CD274 and breast cancer: The phase III KEYNOTE-355 study contained 847 metastatic PNBC patients randomized and treated with pembrolizumab and chemotherapy vs. chemotherapy plus placebo and found pembrolizumab plus chemotherapy to be associated with better progression-free survival (PFS) for breast cancers with PD-L1 (22C3) CPS scores ≥10 in the immunotherapy arm [58].