differentiated gastric cancer with minute submucosal invasion after endoscopic resection is regarded as the curative resection criterion of an expanded indication. However, recent studies have shown a high incidence of lymph node metastasis in those meeting the expanded criteria. The aim of this study was to evaluate the validity of the 500 μm criterion and to determine an optimal cutoff value for the expanded indication.
Methods: We reviewed the clinicopathological data of 1,322 patients who underwent curative resection for submucosal gastric cancer between 2001 and 2013. The full thickness of the submucosa and the incidence of lymph node metastasis according to the depth of the submucosal invasion were evaluated. The sensitivity, specificity, and positive and negative predictive values were calculated with receiver operating characteristic (ROC) curve analysis.
Results: The mean full thickness of the submucosa was 2,605 ± 1,760 μm, and the incidence of lymph node metastasis in 103 tumors meeting the expanded indication was 3.9 % (4/103). In the ROC analysis, the area under the curve was 0.664 (95 % confidence interval 0.538-0.791; p = 0.017), and the highest negative predictive value of 98 % was observed when the cutoff value was 300 μm.
Conclusions: This study suggests that a range reduction in the depth of submucosal invasion is required to obtain a high negative predictive value. Further large-scale studies are required to validate the optimal cutoff value proposed in this study.