PDCD1 and neoplasm: In the last decade, immune checkpoint inhibitors (ICIs) targeting programmed cell death protein-1 (PD-1) and programmed death ligand-1 (PD-L1), such as atezolizumab, avelumab, nivolumab and pembrolizumab, have become first-line options for platinum-unfit patients with PD-L1-positive tumours, and first-line maintenance or second-line options for platinum-fit patients [7, 15].