PDCD1 and metastatic neoplasm: Apart from the clinical approval of epidermal growth factor receptor (EGFR) antibody cetuximab and programmed cell death protein 1 (PD-1) antibodies nivolumab and pembrolizumab for recurrent and/or metastatic diseases, therapy concepts have not substantially changed over the past 15 years (Graham, et al., 2004; Ghanizada et al., 2019).