PDCD1 and cancer: The pooled OR demonstrated that PD-1 inhibitors significantly increased the risks of developing all-grade (OR = 3.90, [95% CI: 1.94–7.85], P = 0.0001) and high-grade (OR = 3.55, [95% CI: 1.29–9.76], P = 0.014) pneumonitis in cancer patients, according to the fixed effects model (Fig. 3A,B).