Impact of GLP-1 receptor agonists in hormone receptor–positive breast cancer patients receiving CDK4/6 inhibitors.

1100 Background: Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are increasingly prescribed for type 2 diabetes and obesity due to their efficacy in weight reduction and glycemic control. Beyond their metabolic benefits, GLP-1 RAs delay gastric emptying, which may affect the absorption of oral medications like cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i). Additionally, CDK4/6i and GLP-1 RAs share overlapping gastrointestinal (GI) toxicities such as diarrhea and nausea, which could impact medication tolerability and clinical outcomes. This investigation aimed to characterize the safety of concomitant GLP-1 RA and CDK4/6i use in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Methods: We performed a single-center, retrospective chart review evaluating adult patients prescribed a CDK4/6i for HR+ breast cancer at Winship Cancer Institute between October 2022 and May 2025. Patients receiving concomitant GLP-1 RA and CDK4/6i (Group 1) were matched 1:1 to patients receiving a CDK4/6i without GLP1-RA (Group 2). Matching criteria included prescribed CDK4/6i, treatment indication (adjuvant or metastatic), age (≥65 years, 45-64 years, and