For patients with ER-negative HER2-ultralow breast cancer, how and when would you incorporate T-DXd?

The DESTINY-Breast06 trial demonstrated significant efficacy for T-DXd in HER2-low and ultralow HER2 breast cancer, particularly in improving PFS compared to chemotherapy. However, ER-negative patients were not included in the trial. If a pathologist can accurately identify HER2-ultralow status, the...

I would use T-DXd in this population once I had exhausted other options (e.g., I would first use sacituzumab govitecan, and other standard later-line chemotherapies like eribulin, but then I would use T-DXd if I were able to get insurance coverage). In a case like this, I would acknowledge to the pa...