Development and Validation of an Age-Related Gastric Cancer-Specific Immune Index

BACKGROUND: Aging has a negative impact on the immune function of patients. The purpose of this study was to construct an age-related specific immune index according to the immune aging phenomenon of gastric cancer (GC) and explore its prognostic value. METHODS: This study retrospectively analyzed patients who underwent radical GC surgery in the Department of Gastrointestinal Surgery, Affiliated Cancer Hospital of Harbin Medical University, from August 2014 to December 2016 and divided them into a training cohort and a validation cohort. A new immune score, the GC-specific immune index (GSII), was developed as a series of lymphocyte subsets associated with the prognosis of patients with GC. Then, the receiver operating characteristic (ROC) curve was used to compare the prediction performance. The Kaplan‒Meier method and Log rank test were used to analyze the overall survival of patients. Cox hazard regression models were used to identify independent risk factors associated with prognosis. Finally, a nomogram model was constructed by combining the GSII and clinicopathological characteristics, and the calibration chart, consistency index, and decision curve were used to test the performance of the model. RESULTS: Aging did not significantly affect CD8 cell counts but decreased CD4 and CD19 cell counts. Based on the Cox analysis, the GSII of patients ≤60 years old was 0.079×lg CD4+0.348×lg CD19, and the GSII of patients >60 years old was 0.058×lg CD4. A decreased GSII was indicative of a poor prognosis and was an independent risk factor associated with patient outcomes. The nomogram constructed based on the GSII and clinicopathological features accurately predicted patient prognosis. Furthermore, the GSII was well validated in the validation cohort. CONCLUSION: The GSII constructed for the special immune aging phenomenon of GC can accurately predict patient prognosis.