PDCD1 and head and neck squamous cell carcinoma: In a curative setting, pre-surgery, neoadjuvant anti-PD-1 monotherapy alone or combined with cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) ICB induces a major response, with >90% pathological tumor regression in 20–35% of HNSCC patients [7,8].