In the DESTINY-Breast04 study involving patients with advanced breast cancer and HER-2 low expression who had previously received first- or second-line hormone receptor-positive (HR+) endocrine therapy, trastuzumab deruxtecan (T-DXd) significantly improved the progression-free survival (PFS) and overall survival (OS) compared with physician-selected chemotherapy (median PFS [mPFS], 10.1 months vs 5.4 months, P < 0.05). Here, ERBB2 is linked to breast cancer.