Utility of intravoxel incoherent motion MRI derived parameters for prediction of aggressiveness in urothelial bladder carcinoma

Background: Preoperative accurate judgment of aggressiveness is of great importance to determine treatment and prognosis of bladder cancers.

Purpose: To evaluate the utility of IVIM-MRI parameters in predicting aggressiveness of bladder urothelial carcinoma.

Study type: Prospective.

Population model: Sixty-seven patients with bladder urothelial cancer.

Field strength/sequence: 3.0 T/T2WI and IVIM-MRI.

Assessment: All cases were categorized in low-, intermediate-, or high-aggressiveness proposed by Kobayashi depending on the T stage and pathological grade. Images analysis and IVIM-derived parameters (apparent diffusion coefficient standard ADC, true diffusion coefficient D, pseudodiffusion coefficient D*, and perfusion fraction f) measurements were performed independently by two radiologists.

Statistical tests: Comparisons of IVIM-derived parameters in different aggressiveness levels were performed using one-way analysis of variance or Kruskal-Wallis test. Binary logistic regression models were used to calculate predicted probability of combined parameters. Diagnostic performance of individual and combined parameters for distinguishing high- from low-/intermediate-aggressiveness was assessed by using the receiver operating characteristics (ROC) curve.

Results: The ADC and D values differed significantly among low-, intermediate-, and high-aggressive urothelial bladder carcinoma, respectively (P < 0.05). The f value showed significant differences between low- and high-aggressive and between intermediate- and high-aggressive bladder carcinoma (P < 0.05). The best parameter for differentiating high- from low-/intermediate-aggressive urothelial bladder carcinoma was ADC value, with the area under ROC curve (AUC) and accuracy of 0.895 and 85.97%, followed by f and D values with AUCs of 0.873 and 0.862, respectively. The best combination of parameters was combined D and f values, with AUC and accuracy of 0.931 and 91.82%.

Data conclusion: ADC value showed slightly better diagnostic performance than D and f values in predicting bladder cancer aggressiveness. The combination of D and f model can produce a robust value than single parameter in evaluating aggressiveness.

Level of evidence: 1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;48:1648-1656.