The role of diffusion-weighted magnetic resonance imaging in T staging and grading of urinary bladder cancer

Accuracy of diffusion-weighted magnetic resonance imaging in evaluation of muscle invasion and histologic grading of the urinary bladder carcinoma

Background

Carcinoma of the urinary bladder is a common malignant tumor of the urinary tract in both men and women. Proper management of the urinary bladder cancer depends on the stage of the lesions. The aim of this prospective study was to determine the accuracy of diffusion-weighted images in early detection of muscle invasion, local tumor staging of urinary bladder carcinoma, and to measure the correlation between apparent diffusion coefficient (ADC) and histologic grade. Sixty patients with urinary bladder mass lesions underwent transurethral cystoscopy and biopsy after MR imaging. Radical cystectomy was done for lesions infiltrating muscularis propria. Different MR image sets (T2WIs, DWIs images) were interpreted; ADC values of tumors were calculated.

Results

Kappa agreement was better in DWI than T2WI (Kappa was 0.756 and 0.484) and the overall agreement was (83.6% and 63.6%) among both respectively. Accuracy of DWI in diagnosis of tumor stages were 80%, 43%, 96%, and 100% while in T2WI were 55%, 43%, 74%, and 80% for T1, T2, T3, and T4 stages respectively. ANOVA test showed statistically significant difference between mean ADC values of different tumor grades.

Conclusion

DWI showed higher accuracy than T2WI in detection of the degree of muscle invasion of the urinary bladder carcinoma, so it can be added to the routine protocol of MRI examination especially in patients with renal impairment. ADC value can predict the histological grade of the tumor.