Estrogen Receptor Binding (18F-FES PET) and Glycolytic Activity (18F-FDG PET) Predict Progression-Free Survival on Endocrine Therapy in Patients with ER+ Breast Cancer.

Purpose: F-fluoroestradiol (FES) PET scans measure regional estrogen binding, and F-fluorodeoxyglucose (FDG) PET measures tumor glycolytic activity. We examined quantitative and qualitative imaging biomarkers of progression-free survival (PFS) in breast cancer patients receiving endocrine therapy.

Experimental Design: Ninety patients with breast cancer from an estrogen receptor-positive (ER), HER2 primary tumor underwent FES PET and FDG PET scans prior to endocrine therapy (63% aromatase inhibitor, 22% aromatase inhibitor and fulvestrant, 15% other).

Temporal Heterogeneity of Estrogen Receptor Expression in Bone-Dominant Breast Cancer: 18F-Fluoroestradiol PET Imaging Shows Return of ER Expression.

Changes in estrogen receptor (ER) expression over the course of therapy may affect response to endocrine therapy. However, measuring temporal changes in ER expression requires serial biopsies, which are impractical and poorly tolerated by most patients. Functional ER imaging using (18)F-fluoroestradiol (FES)-PET provides a noninvasive measure of regional ER expression and is ideally suited to serial studies.

Predicting Breast Cancer Endocrine Responsiveness Using Molecular Imaging.

The estrogen receptor (ER) is expressed on the vast majority of newly diagnosed breast cancers, yet not all ER-positive tumors will respond to endocrine therapy. Selecting patients for endocrine therapy can be considered as a series of predictive tests: does the tumor express the ER and if so, will the endocrine therapy interact with the target to produce a response? These are both challenges to which molecular imaging is functionally suited. Imaging of the ER has been most successful using 16-α[18F]-flouro-17β-estradiol (FES) positron emission tomography (PET).