IFNG and esophageal cancer: Additionally, a candidate IFNγ-gene signature including six candidate genes IDO1, CXCL10, CXCL9, HLA-DRA, STAT1 and IFN gamma developed from RNA extracted from formalin fixed paraffin embedded slides (FFPE), was also associated with ORR, PFS and OS to Pembrolizumab in head and neck, gastric and esophageal cancer [57,58].