CD274 and breast cancer: PD-L1 is one of the first biomarkers investigated to predict response among patients with various cancers.18 In patients with breast cancer, while PD-L1 expression predicted response to pembrolizumab in the metastatic setting, improved responses to ICIs were seen regardless of PD-L1 status in the early-stage setting12,19,20; therefore, its value in predicting benefit to ICIs in patients with non-metastatic breast cancer is limited.