This study comprehensively examines metabolic and lipidomic dynamics in gastric cancer patients initiating PD-1/PD-L1 inhibitor therapy, employing a longitudinal design with pre- and post-treatment patients. The primary objectives include identifying irAE-associated metabolic and lipid biomarkers, developing predictive risk models, and evaluating the prognostic value of these molecular profiles. The findings are expected to contribute significantly to personalized treatment strategies and improved clinical decision-making in immunooncology.