18F-Fluoroestradiol PET: Current Status and Potential Future Clinical Applications

Estrogen receptor (ER) expression in breast cancer is associated with a more favorable prognosis and is necessary for a response to endocrine therapies. Traditionally, ER expression is assessed by in vitro assays on biopsied tumor tissue. However, recent advances have allowed in vivo evaluation of ER expression with F-18-fluoroestradiol (F-18-FES) PET. Clinical studies have demonstrated the use of F-18-FES PET as a method for quantifying in vivo ER expression and have explored its potential as a predictive assay and method of assessing in vivo pharmacodynamic response to endocrine therapy. This review outlines the biology and pharmacokinetics of F-18-FES, highlights the current experience with F-18-FES in patient studies on breast cancer and other diseases, and discusses potential clinical applications and the possible future clinical use of F-18-FES PET.