ROSHER

THIS IS A DATA-DRIVEN, RETROSPECTIVE, LONGITUDINAL, POPULATION BASED, OBSERVATIONAL, MULTI-CENTERED STUDY USING SECONDARY DATA CAPTURED FROM CONGRUENT ELECTRONIC HEALTH RECORDS. THE TARGET POPULATION OF INTEREST IN THIS STUDY IS PATHOLOGICALLY DOCUMENTED 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. THE MAIN OBJECTIVE IS TO ASSESS THE PREVALENCE OF HER2 EXPRESSION CHANGE BETWEEN INITIAL DIAGNOSIS VERSUS ANY OF SUBSEQUENT BREAST CANCER RELAPSES.