Detection and localisation of primary prostate cancer using 68 Ga-PSMA PET/CT compared with mpMRI and radical prostatectomy specimens.

Abstract

To compare the accuracy of 68 Gallium prostate-specific membrane antigen positron emission tomography/computed tomography (68 Ga-PSMA PET/CT) with mpMRI in detecting and localising primary prostate cancer when compared with radical prostatectomy (RP) pathology. Retrospective review of men who underwent 68 Ga-PSMA PET/CT and mpMRI for primary prostate cancer prior to RP across four centres between 2015 and 2018. Patients undergoing imaging for recurrent disease or prior to non-surgical treatment were excluded. We defined pathological index tumour as the lesion with highest ISUP Grade Group (GG) on RP. Our primary outcomes were rates of accurate detection and localisation of RP index tumour using 68 Ga-PSMA PET/CT or mpMRI. We defined tumour detection as imaging lesion corresponding with RP tumour on any imaging plane, and localisation as imaging lesion matching RP index tumour in all sagittal, axial and coronal planes. Secondary outcomes included localisation of clinically significant and transition zone index tumours. We defined clinically significant disease as GG 3-5. We used descriptive statistics and Mann-Whitney U test to define and compare demographic and pathological characteristics between detected, missed and localised tumours using either imaging modality. We used the McNemar test to compare detection and localisation rates using 68Ga-PSMA PET/CT and mpMRI. 205 men were included in our analysis, including 133 with clinically significant disease. There was no significant difference between 68 Ga-PSMA PET/CT and mpMRI in the detection of any tumour (94% vs 95%, p>0.9). There was also no significant difference between localisation of all index tumours (91% vs 89%, p=0.47), clinically significant index tumours (96% vs 91%, p=0.15), or transition zone tumours (85% vs 80%, p>0.9) using 68 Ga-PSMA PET/CT and mpMRI. Limitations include retrospective study design and non-central review of imaging and pathology. We found no significant difference in the detection or localisation of primary prostate cancer between 68 Ga-PSMA PET/CT and mpMRI. Further prospective studies are required to evaluate a combined PET/MRI model in minimising tumours missed by either modality. This article is protected by copyright. All rights reserved.