PDCD1 and colitis: A meta-analysis by Wang et al. in 2018 227 indicated colitis for CTLA-4 inhibitors (70%, 135/193 deaths), pneumonitis (35%, 115/333 deaths) for PD-1 or PD-L1 inhibitors, and colitis (37%, 32/87) for the combination PD-1 and CTLA-4 inhibition as the most frequent causes of death as an irAE.