Diffusion-weighted magnetic resonance imaging in prostate cancer patients on active surveillance one year after diagnosis and before repeat biopsy

Abstract

Objective. The aim of this study was to evaluate prospectively whether diffusion-weighted magnetic resonance imaging (DW-MRI), interpreted in a routine clinical setting, can serve as a diagnostic and prognostic tool for prostate carcinoma patients on active surveillance (AS). Material and methods. Eighty men enrolled in the Finnish arm of the PRIAS (Prostate Cancer Research International: Active Surveillance) study were followed for at least 1 year and had DW-MRI scans taken in addition to repeat biopsy. Spearman's correlations were analysed between tumour appearance on DW-MRI and clinical variables [age, prostate-specific antigen (PSA), free PSA, PSA doubling time, prostate volume, percentage of cancer at diagnostic biopsy]. The Pearson chi-squared test clarified associations between outcome factors (number of positive cores and Gleason score on repeat biopsy, treatment change) and DW-MRI results. Assumed predictors of deferred radical treatment were examined with logistic regression analysis. Accuracy of tumour localization by DW-MRI compared to repeat biopsy findings was analysed by the chi-squared test. Results. DW-MRI revealed an anatomical lesion suggestive of cancer in 40 patients (50%). MRI positivity showed no significant correlation with clinical variables. No associations existed between tumour appearance on DW-MRI and biopsy findings or discontinuation of AS. The only variable predicting treatment change was higher PSA at discontinuation (p = 0.002). Appearance of tumour, either on T2-weighted MRI (p = 0.273) or on apparent diffusion coefficient maps (p = 0.691), was not a significant predictor of treatment change. Conclusions. Localized low-grade prostate cancer is challenging to visualize in DW-MRI, and this imaging technique provides no additional prognostic benefit compared to PSA and repeat biopsies.

Key Words::

• active surveillance
• diffusion-weighted MRI
• MRI
• prostate cancer

Acknowledgements

We thank our prostate cancer nurses. This study was supported by grants from the Finnish Cancer Society and Ida Montini Foundation.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.