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IMAGING
Prostate
cancer: sextant localization at MR imaging and MR spectroscopic imaging
before prostatectomy--results of ACRIN prospective multi-institutional
clinicopathologic study
Weinreb JC, Blume JD, Coakley FV, Wheeler TM, Cormack JB, Sotto CK, Cho H, Kawashima
A, Tempany-Afdhal CM, Macura KJ, Rosen M, Gerst SR, Kurhanewicz J
Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
Radiology. 2009; 251: 122-33
- Purpose: To determine the incremental benefit of combined endorectal
magnetic resonance (MR) imaging and MR spectroscopic imaging, as compared
with endorectal MR imaging alone, for sextant localization of peripheral
zone (PZ) prostate cancer.
- Materials
and Methods: This prospective multicenter study, conducted
by the American College of Radiology Imaging Network (ACRIN)
from February 2004 to
June 2005, was institutional review board approved and HIPAA compliant.
Research associates were required to follow consent guidelines
approved by the Office
for Human Research Protection and established by the institutional review
boards. One hundred thirty-four patients with biopsy-proved
prostate adenocarcinoma
and scheduled to undergo radical prostatectomy were recruited at seven
institutions. T1-weighted, T2-weighted, and spectroscopic MR
sequences were performed at
1.5 T by using a pelvic phased-array coil in combination with an endorectal
coil. Eight readers independently rated the likelihood of the presence
of PZ cancer in each sextant by using a five-point scale-first
on MR images alone
and later on combined MR-MR spectroscopic images. Areas under the receiver
operating characteristic curve (AUCs) were calculated with sextant as
the unit of analysis. The presence or absence of cancer at
centralized histopathologic
evaluation of prostate specimens was the reference standard. Reader-specific
receiver operating characteristic curves for values obtained with MR
imaging alone and with combined MR imaging-MR spectroscopic
imaging were developed.
The AUCs were estimated by using Mann-Whitney statistics and appropriate
95% confidence intervals.
- Results: Complete data were available for 110 patients (mean age,
58 years; range, 45-72 years). MR imaging alone and combined
MR imaging-MR
spectroscopic
imaging had similar accuracy in PZ cancer localization (AUC, 0.60 vs.
0.58, respectively; P > .05). AUCs for individual readers were 0.57-0.63 for MR
imaging alone and 0.54-0.61 for combined MR imaging-MR spectroscopic imaging.
- Conclusion: In patients who undergo radical prostatectomy, the
accuracy of combined 1.5-T endorectal MR imaging-MR spectroscopic
imaging for
sextant localization
of PZ prostate cancer is equal to that of MR imaging alone.
- Editorial Comment
Endorectal prostate cancer imaging protocols remain subject of much debate,
and undergo continuous evaluation and review. The results of this multi-institutional
trial showed that magnetic resonance spectroscopic imaging (MRSI) shows no
advantages over conventional magnetic resonance imaging (MRI) alone, for
localization of peripheral zone prostate cancer. Similarly to other radiologic
centers, since 2005, combined conventional endorectal MRI + MRSI has become
routinely practice in our institution, in two main clinical situations. First,
in the preoperative staging work-up for patients with moderate or high risk
of extraprostatic extension and second in patients with negative biopsies
and elevated or rising PSA.
Patients without signs of extraprostatic extension on conventional endorectal
MRI, are usually further evaluated with spectroscopy since the number of voxels
per section, highly suspicious for cancer on the basis of an elevated ratio
choline + creatine / citrate is useful to predict extra-prostatic extension
(1). Presence of more than four, contiguous highly suspicious voxels located
adjacent to the capsule in an otherwise confined tumor on T2-weighted image,
may be associated with extra-prostatic extension on microscopic analysis.
Similarly since 2005, we have been using the multiparametric evaluation for
the detection of prostate cancer in patients with elevated PSA and negative
prostate biopsies. Multiparametric evaluation is a combination of conventional
endorectal T2-weighted image, spectroscopy, diffusion-weighted image and perfusion
study (dynamic contrast-enhanced MRI). Using only MRI and MRSI results to target
an endorectal sonographically guided biopsy in men with highly suspicious spectral
trace for prostate cancer the sensitivity, specificity, positive and negative
predictive values, and accuracy were 71%, 84%, 75%, 81%, and 79%, respectively
(2). In this group of patients with at least two negative biopsies the finding
of more than one focal area with low-signal intensity on T2-weighted image,
suspicious for cancer, is not infrequent. These focal areas with reduced T2
signal intensity in peripheral zone are probably related to post-biopsies scarring.
In our experience these abnormalities may be disregarded as a suspicious lesions
based on spectroscopic imaging alone or combined with diffusion-weighted image
and perfusion study. Based on this complete MRI work-up an similarly to cancer
of transition zone (3), we feel that the best results for the detection of
cancer of the peripheral zone in patients with negative biopsies, will be accomplished
by the combination of the results of these 4 techniques (a retrospective analysis
of this materials and methods has already been initiated). It is interesting
to emphasize that these techniques are complimentary since they are based in
different biologic principles. In view of the results of this well designed
multicenter trial, perhaps in the near future, it will be interesting to confirm
if multiparametric MRI evaluation is of incremental value for the detection
of prostate cancer in the larger group of patients without previous biopsy.
References
1. Yu KK, Scheidler J, Hricak H, Vigneron DB, Zaloudek CJ, Males RG, et al.:
Prostate cancer: prediction of extracapsular extension with endorectal MR
imaging and three-dimensional proton MR spectroscopic imaging. Radiology.
1999; 213: 481-8.
2. Prando A, Kurhanewicz J, Borges AP, Oliveira EM Jr, Figueiredo E: Prostatic
biopsy directed with endorectal MR spectroscopic imaging findings in patients
with elevated prostate specific antigen levels and prior negative biopsy findings:
early experience. Radiology. 2005; 236: 903-10.
3. Prando A, Borges AP, Oliveira EM: Detection of Transition Zone Prostate
Cancer: The Role of Color Doppler Transrectal Ultrasound and MR Imaging with
Conventional and Functional Studies. Educational Exhibit, RSNA 2007. LL-UR2682.
Available at: http://rsna2007.rsna.org/V2007/documents/content_brochures/SSC_Ultrasound.pdf
Dr. Adilson Prando
Chief, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com
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