Role of diffusion-weighted magnetic resonance imaging as an imaging biomarker of urothelial carcinoma.

Diffusion-weighted magnetic resonance imaging is a type of functional imaging that is increasingly being applied in the management of upper tract urothelial carcinoma and bladder cancer. The image contrast is derived from differences in the Brownian motion of water molecules in tissues. The homogenous high signal intensity of upper tract urothelial carcinoma and bladder cancer on diffusion-weighted magnetic resonance imaging provides helpful diagnostic information for the presence of cancerous lesions in a non-invasive manner. Recently, growing evidence has emerged showing that diffusion-weighted magnetic resonance imaging can serve as an imaging biomarker for characterizing cancer pathophysiology, because the signal reflects biophysical information about the tissues. Quantitative analysis by evaluating the apparent diffusion coefficient values potentially reflects the histological grade and the biological aggressiveness of urothelial carcinoma. The apparent diffusion coefficient value could be a biomarker predicting the clinical course of upper tract urothelial carcinoma and bladder cancer. In addition, in chemoradiotherapy-based bladder-sparing approaches against muscle-invasive bladder cancer, the role of diffusion-weighted magnetic resonance imaging for predicting the chemoradiosensitivity and for monitoring therapeutic response has been shown. Diffusion-weighted magnetic resonance imaging is expected to improve the diagnostic accuracy, and this qualitative information might allow individualized treatment strategies for patients with urothelial carcinoma.