Towards standardization of lymph-node ratio classifications: Validation and comparison of different lymph node ratio classifications for predicting prognosis of patients with resected gastric cancer

Introduction: The TNM staging system is the main prognostic tool for GC, but the number of metastatic lymph nodes (LN) can be affected by surgical, pathological, tumor or host factors. Several authors have shown that lymph node ratio (LNR) may be superior to TNM staging in GC. However, cut-off values vary between studies and LNR assessment is not standardized. Material and methods: Retrospective study of all GC resected in a western tertiary center (N = 377). Clinical features were collected and pathological features were assessed by two independent pathologists. Eight LNR classifications were selected and applied to our patients. Statistical analyses were performed. Results: 315 patients were included. Most tumors were T3 (49.2%) N+ (59.3%). During follow-up, 36.7% of patients progressed and 27.4% died due to tumor. All LNR classifications were significantly associated with clinicopathological features such as Lauren subtype, lymphovascular invasion, perineural infiltration, T stage, tumor progression or death. All LNR classifications were independent prognostic factors for OS and DFS, and ROC analyses calculated similar AUC values for all staging systems. Kaplan-Meier curves showed that Pedrazzani, Wang, Liu and Huang classifications stratified patients better into three (Pedrazzani) or four categories. These classifications tended to downstage TNM N2 and N3 tumors. In cases with less than 16 LNs resected, Pedrazzani and Wang classifications showed the best prognostic performance. Conclusions: Pedrazzani, Wang, Liu and Huang classifications showed good prognostic performance in western GC patients. Larger studies in other cohorts are needed to identify the most consistent LNR classification for GC.