Quantitative multiparametric MRI as a promising tool for the assessment of early response to neoadjuvant chemotherapy in bladder cancer

Purpose: Magnetic resonance imaging (MRI) has been applied to predict the neoadjuvant chemotherapy (NAC) response of bladder cancer at an early stage, but the performance remains poor. A tool for the selection of pa-tients with muscle-invasive bladder cancer (MIBC) with high probability of benefitting from NAC is not yet available. We designed a prospective study to assess a quantitative MRI for predicting the early response of MIBC to NAC.Methods: All individuals underwent a time-course MRI at pre-NAC, 24 h after initial cisplatin medication (24 h-NAC) and post-NAC. Chemosensitivity was evaluated according to pathological response. The transfer constant (Ktrans), plasma volume (Vp), extravascular extracellular space (Ve), and apparent diffusion coefficient (ADC) were quantitated based on dynamic contrast-enhanced and diffusion-weighted imaging. Quantitative RECIST criteria were constructed by modelling pre-NAC and 24 h-NAC MRI measures, and then compared with con-ventional RECIST by using pre-and post-NAC MRI measures.Results: In this pilot study, a total of 24 patients were enrolled into the study. Eight patients were pathologically confirmed to be NAC-responders. After a thorough evaluation of these parameters, different parameters showed good discrimination at different point in time. ROC curves showed quantitative MRI can predict the response to NAC, especially ADC_M (AUC = 0.859, P = 0.005) and ADC index (AUC = 0.844, P = 0.007) at pre-NAC timing and ADC_M (AUC = 0.816, P = 0.013) at 24 h-NAC timing. Then, a qRECIST model was established for predicting NAC sensitivity, with AUC of 0.91, TP rate of 0.8, and accuracy of 0.75.Conclusion: The diagnostic performance of mpMRI parameters for NAC response is excellent. The qRECIST derived between pre-and 24 h NAC MRI could predict the early response of MIBC to NAC and help for candidate selection.