Abstract
Approximately 75% of breast cancer cells express estrogen receptor positive, being the second leading cause of cancer death among women worldwide with an incidence of 25% per year. 16α-[18F]-fluoro-17β-estradiol, FES-18F, is a radiopharmaceutical that binds to estrogen receptors enabling the acquisition of molecular images for non-invasive diagnosis of primary and metastatic breast cancer using PET-CT. The objective of this work was to study the synthesis of FES-18F in the GE TRACERlab® MXFDG module, using the chemical kit and the ABX® disposable cassette, and to determine the process yield and the analytical parameters to be used in the routine production of this radiopharmaceutical. Automated synthesis occurs in 75 minutes and includes percolation of [18F-] fluoride into an anion exchange cartridge, cartridge elution, 3-step azeotropic drying, labeling using precursor 3-methoxymethyl-16β,17β-epiestriol-O-cyclic sulfone (MMSE) and a hydrolysis step. Product purification is done in the module using solid phase extraction (SPE) cartridges. The radiochemical yield was reproductive, regardless of fluor-18 activity at entry into the module, and the results of quality control tests suggest that the radiopharmaceutical meets the criteria established for other fluor-18-labelled radiopharmaceuticals that have monographs in official compendiums. In vivo biodistribution studies in healthy animals and with a tumor model developed with MCF-7 cells, demonstrated radiopharmaceutical uptake in excretory organs and specificity for breast tumor cells.
Highlights
The radiochemical purity was determined by high-performance liquid chromatography (HPLC) and thin layer chromatography (TLC) techniques
The software provided by ABX for [18F]FES synthesis, had routine adapted in the step corresponding to the final transfer of the product, because in the production facility of IPEN, the module was installed in a cell and the sterilizing filtration was performed in another cell
Thorough analysis was performed of all components and materials that are provided by ABX
Summary
According to the National Cancer Institute, breast cancer is the second cause of death globally, and the incidence rate has increased 25% each year. The radiopharmaceutical 16α-[18F]fluoro-17β-estradiol, [18F]FES, has an in vivo lipophilic characteristic, similar to estradiol, and binds to estrogen receptors that are over expressed in breast cancer. They are an alternative to ER positive metastases, especially when biopsy from multiple foci becomes unfeasible [4,5,6]. The radiopharmaceutical [18F]FDG ([18F]fludesoxyglucose) is currently used in PET-CT, [7] being a non-specific tumor marker, since glucose metabolism is increased in tumor cells compared to non-tumor cells [8]
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