The study will involve patients diagnosed with HER2-positive unresectable or mBC since the earlier date between the date of trastuzumab emtansine ([T-DM1] Kadcyla) becoming available through reimbursement or patient access programme as a valid local treatment option or 01 January 2017 and who received at least 1 LOT. The data will be collected from the date of diagnosis of unresectable or mBC (index date) to the end of follow-up (ie, until death, the last medical record entry, or date of data extraction, whichever is earlier). The study will not have any study-specific patient visits or a longitudinal follow-up. All available data will be extracted from patients' medical records or obtained from patients themselves after obtaining an informed consent unless a waiver is granted by the local Institutional Review Board (IRB)/Institutional Ethics Committee (IEC)/Ethics Committee (EC). The informed consent may be obtained at the time of patients routine clinical care visit to the oncology centre. The data on different types of treatment received by the patients, socio-demographics, and clinico-pathological characteristics will be extracted from patients medical records up to the date informed consent was obtained.~This study will be conducted in non-US and non-European countries including Australia, Brazil, Hong Kong, Korea, Singapore and Taiwan. The total number of patients in the study will be approximately a minimum of 570 and a maximum of 830 patients. The study will be implemented at approximately 50 to 100 oncology centres spanning across 6 countries in the AstraZeneca (AZ) International Region (ie, non-US, non-European countries).
This multicountry, multicenter, retrospective, non-interventional study involving patients diagnosed with HER2-positive unresectable or metastatic breast cancer mBC will be conducted to understand the demographic and clinico-pathological profile of the patients, diagnostic practices for human epidermal growth factor receptor 2 (HER2) status, current treatment landscape and sequencing of therapies, associated burden of toxicities with all lines of treatment (LOTs), and survival outcomes in the real-world setting.