Equivalent tumor detection for early and late FAPI-46 PET acquisition.

INTRODUCTION: Positron emission tomography (PET) using small ligands of the fibroblast activation protein (FAP) was recently introduced. However, optimal uptake time has not been defined yet. Here, we systematically compare early (~ 10 min p.i.) and late (~ 60 min p.i.) FAPI-46 imaging in patients with various types of cancer. METHODS: This is a retrospective single-institutional study. Imaging was performed at the Essen University Hospital, Germany. A total of 69 patients who underwent dual time-point imaging for either restaging (n = 52, 75%) or staging (n = 17, 25%) of cancer were included. Patients underwent PET with two acquisitions: early (mean 11 min, SD 4) and late (mean 66 min, SD 9). Mean injected activity was 148 MBq (SD 33). RESULTS: In total, 400 lesions were detected in 69 patients. Two of 400 (0.5%) lesions were only seen in early time-point imaging but not in late time-point imaging. On a per-patient level, there was no significant difference between SUVmax of hottest tumor lesions (Wilcoxon: P = 0.73). Organ uptake demonstrated significant early to late decrease in SUVmean (average ∆SUVmean: - 0.48, - 0.14, - 0.27 for gluteus, liver, and mediastinum, respectively; Wilcoxon: P < 0.001). On a per-lesion basis, a slight increase of SUVmax was observed (average ∆SUVmax: + 0.4, Wilcoxon: P = 0.03). CONCLUSION: In conclusion, early (~ 10 min p.i.) versus late (~ 60 min p.i.) FAPI-46 imaging resulted in equivalent lesion uptake and tumor detection. For improved feasibility and scan volume, we implement early FAPI-46 PET in future clinical and research protocols.

Neither azeotropic drying, nor base nor other additives: a minimalist approach to (18)F-labeling.

A novel, efficient, time-saving and reliable radiolabeling procedure via nucleophilic substitution with [(18)F]fluoride is described. Different radiolabeled aliphatic and aromatic compounds were prepared in high radiochemical yields simply by heating of quaternary anilinium, diaryliodonium and triarylsulfonium [(18)F]fluorides in suitable solvents. The latter were obtained via direct elution of (18)F(-) from an anion exchange resin with alcoholic solutions of onium precursors. Neither azeotropic evaporation of water, nor a base, nor any other additives like cryptands or crown ethers were necessary. Due to its simplicity this method should be highly suitable for automated radiosyntheses, especially in microfluidic devices.

[68Ga]/[90Y]FAPI-46: Automated production and analytical validation of a theranostic pair.

INTRODUCTION: With respect to the broad application of FAPI-46 in therapy and diagnostics, there is a need for an efficient as well as convenient way for routine production and quality control of the theranostic pair [90Y]Y/[68Ga]Ga-FAPI-46, since no monograph is currently available for radiolabelled FAPI derivatives. The aim of the current work is to create a GMP compliant theranostic set up for the production and quality control of the diagnostic [68Ga]Ga-FAPI-46 as well as the therapeutic drug [90 Y]Y-FAPI-46, which can be the basis for future monographic standards. METHODS: Sterile [90Y]yttrium chloride solution and a pharmaceutical grade 68Ge/68Ga generator were applied for the labelling of FAPI-46 using the cassette based synthesis module Trasis EASYONE. All chemicals were GMP-grade and excipients were with marketing authorisation. The quality control included test procedures according to Ph. Eur. RESULTS: Fully automated synthesis of the theranostic pair [90Y]Y/[68Ga]Ga-FAPI-46 was achieved on the Trasis EasyOne synthesizer with a radiochemical yield of 88 ± 7% and 56 ± 5% with a radiochemical purity of >99%. Stability experiments showed a durability for [68Ga]Ga-FAPI-46 within 4 h and for [90Y]Y-FAPI-46 within 24 h. All obtained specifications and validations were compliant with the European Pharmacopoeia and regulatory guidelines. Both products were successfully applied in cancer patients. CONCLUSION: In the present work, efficient and robust procedures for the automated production and quality control of the theranostic pair [68Ga]/[90Y]FAPI 46 were developed and validated using the same synthetic platform. The described methods were evaluated in accordance with existing guidelines and toxicological limits, which can be a valuable basis for future monographic standards.