Elsevier

European Urology

Volume 62, Issue 1, July 2012, Pages 68-75
European Urology

Platinum Priority – Prostate Cancer
Editorial by Kate D. Linton and James W. F. Catto on pp. 76–77 of this issue
Can Whole-body Magnetic Resonance Imaging with Diffusion-weighted Imaging Replace Tc 99m Bone Scanning and Computed Tomography for Single-step Detection of Metastases in Patients with High-risk Prostate Cancer?

https://doi.org/10.1016/j.eururo.2012.02.020Get rights and content

Abstract

Background

Technetium Tc 99m bone scintigraphy (BS) and contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) of the pelvis and abdomen are universally recommended for detecting prostate cancer (PCa) metastases in cancer of all stages. However, this two-step approach has limited sensitivity and specificity.

Objective

Evaluate the diagnostic accuracy of whole-body MRI (WBMRI) as a one-step screening test for PCa metastases.

Design, setting, and participants

One hundred consecutive PCa patients at high risk for metastases prospectively underwent WBMRI, CT, and BS completed with targeted x-rays (BS/TXR) in case of equivocal BS. Four independent reviewers reviewed the images.

Measurements

This study compares the diagnostic performance of WBMRI, CT, BS, and BS/TXR in detecting PCa metastases using area under the curve (AUC) receiver operator characteristics. A best valuable comparator (BVC) approach was used to adjudicate final metastatic status in the absence of pathologic evaluation.

Results and limitations

Based on the BVC, 68 patients had metastases. The sensitivity of BS/TXR and WBMRI for detecting bone metastases was 86% and 98–100%, respectively (p < 0.04), and specificity was 98% and 98–100%, respectively. The first and second WBMRI readers respectively identified bone metastases in 7 and 8 of 55 patients with negative BS/TXR. The sensitivity of CT and WBMRI for detecting enlarged lymph nodes was similar, at 77–82% for both; specificity was 95–96% and 96–98%, respectively. The sensitivity of the combination of BS/TXR plus CT and WBMRI for detecting bone metastases and/or enlarged lymph nodes was 84% and 91–94%, respectively (p = 0.03–0.10); specificities were 94–97% and 91–96%, respectively. The 95% confidence interval of the difference between the AUC of the worst WBMRI reading and the AUC of any of the BS/TXR plus CT lay within the noninferiority margin of ±10% AUC.

Conclusions

WBMRI outperforms BS/TXR in detecting bone metastases and performs as well as CT for enlarged lymph node evaluation. WBMRI can replace the current multimodality metastatic work-up for the concurrent evaluation of bones and lymph nodes in high-risk PCa patients.

Introduction

Less than 10% of prostate cancer (PCa) patients are diagnosed with metastases, and another 20–30% develop systemic disease after local treatment preferentially in the pelvic and lumbar lymph nodes and in the skeleton [1], [2]. Nonlymphatic visceral metastases are detected in around 10% of castration-resistant PCa (CRPC) patients [3]. Accordingly, practice guidelines recommend technetium Tc 99m bone scintigraphy (BS) and contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) of the pelvis and abdomen to define the metastatic status in patients at high risk for metastases, that is, those with a high prostate-specific antigen (PSA) or a high Gleason score at diagnosis or a rapid PSA progression during follow-up [2], [3], [4], [5].

The diagnostic accuracy of BS is poor. Its lack of specificity frequently leads to the indication of second-line examinations, most often plain x-rays [6], [7]. Axial skeleton and whole-body MRI (WBMRI) have better sensitivity and specificity than BS [8], [9]. In addition, MRI allows objective measurement of metastases and assessment of tumour response in bone [10]. The addition of diffusion-weighted imaging (DWI) to WBMRI enables the study of extraskeletal involvement, including lymph nodes and other soft-tissue metastases, without requiring intravenous contrast agents [11], [12], [13]. Therefore, WBMRI/DWI positions itself as a potential single-step alternative to the combination of BS and CT or MRI in patients with high-risk PCa by improving the detection and measurability of metastases with the convenience of a single-step imaging technique.

This study is the first to compare prospectively the diagnostic accuracy of WBMRI/DWI against the standard combination of BS completed with targeted x-rays (BS/TXR) and CT for the detection of skeletal and visceral metastases in high-risk PCa patients.

Section snippets

Patients

Patients were included between March 2007 and March 2010 if they presented at diagnosis with a Gleason score ≥8 and/or a PSA ≥20 ng/ml or with a PSA recurrence with a PSA doubling time (DT) ≤12 mo after radical treatment or when receiving androgen-deprivation therapy (ADT). Patients underwent Tc 99m BS/TXR, contrast-enhanced thoraco-abdomino-pelvic CT, and WBMRI, including DWI, within 60 d of inclusion. The local ethics committee approved the study, and informed consent was obtained from all

Results

Patient characteristics are summarised in Table 1. One hundred patients were prospectively enrolled: 44 at initial diagnosis because of a Gleason score ≥8 and/or a PSA ≥20 ng/ml and 56 with a rapid PSA recurrence (PSA DT ≤12 mo), including 35 receiving ADT. The mean age was 69 yr of age (range: 53–88).

Discussion

Treatment guidelines universally recommend Tc 99m BS/TXR and CT or MRI to assess metastases at diagnosis in patients with a high PSA (>20 ng/ml) and/or high Gleason score (≥8) and in patients progressing after local treatment or ADT in cases of a short PSA DT [2], [3], [4], [5], [17]. Because any universal one-step substitute must be effective across all PCa stages, this study enrolled patients fulfilling one of these descriptions. Based on BVC assessment, 68% of the patients were considered

Conclusions

WBMRI is a promising, sensitive, and specific one-step technique for detecting bone metastases, enlarged lymph nodes, and visceral metastases in patients with high-risk PCa.

Acknowledgment

The authors thank N. deSouza, A. Baur, and F. Cornud for the input in the health-economic issue.

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