Quantitative ADC Measurements More Important Than DCE for PI-RADS Stratification
A study published in Radiology reports that quantitative apparent diffusion coefficient (ADC) values were helpful in up-grading Prostate Imaging Reporting and Data System (PI-RADS) 3 and PI-RADS 4 lesions. The researchers also found that quantitative or qualitative dynamic contrast-enhanced MRI was not relevant for PI-RADS 3 lesion risk stratification. Quantitative ADC measurement may be more important for risk stratification than current methods, in future versions of PI-RADS, the authors conclude. Currently, PI-RADS version 2.0 requires multiparametric MRI of the prostate, including diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) imaging sequences.
The retrospective study analyzed quantitatively clinically reported PI-RADS lesions in consecutive men who underwent 3T multiparametric MRI (T2-weighted, DWI, and DCE MRI) using the standard multichannel body coil and integrated spine phased-array coil, according to European Society of Urogenital Radiology guidelines, from May 2015 to September 2016 and compared it with systematic and targeted MRI–transrectal US fusion biopsy. The ADC measurement, normalized T2 signal (nT2), mean early-phase DCE signal (mDCE), and heuristic DCE parameters were all calculated. Logistic regression analysis indicated the most predictive DCE parameters for csPCa (Gleason grade group ≥2). Receiver operating characteristic parameter models were compared using the Obuchowski test. Recursive partitioning analysis determined ADC and mDCE value ranges for combined use with PI-RADS.
In the analysis, 260 men (432 lesions), quantitative or qualitative dynamic contrast-enhanced MRI did not assist with PI-RADS 3 lesion risk stratification. ADC values less than or equal to 0.90 x 10-3 mm2/sec supported upgrading of ADC PI-RADS 3 (P = .007) and ADC PI-RADS 4 (P < .001) lesions. Lesion size equal or greater than 1.5 cm was no a classifier in the model (P = .10).
In conclusion, the authors wrote, “our study may reconcile controversial results from previous studies regarding the usefulness of dynamic contrast-enhanced (DCE) sequence evaluation in multiparametric prostate MRI. Our data support that neither qualitative nor quantitative DCE assessment may be required in prostate MRI and, rather, that quantitative apparent diffusion coefficient (ADC) measurements should be used for decision-making in Prostate Imaging Reporting and Data System (PI-RADS) 3 lesions.” They added that as MRI screening and quality contribute to the detection of smaller cancers in the future, quantitative ADC measurement may be considered instead of a lesion size criterion with a 1.5-cm cutoff in PI-RADS 4 and 5 differentiation.