PDCD1 and melanoma: A subgroup analysis (Fig. 5) was also conducted, and the results showed that in 1st line (RR 1.54, 95% CI 1.25-1.90, p < 0.0001, Fig. 5a), anti-PD-1 (control group) (RR 1.24, 95% CI 1.07-1.43, p = 0.003, Fig. 5c), anti-CTLA-4 (control group) (RR 1.71, 95% CI 1.45-2.02, p < 0.00001, Fig. 5e) and melanoma (RR 1.56, 95% CI 1.29-1.89, p < 0.00001, Fig. 5f) groups, the DCR of ICI combination therapy was significantly higher than that of ICI monotherapy.