Predictive value of the preoperative systemic immune-inflammation index for primary chemotherapy resistance risk in patients with advanced gastric cancer

First-line systemic chemotherapy is a standard treatment for advanced gastric cancer, yet substantial heterogeneity exists in treatment response, with a considerable proportion of patients developing early resistance. Reliable pre-treatment biomarkers to identify patients at high risk of primary chemotherapy resistance are lacking. The systemic immune-inflammation index (SII) reflects host inflammatory and immune status. This study aimed to investigate the predictive value of pre-treatment SII for primary chemotherapy resistance in patients with advanced gastric cancer and to further evaluate its incremental value for survival risk stratification and exploratory predictive modeling.