Trastuzumab Deruxtecan in Residual HER2-Positive Early Breast Cancer

A total of 1635 patients were randomly assigned (in a 1:1 ratio) to receive T-DXd (818 patients) or T-DM1 (817 patients). Invasive-disease events or deaths were reported in 51 patients (6.2%) in the T-DXd group and 102 patients (12.5%) in the T-DM1 group (hazard ratio, 0.47; P<0.001); 3-year invasive disease-free survival was 92.4% and 83.7%, respectively. Invasive-disease events, noninvasive-disease events, or deaths were reported in 52 patients (6.4%) in the T-DXd group and 103 patients (12.6%) in the T-DM1 group (hazard ratio, 0.47; P<0.001); 3-year disease-free survival was 92.3% and 83.5%, respectively.  In patients with high-risk, residual invasive HER2-positive breast cancer, postneoadjuvant T-DXd resulted in a significantly higher likelihood of invasive disease-free survival than T-DM1; toxic effects were mainly gastrointestinal and hematologic. An important identified risk of T-DXd is interstitial lung disease, which requires appropriate monitoring and management.