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Published online before print November 16, 2007, 10.1148/radiol.2453062042
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(Radiology 2008;246:177-184.)
© RSNA, 2007

Genitourinary Imaging

Peripheral Zone Prostate Cancer: Accuracy of Different Interpretative Approaches with MR and MR Spectroscopic Imaging1

Antonio C. Westphalen, MD, Fergus V. Coakley, MD, Aliya Qayyum, MBBS, Mark Swanson, PhD, Jeffry P. Simko, MD, PhD, Ying Lu, PhD, Shoujun Zhao, PhD, Peter R. Carroll, MD, Benjamin M. Yeh, MD, and John Kurhanewicz, PhD

1 From the Departments of Radiology (A.C.W., F.V.C., A.Q., M.S., Y.L., S.Z., B.M.Y., J.K.), Anatomic Pathology (J.P.S.), Urology (P.R.C.), and Epidemiology and Biostatistics (Y.L., S.Z.), University of California San Francisco, 505 Parnassus Ave, Box 0628, M-372, San Francisco, CA 94143-0628. Received November 30, 2006; revision requested January 31, 2007; revision received March 1; accepted March 21; final version accepted May 7. Supported by National Institutes of Health grants IRGICA76423-0IRI, R01 CA59897, and R01 CA79980. A.C.W. supported by National Institute of Biomedical Imaging and Bioengineering T32 Training Grant 1 T32 EB001631-01A1. Address correspondence to A.C.W. (e-mail: Antonio.Westphalen{at}radiology.ucsf.edu).

Purpose: To retrospectively compare relative accuracy of different interpretative approaches to magnetic resonance (MR) and MR spectroscopic imaging of peripheral zone prostate cancer, by using histologic examination results as the reference standard.

Materials and Methods: This HIPAA-compliant study had institutional Committee on Human Research approval, with waiver of written consent requirement. Spectroscopic voxels of unequivocally benign (n = 66) or malignant (n = 77) peripheral zone tissue were identified by using step-section histopathologic tumor maps created for 28 men (mean age, 60 years; range, 46–71 years) who underwent endorectal MR and MR spectroscopic imaging before radical prostatectomy. Two readers (9 and 8 years of experience) independently scored the selected voxels on a scale from 1 (likely benign) to 5 (likely malignant) at randomized review of the corresponding tissue outlined on a transverse T2-weighted MR image (T2 approach), the MR spectrum from the selected voxel only (single-voxel approach), the MR spectra from all voxels at the same axial level (multivoxel approach), and both the corresponding tissue outlined on a transverse T2-weighted image and the MR spectra from all voxels at the same axial level (integrated approach). Readers were aware that spectra were derived in patients with biopsy-proved diagnoses of prostate cancer and represented either benign or malignant tissue but were unaware of which voxels had been labeled benign or malignant and of all other clinical, histopathologic, and MR imaging findings. Receiver operating characteristic (ROC) curve analysis was performed. Generalized estimating equation method was used to estimate sensitivity and specificity for specific cutoff values.

Results: Mean areas under the ROC curve (AUCs) for the T2, single-voxel, multivoxel, and integrated approaches were 0.69, 0.72, 0.72, and 0.76, respectively. AUC of the integrated approach was significantly higher than those of the other three approaches (P < .001). {kappa} Values for assessment of interobserver variability for the T2, single-voxel, multivoxel, and integrated approaches were 0.39, 0.39, 0.34, and 0.48, respectively.

Conclusion: Addition of MR spectroscopic imaging to MR imaging significantly improves characterization of peripheral zone prostate tissue as benign or malignant; improved performance is obtained when both data sets are interpreted in an integrated fashion.

© RSNA, 2007