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

This study tests whether genetic tumor profiling can guide which chemotherapy is best for people with hormone receptor-positive, HER2-negative advanced breast cancer — a type of breast cancer that feeds on estrogen or progesterone signals. It focuses on diverse patient populations who have already tried hormone-blocking therapies. **You may be eligible if...** - You are 18 or older with stage IV breast cancer (or locally advanced breast cancer that can't be surgically removed) that is ER+ and/or PR+ and HER2-negative - You have previously received an aromatase inhibitor or similar hormone-blocking drug plus a CDK4/6 inhibitor - Your performance level allows you to carry out daily activities with minimal limitation - You have at least one measurable or evaluable area of cancer **You may NOT be eligible if...** - You have already received chemotherapy for metastatic disease - You have had another cancer in the last 2 years (some exceptions apply) - You are pregnant or breastfeeding - You have unresolved significant side effects from previous treatments Talk to your doctor to see if this trial is right for you.