Diagnostic accuracy of 68 Ga-PSMA PET/MRI and multiparametric MRI in detecting index tumours in radical prostatectomy specimen.

OBJECTIVE: To evaluate the diagnostic accuracy of the 68 gallium (68 Ga) prostate-specific membrane antigen (PSMA) positron emission tomography/magnetic resonance imaging (PET/MRI) and multiparametric MRI (mpMRI) by region-based comparison of index tumour localisations using histopathological tumour maps of patients who underwent radical prostatectomy because of clinically significant prostate cancer. PATIENTS AND METHODS: The study included 64 patients who underwent radical prostatectomy after primary staging with mpMRI and 68 Ga-PSMA PET/MRI. Diagnostic analysis was performed by dividing the prostate into four anatomic regions as left/right anterior and left/right posterior. The extension of the lesions in mpMRI and the pathological uptake in 68 Ga-PSMA PET/MRI were matched separately for each region with the extension of the index tumour into each region. RESULTS: The sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, and the accuracy of mpMRI and 68 Ga-PSMA PET/MRI are shown as 55.7%, 91.8%, 80.6%, 77.2%, 78.1%, and 60.8%, 94.3%, 86.8% 79.8%, 83.5%, respectively. 68 Ga-PSMA PET/MRI has higher sensitivity and specificity compared with mpMRI. However, no statistically significant difference was found (P = .464). Combined imaging had significantly higher diagnostic accuracy compared with mpMRI and 68 Ga-PSMA PET/MRI (change in AUC: 0.084 and 0.046, P < .001 and P = .028, respectively), while no statistically significant difference was found between mpMRI and 68 Ga-PSMA PET/MRI (change in AUC: 0.038, P = .246). CONCLUSION: 68 Ga-PSMA PET/MRI had higher clinical diagnostic accuracy in prostate cancer compared with mpMRI. Diagnostic accuracy was significantly increased in the combined use of both imaging modalities.