ERBB2 and breast cancer: In this study, we conducted a cost-effectiveness analysis of T-DXd vs chemotherapy for previously treated HER2-low advanced BC, and the results revealed that compared with chemotherapy, the ICERs of T-DXd was $83,892/QALY, $82,808/QALY, and $93,358/QALY in all HER2-Low advanced BC patients (Scenario 1), HER2+ advanced BC patients (Scenario 2) and HER2- advanced BC patients (Scenario 3), respectively.