[18F]PSMA-HBED For PET Imaging Of Prostate Cancer: First-In-Human Results

Introduction: Biochemical recurrence of prostate cancer (PCa) is a frequently occurring problem after initial treatment. In this subpopulation detection of all the metastatic lesions is of great importance to determine further treatment options. Recently, [⁶⁸Ga]PSMA-HBED has been developed for visualization of increased expression of prostate specific membrane antigen (PSMA) in PCa (metastasis). In this study PSMA-HBED was labeled with ¹⁸F. The aim of this phase 1 study is to assess the safety of administration and the radiation dosimetry of [¹⁸F]PSMA-HBED.  Subjects and methods [¹⁸F]PSMA-HBED was produced as described by Kersemans et al. Six patients (median 66.5y, range 62-68y) with suspected prostate cancer recurrence (4 hormone sensitive and 2 castration-resistant PCa) received 5 PET/CT_low-dose scans. To evaluate toxicity, blood count and biochemical parameters were determined. To assess the safety of administration, vital parameters were observed. Eight small samples of venous blood were collected between 5 and 300 min p.i. to evaluate blood activity curves. Radiation dosimetry analysis was performed using the RADAR method as implemented in the OLINDA/EXM software.  Results No adverse events related to the study drug were observed. The observed physiological uptake was similar to that of [⁶⁸Ga]PSMA-HBED. Directly after administration of the tracer, vascular structures and kidneys can be seen. Twenty minutes p.i., a physiological high tracer uptake is detected in lacrimal and salivary glands, kidneys, ureters, bladder, liver en spleen. Physiological moderate uptake is observed in the pancreas and intestines. In addition, all patients had focal uptake in the skeleton (axial and peripheral), 4 of them in the lymph node regions (para-aortic, para-iliacal and/or inguinal), only 1 patient had uptake in the lungs, and 1 in the prostate region. Approximately 50 % of the injected activity was cleared from the blood within 30 min p.i. Renal clearance reached 29.0 ± 5.9 % of the activity 5h p.i. Dosimetry is calculated for 2 patients. The mean effective dose of 0.012 ± 0.001 mSv/MBq makes the total radiation exposure of [¹⁸F]PSMA-HBED similar to [⁶⁸Ga]-PSMA-HBED and lower compared to other ¹⁸F-labeled PSMA PET agents. Conclusion [¹⁸F]PSMA-HBED can be administered safely and results in a mean effective dose of 0.012 ± 0.001 mSv/MBq. Therefore, the total radiation dose is in the same range of [⁶⁸Ga]PSMA-HBED and lower compared to other [¹⁸F]-PSMA agents.