Multiparametric magnetic resonance imaging in locally advanced prostate cancer: the radiologist’s perspective on staging, treatment planning, and response assessment

Clinically locally advanced prostate cancer (PCa) is usually defined as cT3-T4 disease with or without regional nodal involvement. Multiparametric magnetic resonance imaging (mpMRI) is still the reference examination for local T staging because it combines high-resolution anatomic evaluation with functional information from diffusion-weighted imaging and, when performed, dynamic contrast-enhanced imaging. Its main strengths are the depiction of extraprostatic extension, seminal vesicle invasion, apical or bladder-neck involvement, and the delivery of side-specific information that surgeons and radiation oncologists need for planning. Its main limitation is reduced sensitivity for focal microscopic extension and for nodal metastases, for which prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) is more sensitive. In current practice, mpMRI and PSMA PET/CT therefore play complementary rather than competing roles: mpMRI defines the local extent of disease, whereas PSMA PET/CT refines nodal and distant staging. Beyond initial staging, mpMRI also contributes to surgical evaluation, radiotherapy target delineation, adaptive replanning after androgen deprivation therapy, and the detection of recurrence after treatment. Interpretation after hormonal therapy, surgery, or radiotherapy, however, requires awareness of treatment-related signal changes and of the risk of both under- and overcalling recurrence. This narrative review summarizes the radiologist's perspective on how mpMRI should be performed, interpreted, and reported in clinically locally advanced PCa. Particular emphasis is placed on staging, treatment planning, and response assessment within a multimodality imaging pathway.