The C-PLAN index, a novel composite score integrating C-Reactive Protein (CRP), lymphocyte dynamics, nutritional risk, and the Neutrophil-to-Lymphocyte Ratio (NLR), was developed to serve as a potential prognostic tool in this setting.<h4>Methods</h4>This study included 228 patients with advanced esophageal cancer who received PD-1/PD-L1 inhibitors between January 2018 and March 2023. Here, CRP is linked to esophageal cancer.