PDCD1 and head and neck squamous cell carcinoma: Although the interplay between EGFR signaling and the PD-L1 /PD-1 pathway is complex and still needs to be fully understood [176], these observations offer a rationale for using anti-EFGR cetuximab in combination with anti-PD-1 or PD-L1 in HNSCC or NSCLC (Table 6).