Abstract

Purpose
Guidelines from the aromatase inhibitor era for early breast cancer (EBC) treatment recommend maintaining a body mass index (BMI) below 25. In the current era of CDK 4/6 inhibitors, now standard in metastatic breast cancer (MBC), limited data exist on treatment outcomes in obese patients. This study investigates how adiposity affects the treatment outcome of CDK 4/6 inhibitors in patients with hormone receptor (HR)-positive, HER2-negative MBC.
Materials and Methods
We searched PubMed, MEDLINE, and Embase databases, assessing efficacy outcomes such as progression-free survival (PFS) based on obesity markers, including BMI and visceral adipose tissue (VAT) index.
Results
Twelve studies were reviewed, with seven studies and 1,812 patients included in a pooled meta-analysis. Among patients with BMI ≥25, modest improvement in PFS was observed, with a pooled hazard ratio (HR) of 0.944 (95% CI, 0.909-0.980; p = 0.003). Besides, add-on analysis using VAT to define obesity revealed a notable PFS improvement, with a pooled HR of 0.452 (95% CI, 0.256-0.798; p = 0.006).
Conclusion
While BMI-defined obesity showed slight PFS improvement with CDK 4/6 inhibitors and endocrine therapy, using VAT to define obesity revealed significant PFS gains. This highlights the need for further research on biomarker to clarify the role of adiposity in MBC, which may differ from its impact in EBC.

• Keywords: Obesity, Breast neoplasms, Neoplasm metastasis, Body mass index, Cyclin-dependent kinase inhibitors, Visceral fat