Prediction of Organ-confined Prostate Cancer: Incremental Value of MR Imaging and MR Spectroscopic Imaging to Staging Nomograms

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Abstract
Purpose: To assess retrospectively the incremental value of endorectal coil magnetic resonance (MR) imaging and combined endorectal MR imaging–MR spectroscopic imaging to the staging nomograms for predicting organ-confined prostate cancer (OCPC). Materials and Methods: The institutional review board approved this HIPAA-compliant study and issued a waiver of informed consent for review of the MR reports and clinical data. Between November 1, 1999, and November 1, 2004, 229 patients underwent endorectal MR imaging and 383 underwent combined endorectal MR imaging–MR spectroscopic imaging before radical prostatectomy. Mean patient age was 58 years (range, 32–74 years). MR studies were interpreted prospectively by 12 radiologists who were informed of patients' clinical data. On the basis of the MR reports, the risks of extracapsular extension, seminal vesicle invasion, and lymph node metastasis were scored retrospectively from 1 to 5; the highest score was subtracted from 6 to determine a score (from 1 to 5) for the likelihood of OCPC on MR studies. The staging nomograms were used to calculate the likelihood of OCPC on the basis of serum prostate-specific antigen level, Gleason grade at biopsy, and clinical stage. Histopathologic findings constituted the reference standard. Logistic regression was used to estimate the multivariable relations between OCPC and MR findings. The area under the receiver operator characteristic curve was calculated for each model. The jackknife method was used for bias correction. Results: MR findings contributed significant incremental value (P ≤ .02) to the nomograms in the overall study population. The contribution of MR findings was significant in all risk groups but was greatest in the intermediate- and high-risk groups (P < .01 for both). Accuracy in the prediction of OCPC with MR was higher when MR spectroscopic imaging was used, but the difference was not significant. Conclusion: Endorectal MR imaging and combined endorectal MR imaging–MR spectroscopic imaging contribute significant incremental value to the staging nomograms in predicting OCPC. © RSNA, 2005

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