Exploring the potential of the combined diagnostic model of ADC value and bp-MRI VI-RADS in the evaluation of muscle invasion in bladder Cancer

Objective: This study investigates the diagnostic value of Vesical Imaging Reporting and Data System (VI-RADS) in biparametric MRI (bp-MRI) for the detection of muscular infiltration in bladder cancer, and to investigate whether apparent diffusion coefficient (ADC) value can function as a potential indicator of bp-MRI VI-RADS for patient benefit.

Materials and methods: This single-center retrospective study enrolled 81 patients with pathologically confirmed bladder cancer from October 2019 to November 2021. Two readers independently scored the T2-weighted images and diffusion-weighted images of each index lesion based on the VI-RADS criteria, subsequently deriving the bp-MRI VI-RADS scores. Both ADC values and bp-MRI VI-RADS scores were utilized to develop a simple model by logistic regression. Receiver-operating characteristic curve assessed all systems, while decision curve analysis (DCA) and calibration curves evaluated the model's performance.

Results: The area under the curve (AUC) of bp-MRI VI-RADS was 0.886 (95% confidence interval [CI]: 0.801-0.971), with the diagnostic accuracy, sensitivity, and specificity being 0.753, 0.962, and 0.655 respectively. Regarding the ADC value, its AUC was 0.899 (95% CI: 0.821-0.977), and the diagnostic accuracy, sensitivity, and specificity were 0.877, 0.846, and 0.891. The AUC of the simple combined model achieved 0.942 (95% CI: 0.881-0.999), and the diagnostic accuracy, sensitivity, and specificity were 0.889, 0.885, and 0.891. The DeLong test verified that there was a statistically significant difference in AUC between the model and bp-MRI VI-RADS alone (P < 0.05). The simple model demonstrated excellent clinical applicability via DCA and calibration plots.

Conclusions: The contrast-free bp-MRI VI-RADS demonstrates commendable diagnostic efficacy for diagnosing muscular infiltration in bladder cancer. Additionally, ADC values can complement bp-MRI VI-RADS, enhancing diagnostic performance.