The first approval by the U.S. Food and Drug Administration (FDA) was granted in 2019 following the Destiny-Breast01 trial, which included 184 patients with unresectable and/or metastatic HER2-positive breast cancer and demonstrated promising response rates.(14) Building on these findings, the Destiny-Breast 04 trial was conducted to evaluate the positive outcomes of using T-DXd in patients with low HER2 expression. This evidence concerns the gene ERBB2 and breast carcinoma.