Trastuzumab Deruxtecan versus Trastuzumab Emtansine for Breast Cancer: a plain language summary of the DESTINY-Breast03 study.

This is a summary of a publication about the DESTINY-Breast03 study, which was published in the Researchers in this study found that the risk of dying or the participants' cancer getting worse was reduced by 72% in the T-DXd group compared with the T-DM1 group. This is also called progression-free survival. 79.7% of participants in the T-DXd group had their tumors shrink significantly or disappear, compared to 34.2% of those in the T-DM1 group. During the study, 10.9% of participants who received T-DXd had serious drug-related medical problems, compared to 6.1% who received T-DM1. Of the participants who received T-DXd, 10.5% experienced drug-related interstitial lung disease (ILD) or pneumonitis, compared to 1.9% of those who received T-DM1. ILD and pneumonitis are potentially serious lung problems. When the researchers first looked at the results, they could not yet be certain that T-DXd helped participants survive longer overall than T-DM1. But, when they looked at the results later in the study, they found that T-DXd did help participants to survive longer overall than T-DM1. These newer results were published separately and are not part of this summary. A link to more information about the newer results can be found at the end of this summary. T-DXd gave participants a meaningful benefit overall compared to T-DM1. T-DXd could be a treatment option for people with advanced HER2-positive breast cancer that has been previously treated.