Transition zone prostate cancer: detection and localization with 3-T multiparametric MR imaging.

Purpose: To retrospectively compare transition zone (TZ) cancer detection and localization accuracy of 3-T T2-weighted magnetic resonance (MR) imaging with that of multiparametric (MP) MR imaging, with radical prostatectomy specimens as the reference standard.
Materials and Methods: The informed consent requirement was waived by the institutional review board. Inclusion criteria were radical prostatectomy specimen TZ cancer larger than 0.5 cm(3) and 3-T endorectal presurgery MP MR imaging (T2-weighted imaging, diffusion-weighted [DW] imaging apparent diffusion coefficient [ADC] maps [b < 1000 sec/mm(2)], and dynamic contrast material-enhanced [DCE] MR imaging). From 197 patients with radical prostatectomy specimens, 28 patients with TZ cancer were included. Thirty-five patients without TZ cancer were randomly selected as a control group. Four radiologists randomly scored T2-weighted and DW ADC images, T2-weighted and DCE MR images, and T2-weighted, DW ADC, and DCE MR images. TZ cancer suspicion was rated on a five-point scale in six TZ regions of interest (ROIs). A score of 4-5 was considered a positive finding. A score of 4 or higher for any ROI containing TZ cancer was considered a positive detection result at the patient level. Generalized estimating equations were used to analyze detection and localization accuracy by using ROI-receiver operating characteristics (ROC) curve analyses for the latter. Gleason grade (GG) 4-5 and GG 2-3 cancers were analyzed separately.
Results: Detection accuracy did not differ between T2-weighted and MP MR imaging for all TZ cancers (68% vs 66%, P = .85), GG 4-5 TZ cancers (79% vs 72%-75%, P = .13), and GG 2-3 TZ cancers (66% vs 62%-65%, P = .47). MP MR imaging (area under the ROC curve, 0.70-0.77) did not improve T2-weighted imaging localization accuracy (AUC = 0.72) (P > .05).
Conclusion: Use of 3-T MP MR imaging, consisting of T2-weighted imaging, DW imaging ADC maps (b values, 50, 500, and 800 sec/mm(2)), and DCE MR imaging may not improve TZ cancer detection and localization accuracy compared with T2-weighted imaging.
Supplemental Material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120281/-/DC1.
(RSNA, 2012)