The DB-04 study (NCT03734029) demonstrated that, after 1–2 lines of chemotherapy, T-DXd significantly outperformed the TPC regimen in patients with HER2-low (IHC 1-2+/ISH-) advanced breast cancer, with a median PFS of 9.9 months vs. 5.1 months (P<0.001). Here, ERBB2 is linked to breast carcinoma.