Whole body magnetic resonance imaging (WB MRI) in the diagnosis and evaluation of the effectiveness of treatment of metastatic prostate cancer: Met-RADS-P system standards

INTRODUCTION: Whole-body magnetic resonance imaging (WB MRI) including diffusion-weighted imaging (DWI) is increasingly used in clinical practice. For metastatic prostate cancer, the radiologic reporting and data system Met-RADS-P (METastasis Reporting and Data System for Prostate Cancer) has been proposed to determine the prevalence of the metastatic process and subsequently evaluate the response to specific treatment based on WB MRI data. OBJECTIVE: To present an overview of the methodological aspects of WB MRI in patients with metastatic prostate cancer in relation to the Met-RADS-P system, to outline its terminology and principles for assessing study results, and to discuss the possibilities of its clinical use. MATERIALS AND METHODS: A search was conducted for publications for the period from January 1, 2017 to December 1, 2023 in Russian and English in the electronic databases eLibrary, Medline, PubMed, using the keywords: «диффузионно-взвешенная томография всего тела», «метастатический рак предстательной железы», «Met-RADS-P», «Whole Body MRI, WB MRI», «Whole Body DWI, WB DWI», «metastatic prostate cancer», supplemented by examination of references in the retrieved articles. RESULTS: Based on the literature data and our own experience, WB MRI protocols in patients with metastatic prostate cancer are described, the algorithm of MR image analysis, the criteria for evaluating the response of metastatic foci in the skeleton, lymph nodes, and internal organs, and the response assessment categories according to the RAC (response assessment categories) scale, as well as summarize the results and discuss the prospects for the clinical use of Met-RADS-P. DISCUSSION: The few publications in the literature using the Met-RADS-P system primarily concern the assessment of its reliability (inter-reader agreement). The authors conclude that it is appropriate to use it in monitoring metastases in patients with castration-resistant prostate cancer, emphasizing the clinical importance of identifying discordant responses after therapy. They also note the obstacles to the widespread introduction of WB MRI imaging into clinical practice, including the duration of the examination procedure and the large volume of diagnostic data that requires significant time for analysis and reporting, which can be overcome by automating the assessment of MR images using artificial intelligence. CONCLUSION: The Met-RADS-P system systematizes the approach to performing and describing WB MRI in patients with advanced prostate cancer, allowing the technique to be reproduced on virtually any modern scanner, from the scan protocol to a standardized report of findings. This makes the WB MRI technique reproducible in a variety of medical settings, and therefore increases its value. Nevertheless, Met-RADS-P is a relatively new system and requires large multicenter clinical trials to confirm its efficacy and representativeness, as well as to level out its shortcomings.