Utility of PSMA-PET derived volumetric parameters in initial risk stratification and prediction of prostate cancer metastasis – a head-to-head comparison of the radiotracers 18F-PSMA-1007 and 68Ga-PSMA-11

<jats:sec> <jats:title>Objective</jats:title> <jats:p>This study aimed to explore and compare the utility of baseline <jats:sup>18</jats:sup>F-PSMA-1007 and <jats:sup>68</jats:sup>Ga-PSMA-11 PET/computed tomography (CT) derived volumetric parameters in initial risk stratification and prediction of prostate cancer (PCa) metastasis.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Forty treatment-naïve, biopsy-proven intermediate-/high-risk PCa patients were prospectively recruited. Each patient underwent PET/CT with <jats:sup>68</jats:sup>Ga-PSMA-11 and <jats:sup>18</jats:sup>F-PSMA-1007 (within 2 weeks). The maximum and mean standardized uptake values (SUVmax and SUVmean) of primary tumor, prostate PSMA-tumor volume (PSMA-TVp), and prostate total lesion PSMA (TL-PSMAp) were measured.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>PSMA-TVp and TL-PSMAp (with both radiotracers) mostly exhibited moderate-to-strong correlation with Gleason score, serum prostate-specific antigen level and clinical tumor stage (Spearman <jats:italic toggle="yes">ρ</jats:italic> = 0.361–0.783, <jats:italic toggle="yes">P</jats:italic>-values ≤0.022). Primary tumor SUVmax values were similar across initial risk categories. PSMA-TVp and TL-PSMAp, however, were significantly higher in high-risk PCa compared to intermediate-risk PCa (<jats:italic toggle="yes">P</jats:italic>-values ≤0.001). Receiver operating characteristic (ROC) curve analysis revealed that F-PSMA-TVp, Ga-PSMA-TVp, F-TL-PSMAp, and Ga-TL-PSMAp (optimal cutoff values of 20.9, 23.4, 142.5, and 144.8, respectively) could effectively differentiate high-risk from intermediate-risk PCa [area under the ROC curve (AUCs) 0.859–0.898, <jats:italic toggle="yes">P</jats:italic>-values <0.001] with high sensitivity (~68.8–75%) and excellent specificity (100%). PSMA-TVp and TL-PSMAp (with both radiotracers) could predict presence of regional and extraregional nodal metastasis (AUCs 0.703–0.801, <jats:italic toggle="yes">P</jats:italic>-values ≤0.03) with moderate sensitivity (~47.8–70.6%) and excellent specificity (~82.6–94.1%).</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Our results suggest that baseline PSMA-PET primary tumor volumetric parameters provide a noninvasive, objective, and accurate index for initial risk stratification and can predict presence of regional and extraregional nodal metastasis in PCa patients. Larger studies are warranted to evaluate their incremental role over conventional parameters.</jats:p> </jats:sec>