The usefulness of diffusion-weighted magnetic resonance imaging in bladder cancer staging and functional analysis

We assessed the effect of adding diffusion-weighted magnetic resonance imaging (DW-MRI) to conventional MRI for T staging and the correlation between apparent diffusion coefficient (ADC) values and clinicopathological parameters for patients with bladder cancer.

We retrospectively reviewed the records of 160 patients with bladder cancer who underwent MRI at our institute. All patients were routinely assessed with conventional MR imaging. Since January 2008, we added DW-MRI.

In these 160 patients, 127 (79.4%) tumors were detectable by MRI. In all patients with detectable tumors, on a stage-by-stage basis, 96 (75.6%) of 127 patients received the correct diagnosis. With DW-MRI, accurate diagnosis was obtained in 80 (80.0%) of 100 cases; without DWI in only 16 (59.3%) of 27 cases (P=0.026). For T staging, the accuracy for distinguishing muscle invasion (T≦1 vs T≧2) with DW-MRI (83.0%) was superior to that without DW-MRI (66.7%). The accuracy for distinguishing perivesical fat invasion (T≦2 vs T≧3) with DW-MRI (98.0%) was also superior to that without DW-MRI (92.6%). The ADC values were significantly related with tumor diameter (<3 cm vs ≧3 cm, P<0.001), histopathological grade (low grade vs high grade, P<0.001), T stage (≦T1 vs ≧T2, P<0.001), and operative method (transurethral resection vs total cystectomy, P<0.001).

We demonstrated that DW-MRI is not only useful for bladder cancer T staging, but also a prognostic factor for patients with bladder cancer.