Diffusion‐weighted imaging predicts upgrading of Gleason score in biopsy‐proven low grade prostate cancers

Objective To analyse whether diffusion‐weighted imaging ( DWI ) predicts Gleason score ( GS ) upgrading in biopsy‐proven low grade prostate cancer ( PC a). Patients and Methods A total of 132 patients who had biopsy‐proven low grade ( GS < 7) PC a, 3T DWI results, and surgical confirmation were retrospectively included in the study. Clinical variables (prostate‐specific antigen, greatest percentage of cancer in a biopsy core and percentage of positive cores) and DWI variables (minimum apparent diffusion coefficient [ ADC min ] and mean ADC [ ADC mean ]) were evaluated. ADC min was measured, by two independent, blinded readers, using a region of interest ( ROI ) of 5–10 mm 2 at the area of lowest ADC value within a cancer, while ADC mean was measured using an ROI covering more than half of a cancer. Logistic regression and receiver‐operating characteristic curve analyses were performed. Results The rate of GS upgrading was 46.1% (61/132). In both univariate and multivariate analyses, ADC min and ADC mean were persistently significant for predicting GS upgrading ( P < 0.05), whereas clinical variables were not ( P > 0.05). In both readers’ results, the area under the curve ( AUC ) of ADC min was significantly greater than that of ADC mean (reader 1: AUC 0.760 vs 0.711; P < 0.001; reader 2: AUC 0.752 vs 0.714; P  =   0.003). Conclusion Our results showed that DWI may predict GS upgrading of biopsy‐proven low grade PC a. The variable ADC min in PC a may perform better than ADC mean .