About 60% of breast cancers traditionally categorised as HER2-negative in fact express low levels of HER2 (defined as tumours with HER2 IHC expression 1+ or 2+ without HER2 gene amplification). Last year, the DESTINY-Breast04 trial demonstrated notable efficacy of the HER2 antibody-drug conjugate trastuzumab deruxtecan (T-DXd), in patients whose tumours are not conventionally HER2+, but defined as HER2-low. As a result, HER2-low has become a clinically relevant HER2 status among patients with breast cancer, warranting a better understanding of this disease entity. As such, it was no surprise to see that at SABCS 2022, a special session was entirely devoted to HER2-low disease. Below, some key presentations of this session are summarized.
