Apparent diffusion coefficient ratio correlates significantly with prostate cancer gleason score at final pathology

PurposeTo evaluate the correlation between apparent diffusion coefficient measurements (ADC(tumor) and ADC(ratio)) and the Gleason score from radical prostatectomy specimens. Materials and MethodsSeventy-one patients with clinically localized prostate cancer scheduled for radical prostatectomy were prospectively enrolled. Multiparametric magnetic resonance imaging (MRI) was performed prior to prostatectomy and mean ADC values from both cancerous (ADC(tumor)) and benign (ADC(benign)) tissue were measured to calculate the ADC(ratio) (ADC(tumor) divided by ADC(benign)). The ADC measurements were correlated with the Gleason score from the prostatectomy specimens. ResultsThe association between ADC measurements and Gleason score showed a significant negative correlation (P<0.001) with Spearman's rho for ADC(tumor) (-0.421) and ADC(ratio) (-0.649). There was a statistically significant difference between ADC measurements and the Gleason score for all tumors (P=0.001). Receiver operating characteristic curve analysis showed an overall area under the curve (AUC) of 0.73 (ADC(tumor)) to 0.80 (ADC(ratio)) in discriminating Gleason score 6 from Gleason score 7 tumors. The AUC changed to 0.72 (ADC(tumor)) and 0.90 (ADC(ratio)) when discriminating Gleason score 7(3+4) from Gleason score 7(4+3). ConclusionADC measurements showed a significant correlation with tumor Gleason score at final pathology. The ADC(ratio) demonstrated the best correlation compared to the ADC(tumor) value and radically improved accuracy in discriminating Gleason score 7(3+4) from Gleason score 7(4+3) tumors. J. Magn. Reson. Imaging 2014. J. Magn. Reson. Imaging 2015;42:446-453.