Fast (< 30 min) "All-in-One" whole-body MRI for TNM staging in high-risk prostate cancer (PCa): Feasibility and comparison to ⁶⁸Ga-Prostate Specific Membrane Antigen (PSMA)-PET/CT

Next-generation imaging techniques, including PSMA-PET/CT and whole-body MRI (WB-MRI), are disrupting the management of prostate cancer (PCa). This study aimed to build a fast "All-In-One" WB-MRI protocol and to compare it to ⁶⁸Ga-PSMA-PET/CT for local (T), nodal (N), and distant staging (M1a, M1b, M1c).

Fifty-two PCa patients at high-risk for metastases underwent a fast "All-in-One" WB-MRI (combining biparametric prostate assessment based on rapid T2-weighted and diffusion-weighted imaging (DWI) following the PI-RADS v2.1 guidelines and the MET-RADS-P guidelines). This WB-MRI prococol was compared to routinely performed PSMA-PET/CT read according to PSMA-RADS 1.0. Inter-technique agreement on staging and proportion differences in positive findings were assessed using Gwet's AC1 and Exact test.

Fast "All-in-One" WB-MRI better detected local tumors (T) (87 % vs 77 %, p = 0.063), while PSMA-PET/CT detected more nodes (40 % vs 29 %, p = 0.031) with a median small axis of 5 mm. No proportion difference was observed in the detection of extra nodal metastases (M1b) (p > 0.999). Inter-technique agreement ranged from good (AC1^M1a = 0.68, AC1^N = 0.79) to very good (AC1^T = 0.86, AC1^EPE = 0.89, AC1^M1b = 0.93, AC1^M1c = 0.96). Fewer oligometastatic patients were detected with PSMA-PET/CT (11 %) compared to WB-MRI (19 %).

A fast (<30 min) "All-In-One" WB-MRI protocol can be implemented in clinical routine. It provides better anatomical characterization of the T2/T3 stage than ⁶⁸Ga-PSMA-PET/CT, similar distant metastasis detection rate, but slightly inferior detection rate of nodal metastases.