In the meta-analysis by Qi et al. [80] considering six studies of advanced breast cancer including TNBC and HR+ HER2− patients who had received anti-PD-1/PD-L1 monotherapy, the response rate as reported was closely associated with the expression of the PD-L1 biomarker (PD-L1+ vs. PD-L1−). This evidence concerns the gene CD274 and breast cancer.