Radiation dosimetry and biodistribution of 18F-PSMA-11 for PET imaging of prostate cancer

Prostate-specific membrane antigen (PSMA) is highly overexpressed in prostate cancer. Many PSMA analog radiotracers for PET/CT prostate cancer staging have been developed, such as Ga-68-PSMA-11. This radiotracer has achieved good results in multiple clinical trials, but because of the superior imaging characteristics of F-18-fluoride, F-18-PSMA-11 was developed. The aim of this study was to evaluate the administration safety and radiation dosimetry of F-18-PSMA-11. Methods: Six patients (aged 62-68 y; mean, 66 +/- 2 y) with suspected prostate cancer recurrence after previous treatment were administered 2 MBq of F-18-PSMA-11 per kilogram of body weight and then underwent low-dose PET/CT imaging at 0, 20, 50, 90, and 300 min after injection. To evaluate the safety of administration, vital parameters were monitored. To assess toxicity, full blood count and biochemical parameters were determined. According to the latest International Commission on Radiological Protection recommendations, radiation dosimetry analysis was performed using IDAC-Dose 2.1. For blood activity measurement, small samples of venous blood were collected at various time points after injection. The un-bound F-18-fluoride fraction was determined in plasma at 20, 50, and 90 min after administration to evaluate the defluorination rate of F-18-PSMA-11. Results: After injection, F-18-PSMA-11 cleared rapidly from the blood. At 5 h after injection, 29.0% +/- 5.9% of the activity was excreted in urine. The free F-18 fraction in plasma increased from 9.7% +/- 1.0% 20 min after injection to 22.2% +/- 1.5% 90 min after injection. The highest tracer uptake was observed in kidneys, bladder, spleen, and liver. No study drug-related adverse events were observed. The calculated mean effective dose was 12.8 +/- 0.6 mu Sv/MBq. Conclusion: F-18-PSMA-11 can be safely administered and results in a mean effective dose of 12.8 +/- 0.6 mu Sv/MBq. Therefore, the total radiation dose is lower than for other PSMA PET agents and in the same range as F-18-DCFPyL.