Beyond PI-RADS: Combining MRI PI-RADS and PSMA-PET/CT PRIMARY Score in a Composite (P) Score for More Accurate Diagnosis of Clinically Significant Prostate Cancer.

BACKGROUND:The PI-RADS score is standard of care for clinically significant prostate cancer (csPCa) diagnosis. The PRIMARY-score (PSMA-PET/CT) also has high diagnostic accuracy for csPCa. This study aimed to develop an easily calculated combined (P) score for csPCa detection (ISUP ≥ 2) incorporating separately read PI-RADS and PRIMARY scores, with external validation. MATERIALS AND METHODS:Two datasets of men with suspected PCa, no prior biopsy, recent MRI and 68Ga-PSMA-11-PET/CT, and subsequent trans-perineal biopsy were evaluated. The development sample (n = 291, 56% csPCa) a prospective trial and the validation sample (n = 227, 67% csPCa) a multi-centre retrospective database. Primary outcome was detection of csPCa (ISUP ≥ 2), with ISUP ≥ 3 cancer detection a secondary outcome. Score performance was evaluated by AUC, sensitivity, specificity, and decision curve analysis. RESULTS:The 5-point combined (P) score was developed in a prospective dataset. In the validation dataset, csPCa was identified in 0%, 20%, 52%, 96% and 100% for P score 1 to 5. The AUC was 0.93 (95%CI: 0.90-0.96), higher than PI-RADS 0.89 (95%CI: 0.85-0.93, P = .039) and PRIMARY score alone 0.84 (95%CI: 0.79-0.89, P < .001). Splitting scores at 1/2 (negative) vs 3/4/5 (positive), P score sensitivity was 94% (95%CI: 89-97) compared to PI-RADS 89% (95%CI: 83-93) and PRIMARY score 86% (95%CI: 79-91). For ISUP ≥ 3, P score sensitivity was 99% (95%CI: 95-100) vs 94% (95%CI: 88-98) and 92% (95%CI: 85-97) for PI-RADS and PRIMARY scores respectively. An SUVmax > 12 (P score 5) was ISUP ≥ 2 in all cases with 93% ISUP ≥ 3. CONCLUSIONS:The P-score is easily calculated and improves accuracy for csPCa over both PI-RADS and PRIMARY scores. It should be considered when PSMA-PET is undertaken for diagnosis.