Pts with HER2-low (HER2 IHC 1+ or IHC 2+/ISH−) mBC who had been previously treated with 1 or 2 lines of chemotherapy were randomly assigned (2:1) to either T-DXd or TPC (physician’s choice of chemotherapy)….110 pts were included (ER IHC 0% n = 58; ER IHC 1-10% n = 52). Efficacy results are shown in the table. Pts with ER IHC 1-10% treated with T-DXd had longer PFS (median PFS, 8.4 months with T-DXd vs 2.6 months with TPC....Efficacy, including survival, of T-DXd over TPC in pts with HER2-low ER 1-10% mBC was consistent with the outcomes observed in pts with HER2-low ER 0% mBC.