Preoperative Evaluation of Prostate Cancer Aggressiveness: Using ADC and ADC Ratio in Determining Gleason Score

The objective of our study was to evaluate apparent diffusion coefficient (ADC) and various ADC ratios in determining aggressiveness of prostate cancer. One hundred sixty-five patients with biopsy-proven prostate cancer underwent 3-T MRI followed by radical prostatectomy. ADC and ADC ratios were calculated using the peripheral zone, transition zone, same zone as the tumor, and urinary bladder as references. ADC and ADC ratios were correlated with Gleason score using the Spearman correlation coefficient (ρ) and were compared between low-grade (Gleason score = 6) and high-grade (Gleason score ≥ 7) prostate cancer using the unpaired t test. ROC curves were used to compare diagnostic accuracies of ADC and ADC ratios in determining high-grade prostate cancer. Fifty-six (33.9%) and 109 (66.1%) patients had low- and high-grade prostate cancer, respectively. ADC (ρ = -0.476) and all ADC ratios (ρ = -0.397, -0.412, -0.381, and -0.474, respectively) correlated significantly with Gleason score (p < 0.001) and were significantly lower in patients with high-grade prostate cancer (p < 0.001). For predicting high-grade prostate cancer, tumor ADC and tumor-to-urinary bladder ADC ratio showed the highest AUC (0.794 and 0.790, respectively) but without statistically significant difference (p = 0.803). AUC of tumor ADC (0.794) was statistically significantly higher than those of the tumor-to-peripheral zone and tumor-to-transition zone ADC ratios (0.746, p = 0.039; 0.751, p = 0.027; respectively). AUC of tumor ADC was not statistically significantly higher than that of the tumor-to-tumor zone ADC ratio (0.763, p = 0.193). AUC calculated using the tumor-to-urinary bladder ADC ratio was statistically significantly higher than that using the tumor-to-transition zone ADC ratio (p = 0.028) and marginally higher than that from tumor-to-peripheral zone ADC ratio (p = 0.080). Otherwise, no significant differences were seen in the AUCs (p = 0.193-0.828). Both ADC and various ADC ratios correlated significantly with Gleason score and were significant predictors of high-grade prostate cancer. However, no benefit was found in using ADC ratio over ADC.