CD274 and breast cancer: Forty patients with advanced HER2+ PD-L1 unselected BC will be randomized to receive vinorelbine, trastuzumab, and avelumab; vinorelbine and trastuzumab; or vinorelbine, trastuzumab, avelumab, and utomilumab, a fully human IgG2 agonist mAb that binds to the ECD of CD137.