IMAGING

Prediction of Organ-Confined Prostate Cancer: Incremental Value of MR Imaging and MR Spectroscopic Imaging to Staging Nomograms
Wang L, Hricak H, Kattan MW, Chen HN, Scardino PT, Kuroiwa K
Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
Radiology. 2006; 238: 597-603

• 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.
  
  
• Editorial Comment
  Following strict criteria of macroscopic disease, endorectal MR imaging associated with superficial phased array coil, allows an overall accuracy of 83% and specificity of 98 % for detecting extraprostatic disease. In this very well designed study 383 patients underwent endorectal MR imaging combined with MR spectroscopic imaging, and 229 underwent endorectal MR imaging alone. Mean patient age was 58 years (range, 32–74 years). None of the patients received neoadjuvant hormonal or radiation therapy prior to surgery. Pathological diagnosis of prostate cancer was made at biopsy in all patients. Clinical stage (determined by means of digital rectal examination), serum PSA level, and Gleason grade in the biopsy specimen, as well as MR data, were recorded retrospectively from the patients’ medical records by two coauthors. Overall, in the prediction of OCPC, the area under the ROC curve for the staging nomograms was 0.80, while the area under the ROC curve for the staging nomograms plus MR findings was 0.88; the difference was significant (P < .01). The incremental value of MR findings to the staging nomograms was significant in all three risk groups, although it was greater in the intermediate- and high-risk groups (P < .01 for both) than in the low-risk group (P = .02). In the combined endorectal MR imaging–MR spectroscopic imaging group, the areas under the ROC curves were 0.81 for the staging nomograms and 0.90 for the staging nomograms plus MR findings; the difference was significant (P < .01). The authors nicely show that, the addition of MR findings to the “ Partin Tables” (2001 version), significantly improved the prediction of OCPC for the overall patient population (P < .01).
  Additional advantages of MR imaging combined with MR spectroscopy is the ability of these imaging methods to predict the risk of positive surgical margins, demonstrate the exact site of extraprostatic extension and to improve the surgeon’s decision to preserve or to resect the neurovascular bundle during radical prostatectomy. Based on our limited experience, using routinely combined endorectal MR imaging with MR spectroscopy for staging prostatic cancer, in the last 16 months, we agree with the authors conclusion. Endorectal MR imaging should be included into future staging nomograms for the prediction of OCPC particularly in those patients with intermediate and high risk for presenting extraprostatic disease. Obviously further multicenter confirmatory studies are still mandatory.

Dr. Adilson Prando
Chief, Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil