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

To evaluate the diagnostic accuracy of the gallium ( 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.The study included 64 patients who underwent radical prostatectomy after primary staging with mpMRI and 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 Ga-PSMA PET/MRI were matched separately for each region with the extension of the index tumour into each region.The sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, and the accuracy of mpMRI and 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. 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 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 Ga-PSMA PET/MRI (change in AUC: 0.038, P = .246). 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.