BEYOND Study: A Multicentre, Prospective, Observational Study of Real-world Treatment Patterns and Outcomes of Trastuzumab Deruxtecan in Patients with HR positive, HER2-low or Ultra-low Metastatic Breast Cancer Previously Treated with Endocrine Therapy - BEYOND

Inclusion Criteria

• Inclusion Criteria:
• - -Female patients aged ≥18 years old at the time of T-DXd initiation
• - Patients with a confirmed histological or cytologically based diagnosis of HR-positive
• mBC.
• - Patients who were classified as HER2-low or HER2-ultralow mBC confirmed by the
• closest locally obtained HER2 test prior to or on the index date, and who meet the
• following definitions:
• - HER2-low status defined as IHC scores 1+ and 2+ without ISH gene amplification
• based on the pathology report.
• - HER2-ultralow status defined as IHC 0 with membrane staining based on the
• pathology report.
• - Patient who received at least one prior line of ET (± targeted therapy) in the metastatic
• setting.
• - Patients who are chemotherapy-naïve in the metastatic setting.
• - Patients who initiated T-DXd up to 30 days before the signature of the ICF. The decision
• to initiate T-DXd must be made independently by treating physicians as part of routine
• clinical practice.
• - Patients are willing to sign the written ICF, indicating that they understand the purpose
• of the study and procedures required for participation.
• Exclusion Criteria:
• - -Patients with a history of other malignancies, other than basal cell carcinoma of the skin
• and squamous cell carcinoma of the skin.
• - Patients who received prior chemotherapy in the metastatic setting.
• - Patients with Eastern Cooperative Oncology Group (ECOG) status ≥2 or missing ECOG
• status at the time of initiation of T-DXd (index date).
• - Patients with a history of participation in another clinical trial in the metastatic setting.
• - Female patient with current or planned pregnancy, or breastfeeding.