ERBB2 and breast cancer: In clinical trials of patients with HER2+ metastatic BC, T-DXd showed durable antitumor activity and progression-free survival in a T-DM1–pretreated population (DESTINY-Breast01 and DESTINY-Breast02 trials) [9, 10], and had better therapeutic efficacy than T-DM1 (DESTINY-Breast03 trial) [11].