CD274 and esophageal squamous cell carcinoma: Based on the results of the KEYNOTE-181 trial [NCT02564263], in July 2019 the FDA approved pembrolizumab for the second-line treatment of patients with PD-L1-positive, locally advanced or metastatic esophageal squamous cell carcinoma and also approved PD-L1 Dako 22C3 pharmDx test as a companion diagnostic for pembrolizumab.