Simultaneous 68Ga-PSMA HBED-CC PET/MRI Improves the Localization of Primary Prostate Cancer

Abstract

BackgroundLigands of the prostate-specific membrane antigen (PSMA) show promising results in positron emission tomography (PET) imaging of prostate cancer (PCa). ObjectiveTo compare the diagnostic performance of simultaneous gallium 68 (68Ga)-PSMA HBED-CC PET/magnetic resonance imaging (MRI) for localization of primary PCa with multiparametric magnetic resonance imaging (mpMRI) and PET alone. Design, setting, and participantsWe performed 68Ga-PSMA HBED-CC PET/MRI in 66 men with biopsy-proven PCa. InterventionPET, mpMRI, and combined 68Ga-PSMA HBED-CC PET/MRI were independently evaluated using Prostate Imaging Reporting and Data System criteria or a 5-point Likert scale. Outcome measurements and statistical analysisThe prostate was divided into sextants for histopathology and coregistered with imaging. Diagnostic performance for localization of malignancy was calculated based on receiver operating characteristics analysis for each modality. Regional quantitative PET tracer uptake was recorded; uptake ratio was defined as the ratio of malignant to nonmalignant prostate tissue. Results and limitationsA total of 53 of 66 patients were eligible for analysis. mpMRI, PET, and PET/MRI detected cancer in 66% (35 of 53), 92% (49 of 53), and 98% (52 of 53) of the patients, respectively. Overall, 202 of 318 sextants (63.5%) contained cancer at pathologic examination. Simultaneous PET/MRI statistically outperformed mpMRI (area under the curve [AUC]: 0.88 vs 0.73; p<0.001) and PET imaging (AUC: 0.88 vs 0.83; p=0.002) for localization of PCa. Compared with mpMRI, PET imaging was more accurate (AUC: 0.83 vs 0.73; p=0.003). PET provided a high uptake ratio between malignant versus nonmalignant tissue (5.02 [range: 0.89–29.8]), but no significant correlation was observed between quantitative PET parameters and Gleason score or prostate-specific antigen value. ConclusionsSimultaneous 68Ga-PSMA HBED-CC PET/MRI improves diagnostic accuracy for PCa localization both compared with mpMRI and with PET imaging alone. Further prospective studies are warranted to evaluate its potential (eg, for biopsy guidance). Patient summaryWe examined gallium 68 (68Ga)-prostate-specific membrane antigen (PSMA) HBED-CC positron emission tomography/magnetic resonance imaging (PET/MRI) for primary prostate cancer (PCa) and compared it with multiparametric MRI and PET alone. Our results indicate a higher diagnostic accuracy for 68Ga-PSMA HBED-CC PET/MRI that may help localize PCa.