18F-FES

16α-[18F] fluoroestradiol ([18F] FES) as radiofluorinated analogous estradiol has been the first positron emission tomography (PET) imaging agent for a receptor target in cancer. Estradiol receptors are highly expressed in 70–80% of breast cancers and play a central role in prognosis and treatment selection for patients with breast cancer. [18F]-FES PET imaging has been demonstrated to distinguish tumors with intrinsically good or poor prognosis, alone or in combination with [18F]-FDG, and to determine which therapies could be effective in which patients. In France, the [18F]-FES is approved for the whole-body evaluation of recurrent ER-positive breast cancer in place of biopsy. Thus, it is a powerful diagnostic tool able to solve clinical dilemmas and provide systemic staging of breast cancer patients.