Approximately 500 eligible participants will be enrolled into 1 of 2 cohorts (250 participants in each cohort) according to the presence or absence of BMs at baseline. Cohort 1 will include participants without BM at baseline and Cohort 2 will consist of participants with BM at baseline.~After study intervention discontinuation, all participants will undergo an end-of-treatment visit (within 7 days of discontinuation) and will be followed up for safety assessments 40 (+ up to 7) days after the discontinuation of all study intervention.~All participants will be followed up for survival status and duration of treatment on subsequent therapies after intervention discontinuation every 3 months (± 14 days) from the date of the safety follow-up until death, withdrawal of consent, or the end of the study, as per defined in the protocol.
This is open-label, multicenter, international study, assessing the efficacy and safety of Trastuzumab deruxtecan (T-DXd) in participants with or without brain metastasis (BMs), with previously-treated advanced/metastatic HER2-positive breast cancer whose disease has progressed on prior anti-HER2-based regimens and who received no more than 2 lines/regimens of therapy in the metastatic setting (excluding tucatinib).