The diagnostic value of mpMRI and PSMA-targeted PET/CT in radiorecurrent prostate cancer: a narrative review

Background: Biochemical recurrence after radiotherapy is common and clinically challenging in prostate cancer (PCa), as accurate restaging is required to identify patients eligible for local salvage therapy and distinguish them from those requiring systemic or metastasis-directed treatment. This review evaluates the diagnostic value of multiparametric MRI (mpMRI) and prostate-specific membrane antigen-targeted PET/CT (PSMA-targeted PET/CT) for restaging radiorecurrent prostate cancer. Methods: A narrative review was conducted using PubMed and Scopus. Original English-language studies published within the last 10 years were included if they reported the diagnostic performance of mpMRI, PSMA-targeted PET/CT, or combined imaging in patients with suspected radiorecurrent prostate cancer, using histopathology as the reference standard. Evidence was synthesized with particular attention to intraprostatic recurrence, extraprostatic disease, and imaging performance after brachytherapy. Results: Ten studies (4 prospective and 6 retrospective) met the inclusion criteria. mpMRI demonstrated heterogeneous sensitivity for intraprostatic recurrence with moderate-to-high specificity (64-87%), and frequently underestimated multifocal disease, particularly in the post-brachytherapy setting. PSMA-targeted PET/CT showed high sensitivity for intraprostatic recurrence (up to ~89%) and superior detection of nodal and distant metastases, although very small or low-PSMA-expressing intraprostatic lesions may remain undetected. The combination of mpMRI and PSMA-targeted PET/CT provided the highest diagnostic confidence: concordant findings achieved a positive predictive value of 97.6%, supporting improved patient selection for salvage treatment strategies. Conclusions: mpMRI and PSMA-targeted PET/CT provide complementary diagnostic information rather than being interchangeable modalities. A multimodal imaging approach improves restaging accuracy in radiorecurrent prostate cancer and may better guide biopsy targeting and selection of candidates for salvage therapy. Nevertheless, histological confirmation remains mandatory before local salvage treatment.