PDCD1 and head and neck cancer: ICI using monoclonal antibodies against the cytotoxic T lymphocyte associated protein 4 (CTLA-4), the programmed cell death protein 1 (PD-1) or the programmed cell death ligand 1 (PD-1 L) (1) are now considered the standard of care in numerous solid and hematologic malignancies including advanced-stage melanoma, non-small-cell lung cancer (NSCLC), head and neck cancer, bladder cancer, or renal cell carcinoma (2).