Diagnostic Accuracy and Discriminative Power of Biparametric Versus Multiparametric MRI in Predicting Muscle-invasive Bladder Cancer

Purpose: Investigate and compare the diagnostic accuracy and discriminative power of biparametric MRI (bp-MRI) and multiparametric MRI (mp-MRI) in predicting muscle-invasive bladder cancer (MIBC) based on Vesical Imaging-Reporting and Data System (VI-RADS) scoring and evaluate potentially influencing factors on both protocols' accuracy.

Method: This retrospective study included 54 bladder cancer (BC) patients who underwent bladder MRI and histo-pathological assessment. Three readers independently reviewed the MRI studies and assigned a 1-5 score for T2-weighted, diffusion-weighted, and dynamic contrast-enhanced images. Then, bp-MRI and mp-MRI final VI-RADS scores were recorded for each BC. Diagnostic tables, chi-square test, kappa score (k), logistic regression, receiver operating characteristics (ROC) curves, areas under the curves (AUCs), and VI-RADS cut-off values were calculated. A Delong test was performed for ROC curve comparison. A P-value<0.05 was considered significant.

Results: In predicting MIBC, bp-MRI and mp-MRI had comparable diagnostic accuracy with insignificant differences for the three readers (P = 0.364,0.718,0.702). Radiologists' experience, and tumors' size and morphology had insignificant effect on bp-MRI accuracy (P = 0.086, 0.392,0.294), respectively. Tumors' size significantly influenced mp-MRI accuracy (P = 0.039). Bp-MRI and mp-MRI had comparable discriminative power with insignificant differences for all readers (P > 0.05). Using VI-RADS > 3 cut-off value improved the discriminative power of bp-MRI. Excellent inter-reader agreement in VI-RADS scoring for bp-MRI (k range, 0.814-0.867) and mp-MRI (k range, 0.787-0.859) was observed.

Conclusion: Bp-MRI and mp-MRI demonstrated comparable diagnostic accuracy and discriminative power in predicting MIBC. The accuracy of bp-MRI was not influenced by radiologists' experience, or tumors' size and morphology.