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Real-world progression-free survival of CDK4/6 inhibitors plus an aromatase inhibitor in HR-positive/HER2-negative metastatic breast cancer in United States routine clinical practice

Published

September 2025

Citation

Rugo H, Layman R, Lynce F, et al. Real-world progression-free survival of CDK4/6 inhibitors plus an aromatase inhibitor in HR-positive/HER2-negative metastatic breast cancer in United States routine clinical practice. ESMO Open. 2025. https://www.esmoopen.com/article/S2059-7029(25)01439-5/fulltext

Overview

The treatment landscape for HR-positive/HER2-negative mBC has evolved significantly with the introduction of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i). These include palbociclib, ribociclib, and abemaciclib, which, when combined with aromatase inhibitors (AI), have shown to significantly prolong progression-free survival (PFS) in clinical trials. However, direct comparisons of these treatments in real-world settings have been limited. 

This study used the Flatiron Health EHR-derived Panoramic database comprised of >940K patients with breast cancer to compare real-world progression free survival (rwPFS) of nearly 10,000 patients treated with palbociclib, ribociclib, and abemaciclib in combination with an aromatase inhibitor. This research found no significant rwPFS difference across the three CDK4/6is when treating patients with HR+/HER2- mBC.

Why this matters

This research is the largest real-world study to date that evaluated the comparative effectiveness of the three approved CDK4/6 inhibitors. These therapies will likely never be compared against each other in a trial. Thus, using novel real-world data solutions provides evidence that improves our understanding of treatment options and outcomes for patients with mBC. Flatiron’s Panoramic datasets offer a scaled, comprehensive, disease-specific solution to answer questions not previously possible, unlocking critical information to improve care and outcomes for people with cancer.

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