Dr. Hamilton on the Efficacy of Trastuzumab Deruxtecan in HER2-Low Breast Cancer

Erika P. Hamilton, MD, director of the Breast Cancer and Gynecologic Cancer Research Program and principal investigator at the Sarah Cannon Research Institute, discusses the efficacy of fam-trastuzumab deruxtecan-nxki (Enhertu) in HER2-low breast cancer.

There are a lot of data on the use of trastuzumab deruxtecan in HER2-low–expressing breast cancers, says Hamilton. This is impressive because it is not the first time the field has looked at this antibody-drug conjugate (ADC) in HER2-low disease, according to Hamilton.

A few years ago, at a San Antonio Breast Cancer Symposium, data were presented in this space, although they were negative. This speaks to the unique mechanism of action of the ADC; it is a unique molecule that can be very effective, says Hamilton. In patients with HER2-low breast cancer, trastuzumab deruxtecan has a bystander effect; even if a small amount of trastuzumab deruxtecan binds, it can kill neighboring cells that may not have much HER2 expression at all, explains Hamilton. Impressive response rates have been reported with this agent in the HER2-low space.

Notably, the minority of patients are HER2-overexpressing, meaning they're 3+ or amplified; more patients that are 1+ or 2+ and FISH negative, says Hamilton. As such, it will be exciting to see how many patients may be reached with this approach in the future, concludes Hamilton.