Objective To compare the accuracy of 68gallium prostate‐specific membrane antigen positron emission tomography/computed tomography (68Ga‐PSMA PET/CT) with multiparametric MRI (mpMRI) in detecting and localising primary prostate cancer when compared with radical prostatectomy (RP) specimen pathology. Patients and methods Retrospective review of men who underwent 68Ga‐PSMA PET/CT and mpMRI for primary prostate cancer before RP across four centres between 2015 and 2018. Patients undergoing imaging for recurrent disease or before non‐surgical treatment were excluded. We defined pathological index tumour as the lesion with highest International Society of Urological Pathology Grade Group (GG) on RP specimen pathology. Our primary outcomes were rates of accurate detection and localisation of RP specimen pathology index tumour using 68Ga‐PSMA PET/CT or mpMRI. We defined tumour detection as imaging lesion corresponding with RP specimen tumour on any imaging plane, and localisation as imaging lesion matching RP specimen index tumour in all sagittal, axial, and coronal planes. Secondary outcomes included localisation of clinically significant and transition zone (TZ) index tumours. We defined clinically significant disease as GG 3–5. We used descriptive statistics and the 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. Results In all, 205 men were included in our analysis, including 133 with clinically significant disease. There was no significant difference between 68Ga‐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 TZ tumours (85% vs 80%, P > 0.9) using 68Ga‐PSMA PET/CT and mpMRI. Limitations include retrospective study design and non‐central review of imaging and pathology. Conclusion We found no significant difference in the detection or localisation of primary prostate cancer between 68Ga‐PSMA PET/CT and mpMRI. Further prospective studies are required to evaluate a combined PET/MRI model in minimising tumours missed by either modality.

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Background: 68 Gallium-labelled prostate-specific membrane antigen positron emission tomography ( 68 Ga-PSMA-11 PET) is a valuable staging tool, but its utility in characterising primary prostate cancer remains unclear. The maximum standardised uptake value (SUVmax) is a quantification measure of highest radiotracer uptake within PET-avid lesions. Objective: To assess the utility of SUVmax in detecting clinically significant prostate cancer (csPCa) on biopsy alone and in combination with multiparametric magnetic resonance imaging (mpMRI). Design, setting, and participants: This was a retrospective analysis of 200 men who underwent 68 Ga-PSMA-11 PET/CT, mpMRI, and transperineal template prostate biopsy between 2016 and 2018. Outcome measurements and statistical analysis: The primary and secondary outcomes were detection of grade group (GG) 3-5 and GG 2-5 prostate cancer, respectively. We used the Mann-Whitney U test to compare SUVmax by GG, and calculated sensitivity and specificity for csPCa detection via 68 Ga-PSMA-11 PET/CT, mpMRI, and both. Multivariable logistic regression analyses were used to identify predictors of csPCa on biopsy. Results and limitations: The median SUVmax was greater for GG 3-5 tumours (6.40, interquartile range [IQR] 4.47-11.0) than for benign and GG 1-2 tumours (3.14, IQR 2.55-3.91; p < 0.001). The median SUVmax was greater for GG 3 (5.70,) than for GG 2 (3.47, IQR 2.70-4.74; p < 0.001). For GG 3-5 disease, sensitivity was 86.5%, 95.9%, and 98.6%, and the negative predictive value (NPV) was 88.4%, 88.5%, and 93.3% using SUVmax !4, a Prostate Imaging-Reporting and Data System (PI-RADS) score of 3-5, and both, respectively. This combined model detected more GG 3-5 disease than mpMRI alone (98.6% vs 95.9%; p = 0.04).

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Purpose:Accurate risk stratification remains a barrier for the safety of active surveillance in patients with intermediate-risk prostate cancer. [68Ga]Ga-PSMA-11 prostate-specific membrane antigen positron emission tomography/computerized tomography (68Ga-PSMA PET/CT) and the maximum standardized uptake value (SUVmax) may improve risk stratification within this population.Materials and Methods:We reviewed men with International Society for Urological Pathology Grade Group (GG) 2–3 disease on transperineal template biopsy undergoing 68Ga-PSMA PET/CT from November 2015 to January 2021. Primary outcome was the presence of high percentage Gleason pattern 4 (GP4) disease per segment at surgery at 3 thresholds: >/<50% GP4, >/<20% GP4, and >/<10% GP4. SUVmax was compared by GP4, and multivariable logistic regression examined the relationship between SUVmax and GP4. Secondary outcome was association between SUVmax and pathological upgrading (GG 1/2 to GG ≥3 from biopsy to surgery).Results:Of 220 men who underwent biopsy, 135 men underwent surgery. SUVmax was higher in high GP4 groups: 5.51 (IQR 4.19–8.49) vs 3.31 (2.64–4.41) >/<50% GP4 (p <0.001); 4.77 (3.31–7.00) vs 3.13 (2.64–4.41) >/<20% GP4 (p <0.001); and 4.54 (6.10–3.13) vs 3.03 (2.45–3.70) >/<10% GP4 (p <0.001). SUVmax remained an independent predictor of >50% (OR=1.39 [95%CI 1.18–1.65], p <0.001) and >20% (OR=1.24 [1.04–1.47], p=0.015) GP4 disease per-segment, and of pathological upgrading (OR=1.22 [1.01–1.48], p=0.036). SUVmax threshold 4.5 predicted >20% GP4 with 58% specificity, 85% sensitivity, positive predictive value 75% and negative predictive value 72%. Threshold 5.4 predicted pathological upgrading with 91% specificity and negative predictive value 94%.Conclusions:SUVmax on 68Ga-PSMA PET/CT is associated with GP4. SUVmax may improve risk stratification for men with intermediate-risk prostate cancer.