Patients with pathologically documented an initial breast cancer diagnostic (early breast cancer (BC) or locally advanced BC or de novo metastatic BC) with documented human epidermal growth factor receptor 2 (HER2) and estrogen receptor (ER)/progesterone receptor (PgR) expression status at the time of diagnosis.~Data to determine the primary endpoint is estimated to be derived from the EHRs of over 2,000 patients that have an initial diagnosis of early BC, or locally advanced BC, or de novo metastatic BC (mBC) between the 1st of January 2005 and the 31st of December 2021, and who had at least one subsequent relapse until the 31st of December 2021 in at least 10 clinical centers.~The secondary endpoints utilize a larger collection of data from over 30,000 patients that have an initial diagnosis of early BC, or locally advanced BC, or de novo mBC between the 1st of January 2005 and the 31st of December 2021.
This is a data-driven, retrospective, longitudinal, population- based, observational, multi-centered study using secondary data captured from congruent electronic health records (EHRs).