Could ¹⁸F-FES PET Be a New Driver in Therapeutic Choice for Metastatic HR+/HER2- Patients?

Hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer is the most prevalent subtype. Positron emission tomography (PET) imaging with 16α-18F-fluoro-17β-fluoroestradiol (¹⁸F-FES), a radiolabeled form of estradiol, enables the assessment in vivo of ER expression, ER heterogeneity in metastatic sites and functionally active ER capable of ligand binding. This imaging modality has been recently approved as a diagnostic tool for detecting ER-positive lesions in patients with recurrent or metastatic breast cancer. Despite promising activity, the role of this powerful tool is still debated. Herein we critically analyzed current evidence supporting the use of 18F-FES PET in metastatic ER+/HER2- breast cancer, highlighting the potential challenges for clinical implementation.