A comparison of the diagnostic performance of 18 F-PSMA-1007 and 68 GA-PSMA-11 in the same patients presenting with early biochemical recurrence.

Objective: Accurate early assessment of biochemical recurrence is essential in determining the correct treatment plan for patients with prostate cancer. Gallium-68-prostate-specific membrane antigen-11 ( ⁶⁸ Ga-PSMA-11) targeting PSMA has been at the forefront of imaging in biochemical recurrence however the emergence of fluorine-18 ( ¹⁸ F)-PSMA-1007 may prove to be advantageous over the ⁶⁸ Ga-PSMA-11 molecule due to its physical and physiologic al attributes. The aim of our study was to assess the diagnostic performance of ¹⁸ F-PSMA-1007 as compared to that of ⁶⁸ Ga-PSMA-11 in the same patients who presented with biochemical recurrence.
Material and Methods: Twenty-one patients with biochemical recurrence prostate cancer were prospectively enrolled into the study. Fluorine-18-PSMA-1007 positron emission tomography/computed tomography (PET/CT) was performed on the same patient after ⁶⁸ Ga-PSMA-11 PET/CT had been performed. Recurrence diagnosed on each of these studies was compared against a final diagnosis based on clinical follow-up and histological correlation where available.
Results: Gallium-68-PSMA-11 identified fifteen (71,4%) patients as being negative for recurrence whilst five (23.8%) were identified as positive and one (4.8%) as uncertain. In comparison ¹⁸ F-PSMA-1007 identified eight (38.1%) as being positive with thirteen (61.9%) patients' scans identified as negative for recurrence. No scans were classified as uncertain for the ¹⁸ F-PSMA-1007 group. Fluorine-18-PSMA-1007 identified 8 lesions as positive for disease recurrence whilst only 6 lesions were identified on ⁶⁸ Ga-PSMA-11. Of the 8 patients identified as having recurrence on ¹⁸ F-PSMA-1007 4 of those demonstrated local prostatic recurrence. The rest demonstrated local nodal recurrence and skeletal metastases. Fluorine-18-PSMA-1007 demonstrated a sensitivity, specificity, positive and negative predictive value of 88.9%, 100%, 100%, and 92.3% respectively whilst ⁶⁸ Ga-PSMA-11 demonstrated a sensitivity, specificity, positive and negative predictive value of 44.4%, 83.3%, 80%, and 66.6%, respectively.
Conclusion: In our pilot study ¹⁸ F-PSMA-1007 was able to detect more sites of recurrence as compared to ⁶⁸ Ga-PSMA-11 which were mainly within the prostate and surrounding pelvic structures.