Transition zone prostate cancer: revisiting the role of multiparametric MRI at 3 T

Abstract

OBJECTIVE. The purpose of this study was to retrospectively evaluate the impact of multiparametric prostate MRI, including diffusion-weighted imaging (DWI) performed using different b values as well as dynamic contrast-enhanced MRI (DCE-MRI) on the accuracy, sensitivity, and specificity for transition zone (TZ) tumor detection and localization. MATERIALS AND METHODS. We included 106 prostate cancer patients (mean age [± SD], 62 ± 7 years) who underwent 3-T MRI with a pelvic phased-array coil before radical prostatectomy. Three radiologists independently reviewed cases to record the likelihood of tumor in each of six TZ regions. Scores were initially assigned using T2-weighted imaging alone, reassigned after integration of DWI at b = 1000 s/mm(2) and corresponding apparent diffusion coefficient (ADC) maps, reassigned again after integration of DWI at b = 2000 s/mm(2), and reassigned a final time after integration of DCE-MRI. Generalized estimating equations based on binary logistic regression were used to compare sessions for TZ tumor detection, using prostatectomy findings as reference standard. RESULTS. Of the TZ sextants, 9.7% (62/636) contained tumor. All readers had higher sensitivity for T2-weighted imaging integrated with DWI at b = 1000 s/mm(2) and ADC compared with T2-weighted imaging alone (reader 1, 54.8% vs 33.9%; reader 2, 53.2% vs 22.6%; and reader 3, 50.0% vs 19.4% [p ≤ 0.002]); two readers had further increased sensitivity also incorporating b = 2000 s/mm(2) (reader 1, 74.2% and reader 2, 62.9%; p ≤ 0.011), and one reader had further increased sensitivity also incorporating both b = 2000 s/mm(2) and DCE-MRI (reader 3, 61.3%, p = 0.013). DCE-MRI otherwise did not improve sensitivity (p ≥ 0.054). Other measures were similar across the four sessions (reader 1, specificity 97.4-98.3% and accuracy 91.2-95.9%; reader 2, specificity 95.8-98.4% and accuracy 91.0-92.6%; reader 3, specificity 90.9-96.7% and accuracy 88.1-89.2%). CONCLUSION. DWI assists TZ tumor detection through higher sensitivity, particularly when using a very high b value; DCE-MRI lacks further additional benefit.

Keywords: MRI; diffusion-weighted imaging; dynamic contrast-enhanced imaging; prostate cancer; transition zone.