Evaluation of diffusion-weighted MR imaging at inclusion in an active surveillance protocol for low-risk prostate cancer.

PURPOSE: We aimed to determine whether diffusion-weighted magnetic resonance imaging, by means of the apparent diffusion coefficient (ADC), is able to guide magnetic resonance-guided biopsy in patients fit for active surveillance (AS) and identify patients harboring high-grade Gleason components not suitable for AS.
MATERIALS AND METHODS: Our study was approved by the institutional review board of all participating hospitals, and all patients signed informed consent at inclusion. Fifty-four consecutive patients with low-risk prostate cancer (PCa) underwent multiparametric magnetic resonance imaging (MP-MRI) at inclusion for AS. Cancer-suspicious regions (CSRs) upon 3-T MP-MRI were identified in all patients, and magnetic resonance-guided biopsy was performed in all CSRs to obtain histopathological verification. For all CSRs, a median ADC (mADC) was calculated. Wilcoxon signed ranks and Mann-Whitney tests was performed to detect differences between the groups. We used the area under the receiver operating characteristic curve to evaluate the accuracy of mADC to predict the presence of PCa in a CSR. Level of statistical significance was set at P < 0.05.
RESULTS: Mean mADC in the CSRs with PCa was 1.04 × 10⁻³ mm²/s (SD, 0.29), whereas the CSRs with no PCa displayed a mean mADC of 1.26 × 10⁻³ mm²/s (SD, 0.25; P < 0.001). Cancer-suspicious regions with a high-grade Gleason component displayed a mean mADC of 0.84 × 10⁻³ mm²/s (SD, 0.35) vs a mean mADC for the low-grade CSRs of 1.09 × 10⁻³ mm²/s (SD, 0.25; P < 0.05). A diagnostic accuracy of mADC for predicting the presence of PCa in a CSR with an area under the receiver operating characteristic curve of 0.73 was established (95% confidence interval, 0.61-0.84).
CONCLUSIONS: Median ADC is able to predict the presence and grade of PCa in CSRs identified by MP-MRI.