Objective: The purpose of this study was to compare the efficacy of submucosal enhancement on dynamic contrast-enhanced MRI (DCE-MRI) and detection of a stalk on DWI for differentiating stage T1 from stage T2 bladder urothelial carcinoma.
Subjects and methods: Our prospective study was approved by the institutional medical ethics committee and informed consent was obtained from all patients. Fifty-nine patients (92 tumors in total) with urothelial bladder cancer underwent MRI within 2 weeks before surgery. Two image sets of T2-weighted MRI with DWI and T2-weighted with DCE-MRI were interpreted independently at 2-week intervals by two uroradiologists without any knowledge of the surgical or histologic findings. The tumor was categorized as stage T1 or lower when a stalk was evident at the tumor base on DWI or when continuous linear submucosal enhancement was detected in the early phase of DCE-MRI. Tumors without stalks or with discontinuous linear submucosal enhancement were categorized as stage T2.
Results: Of the 42 tumors with stalks on DWI, 41 showed continuous and one had discontinuous submucosal enhancement on DCE-MRI. In 50 carcinomas without stalks on DWI, submucosal enhancement was absent in 34, continuous in 12, and discontinuous in four. The staging accuracy of DWI (91.3%, 84/92) and DCE-MRI (91.3%, 84/92) was improved to 94.6% (87/92) by combining the interpretations of both DWI and DCE-MRI.
Conclusion: Submucosal linear enhancement under the tumor base on DCE-MRI complements tumor stalk detection on DWI for differentiating stage T1 from stage T2 bladder urothelial carcinoma.
Keywords: DWI; bladder urothelial carcinoma; dynamic contrast-enhanced MRI; staging; stalk.