Combined Utility of 68Ga-Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography and Multiparametric Magnetic Resonance Imaging in Predicting Prostate Biopsy Pathology

68Gallium-labelled prostate-specific membrane antigen positron emission tomography (68Ga-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.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).This was a retrospective analysis of 200 men who underwent 68Ga-PSMA-11 PET/CT, mpMRI, and transperineal template prostate biopsy between 2016 and 2018.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 68Ga-PSMA-11 PET/CT, mpMRI, and both. Multivariable logistic regression analyses were used to identify predictors of csPCa on biopsy.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, IQR 3.68-8.67) 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). SUVmax was an independent predictor of csPCa for GG 3-5 disease only (odds ratio 1.27 per unit, 95% confidence interval 1.13-1.45). Our results are limited by the retrospective study design.Greater SUVmax on 68Ga-PSMA-11 PET/CT is associated with detection of GG 3-5 cancer on biopsy. The combination of PI-RADS score and SUVmax provides higher sensitivity and NPV than either alone. 68Ga-PSMA-11 PET/CT may be useful alongside mpMRI in improving risk stratification for localised disease.The amount of a radioactive tracer taken up in the prostate during a type of scan called PET (positron emission tomography) can predict whether aggressive prostate cancer is likely to be found on biopsy. This may complement the more usual type of scan, MRI (magnetic resonance imaging), used to detect prostate cancer.