Compared to healthy individuals, patients with gastric cancer exhibit elevated serum levels of IL-17A, with overall survival (OS) significantly correlated with IL-2, IL-6, IFN-γ, IL-17A, NLR, and ECOG (all p < 0.05). The activity of IL-17A may contribute to resistance against anti-tumor immunity and play a role in treatment failure. This evidence concerns the gene IL2 and gastric cancer.