Patients with esophageal squamous cell carcinoma, and in particular high programmed cell death ligand-1 expression, derive survival benefit when treated with IO in the second-line setting (HR = 0.74, 95% CI = 0.68 to 0.82, P < .001; for any level of programmed cell death ligand-1 expression). Here, CD274 is linked to esophageal squamous cell carcinoma.