Assessing the aggressiveness of prostate cancer using ADC and relaxation maps from synthetic MRI

Background: Emerging evidence suggests multiparametric prostate MRI's role in evaluating prostate cancer (PCa) aggressiveness. Purpose: To evaluate the utility of quantitative sequences in prostate MRI for assessing peripheral zone PCa aggressiveness, focusing on added value of relaxation maps to ADC. Material and Methods: In total, 64 men undergoing preoperative bi-parametric prostate MRI with synthetic sequences were retrospectively enrolled. Radiologists delineated lesions on ADC maps and synthetic MRI, matched with digitized whole-mount specimens. PCa was graded as low, intermediate, or high based on Gleason grade. Statistical analyses assessed differences in T1, T2, PD, and ADC values across grades. For significant variables, AUC curves were generated. A logistic regression model evaluated the added diagnostic value of relaxation maps to ADC. Results: Of the 95 PCa foci, 11 were low-grade, 45 intermediate-grade, and 39 high-grade. T1 (P = 0.4) and PD (P = 0.3) showed no significant differences, while T2 and ADC differed significantly (P < 0.001). Median T2 values were 98 ms (low-grade), 81 ms (intermediate), and 73 ms (high-grade), and median ADC values were 1006 mm²/s, 836 mm²/s, and 721 mm²/s, respectively. ADC yielded AUCs of 0.888 (95% CI=0.794–0.963; P < 0.0001) for low- versus intermediate-to-high-grade PCa, and 0.825 (95% CI=0.724–0.901; P < 0.0001) for low-to-intermediate versus high-grade. T2 AUCs were 0.770 (95% CI=0.605–0.908; P = 0.021) and 0.755 (95% CI=0.648–0.864; P = 0.0051), respectively. A logistic regression model combining T2 and ADC showed no significant improvement over ADC alone in differentiating low- versus intermediate-to-high-grade and low-to-intermediate versus high-grade PCa (P > 0.05). Conclusion: T1 and PD maps from synthetic MRI showed limited utility in grading PCa. Although T2 values were effective, ADC values were superior in assessing PCa aggressiveness. The addition of T2 to ADC did not significantly improve diagnostic performance.