fluoroestradiol F 18

Action and Spectrum

Actions and Spectrum: 

Action:  

fluoroestradiol F 18 works by binding to estrogen receptors in the body, particularly to the estrogen receptor alpha (ERα) subtype. These receptors are often overexpressed in certain hormone-sensitive cancers, such as breast cancer and some gynecological cancers.  

By introducing a positron-emitting fluorine-18 isotope into the estradiol molecule, fluoroestradiol F 18 becomes a radioactive tracer. This radiotracer is administered intravenously to the patient and, once in the body, it targets and binds to estrogen receptors on cancer cells that may be present in tumors.  

The radiotracer emits positrons as it decays, leading to the emission of gamma rays. These gamma rays are detected by a positron emission tomography (PET) scanner, which allows for the visualization and quantification of estrogen receptor expression in the tissues. 

Spectrum: 

Breast cancer: fluoroestradiol F 18 PET can help determine the estrogen receptor status of breast tumors. This information is crucial for selecting appropriate treatments, such as hormone therapy, as estrogen receptor-positive tumors are more likely to respond to anti-estrogen therapies. 

Gynecological cancers: It can also be used to assess ER status in gynecological cancers like endometrial cancer and ovarian cancer. Like breast cancer, this information aids in tailoring treatments to the specific characteristics of the tumor. 

Drug Interaction

Adverse Reaction

Frequency defined  

<1% 

Neurological and gastrointestinal disorders: Dysgeusia 

General disorders: Injection-site pain 

Black Box Warning

Black Box Warning:  

None

Contraindication / Caution

Contraindication/Caution:  

Hypersensitivity: Patients with a known hypersensitivity or allergy to fluoroestradiol F 18 or any of its components should not receive this tracer. 

Pregnancy and Breastfeeding: fluoroestradiol F 18 may pose risks to the developing fetus during pregnancy and can be excreted in breast milk, potentially affecting a nursing baby. Pregnant and breastfeeding women should avoid this tracer unless deemed absolutely necessary and safe by the treating physician. 

Acute Medical Conditions: Patients with severe or unstable medical conditions, such as acute cardiac or respiratory distress, may not be suitable candidates for fluoroestradiol F 18 PET imaging. 

Endocrine Disorders: Individuals with severe endocrine disorders, especially those related to estrogen regulation, may have altered fluoroestradiol F 18 uptake, leading to inaccurate results. 

Young Age: The safety and effectiveness of fluoroestradiol F 18 PET imaging have not been adequately studied in pediatric populations, so its use is generally not recommended for children. 

Inability to Cooperate: Patients who are unable to remain still during the imaging procedure or cannot cooperate with the imaging instructions may not be suitable candidates for fluoroestradiol F 18 PET scans. 

Previous Radiopharmaceutical Exposure: Prior exposure to other radiopharmaceuticals may interfere with the accuracy and interpretation of fluoroestradiol F 18 PET imaging results. 

Pregnancy / Lactation

Pregnancy warnings:     

Pregnancy category: N/A 

Lactation: Excreted into human milk is unknown 

Pregnancy Categories:         

Category A: Studies that were well-controlled and met expectations revealed no risk to the fetus in either the first or second trimester. 

Category B: There were a lack of studies on pregnant women and no evidence of risk to the fetus in animal experiments.   

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.   

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category

Pharmacology

Pharmacology:  

fluoroestradiol F 18, also known as 18F-fluoroestradiol (18F-FES), is a radiopharmaceutical used in positron emission tomography (PET) imaging to visualize estrogen receptor (ER) expression in certain tissues. 

Pharmacodynamics:  

Estrogen Receptor Binding: fluoroestradiol F 18 is structurally similar to estradiol, the primary endogenous female sex hormone. When administered, FES binds to estrogen receptors, particularly the estrogen receptor alpha (ERα) subtype, which are overexpressed in certain hormone receptor-positive breast cancers. The binding of FES to ERα helps visualize and quantify the estrogen receptor status of tumors in PET imaging. 

Imaging Estrogen Receptor Status: The main purpose of using FES in PET imaging is to assess the estrogen receptor status of breast tumors. A positive FES-PET scan indicates that estrogen receptors are present in the tumor, suggesting potential responsiveness to hormone therapy (e.g., anti-estrogen drugs). On the other hand, a negative FES-PET scan indicates a lack of estrogen receptor expression, suggesting that hormone therapy may not be effective, and other treatment options should be considered.   

Pharmacokinetics: 

Absorption 

fluoroestradiol F 18 is administered intravenously as a radiotracer. After injection, it enters the bloodstream and rapidly distributes throughout the body. 

Distribution 

Once in the bloodstream, fluoroestradiol F 18 binds to estrogen receptors, especially in tissues that express high levels of estrogen receptors, such as breast tissue. This selective binding allows for the visualization of estrogen receptor-positive tumors during PET imaging. 

Metabolism 

fluoroestradiol F 18 is metabolized in the body, primarily by the liver. Metabolism involves breaking down the radiotracer into various metabolites. The primary metabolic pathway for FES involves the hydroxylation of the C-16 position and glucuronidation at the 3-hydroxyl group of estradiol. These metabolites are less active than the parent compound. 

Excretion and Elimination 

After undergoing metabolism, the metabolites of fluoroestradiol F 18 are excreted from the body, mainly through the urine. A smaller portion may also be eliminated through feces. 

Adminstartion

Administration:  

Dosage: The dosage and administration procedure may vary based on the specific clinical indications and the patient’s condition. The appropriate dose will be determined by the physician based on factors such as body weight, age, and overall health. 

Injection: fluoroestradiol F-18 is administered as an intravenous injection. The radiotracer is introduced into the bloodstream to allow it to circulate and target estrogen receptors. 

Imaging Procedure: After the injection, the patient will undergo a PET scan at a specific time interval, typically around 60 to 120 minutes after the injection. The timing of the scan is crucial to allow sufficient uptake of the radiotracer in the target tissues. 

Imaging Process: During the PET scan, the patient will lie still on a scanning bed while a PET scanner detects the positron emissions from the fluoroestradiol F-18. The data is then reconstructed to produce detailed images of the distribution of the radiotracer in the body. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: fluoroestradiol F 18 

Why do we use fluoroestradiol F 18?  

Estrogen receptor imaging: fluoroestradiol F 18 is utilized to assess the presence and activity of estrogen receptors in certain tissues, particularly in hormone receptor-positive breast cancer. This helps in determining the receptor status of the tumor and the effectiveness of hormone therapy in breast cancer patients. The tracer allows physicians to identify estrogen receptor-positive lesions non-invasively, providing valuable information for personalized treatment plans. 

Breast cancer staging and restaging: PET scans with fluoroestradiol F 18 can help stage breast cancer and evaluate the extent of the disease in the body. By mapping the distribution of estrogen receptors, doctors can determine whether the cancer has spread to other regions beyond the breast, such as lymph nodes or distant metastatic sites. This information aids in deciding the appropriate treatment strategy and monitoring treatment response. 

Assessing endocrine therapy response: In patients undergoing endocrine therapy for hormone receptor-positive breast cancer, fluoroestradiol F 18 PET scans can assess the effectiveness of treatment. By visualizing estrogen receptor activity over time, doctors can determine whether the therapy is working as expected or if there is a need for alternative treatments.