An MRI-based clinical decision tool to identify patients benefiting from PSMA PET/MRI in intermediate/high-risk prostate cancer

To evaluate the diagnostic superiority of PSMA PET/MRI over conventional MRI for lymph node staging in prostate cancer and to develop a clinically applicable prediction model for precise patient selection. This retrospective diagnostic study enrolled 95 intermediate-/high-risk prostate cancer patients (2021–2024), all of whom underwent both ¹⁸F-PSMA-1007 PET/MRI and multiparametric MRI before radical prostatectomy. Pelvic lymph node dissection (PLND) or extended pelvic lymph node dissection (EPLND) with pathological correlation was performed in 73 patients. Diagnostic performance was evaluated using sensitivity/specificity analysis. Two predictive models incorporating MRI-derived T stage or tumor site together with N stage were developed through multivariate logistic regression and validated via Receiver Operating Characteristic (ROC) curve, calibration curve, and decision curve analysis. PSMA PET/MRI showed significantly higher sensitivity than mpMRI for detecting pelvic lymph node metastases (87.5% vs. 35.0%, P < 0.001), while specificity remained high for both modalities (96.8% vs. 100.0%). Model 2, incorporating tumor site and N stage, demonstrated greater discriminative ability than the T-stage-based model (AUC, 0.850; 95% CI, 0.770–0.931 vs. 0.734; P = 0.0024). PSMA PET/MRI provided additional staging-relevant information in 35 of 95 patients (36.8%). Among 89 patients with complete comparative staging data, 31 (34.8%) experienced AJCC stage migration, including 30 upstaged to stage IVB and 1 downstaged from stage IVA to IIC. PSMA PET/MRI improves nodal staging sensitivity and provides additional staging information beyond mpMRI in intermediate- and high-risk prostate cancer. A prediction model based on MRI-assessed tumor site and N stage may help identify patients most likely to derive additional staging benefit from PSMA PET/MRI. Not applicable.