This study aimed to develop a novel Prognostic Oxidative Stress-Immune-Inflammatory Score (POSII Score) and introduce an innovative online calculator designed to predict long-term survival and assess the recurrence risk of gastric cancer (GC).

From 2009 to 2020, this study analyzed GC patients underwent Radical Gastrectomy at three hospitals, dividing them into training, internal, and external validation cohorts. Twelve blood indicators were analyzed. The POSII Score was developed in the training cohort using the Least Absolute Shrinkage and Selection Operator (LASSO) technique. Additionally, two online nomogram calculators were created based on multivariate Cox regression within the training cohort and subsequently validated in internal and external validation cohorts.

Inclusion Criteria:1) histopathologically diagnosed gastric adenocarcinoma, 2) undergoing radical gastrectomy for GC, 3) absence of tumor invasion into adjacent organs or distant metastasis, and 4) availability of complete laboratory data.

Exclusion Criteria: 1) non-adenocarcinoma gastric cancers, 2) gastric stump cancer, 3) receipt of neoadjuvant therapy, 4) a history of other malignancies, and 5) insufficient clinical data or follow-up information.

This study is a multicenter, retrospective cohort investigation involving GC patients who underwent radical gastrectomy at the Fujian Medical University Union Hospital (FMUUH), the First Affiliated Hospital of Gannan Medical University (FAHGMU) and Quzhou Affiliated Hospital of Wenzhou Medical University (QAHWMU) between January 2009 and June 2020.