In a subset of patients with HR+ HER2-low breast cancer (88% of study participants), patients treated with T-DXd as compared to the physician’s choice of treatment had a significant improvement in PFS (10.1 vs. 5.4 months, HR = 0.51, 95% CI: 0.4–0.64; p < 0.001) and OS (23.9 vs. 17.5 months, HR = 0.64, 95% CI: 0.48–0.86; p = 0.003). Here, ERBB2 is linked to breast cancer.