PDCD1 and pneumonitis: Generally, irAEs with anti–PD-1/PD-L1 therapy occur less frequently compared with anti–CTLA-4 monotherapy; however, pneumonitis occurs more frequently in patients receiving anti–PD-1/PD-L1 therapy compared to CTLA-4 inhibitors (Boutros et al., 2016; Friedman, Proverbs-Singh, & Postow, 2016).