PDCD1 and cancer: ICB treatment, such as those programmed cell death protein 1 (PD1), programmed death-ligand 1 (PDL1) and cytotoxic T-lymphocyte antigen 4 (CTLA-4) is now the first class of immunotherapy to have a broad impact on survival for cancer patients, across a wide variety of tumour histologies and treatment settings (Littman, 2015; Lonberg and Korman, 2017; Ribas and Wolchok, 2018; Wieder et al., 2018).