18F-PSMA

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

Felix Dietlein, Carsten Kobe, Melanie Hohberg, Boris D. Zlatopolskiy, Philipp Krapf, Heike Endepols, Philipp Täger, Jochen Hammes, Axel Heidenreich, Thorsten Persigehl, Bernd Neumaier, Alexander Drzezga, and Markus Dietlein

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 5 0.024), and reader 2 reported a significantly higher rate of suspected lesions that were falsely interpreted as probably benign in PET-1 (P 5 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 5 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.

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