Second, due to the utilization of summary statistics instead of raw data in the analysis, subgroup analyses based on ICIs regimes (e.g., PD-1/PD-L1 group, CTLA-4 group, and combined therapy group) or different cancer subtypes (e.g., gastrointestinal cancer and genitourinary cancer) could not be performed. This evidence concerns the gene CTLA4 and cancer.