METastasis Reporting and Data System for Prostate Cancer: Practical Guidelines for Acquisition, Interpretation, and Reporting of Whole-body Magnetic Resonance Imaging-based Evaluations of Multiorgan Involvement in Advanced Prostate Cancer

Abstract

Context: Comparative reviews of whole-body magnetic resonance imaging (WB-MRI) and positron emission tomography/computed tomography (CT; with different radiotracers) have shown that metastasis detection in advanced cancers is more accurate than with currently used CT and bone scans. However, the ability of WB-MRI and positron emission tomography/CT to assess therapeutic benefits has not been comprehensively evaluated. There is also considerable variability in the availability and quality of WB-MRI, which is an impediment to clinical development. Expert recommendations for standardising WB-MRI scans are needed, in order to assess its performance in advanced prostate cancer (APC) clinical trials.

Objective: To design recommendations that promote standardisation and diminish variations in the acquisition, interpretation, and reporting of WB-MRI scans for use in APC.

Evidence acquisition: An international expert panel of oncologic imagers and oncologists with clinical and research interests in APC management assessed biomarker requirements for clinical care and clinical trials. Key requirements for a workable WB-MRI protocol, achievable quality standards, and interpretation criteria were identified and synthesised in a white paper.

Evidence synthesis: The METastasis Reporting and Data System for Prostate Cancer guidelines were formulated for use in all oncologic manifestations of APC.

Conclusions: Uniformity in imaging data acquisition, quality, and interpretation of WB-MRI are essential for assessing the test performance of WB-MRI. The METastasis Reporting and Data System for Prostate Cancer standard requires validation in clinical trials of treatment approaches in APC.

Patient summary: METastasis Reporting and Data System for Prostate Cancer represents the consensus recommendations on the performance, quality standards, and reporting of whole-body magnetic resonance imaging, for use in all oncologic manifestations of advanced prostate cancer. These new criteria require validation in clinical trials of established and new treatment approaches in advanced prostate cancer.

Keywords: Advanced prostate cancer; Clinical trials; Diffusion MRI; Guidelines; Metastatic castrate-resistant prostate cancer; Response assessment; Whole-body MRI.

Fig. 1

Typical core whole-body magnetic resonance imaging (MRI) protocol depicting extensive metastatic bone disease. Clinical details: 76-yr-old man previously treated with low dose rate brachytherapy for prostate cancer, now with biochemical recurrence (prostate-specific antigen 8.9 ng/ml). Good performance status: PS-1. Clinical question: suitability for salvage therapy. Typical core whole-body MRI examination undertaken using a 1.5T scanner (30 min). Panels 1 and 2: sagittal short tau inversion recovery and T1 weighted (W) turbo spin-echo images of the spine showing a metastasis in the T8 vertebral body (arrow). The lower signal in the centre of the lesion on the short tau inversion recovery image is consistent with mineralisation. No other spinal lesions are visible. Panel 3: coronal T1W gradient-recalled echo sequence shows the presence of a metal artefact from a right hip replacement (asterisk). Panel 4: coronal b900 diffusion weighted image (multiplanar reconstruction [MPR] from a stacked series of axially acquired b900 images) showing multiple hyperintense foci consistent with bone metastases. Note that the artefact from the right hip replacement (asterisk) is larger than on the T1W-gradient-recalled echo but only obscures the image locally. Panels 5 and 6: the diffusion weighted b900 image stack was reconstructed as a three-dimensional maximum intensity projection (MIP) image and displayed using an inverted blue scale. Coronal and sagittal projection MIP images show multiple bone metastases (as dark focal areas) that are seen in the spine, pelvis, sternal bone, and left femur. Note that the dark signal of the brain, spleen, spinal cord, and testicles is a normal finding, as are the small but prominent lymph nodes in the neck, axilla, and groin. Given the presence of extensive bone metastases, there is no need for dedicated local restaging prostate MRI.

Fig. 2

Typical comprehensive whole-body magnetic resonance imaging protocol depicting extensive metastatic bone disease. Clinical details: 73-yr-old man with known prostate cancer recurrence, bone and nodal metastases on abiraterone treatment, and rising prostate-specific antigen (49.9 ng/ml). Restaging examination. Typical comprehensive whole-body magnetic resonance imaging examination undertaken using a 3.0T scanner (45min). (A) Panels 1 and 2: zoomed sagittal T1 weighted (W) turbo spin-echo and sagittal short tau inversion recovery (STIR) images of the spine showing multiple metastases with proximal caudal equina impingement at L1. General narrowing of the lumbar spinal canal due to disc degeneration. Panel 3: coronal T1W gradient-recalled echo (GRE) sequence shows the metastasis at L1 (horizontal arrow) but the deposits in the adjacent vertebrae are less conspicuous. Deposits are visible in the sacrum and in both ischia (slanting arrows). Panel 4: coronal b900 diffusion weighted image (multiplanar reconstruction [MPR]) showing multiple hyperintense foci at the bone metastatic sites (except the left ischium). Panels 5 and 6: b900 three dimensional MIP images with coronal and sagittal projections confirm multiple bone metastases (as dark regions). Note that the dark signal of the brain, spleen, spinal cord, and testicles is a normal finding, as are the small lymph nodes in the neck, axillae, and groin. (B) Zoomed T1W images obtained using the Dixon technique with in-phase (IP), opposed-phase (OP), water only (WO), and fat only (FO) reconstructions at the level of the sacrum. Multiple sacral and iliac bone metastases are seen (best depicted on the T1W-IP and FO images; arrows). (C) Zoomed T2W and b900 images in the top row at the same level as B. Increased conspicuity of the metastases on the diffusion weighted b900 image (arrows) due to suppression of the background fat signal. The T1W-fat% (F%) image is calculated using the T1W-wWOand T1W-FO images from B. Small amounts of F are visible with the deposits in the iliac bones on the F% image (arrows on F% image).