Factors involved in HNSCC radioresistance or radiosensitivity are numerous and are generally common to all cancers including traditional variable like cells lesions repair capacity, hypoxia, cell cycle position, and cell growth fraction, but also new “actors” such as hepatocyte growth factor receptor (HGFR) or programmed cell death protein 1 and programmed cell death protein 1 (PD-1) and its ligand, programmed death-ligand 1 (PD-L1) [98,99,100,101]. This evidence concerns the gene PDCD1 and cancer.