Immunotherapy with immune checkpoint inhibitors (ICIs), including agents targeting programmed cell death-ligand 1 (PD-L1) or programmed cell death protein 1 (PD-1), has revolutionised cancer care for many solid tumours by potentially either reinvigorating exhausted tumour-specific cytotoxic CD8 + T cells or recruiting newly activated immune cells (ICs) to tumour sites [13]. This evidence concerns the gene PDCD1 and cancer.