Quantitative Tumor Perfusion Imaging with ⁸²Rb PET/CT in Prostate Cancer: Analytic and Clinical Validation

The aim of this work was to evaluate ⁸²Rb PET/CT as a diagnostic tool for quantitative tumor blood flow (TBF) imaging in prostate cancer (PCa). Study 1 was performed to evaluate ⁸²Rb as a marker of TBF, using ¹⁵O-H₂O PET as a reference method. Study 2 investigated the ability of ⁸²Rb uptake measurements to differentiate between PCa and normal prostate. Methods: Study 1: 9 PCa patients scheduled for radical prostatectomy were included. Prostate multiparametric MRI and both cardiac and pelvic ¹⁵O-H₂O PET and ⁸²Rb PET were performed. PET findings were compared with postprostatectomy Gleason grade group (GGG). Study 2: 15 primary high-risk PCa patients and 12 controls without known prostate disease were included in a clinical drug trial (EudraCT 2016-003185-26). ⁶⁸Ga-prostate-specific membrane antigen PET/CT scans of PCa patients were available. Pelvic ⁸²Rb PET was performed. Results: Study 1: both ⁸²Rb K₁ and ⁸²Rb SUVs correlated strongly with ¹⁵O-H₂O TBF (ρ = 0.95, P < 0.001, and ρ = 0.77, P = 0.015, respectively). ⁸²Rb SUV and K₁ were linearly correlated (r = 0.92, P = 0.001). ⁸²Rb SUV correlated with postprostatectomy GGG (ρ = 0.70, P = 0.03). Study 2: ⁸²Rb SUV in PCa (3.19 ± 0.48) was significantly higher than prostate ⁸²Rb SUV in healthy controls (1.68 ± 0.37) (P < 0.001), with no overlap between groups. Conclusion: Study 1 shows that ⁸²Rb PET/CT can be used for TBF quantification and that TBF can be estimated by simple SUV and suggests that ⁸²Rb SUV is associated with postprostatectomy GGG and, hence, cancer aggressiveness. Study 2 shows that ⁸²Rb uptake is significantly higher in PCa than in normal prostate tissue with no overlap between cohorts, confirming the primary hypothesis of the clinical trial. Consequently, ⁸²Rb PET/CT may have potential as a noninvasive tool for evaluation of tumor aggressiveness and monitoring in nonmetastatic PCa.