Deep proteomic analysis of plasma exosomes in patients with advanced, hormone receptor-positive breast cancer treated with palbociclib and tamoxifen.

1030 Background: Combining a CDK4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) in advanced, hormone receptor (HR)-positive, HER2-negative breast cancer (BC) doubles median progression-free survival, but eventually drug resistance and disease progression occur. For most patients, the mechanism of resistance is unknown. Exosomes are membrane-bound extracellular vesicles that contain lipids, proteins, and nucleic acids, and are released from...