Intraindividual Comparison of 18F-PSMA-1007 with Renally Excreted PSMA Ligands for PSMA PET Imaging in Patients with Relapsed Prostate Cancer

Abstract

18F-prostate-specific membrane antigen (PSMA)-1007 is excreted mainly through the liver. We benchmarked the performance of 18F-PSMA-1007 against 3 renally excreted PSMA tracers. Methods: Among 668 patients, we selected 27 in whom PET/CT results obtained with 68Ga-PSMA-11, 18F-DCFPyL (2-(3-(1-carboxy-5-[(6-[18F]fluoro-pyridine-3-carbonyl)-amino]-pentyl)-ureido)-pentanedioic acid), or 18F-JK-PSMA-7 (JK, Juelich-Koeln) were interpreted as equivocal or negative or as oligometastatic disease (PET-1). Within 3 wk, a second PET scan with 18F-PSMA-1007 was performed (PET-2). The confidence in the interpretation of PSMA-positive locoregional findings was scored on a 5-point scale, first in routine diagnostics (reader 1) and then by an independent second evaluation (reader 2). Discordant PSMA-positive skeletal findings were examined by contrast-enhanced MRI. Results: For both readers, 18F-PSMA-1007 facilitated the interpretability of 27 locoregional lesions. In PET-2, the clinical readout led to a significantly lower number of equivocal locoregional lesions (P = 0.024), and reader 2 reported a significantly higher rate of suspected lesions that were falsely interpreted as probably benign in PET-1 (P = 0.023). Exclusively in PET-2, we observed a total of 15 PSMA-positive spots in the bone marrow of 6 patients (22%). None of the 15 discordant spots had a morphologic correlate on the corresponding CT scan or on the subsequent MRI scan. Thus, 18F-PSMA-1007 exhibits a significantly higher rate of unspecific medullary spots (P = 0.0006). Conclusion: 18F-PSMA-1007 may increase confidence in interpreting small locoregional lesions adjacent to the urinary tract but may decrease the interpretability of skeletal lesions.