In the phase III TROPION-Breast01 study for patients with hormone receptor-positive/human epidermal growth factor receptor 2–negative (HR+/HER2−) breast cancer, Dato-DXd significantly reduced the risk of progression or death versus ICC (PFS by BICR hazard ratio [HR], 0.63 [95% CI, 0.52 to 0.76]; p < 0.0001). This evidence concerns the gene ERBB2 and breast cancer.