The programmed cell death protein 1 (PD-1) inhibitor pembrolizumab in combination with chemotherapy (pembrolizumab–chemotherapy) is currently a standard-of-care first-line treatment for patients with radically unresectable, advanced, or recurrent esophageal cancer based on the results of the randomized, placebo-controlled, phase 3 KEYNOTE-590 study [1–4]. The gene discussed is PDCD1; the disease is esophageal cancer.