The aim of this work is to compare [⁶⁸Ga]Ga-PSMA-11 and [¹⁸F]PSMA-1007 PET/CT as imaging agents in patients with prostate cancer (PCa). Comparisons were made by evaluating times and costs of the radiolabeling process, imaging features including pharmacokinetics, and impact on patient management. The analysis of advantages and drawbacks of both radioligands might help to make a better choice based on firm data. For [⁶⁸Ga]Ga-PSMA-11, the radiochemical yield (RCY) using a low starting activity (L, average activity of 596.55 ± 37.97 MBq) was of 80.98 ± 0.05%, while using a high one (H, average activity of 1436.27 ± 68.68 MBq), the RCY was 71.48 ± 0.04%. Thus, increased starting activities of [⁶⁸Ga]-chloride negatively influenced the RCY. A similar scenario occurred for [¹⁸F]PSMA-1007. The rate of detection of PCa lesions by Positron Emission Tomography/Computed Tomography (PET/CT) was similar for both radioligands, while their distribution in normal organs significantly differed. Furthermore, similar patterns of biodistribution were found among [¹⁸F]PSMA-1007, [⁶⁸Ga]Ga-PSMA-11, and [¹⁷⁷Lu]Lu-PSMA-617, the most used agent for RLT. Moreover, the analysis of economical aspects for each single batch of production corrected for the number of allowed PET/CT examinations suggested major advantages of [¹⁸F]PSMA-1007 compared with [⁶⁸Ga]Ga-PSMA-11. Data from this study should support the proper choice in the selection of the PSMA PET radioligand to use on the basis of the cases to study.

BackgroundProstate-Specific Membrane Antigen is overexpressed in prostate cancer and it is considered a good target for staging of primary and recurrences as well as for radioligand therapy. Different PSMA-analogues have been investigated, labeled with [⁶⁸Ga], showing excellent imaging properties; although, only small amounts can be produced for single synthesis. Recently, a fluorinated PSMA-inhibitor, [¹⁸F]-PSMA-1007, has been introduced, ensuring large-scale productions. In this study, the radiosynthesis of [¹⁸F]-PSMA-1007 using low (A), medium (B) and high (C) starting activities of [¹⁸F]-Fluoride, has been fully tested. The following parameters radiochemical yield, radiochemical purity and stability of [¹⁸F]-PSMA-1007 have been measured in 65, consecutive batches to verify the effects of the three different conditions. In addition, the analysis of the costs for the production has been performed. ResultsThe radiochemical yield percentage for low and medium range of activities of [¹⁸F]-Fluoride was 52%, while for the high range it decreases to 40%. The radiochemical purity was 99% in all three tested starting activities. [¹⁸F]-PSMA-1007 did not show radiolysis up to 8 hours after the end of synthesis, confirming that the radiopharmaceutical is stable an suitable for PET studies in humans. Furthermore, stability studies performed in fetal bovine serum demonstrated radiochemical stability at 37°C for 120’. ConclusionsA starting activity of [¹⁸F]-Fluoride of 90 GBq (range B) enables a final amount of [¹⁸F]-PSMA-1007 of about 50 GBq, which is powerful for different choices: to perform up to 25 PET/CT scans in a referral institution for prostate cancer, and/or to supply the eventual peripheral PET centers.