Utility of computed diffusion‐weighted MRI for predicting aggressiveness of prostate cancer

Purpose To investigate the value of computed (c) diffusion‐weighted imaging (DWI) in assessing prostate cancer aggressiveness. Materials and Methods Fifty‐five patients with peripheral zone prostate cancer who underwent prebiopsy 1.5T magnetic resonance imaging (including native DWI at b ‐values of 0 and 1000 s/mm 2 ) were included. cDWI signal intensities of peripheral zone prostate cancer and nonmalignant prostate tissue were measured. Association between changes in monoexponentially calculated cDWI signals according to different b ‐values and primary Gleason grades were assessed. Results The cDWI signal intensity of prostate cancer was lower at b = 0 s/mm 2 and higher at b = 1000 s/mm 2 compared to nonmalignant prostate tissue. The b ‐value at which the signal intensities of prostate cancer and nonmalignant prostate tissue were equal was defined as the “iso‐ b ‐value.” On multivariate analysis, only the iso‐ b ‐value was a significant predictor of primary Gleason grade 4/5 cancer ( P = 0.001). The area under the curve (AUC) of the iso‐ b ‐value for diagnosing primary Gleason grade 4/5 cancer was 0.94, and significantly higher than that of the tumor apparent diffusion coefficient (ADC) value with an AUC of 0.68 ( P < 0.001). Conclusion cDWI with iso‐ b ‐value‐based semiquantitative analysis was found to be useful for predicting the aggressiveness of prostate cancer and may potentially outperform tumor ADC measurements in this setting. Level of Evidence: 3 Technical Efficacy : Stage 2 J. MAGN. RESON. IMAGING 2017;46:490–496