However, the response rates reported in clinical trials for breast cancer with PD-1/PD-L1 checkpoint inhibitors as single agents have been rather disappointing (5–10%), although better clinical activities (up to 30%) and durable overall responses have been observed in patients with basal-like/HER2+ breast cancer and positive expression of PD-L1 [24–29]. This evidence concerns the gene ERBB2 and breast cancer.