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

Abstract

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.

Keywords: Apparent diffusion coefficient reference; apparent diffusion coefficient; apparent diffusion coefficient ratio; diffusion-weighted imaging; magnetic resonance imaging; non-muscle invasive bladder cancer.

Figure 1

Flowchart of patient selection. ADC, apparent diffusion coefficient; NMIBC, non-muscle invasive bladder cancer.

Figure 2

A 54-year-old patient with non-muscle-invasive bladder cancer performed different apparent diffusion coefficient (ADC) values and ADC ratios. (a) Three regions of interest (ROI) were drawn, and the average ADC three ROI (ADCt) was calculated as 0.934. (b) Freehand ROI along the low signal of the tumor’s border on ADC maps. The whole ADC (ADCw) was calculated as 1.245. (c) Three ROI were drawn in the center of the bladder, and the average ADC was calculated. The reference ADC was 2.393. Based on these findings, ADCw and ADCwR are consistent with low-grade tumors, whereas ADCtR and ADCt are compatible with high-grade tumors. Histopathological examination revealed high-grade, non-muscle-invasive papillary urothelial carcinoma after transurethral resection of the bladder. ADCtR, three-ROIs method ADC ratio; ADCwR, whole-ROIs method ADC ratio.

Figure 3

Receiver operating characteristic curve analysis for the differentiation of high- and low-grade non-muscle invasive bladder cancer for reader 1 (a) and reader 2 (b). ADC, apparent diffusion coefficient; ADCtR, three-ROIs method ADC ratio; ADCwR, whole-ROIs method ADC ratio.

Figure 4

Receiver operating characteristic curve analysis for the differentiation of pTa- and pT1-stage non-muscle invasive bladder cancer for reader 1 (a) and reader 2 (b). ADC, apparent diffusion coefficient; ADCtR, three-ROIs method ADC ratio; ADCwR, whole-ROIs method ADC ratio.