Hormonal Receptors PET-CT

Sex hormones play an important role in the development and growth of cancer, especially in breast and prostate cancer. The mode of action of these sex hormones is activation of the corresponding hormone receptor in tumor cells. The hormone-bound receptor acts as a transcription factor and activates signaling pathways that induce proliferation and tumor growth. Because of the pivotal role of the sex hormones and their receptors in disease progression of breast cancer and prostate cancer, endocrine therapies are developed, that aim to interfere with hormone receptor-mediated pathways by either reducing the level of the hormone or blocking of the hormone receptor. The most important hormone receptors involved in tumor progression are estrogen and progesterone receptors in breast cancer and androgen receptors (ARs) in prostate cancer. PET allows noninvasive monitoring of receptor expression in patients with hormone-responsive tumors, and thus could potentially provide information that can support therapy management in patients. Since 1980s, many radiolabeled steroids have been evaluated as PET tracers for imaging of the hormone receptors, but most of these tracers failed in preclinical or early-clinical e valuation. So far, only 16 α -[¹⁸ F] fluoro-17 β -estradiol ([¹⁸ F]FES) se ems to be an interesting PET tracer for estrogen receptor (ER) imaging in breast cancer patients and potentially also for endometrial cancer patients. The first clinical studies in patients with prostate cancer indicate that PET imaging of the androgen receptor (AR) with 16 β -[¹⁸ F]fluorodihydrotestosterone ([¹⁸ F]FDHT) is feasible. Clinically useful PET tracers for progesterone receptor imaging are currently not available. Here, we will describe the current experience with [¹⁸ F]FES PET and [¹⁸ F]FDHT PET for imaging the ER and AR, respectively.