PDCD1 and pneumonitis: As shown in Figures 3, 4, compared with chemotherapy, the PD-1 inhibitor nivolumab and pembrolizumab both showed significant increase in grade 1-5 pneumonitis (nivolumab: RR,4.75, 95% CI: 1.54-14.69, p < 0.001; pembrolizumab: RR,5.35, 95% CI:2.61-10.96, p < 0.001), but only pembrolizumab showed significant increase in grade 3-5 pneumonitis.