Apparent Diffusion Coefficient Value as an Imaging Biomarker to Predict Lamina/Muscle Invasion and Histopathological Grading in Bladder Urothelial Carcinomas: A Cross-sectional Study

Purpose: Diffusion-weighted imaging (DWI) is widely used in the early detection of muscle invasion in carcinoma urinary bladder (CA-UB). We investigated the role of apparent diffusion coefficient (ADC) value as an imaging biomarker to predict lamina/muscle invasion and histopathological grading in CA-UB. The diagnostic performance of different sequences in predicting muscle invasion and histopathological grading using Vesical Imaging Reporting and Data System (VI-RADS) was also determined. Methods: The study included 68 patients with CA-UB suspected clinically and/or on ultrasonography. Magnetic resonance imaging (MRI) pelvis was performed in all patients. The scans were interpreted by two independent readers and VIRADS scores were assigned. ADC value was measured in the region of maximum diffusion restriction in the tumour. Imaging findings were compared with histopathological outcomes in all the patients. Results: The cut-off value according to the receiver operating characteristic curve for ADC Values in predicting lamina invasion was ≤1.198 × 10 −3 mm 2 /s, muscle invasion was ≤0.942 × 10 −3 mm 2 /s and high-grade tumours was ≤1.135 × 10 −3 mm 2 /s. There was a significant difference between the muscle-invasive bladder carcinoma (MIBC)/non-muscle-invasive bladder carcinoma (NMIBC) groups ( t = 9.862, P ≤ 0.001) and between the high/low-grade tumours in terms of ADC Values ( t = 9.562, P ≤ 0.001). The diagnostic accuracies of T2-weighted imaging, DWI and dynamic contrast-enhanced MRI in differentiating MIBC from NMIBC were 95%, 93% and 94%, respectively, when a cut-off VI-RADS score >4 was used. Conclusion: ADC value can be used objectively as an imaging biomarker in predicting lamina/muscle invasion and histopathological grading in CA-UB.