Baseline levels of IL-2, IL-6, IL-17A, and Neutrophil-to-Lymphocyte Ratio (NLR), as well as changes in IL-2 levels over time, may serve as convenient predictive biomarkers for identifying GC patients who are likely to benefit from the addition of anti-PD-1 monoclonal antibodies to chemotherapy. The gene discussed is IL17A; the disease is gastric cancer.