A large phase 3 trial tested a targeted drug called trastuzumab deruxtecan (T-DXd) against standard chemotherapy in 866 people with hormone receptor-positive, HER2-low or HER2-ultralow metastatic breast cancer. All participants had already tried at least one hormone therapy.
The study found that T-DXd delayed cancer growth by several months compared to chemotherapy. For example, in people whose cancer had progressed quickly on previous treatment, the median time before the cancer worsened was 14 months with T-DXd versus 6.5 months with chemo. Similar benefits were seen in other groups. The drug also led to higher response rates and longer-lasting responses.
Safety information was not detailed in this report, but the researchers noted that side effects were similar to what has been seen before with these treatments. No serious adverse events or discontinuation rates were reported.
It is important to know that these results come from a subgroup analysis, which means the researchers looked at specific groups after the main study was done. This type of analysis is less reliable than the main findings. Still, the overall trial was a randomized controlled trial, which is a strong study design. These findings suggest T-DXd may be a good option for many people with this type of breast cancer, but more research is needed to confirm the results in these subgroups.
