Breast cancers with immunohistochemical (IHC) analysis score of 1+ or 2+ with negative results on in situ hybridization (ISH) studies are defined as HER2-low.
Agents with efficacy in HER2 – low metastatic breast cancer, include trastuzumab-deruxtecan an ADC agent, and Sacituzumab govitecan also an ADC agent.