Preoperative Local Staging of Prostate Cancer: Comparison of mpMRI and PSMA PET/CT Against Radical Prostatectomy Histopathology

Background: Accurate assessment of local tumour stage (T stage) is essential for selecting optimal treatment in patients with prostate cancer. Multiparametric MRI (mpMRI) is currently the reference imaging modality for local staging, while PSMA PET/CT has emerged as a highly sensitive technique for nodal and distant disease. However, its role in evaluating local tumour extent remains unclear. The aim of this prospective study was to compare the accuracy of mpMRI and PSMA PET/CT in preoperative T staging using radical prostatectomy histopathology as the reference standard. Results: A total of 128 patients with biopsy-proven prostate cancer underwent both mpMRI and PSMA PET/CT before treatment. In a subgroup of 51 patients treated with radical prostatectomy, histopathology confirmed ≥pT3 disease in 25 patients (49%), including 20 cases of pT3a and 5 of pT3b. MpMRI correctly identified the pathological T stage in 17 patients (33%), whereas PSMA PET/CT was concordant in 13 patients (26%). Both modalities matched histopathology in 7 cases (14%). MpMRI overstaged disease in 10% of patients and understaged in 57%, while PSMA PET/CT overstaged in 8% and understaged in 67%. For detection of ≥pT3 disease, mpMRI demonstrated a sensitivity of 68% and specificity of 88.5%, compared with 52% and 92.3% for PSMA PET/CT, respectively. MpMRI showed higher sensitivity for detecting extraprostatic extension (70% vs 25%), whereas PSMA PET/CT demonstrated comparable or slightly higher performance for seminal vesicle invasion (80% vs 60%). Conclusions: MpMRI demonstrated higher sensitivity and overall concordance with histopathology in the assessment of local tumour stage, particularly for extraprostatic extension. PSMA PET/CT showed higher specificity but tended to underestimate local disease extent. These findings support mpMRI as the primary imaging modality for local staging, while PSMA PET/CT should be considered a complementary tool, particularly in the context of combined local and systemic staging.