Staging for Remnant Gastric Cancer: The Metastatic Lymph Node Ratio vs. the UICC 7th Edition System

Background: Unlike primary gastric cancer, a remnant gastric cancer (RGC) staging system has not been established. The retrieved lymph node counts (RLN) in RGC is generally lower than that in primary gastric cancer, so it is unclear whether positive lymph node count reflects the RGC patient’s survival. Therefore, the lymph node ratio (LR) may be more useful for RGC staging than the 7th edition UICC classification. Methods: Patients (n = 191) who underwent gastrectomy with curative intent for RGC participated in this study. LR was classified as LR = 0, 0 < LR ≤ 0.1, 0.1 < LR ≤ 0.4, and 0.4 < LR. Modified TNM staging (mTNM-LR) was established by combining the pT (7th UICC) with LR. The predictive accuracy of LR and mTNM-LR was compared with that of the pN (7th UICC) and TNM (7th UICC), respectively. Results: The mean RLN was 14.4 and that of 128 patients (67 %) was ≤15. Fifty-one patients (27 %) had metastatic lymph nodes. Multivariable analyses revealed that pT (7th UICC) (p < 0.001) and pN (7th UICC) (p = 0.001), but not LR, were independent risk factors for overall survival. The overall c-index (95 % confidence interval) of each staging system was as follows: pN (7th UICC): 0.700 (0.627–0.771); LR: 0.701 (0.627–0.775), TNM (7th UICC): 0.808 (0.761–0.870); mTNM-LR: 0.807 (0.737–0.871). There were no significant differences in the predictive accuracy between pN (7th UICC) and LR, and TNM (7th UICC) and mTNM-LR. Conclusions: LR was not superior to pN (7th UICC). Thus, the 7th edition UICC classification is a practical and reliable staging system for RGC.