DESTINY Breast Respond HER2-low Europe

Inclusion Criteria:

• Adult patient (age ≥ 18 years) with histological or cytological confirmed diagnosisof unresectable and/or mBC

• Documented HER2-low status (IHC1+, IHC2+/ISH-)

• Patients who have received prior chemotherapy in the metastatic setting or patientswho have developed disease recurrence during or within 6 months of completingadjuvant chemotherapy

• Decision to newly initiate therapy of T-DXd or conventional chemotherapy accordingto the physicians choice per SmPC

• Written and signed Informed Consent to participate in the study

Exclusion Criteria:

• Pregnancy or breastfeeding

• Patients who at time of data collection for this study are participating in or haveparticipated in an interventional study that remains blinded.

No specific exclusion criteria are defined, as patients will be treated according to the proposed indication statements in the SmPC.