Evaluation of the PRIMARY Score in the Detection of ISUP ≥ 3 Tumors in Patients with Prostate Cancer Undergoing Surgery

Introduction: Prostate cancer (PCa) varies from indolent to aggressive forms, necessitating the identification of high grade prostate cancer (hgPCa) for effective management. Multiparametric MRI (mpMRI) is standard for prostate evaluation, but PSMA PET has shown promise in enhancing hgPCa detection. The PRIMARY score, combining PSMA uptake patterns and SUVmax, correlates with tumor aggressiveness and may complement mpMRI. This study evaluates the accuracy of the PRIMARY score in identifying ISUP ≥ 3 tumors. Materials and Methods: A retrospective analysis was conducted on prostate cancer patients undergoing robotic radical prostatectomy between 2017 and 2024. Only patients with preoperative PSMA PET were included, with exclusions for missing or external imaging. Data were gathered on demographics, clinical information, and histopathology. Two radiologists reviewed the PSMA PET independently, resolving discrepancies by consensus. PRIMARY scores of 3, 4, and 5 were considered positive for hgPCa. Validity was measured using sensitivity, specificity, PPV, NPV, and AUC. Results: Of 1382 patients, 225 met criteria, with 72% using 18F-PSMA and 23% 68-Gallium. The mean age was 66.2 years; the mean PSA was 8.63 ng/mL. PRIMARY score sensitivity for ISUP ≥ 3 was 94.4%, specificity 22.2%, PPV 75.7%, NPV 60.9%, and AUC 0.697, vs PI-RADS sensitivity of 92.0%, specificity 14.3%, PPV 73.4%, NPV 40.9%, and AUC 0.582. Conclusions: The PRIMARY score shows potential for hgPCa detection (ISUP ≥ 3), possibly complementing mpMRI. Further multicenter studies are needed for validation.