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 cm3 and 3-T endorectal presurgery MP MR imaging (T2-weighted imaging, diffusion-weighted [DW] imaging apparent diffusion coefficient [ADC] maps [b < 1000 sec/mm2], 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/mm2), and DCE MR imaging may not improve TZ cancer detection and localization accuracy compared with T2-weighted imaging.© RSNA, 2012Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120281/-/DC1