18F-fluorothymidine

A radiolabeled nucleoside used in PET imaging

18F-fluorothymidine
INN
Drug class
Routes of administration	Intravenous
Pregnancy category
Bioavailability
Metabolism
Elimination half-life
Excretion
Legal status
CAS Number	209579-74-0
PubChem	6918497
DrugBank
ChemSpider	5293745
KEGG

18F-fluorothymidine (18F-FLT) is a radiolabeled nucleoside analog used in positron emission tomography (PET) imaging to assess cellular proliferation. It is particularly useful in the evaluation of cancer and other diseases characterized by rapid cell division.

Mechanism of Action

18F-FLT is an analog of the nucleoside thymidine, which is a building block of DNA. In the body, 18F-FLT is taken up by cells and phosphorylated by the enzyme thymidine kinase 1 (TK1), which is upregulated in proliferating cells. Unlike thymidine, 18F-FLT is not incorporated into DNA, but its uptake and retention in cells are indicative of cellular proliferation.

Clinical Applications

18F-FLT PET imaging is primarily used in oncology to assess tumor proliferation. It is particularly useful in:

• Lung cancer: Evaluating tumor aggressiveness and response to therapy.
• Breast cancer: Monitoring treatment response and detecting recurrence.
• Lymphoma: Assessing treatment efficacy and disease progression.

18F-FLT can also be used in research settings to study other diseases involving abnormal cell proliferation, such as psoriasis and atherosclerosis.

Advantages and Limitations

Advantages

• Specificity for Proliferation: 18F-FLT uptake correlates with cellular proliferation, providing a more specific marker than 18F-FDG, which is taken up by both proliferating and non-proliferating cells.
• Non-invasive: As a PET imaging agent, 18F-FLT allows for non-invasive assessment of tumor biology.

Limitations

• Limited Sensitivity: 18F-FLT is less sensitive than 18F-FDG in detecting certain types of tumors, particularly those with low proliferation rates.
• Availability: The production of 18F-FLT requires a cyclotron and specialized facilities, limiting its availability.

Safety and Side Effects

18F-FLT is generally well-tolerated, with no significant side effects reported in clinical studies. As with all radiopharmaceuticals, there is a small risk of radiation exposure, but this is minimized by the short half-life of the fluorine-18 isotope.

Also see

• Positron emission tomography
• Radiopharmaceuticals
• Thymidine kinase
• Cancer imaging