Intravoxel incoherent motion diffusion‐weighted imaging in assessing bladder cancer invasiveness and cell proliferation

BACKGROUND: Nonmuscle-invasive bladder cancer (NMIBC, Stage T1 or lower) is treated with transurethral resection (TUR), while muscle-invasive bladder cancer (MIBC, Stage T2 or more) requires neoadjuvant chemotherapy before radical cystectomy. Hence, preoperative differentiation is vital. PURPOSE: To investigate whether intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) can differentiate NMIBC from MIBC and to assess whether there were correlations between IVIM parameters and the Ki-67 labeling index (LI). STUDY TYPE: Retrospective. SUBJECTS: Thirty-six patients diagnosed with bladder cancer confirmed by histopathological findings. FIELD STRENGTH/SEQUENCE: . ASSESSMENT: Molecular diffusion coefficient (D), perfusion-related diffusion coefficient (D*), perfusion fraction (f), and apparent diffusion coefficient (ADC) were calculated by biexponential and monoexponential models fits, respectively. STATISTICAL TESTS: Comparisons were made between the MIBC and NMIBC group, and differences were analyzed by comparing the areas under the receiver-operating characteristic curves (AUCs). The correlations between these parameters and Ki-67 LI were assessed by Spearman's rank correlation analysis. RESULTS: The ADC and D value were significantly lower in patients with MIBC compared to those with NMIBC (P < 0.01). No significant (P > 0.05) differences were observed in D* and f. The AUC of D value (0.894) was significantly (P < 0.05) larger than the ADC value (0.786), with sensitivities and specificities of 95% and 87.5% (D) and 80% and 68.7% (ADC), respectively. In addition, the D and ADC values were significantly correlated with Ki-67 LI (r = -0.785, r = -0.643, respectively; both P < 0.01). DATA CONCLUSION: The D value obtained from IVIM exhibited better performance than conventional DWI for distinguishing NMIBC from MIBC and may serve as a potential imaging biomarker for bladder cancer invasion. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1054-1060.