PDCD1 and cancer: The program cell death-1 (PD-1)/program death ligand-1 (PD-L1) pathway has been extensively studied for its role in regulation of antitumor immunity.1 Single-agent anti-PD-1 or anti-PD-L1 immune checkpoint inhibitor (ICI) therapy has been approved for more than 10 types of advanced cancers, and combination regimens with other immunomodulatory agents, targeted therapy, or cytotoxic chemotherapy may further improve overall survival (OS) or progression-free survival (PFS) in different cancer types.