Objective: To analyse whether diffusion-weighted imaging (DWI) predicts Gleason score (GS) upgrading in biopsy-proven low grade prostate cancer (PCa). Patients and Methods: A total of 132 patients who had biopsy-proven low grade (GS < 7) PCa, 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 [ADCmin] and mean ADC [ADCmean]) were evaluated. ADCmin was measured, by two independent, blinded readers, using a region of interest (ROI) of 5–10 mm2 at the area of lowest ADC value within a cancer, while ADCmean 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, ADCmin and ADCmean 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 ADCmin was significantly greater than that of ADCmean (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 PCa. The variable ADCmin in PCa may perform better than ADCmean.
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