Superiority of lymph node ratio-based staging system for prognostic prediction in 2575 patients with gastric cancer: validation analysis in a large single center

// Lin-Yong Zhao 1, 2, * , Chang-Chun Li 1, 2, * , Lu-Yu Jia 3 , Xiao-Long Chen 1, 2 , Wei-Han Zhang 1, 2 , Xin-Zu Chen 1, 2 , Kun Yang 1, 2 , Kai Liu 1, 2 , Yi-Gao Wang 1, 2 , Lian Xue 1, 2 , Bo Zhang 1 , Zhi-Xin Chen 1 , Jia-Ping Chen 1 , Zong-Guang Zhou 1 , Jian-Kun Hu 1, 2 1 Department of Gastrointestinal Surgery, West China Hospital, Sichuan University, Chengdu, Sichuan, China 2 Laboratory of Gastric Cancer, State Key Laboratory of Biotherapy/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan, China 3 West China School of Pharmacy, Sichuan University, Chengdu, Sichuan, China * These authors contributed equally to this work Correspondence to: Jian-Kun Hu, email: hujkwch@126.com Keywords: gastric cancer, lymph node ratio, staging, prediction Received: March 19, 2016 Accepted: May 17, 2016 Published: May 30, 2016 ABSTRACT This study aimed to evaluate the prognostic significance of node ratio (Nr), the ratio of metastatic to retrieved lymph nodes, and to investigate whether a modified staging system based on Nr can improve prognostic ability for gastric cancer patients following gastrectomy. A total of 2572 patients were randomly divided into training set and validation set, and the cutoff points for Nr were produced using X-tile. The relationships between Nr and other clinicopathologic factors were analyzed, while survival prognostic discriminatory ability and accuracy were compared among different staging systems by AIC and C-index in R program. Patients were categorized into four groups as follows: Nr0, Nr1: 0.00–0.15, Nr2: 0.15–0.40 and Nr3: > 0.40. Nr was significantly associated with clinicopathologic factors including macroscopic type, tumor differentiation, lymphovascular invasion, perineural invasion, tumor size, T stage, N stage and TNM stage. Besides, for all patients, Nr and TNrM staging system showed a smaller AIC and a larger C-index than that of N and TNM staging system, respectively. Moreover, in subgroup analysis for patients with retrieved lymph nodes < 15, Nr was demonstrated to have a smaller AIC and a larger C-index than N staging system. Furthermore, in validation analysis, Nr, categorized by our cutoff points, showed a larger C-index and a smaller AIC value than those produced in previous studies. Nr could be considered as a reliable prognostic factor, even in patients with insufficient (< 15) retrieved lymph nodes, and TNrM staging system may improve the prognostic discriminatory ability and accuracy for gastric cancer patients undergoing radical gastrectomy.