Dynamic contrast enhanced MRI as a predictor of vascular-targeted photodynamic focal ablation therapy outcome in prostate cancer post failed external beam radiation therapy

  • Tristan Barrett Department of Medical Imaging, University Health Network, Toronto, Canada
  • Sean R.H. Davidson Division of Biophysics and Bioimaging, Ontario Cancer Institute, University Health Network, Toronto, Canada
  • Brian C. Wilson Division of Biophysics and Bioimaging, Ontario Cancer Institute, University Health Network, Toronto, Canada
  • Robert A. Weersink Laboratory for Applied Biophysics, Ontario Cancer Institute, University Health Network, 610 University Avenue, Toronto, Ontario M5G 2M9, Canada
  • John Trachtenberg Division of Urology, Department of Surgical Oncology, University Health Network, Toronto, Canada
  • Masoom A. Haider Department of Medical Imaging, Sunnybrook Health Sciences Center and University of Toronto, Toronto, Canada
Keywords: Prostate cancer, Dynamic contrast-enhanced MRI, Radiotherapy failure, Vascular targeted photodynamic therapy

Abstract

Introduction: Photodynamic therapy (PDT) can be employed as a focal therapy for prostate cancer. Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) can potentially help identify tumour recurrence after failed external-beam radiotherapy (EBRT). The purpose of this study was to determine the ability of DCE-MRI to predict early response to PDT salvage treatment.

Methods: Patients with post-EBRT prostate cancer recurrence were prospectively enrolled into a Phase I/II trial of PDT using WST09. A 15-patient subgroup of this cohort undergoing 1.5T DCE-MRI at baseline and 1-week post-PDT was retrospectively analyzed. The reference standard was prostate biopsy obtained 6 months post-PDT. Analysis was performed on a patient-by-patient basis, by prostate gland halves, and by prostate sextants.

Results: Biopsy 6 months post-PDT identified cancer in 10/15 patients (66.7%), and in 24/90 sextants (26.7%). Residual cancer was identified in 22/37 sextants (59.5%) identified as being involved at baseline. DCE-MRI at 1 week correctly predicted recurrent disease with a sensitivity of 100% (10/10), specificity of 60% (3/5), positive predictive value of 83.3% (10/12), negative predictive value of 100% (3/3), and an overall accuracy of 86.7%, (13/15). When analysis was performed on prostate halves, the sensitivity and negative predictive value remained at 100%, with an improvement in specificity to 88.2% (15/17). The overall accuracy of DCE-MRI was similar regardless of analysis method: 86.7% on a patient-by-patient basis, 86.7% by prostate half and 83.3% by sextant. Changes in prostate-specific antigen (PSA) did not correlate to response.

Conclusion: DCE-MRI shows promise as a tool to predict successful outcome when performed 1 week post-PDT and could potentially be used to inform the need for re-treatment at an early time-point.

Author Biography

Tristan Barrett, Department of Medical Imaging, University Health Network, Toronto, Canada

University Lecturer, Radiology

Published
2014-10-22
How to Cite
Barrett, T., Davidson, S. R., Wilson, B. C., Weersink, R. A., Trachtenberg, J., & Haider, M. A. (2014). Dynamic contrast enhanced MRI as a predictor of vascular-targeted photodynamic focal ablation therapy outcome in prostate cancer post failed external beam radiation therapy. Canadian Urological Association Journal, 8(9-10), e708-14. https://doi.org/10.5489/cuaj.2176
Section
Original Research