A meta-analysis comparing the efficacy and safety of PD-L1+Chemo vs. PD-1+Chemo in extensive-stage small cell lung cancer revealed that PD-L1+Chemo tended to reduce the incidence of pneumonia of any grade, compared with PD-1+Chemotherapy (Yu et al., 2022). Here, PDCD1 is linked to susceptibility to pneumonia measurement.