Receiver operating characteristic (ROC) analyses showed that, for advanced HER2-positive breast cancer patients, the CFR results [area under the curve (AUC): 0.708] were better than those for the other factors (AUC: CD8 = 0.681, FOXP3 = 0.639, PD1 = 0.528, PD-L1 = 0.681) (Fig. 4b). This evidence concerns the gene CD8A and breast cancer.