The role of multiparametric magnetic resonance imaging in the differentiation of low- and high-grade non-muscle invasive bladder cancer.

Purpose: To evaluate the diagnostic efficacy of apparent diffusion coefficient (ADC) measurements and semi-quantitative dynamic contrast enhancement (DCE) parameters in predicting the differentiation between low- and high-grade tumors in non-muscle invasive bladder cancers (NMIBC).

Methods: Patients with NMIBC, who were histopathologically confirmed between August 2020 and July 2023, were analyzed by 2 radiologists with different levels of experience. DCE semi-quantitative parameters such as wash-in rate (WiR), wash-out ratio (WoR), time to peak (TTP), and peak enhancement (PE) were calculated. ADC measurements were performed using the three-region-of-interest (ADCt) and whole volume (ADCw) methods; ADCt ratio (ADCtR) and ADCw ratio (ADCwR) were also calculated. Receiver operating characteristic curve analysis was performed to demonstrate the cut-off values of ADCt, ADCw, ADCtR, and ADCwR to differentiate low- and high-grade tumors. The intraclass correlation coefficient was used to evaluate inter-reader agreement.

Results: A total of 89 patients were included in this study. Of these patients, 48 had low-grade NMIBC, and 41 had high-grade NMIBC. There was no significant difference in mean WoR, WiR, TTP, and PE values between low- and high-grade NMIBC (P > 0.05). The ADCt, ADCw, ADCtR, and ADCwR values of high-grade NMIBC were significantly lower than those of low-grade NMIBC (P < 0.001). With cut-off values of 0.449 and 0.435, ADCtR had the best diagnostic value for both readers, showing better accuracy, sensitivity, specificity, and area under the curve (85.4%-83.1%, 87.5%-85.4%, 82.9%-80.4%, and 0.879-0.857, respectively, with confidence intervals). Additionally, ADCtR and ADCt showed acceptable diagnostic performance for both readers, with cut-off values of 0.439 and 0.431, respectively, for differentiating Ta- and T1-stages. The inter-reader agreement was almost perfect for ADC measurements.

Conclusion: While DCE semiquantative parameters did not yield significant outcomes in distinguishing between low and high grades, ADCtR holds promise for enhancing patient management in NMIBC cases and stands as a potential preoperative radiological asset.

Clinical significance: Individuals diagnosed with NMIBC may require different treatment approaches; therefore, it is very important to distinguish between low- and high-grade cases preoperatively. The differentiation between the Ta- and T1-stages is recognized as crucial in patient treatment strategies. Furthermore, ADCtR shows promise for improving patient management in NMIBC cases.