Gene Signatures to Guide HR+MBC Therapy in a Diverse Cohort

Primary Objective: \- Determine the impact of early chemotherapy (i.e., capecitabine) versus endocrine therapy-based regimen on anti-tumor effect in patients with non-Luminal A hormone receptor-positive (HR+) metastatic breast cancer Secondary Objectives: * Compare the safety and tolerability of capecitabine versus endocrine therapy in patients with non-Luminal A hormone receptor-positive (HR+) metastatic breast cancer * Determine the impact of early chemotherapy (i.e., capecitabine) versus endocrine therapy-based regimen on anti-tumor effect in patients with non-Luminal A hormone receptor-positive (HR+) metastatic breast cancer Correlatives: * Determine if the tumor mutations detected in cfDNA are early surrogates of response * Determine if the cfDNA results at disease progression show new genomic alterations potentially associated with resistance to therapy