PDCD1 and melanoma: The results showed that in 1st line (RR 2.77, 95% CI 1.33-5.77, p = 0.006, Fig. 4a), “≥ 2nd line” (RR 1.48, 95% CI 1.10-1.99, p = 0.01, Fig. 4b), anti-PD-1 (control group) (RR 1.48, 95% CI 1.15-1.89, p = 0.002, Fig. 4c), anti-CTLA-4 (control group) (RR 3.14, 95% CI 2.46-4.00, p < 0.00001, Fig. 4e) and melanoma (RR 2.57, 95% CI 1.38-4.79, p = 0.003, Fig. 4f) groups, the ORR of ICI combination therapy was significantly higher than that of ICI monotherapy.