SIU 2017: Accuracy of High B Value Diffusion Weighted MR Imaging in Predicting the Tumor Stage and Grade in Carcinoma of the Urinary Bladder: A Prospective Study on 3 Tesla

Lisbon, Portugal ( TURBT remains the standard of care for diagnosis and staging of bladder cancer, at least in the local setting. While additional modalities may be useful in identification of T3/T4 disease and local extension, TURBT is still the primary diagnostic tool. However, under staging in initial TURBT is well established and the procedure itself can be quite invasive; especially if deep resections for accurate staging are required.

To that effect, in this study, the authors aim to assess of 3T mp MRI with DWI to predict tumor stage and grade. This was a prospective study over 1.5 years, in which 40 patients were enrolled. They were all imaged on a 3T MRI with T1W, T2W and DWI at 4 b-levels (0, 500, 1000, 1500). This was then followed with standard TURBT or radical cystectomy within 20 days of MRI. MRI’s were analyzed by two expert radiologists independently and were blinded to histopathology. They identified 7 indicators of MIBC, 2 of which had never previously been described 

There were 90 evaluable tumors in 40 patients; 23 had single tumor. On univariate analysis, each of the seven features was significantly associated with MIBC on final pathology. 

  • Strongest association with Absent stalk or distorted stalk with high b-value: AUC 0.87, Sens 87.5%, Diagnostic accuracy 94.5%
  • A cutoff ADC of 0.841x10-3 could differentiate high grade from low grade tumors (sens 82.8%, spec 81.8%)
Based on these findings, they argue that 3T MRI is an accurate diagnostic tool for bladder cancer. However, there are some major issues:

1) On patients who underwent TUR – no re-TUR was done to confirm that they weren’t under staged?
2) What is the utility and predictive value of TURBT +/- urine markers? How does it compare to MRI?
3) With MRI, you will never have pathology. Ultimately pathology will be required?
4) What was the indication for cystectomy in those patients? Had they had prior resection?

Ultimately, cost and accessibility to MR may limit the value of this, similar to the story with prostate cancer and TRUS biopsies. 

Presented by: Amlesh Seth
Affiliation: AIMS, New Delhi, India

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Twitter: @tchandra_uromd at the 37th Congress of Société Internationale d’Urologie - October 19-22, 2017- Lisbon, Portugal