RecruitingDrug trialA Study to Assess the Effectiveness of Trastuzumab Deruxtecan in Chinese Breast Cancer Patients (REFRESH)This multi-center observational prospective study will collect real-world clinical and patient-reported outcome data from eligible patients with unresectable or metastatic HER2+ breast cancer who have received one or more prior anti-HER2-based regimens or patients with unresectable or metastatic HER2-low (IHC 1+ or IHC 2+, ISH-) breast cancer who have received at least a prior systemic therapy in the metastatic setting, or developed disease recurrence during or within 6 months of completing adjuvant chemotherapy.