Abstract PS1-12-30: Real-world outcomes of first-line cdk4/6 inhibitor use in hr+/her2− metastatic breast cancer: a single-institution experience

Abstract Background: CDK4/6 inhibitors are a standard first-line treatment for HR+/HER2− metastatic breast cancer (MBC). However, real-world data are needed to confirm their effectiveness outside clinical trial settings. This study evaluates progression-free survival (PFS) and identifies predictors of early progression in patients who received first-line CDK4/6 inhibitors at a tertiary cancer center. Methods: We conducted a retrospective analysis of 82 patients with HR+/HER2− MBC treated at King Fahad Medical City, Riyadh, between January 2021 and December 2023. Patients were categorized based on receipt of first-line CDK4/6 inhibitors (n=59) vs non-CDK therapies (n=22). PFS was estimated using Kaplan-Meier methods. Subgroup analyses and logistic regression were performed to identify predictors of short PFS (