OVERVIEW

[^18F] Fluoroestradiol (FES) is a radiopharmaceutical used in positron emission tomography (PET) imaging for evaluating estrogen receptor (ER) expression in breast cancer and other hormone-related cancers. It is an analog of estradiol, the primary estrogen hormone, and provides a non-invasive method to assess ER status, which is crucial for determining hormone therapy suitability.

Mechanism of Action

FES is an analog of the hormone estradiol, which binds to estrogen receptors in ER+ cells. After administration, FES circulates through the bloodstream and binds to estrogen receptors with high affinity. The fluorine-18 radionuclide emits positrons, which can be detected by PET scanners, allowing for the visualization and quantification of estrogen receptor expression in tissues.

Applications in Oncology

FES PET imaging has several clinical applications in the management of hormone-sensitive cancers:

Breast Cancer

Diagnosis and Characterization: FES PET helps in the initial characterization of breast tumors by assessing ER status. ER-positive tumors will show higher uptake of FES.
Staging: By evaluating the extent of ER-positive disease, FES PET can assist in staging breast cancer, including the detection of metastases.
Therapy Planning: ER status is a key factor in determining the suitability of hormone therapies such as tamoxifen or aromatase inhibitors. FES PET provides a non-invasive method to assess this, aiding in personalized treatment planning.

Other Cancers

Gynecological Cancers: FES PET can assess ER status in certain gynecological cancers, such as endometrial and ovarian cancers, where estrogen receptors may play a role in disease progression and treatment response.

Advantages

FES PET imaging offers several advantages over conventional imaging modalities and other PET tracers:

High Specificity for ER+ Tumors: FES selectively binds to estrogen receptors, providing specific information about ER expression in tumors.
Non-Invasive and Quantitative: PET imaging with FES allows for non-invasive, quantitative assessment of ER status, enabling precise characterization of tumor biology.
Whole-Body Imaging: FES PET provides comprehensive whole-body imaging, allowing for the detection of ER+ lesions throughout the body, including distant metastases.