How it works: The monoclonal antibody trastuzumab is labeled with 89Zr to identify breast cancer cells overexpressing the HER2 receptor, as is the case in luminal B (ER/PgR+, HER2+) and HER2+ (ER/PgR−, HER2+) breast cancer subtypes.43 This evidence concerns the gene ESR1 and breast carcinoma.