Prognostic value of systemic immune-inflammation index in patients with gastric cancer

BACKGROUND Inflammation-based indexes have been used to predict survival and recurrence in cancer patients. Systemic immune-inflammation index (SII) was reported to be associated with prognosis in some malignant tumors. In the present study, we aimed to explore the association between SII and the prognosis of patients with gastric cancer. METHODS We retrospectively analyzed data from 444 gastric cancer patients who underwent gastrectomy at the First Affiliated Hospital of Sun Yat-sen University between January 1994 and December 2005. Preoperative SII was calculated. The Chi square test or Fisher's exact test was used to determine the relationship between preoperative SII and clinicopathologic characteristics. Overall survival (OS) rates were estimated using the Kaplan-Meier method, and the effect of SII on OS was analyzed using the Cox proportional hazards model. Receiver operating characteristic (ROC) curves were used to compare the predictive ability of SII, NLR, and PLR. RESULTS SII equal to or higher than 660 was significantly associated with old age, large tumor size, unfavorable Borrmann classification, advanced tumor invasion, lymph node metastasis, distant metastasis, advanced TNM stage, and high carcino-embryonic antigen level, high neutrophil-lymphocyte ratio, and high platelet-lymphocyte ratio (all P < 0.05). High SII was significantly associated with unfavorable prognosis (P < 0.001) and SII was an independent predictor for OS (P = 0.015). Subgroups analysis further showed significant associations between high SII and short OS in stage I, II, III subgroups (all P < 0.05). SII was superior to NLR and PLR for predicting OS in patients with gastric cancer. CONCLUSION Preoperative SII level is an independent prognostic factor for OS in patients with gastric cancer.