The KEYNOTE-181 trial is the first study to use immunotherapy in second-line ESCC treatment, and the results showed that pembrolizumab prolonged OS versus chemotherapy (paclitaxel/docetaxel/irinotecan) as second-line therapy for advanced ESCC in PD-L1-positive patients (median 8.2 vs 7.1 months, P = 0.0095), with fewer treatment-related adverse events (9). Here, CD274 is linked to esophageal squamous cell carcinoma.