Interim analysis of the IRMAA study: Concordance between MRI and histopathological analysis of bladder cancer

Bladder cancer are common, and their management and prognosis depend on the stage of tumor infiltration, particularly the involvement of the muscular layer. MRI appears to be an effective tool for assessing this infiltration, but its role remains to be determined. The aim of our study was to evaluate the concordance between the VIRADS score established on MRI and the histopathological examination of TURBT samples to access the staging T of bladder cancer.

We conducted an interim analysis on patients enrolled in the prospective, single-center IRMAA study (NCT05464576). All patients underwent bladder MRI prior to surgery. The VIRADS score on MRI was blindly compared to the histopathological results of TURBT samples for tumor staging T. We secondarily evaluated the concordance between the VIRADS score and the histopathological analysis of cystectomy as well as the efficacy of neoadjuvant chemotherapy.

A total of 85 patients were included. 109 lesions were jointly identified on MRI and TURBT, of which 11 were discordant lesions. The concordance rate is 89.91% with a Cohen's Kappa coefficient of 0.74. Sensitivity is 100%, specificity is 87.4%, positive predictive value is 66.7% and negative predictive value is 100%.

MRI is a promising tool for discrimination between NMIBC and MIBC. This interim analysis allowed us to identify discordant cases in order to refine future MRI interpretations for the final analysis of the IRMAA study.