PDCD1 and pneumonitis: Compared with routine chemotherapy such as docetaxel, dacarbazine, paclitaxel and carboplatin, patients treated with PD-1 inhibitors were more susceptible to pneumonitis (all-grade: OR = 3.90, [95% CI: 1.94–7.85], P = 0.0001; high-grade: OR = 3.55, [95% CI: 1.29–9.76], P = 0.014), suggesting that the risk of pneumonitis induced by anti-PD-1 immunotherapy is higher than that of most chemotherapy.