[^18F] Fluorothymidine (FLT) is a radiopharmaceutical used in positron emission tomography (PET) imaging for assessing cell proliferation. It serves as a marker for thymidine kinase 1 (TK1) activity, an enzyme involved in DNA synthesis and cell proliferation. FLT PET imaging provides valuable information about tumor growth and response to therapy in various malignancies.
FLT is a thymidine analog that is phosphorylated by TK1 and trapped within proliferating cells. Unlike thymidine, FLT cannot be incorporated into DNA and acts as a surrogate marker for cell proliferation. Once administered, FLT is rapidly taken up by proliferating cells and phosphorylated to FLT-monophosphate ([^18F]FLT-MP), which accumulates in the cytoplasm. The fluorine-18 radionuclide emits positrons that can be detected by PET scanners, allowing for the visualization and quantification of cell proliferation in tumors.
FLT PET imaging has several clinical applications in oncology:
Primary Tumor Detection: FLT PET helps localize primary tumors and distinguish malignant lesions from benign ones based on their proliferative activity.
Metastatic Disease: It aids in the detection of metastases in various cancers, including lung, breast, and colorectal cancer.
Chemotherapy: FLT PET can assess tumor response to chemotherapy by monitoring changes in tumor proliferation rates. A decrease in FLT uptake indicates a favorable response to treatment.
Radiotherapy: It may help identify radioresistant tumors and guide treatment planning by targeting areas of high proliferation.
Predicting Treatment Outcomes: FLT PET imaging provides prognostic information by assessing tumor proliferation rates. Higher FLT uptake is associated with aggressive tumor behavior and poor prognosis in certain cancers.
FLT PET imaging offers several advantages over conventional imaging modalities:
Specificity for Proliferating Cells: FLT selectively accumulates in proliferating cells, providing a direct measure of tumor proliferation rates.
Early Response Assessment: Changes in FLT uptake occur earlier than changes in tumor size, allowing for early assessment of treatment response.
Non-Invasive and Quantitative: PET imaging provides non-invasive, quantitative assessment of tumor proliferation, enabling precise monitoring of treatment effects over time.