Current Status and Future Perspective for Bladder Cancer MR Imaging and the Vesical Imaging-Reporting and Data System (VI-RADS) in Japan: Challenges and Solutions.

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Abstract

Bladder cancer carries one of the highest lifetime costs among malignancies, and accurate distinction between non-muscle-invasive and muscle-invasive disease is essential for appropriate treatment selection. Multiparametric MRI (mpMRI) and the Vesical Imaging-Reporting and Data System (VI-RADS) have emerged as key tools for standardizing local staging of bladder cancer; however, their clinical uptake in Japan remains limited. This non-systematic narrative review summarizes the fundamentals and current evidence of VI-RADS, outlines Japan-specific barriers to its implementation, and proposes practical solutions and future perspectives. It describes patient preparation and VI-RADS-compliant mpMRI protocols, sequence-specific criteria for estimating muscle invasion, and the diagnostic performance and reproducibility reported in recent meta-analyses. It also evaluates VI-RADS within the context of major international and Japanese guidelines, highlighting the current gap between imaging-based risk stratification and transurethral resection of bladder tumor (TURBT)-centered decision-making. Particular focus is placed on challenges arising from Japan's healthcare structure, heterogeneous MRI quality, and shortage of subspecialized radiologists, as well as common diagnostic pitfalls related to technical, reader, and tumor factors. Recent diagnostic advances-including deep learning-based image reconstruction, improved diffusion and dynamic contrast techniques, and qualitative or quantitative adjunct biomarkers, such as peritumoral enhancement, tumor contact length, diffusion kurtosis metrics, radiomics, and artificial intelligence-based prediction models-are reviewed as promising avenues to enhance diagnostic confidence and inter-reader agreement. Finally, the review discusses MRI-first and MRI-guided clinical pathways under investigation, in which VI-RADS-based risk stratification informs the selective use of TURBT, and facilitates more timely, tailored, definitive therapy. In the future, sustained educational efforts, protocol standardization, quality monitoring, and outcome-based prospective trials will be crucial for establishing bladder MRI and VI-RADS as integral components of personalized bladder cancer care in Japan.

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