PDCD1 and head and neck squamous cell carcinoma: Recently, the anti-programed cell death protein 1 (PD-1) ICI pembrolizumab and nivolumab, in monotherapy, improved overall survival compared with standard of care, in patients with R/M HNSCC that progressed during or after platinum-based chemotherapy (Ferris et al., 2016; Cohen et al., 2019).