The Effect of Prostate MRI on Cancer Staging and Radiotherapy Treatment Recommendations

Jonathan D. Tward, MD, PhD, Breanne E. Terakedis, MD, Marta E. Heilbrun, MD, William T. Lowrance, MD, MPH, Kristine Kokeny, MD, Dennis C. Shrieve, MD, PhD
Published: Tuesday, Mar 08, 2016
Jonathan D. Tward, MD, PhD

About the lead author:

Jonathan D. Tward, MD, PhD
Huntsman Cancer Institute at the University of Utah
Salt Lake City, UT

Expert’s Perspective

Kevin Stephans, MD
Kevin Stephans, MD
Director of Genitourinary
Radiation Oncology
Cleveland Clinic


Why is this article contemporary?
Clinical staging of prostate cancer by digital rectal examination and/or computed tomography scan findings is limited by the incomplete ability to accurately assess disease distribution, volume, and presence of adverse staging findings such as extra-capsular extension (ECE) or seminal vesicle invasion (SVI), which are far more often detected on final surgical pathology. Prostate magnetic resonance imaging (MRI) offers a significant advance in the availability of potential valuable clinical data prior to making a treatment decision.

The challenges in incorporating MRI findings into treatment decision making algorithms include: one, sometimes disparate reports of the sensitivity and specificity of MRI findings for predicting the true extent of disease as reported by surgical pathology; two, understanding the subtleties of MRI versus pathological findings as they relate to prognosis (should MRI find gross but not microscopic ECE or SVI, perhaps MRI findings could represent the more severe cases of these pathological predictors); three, defining the role of MRI in the pre-treatment decision making model; and four, proving that gains in decision making provided by MRI do in fact improve outcomes and are cost-effective.

Answers to each of these questions are needed prior to the routine inclusion of MRI in to the evaluation and decision making algorithm for all patients with prostate cancer. Surgical pathology investigations continue to better define the answers to the first two challenges. Here, the authors present one of the first efforts to address the far more complicated third and fourth question, and begin an investigation that hopefully will be continued and clarified over the next decade.

Abstract

Background and Purpose

To evaluate the role of magnetic resonance imaging (MRI) in the clinical staging of prostate cancer in the definitive and salvage settings, and to identify changes in treatment recommendations.

Materials and Methods

Between November 2008 and November 2011, 114 patients referred for radiotherapy (RT) consultation underwent a prostate-protocol MRI of the prostate and pelvis. Charts were retrospectively reviewed for demographic and clinical information.

Results

Eighty-six patients were evaluated for definitive treatment, 26 for salvage treatment, and 2 for RT planning in the adjuvant setting. Of the definitive subjects, MRI was performed after RT consultation in 68 patients and before consultation in 18 patients. For patients who underwent an MRI after consultation, MRI led to a change in treatment recommendation for 6 of 68 (9%) patients. Androgen deprivation therapy was added or extended in 3, prophylactic nodal RT was added to 3, and definitive nodal RT was added to 1. Active surveillance was no longer recommended in two persons, and brachytherapy alone was no longer an option in two persons. Of the 86 definitive treatment patients, nodal metastases were identified in 6 (7%). For the 26 salvage patients, imaging did not lead to any changes in planned treatment. MRI evaluation can influence clinical decision making for both physician and patient, but how those decisions change outcome is still unresolved.

In most cases when treatment recommendations were modified based on MRI findings, therapy was escalated to correspond with clinical upstaging. It remains to be seen if this translates into improved disease control, and it is possible that the “Will Rogers phenomenon” (when moving an element from one set to another raises the average values of both) will result from incorporating the high-resolution MRI information into clinical decision making.

Introduction

Historically, magnetic resonance imaging (MRI) has not been routinely used for the diagnosis and staging of prostate cancer (PC). Accurate staging is important because there is wide variability in recommended treatment options and expected outcomes for patients with low-risk, intermediate-risk, and high-risk PC.1 Although useful for risk stratification, prostate-specific antigen (PSA) measurements can be unreliable correlates of tumor stage and disease burden.2 In addition, while digital rectal examination (DRE) can detect high-risk features such as extracapsular extension (ECE), DRE has been shown to have a low sensitivity.3,4 MRI has several possible roles in the management of PC, and its utility is being investigated in numerous single-institution studies. MRI findings have been correlated to pathologic features after radical prostatectomy.5-7 MRI is being evaluated as a tool for selecting patients who are appropriate active surveillance (AS) candidates, 8 despite some evidence that it may not be useful at predicting adverse pathologic features,9 or for predicting risk of recurrence based on high-risk features.10-14 A better understanding of tumor extent and location within the gland may lead to improvements in therapeutic decision making and in surgical and radiotherapy (RT) treatment planning. Use of prostate MRI could also lead to delivery of more aggressive therapies because of the detection of adverse features that would otherwise remain occult. We reviewed the use of prostate MRI to characterize its effect on the clinical stage and subsequent treatment recommendations for patients referred for RT consultation.

Materials and Methods

After Institutional Review Board approval was obtained, all patients who were evaluated in the radiation oncology department and underwent a prostate protocol MRI between November 2008 and November 2011 were identified. In total, 114 patients met these criteria. Charts were reviewed for age at diagnosis, PSA level, date of biopsy, Gleason score, and pathologic or DRE-based T-stage. The clinical American Joint Committee on Cancer (AJCC 7th edition) Tumour, Node, Metastases (TNM) stage and the National Comprehensive Cancer Network (NCCN) risk groups were documented. Prostate protocol MRI reports were reviewed, and an MRI stage was assigned by the authors based on the extent of disease identified on imaging. Treatment recommendations, per dictated reports, were given at the time of initial RT consultation and again after MRI information was obtained. In situations where the MRI was obtained before the RT consultation, only one set of recommendations was made.

MR Image Acquisition and Interpretation

MR imaging studies were performed on a whole body 3 Tesla Siemens Magnetom TrioTim or Verio (Siemens Medical Solutions, Erlangen, Germany) with an 8-channel pelvic phased-array coil and spine coil. Routine techniques and sequences were used, including small field of view (FOV) T2-weighted turbo spin-echo sequences in the axial, sagittal, and coronal directions, covering the prostate and seminal vesicles (SVs). Scanning parameters were TR range/TE range, 3000–3300/101-121; slice thickness 3-4 mm; an echo train length of 17-19 and 1-2 averages.


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