Purpose: Gastric cancer (GC) is one of the most common malignancies and has a high mortality rate. In recent years, several nutritional or inflammatory biomarkers have been shown to effectively predict the prognosis of tumors. In this study, we intended to establish a prognostic scoring system for GC patients. 
Patients and methods: Our study included a total of 501 GC patients who were diagnosed with GC stage I–III and received curative gastrectomy with D2 lymphadenectomy between January 2011 and December 2012. Survival analysis was performed using Kaplan–Meier and log-rank tests. Two Cox multivariate models, one for continuous and one for categorical variables, were established to identify independent prognostic factors. All statistical analyses were performed using SPSS 20.0.
Results: Univariate and multivariate analyses revealed that tumor-node-metastasis (TNM) stage, preoperative prognostic nutritional index (PNI), and adjuvant therapy were independent prognostic factors for GC patients. We established a new composite variable, TNM-PNI, which was confirmed to be a major prognostic factor for curative D2 resection, independent of whether adjuvant therapy was administered. GC patients with higher TNM-PNI scores always had worse cancer outcomes. In addition, we found that adjuvant therapy might be beneficial for the survival of GC patients with TNM-PNI =4 or 5.
Conclusion: Preoperative PNI plays a distinctly subsidiary role to the TNM stage when predicting patient prognosis. TNM-PNI is a novel and an effective prognostic index for GC patients with curative D2 resection and a good supplement for the National Comprehensive Cancer Network Guidelines.
Keywords: tumor-node-metastasis stage, prognostic nutritional index, adjuvant therapy, cancer outcome prognosis