ORIGINAL RESEARCH n GENITOURINARY IMAGING Radiology: Volume 268: Number 3—September 2013 n radiology.rsna.org 761 Multiparametric MR Imaging for Detection of Clinically Significant Prostate Cancer: A Validation Cohort Study with Transperineal Template Prostate Mapping as the Reference Standard 1 Nimalan Arumainayagam, MRCS, MBBS Hashim U. Ahmed, MRCS, BM, BCh Caroline M. Moore, FRCS, MD, MBBS Alex Freeman, FRCPath, MD, MBBS Clare Allen, FRCR, BM, BCh S. Aslam Sohaib, FRCR, MBBS Alex Kirkham, FRCR, BM, BCh Jan van der Meulen, PhD Mark Emberton, FRCS, MD, MBBS, BSc Purpose: To evaluate the diagnostic performance of multiparametric (MP) magnetic resonance (MR) imaging for prostate cancer detection by using transperineal template prostate mapping (TTPM) biopsies as the reference standard and to deter- mine the potential ability of MP MR imaging to identify clin- ically significant prostate cancer. Materials and Methods: Institutional review board exemption was granted by the lo- cal research ethics committee for this retrospective study. In- cluded were 64 men (mean age, 62 years [range, 40–76]; mean prostate-specific antigen, 8.2 ng/mL [8.2 mg/L] [range, 2.1–43 ng/mL]), 51 with biopsy-proved cancer and 13 suspected of having clinically significant cancer that was biopsy negative or without prior biopsy. MP MR imaging included T2-weighted, dynamic contrast-enhanced and diffusion-weighted imaging (1.5 T, pelvic phased-array coil). Three radiologists indepen- dently reviewed images and were blinded to results of biopsy. Two-by-two tables were derived by using sectors of analysis of four quadrants, two lobes, and one whole prostate. Primary target definition for clinically significant disease necessary to be present within a sector of analysis on TTPM for that sector to be deemed positive was set at Gleason score of 3+4 or more and/or cancer core length involvement of 4 mm or more. Sen- sitivity, negative predictive value, and negative likelihood ratio were calculated to determine ability of MP MR imaging to rule out cancer. Specificity, positive predictive value, positive likeli- hood ratio, accuracy (overall fraction correct), and area under receiver operating characteristic curves were also calculated. Results: Twenty-eight percent (71 of 256) of sectors had clinically sig- nificant cancer by primary endpoint definition. For primary endpoint definition (4 mm and/or Gleason score 3+4), sensitivity, negative predictive value, and negative likeli- hood ratios were 58%–73%, 84%–89%, and 0.3–0.5, re- spectively. Specificity, positive predictive value, and positive likelihood ratios were 71%–84%, 49%–63%, and 2.–3.44, respectively. Area under the curve values were 0.73–0.84. Conclusion: Results of this study indicate that MP MR imaging has a high negative predictive value to rule out clinically significant prostate cancer and may potentially have clinical use in diag- nostic pathways of men at risk. q RSNA, 2013 Supplemental material: http://radiology.rsna.org/lookup /suppl/doi:10.1148/radiol.13120641/-/DC1 1 From the Division of Surgery and Interventional Sciences, University College, Charles Bell House, 67-73 Riding House St, London W1W 7EJ, England (N.A., H.U.A., C.M.M., M.E.); Departments of Histopathology (A.A.F.) and Radiology (C.A., A.K.), University College Hospital London, London, England; Department of Radiology, Royal Marsden Hospital London, London, England (S.A.S.); Health Services Research Unit, London School of Hygiene and Tropical Medicine, London, England (J.v.d.M.); and NIHR UCLH/UCL Comprehen- sive Biomedical Research Centre, London, England (M.E.).Received April 2, 2012; revision requested May 14; revision received October 4; accepted October 30; final version accepted January 17, 2013. H.U.A. supported by a MRC Clinical Research Training Fellowship. H.U.A. and M.E. supported by the Medical Research Council, Pelican Cancer Foundation, Prostate Action, St Peter’s Trust, Prostate Can- cer Research Foundation, and Prostate Cancer Research Centre. M.E. supported in part by the UK National Institutes of Health Research UCLH/UCL Comprehensive Biomedical Research Centre. S.A.S. supported by RMH/ICR NIHR Biomedical Research Centre Funding. Address correspon- dence to H.U.A. (e-mail: hashim.ahmed@ucl.ac.uk). q RSNA, 2013 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.