Study of Sacituzumab Govitecan Versus Treatment of Physician's Choice in Patients With Hormone Receptor-positive/Human Epidermal Growth Factor Receptor 2 Negative (HR+/HER2-) Metastatic Breast Cancer Who Have Received Endocrine Therapy

Key Inclusion Criteria: * Able to understand and give written informed consent. * Must have adequate tumor tissue sample preferably from locally recurrent or metastatic site. * Documented evidence of HR+ metastatic breast cancer (mBC) confirmed with the most recently available tumor biopsy preferably from a locally recurrent or metastatic site. * Documented evidence of HER2- status. * Documented PD by computed tomography (CT) or magnetic resonance imaging during or after the most recent therapy per RECIST v1.1 criteria. * Candidate for the first chemotherapy in the locally advanced or metastatic setting. * Eligible for capecitabine, nab-paclitaxel, or paclitaxel. * Individuals must have at least one of the following: * Disease progression on at least 2 or more previous lines of endocrine therapy (ET) with or without a targeted therapy in the metastatic setting. * Disease recurrence while on the first 24 months of starting adjuvant ET will be considered a line of therapy; these individuals will only require 1 line of ET in the metastatic setting. * Disease progression within 6 months of starting first-line ET with or without a cyclin-dependent kinase (CDK) 4/6 inhibitor (if ineligible or if unable to access a CDK 4/6 inhibitor) in the metastatic setting. * Disease recurrence while on the first 24 months of starting adjuvant ET with CDK 4/6 inhibitor and if the individual is no longer a candidate for additional ET in the metastatic setting. * Individuals may have r…