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 (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 [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 mm² 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 PCa. The variable ADC_min in PCa may perform better than ADC_mean .