Biokinetics and dosimetry of ¹⁸F-PSMA-1007 in patients with prostate cancer

Purpose: Positron emission tomography-computed tomography (PET-CT) using prostate-specific membrane antigen (PSMA) ligands is a method for imaging prostate cancer. A recent tracer, ¹⁸F-PSMA-1007, offers advantages concerning production and biokinetics compared to the standard tracer (⁶⁸Ga-PSMA-11). Until now, radiation dosimetry data for this ligand was limited to the material of three healthy volunteers. The purpose of this study is to study the biokinetics and dosimetry of ¹⁸F-PSMA-1007. Methods: Twelve patients with prostate cancer were injected with 4 MBq/kg ¹⁸F-PSMA-1007. Eight PET-CT scans with concomitant blood sampling were performed up to 330 min after injection. Urine was collected until the following morning. Volumes of interest for radiation-sensitive organs and organs with high uptake of ¹⁸F-PSMA-1007 were drawn in the PET images. A biokinetic compartment model was developed using activity data from PET images and blood and urine samples. Time-activity curves and time-integrated activity coefficients for all delineated organs were calculated. The software IDAC-dose 2.1 was used to calculate the absorbed and effective doses. Results: High concentrations of activity were noted in the liver, kidneys, parts of the small intestine, spleen, salivary glands, and lacrimal glands. The elimination through urine was 8% of injected activity in 20 h. The highest absorbed doses coefficients were in the lacrimal glands, kidneys, salivary glands, liver, and spleen (98–66 µGy/MBq). The effective dose coefficient was 25 µSv/MBq. Conclusion: The effective dose of ¹⁸F-PSMA-1007 is 6.0–8.0 mSv for a typical patient weighing 80 kg injected with 3–4 MBq/kg.