Development and validation of prostate-specific membrane antigen-adjusted Prostate Imaging Reporting and Data System: A new approach to enhancing the accuracy of diagnosing treatment-naïve primary prostate cancer.

Objective
The diagnostic efficacy of hybrid positron emission tomography (PET)/MRI in detecting primary prostate cancer (PCa) is limited due to the lack of a quantitative integrated analysis. A new Prostate Imaging Reporting and Data System (PI-RADS) incorporating prostate-specific membrane antigen (PSMA) PET for PET/MRI has been introduced to improve primary detection of PCa.Methods
One hundred and twenty consecutive patients with high clinical suspicion of PCa were enrolled in this prospective study to assess the diagnostic performance of PSMA-adjusted PI-RADS (PAPI-RADS) using 68Ga-PSMA-11 PET/MRI. Tumor PSMA uptake was assessed semi-quantitatively using the maximum and peak standardized uptake values. The PAPI-RADS was obtained by combining tumor PSMA uptake with PI-RADS. Patients were divided into two groups: a training group (90 patients) and a validation group (30 patients). The cutoff value of PSMA intensity was determined via receiver operating characteristic analysis. PAPI-RADS was then applied to the validation group. Histopathology was used as the gold standard to verify the diagnostic efficacy.Results
In the training group, PAPI-RADS detected more cases of PCa than PI-RADS. PAPI-RADS had a sensitivity of 99%, specificity of 100%, negative predictive value of 92%, and overall accuracy of 99%. PI-RADS had a sensitivity of 94%, specificity of 75%, negative predictive value of 64%, and overall accuracy of 90%. PAPI-RADS was significantly better than PI-RADS in detecting PCa (χ 2 =6.57, p=0.010). The external validation of this study confirmed the diagnostic efficacy of PAPI-RADS in PCa patients.Conclusion
PAPI-RADS is significantly better than PI-RADS in detecting PCa. PAPI-RADS can improve the diagnostic accuracy of PCa detection, especially in patients with a PI-RADS score <3 lesions. PAPI-RADS can improve the accuracy of PCa diagnosis and avoid unnecessary biopsies.