Whole-body magnetic resonance imaging (WB-MRI) reporting with the METastasis Reporting and Data System for Prostate Cancer (MET-RADS-P): inter-observer agreement between readers of different expertise levels

Abstract

Background The METastasis Reporting and Data System for Prostate Cancer (MET-RADS-P) guidelines are designed to enable reproducible assessment in detecting and quantifying metastatic disease response using whole-body magnetic resonance imaging (WB-MRI) in patients with advanced prostate cancer (APC). The purpose of our study was to evaluate the inter-observer agreement of WB-MRI examination reports produced by readers of different expertise when using the MET-RADS-P guidelines. Methods Fifty consecutive paired WB-MRI examinations, performed from December 2016 to February 2018 on 31 patients, were retrospectively examined to compare reports by a Senior Radiologist (9 years of experience in WB-MRI) and Resident Radiologist (after a 6-months training) using MET-RADS-P guidelines, for detection and for primary/dominant and secondary response assessment categories (RAC) scores assigned to metastatic disease in 14 body regions. Inter-observer agreement regarding RAC score was evaluated for each region by using weighted-Cohen’s Kappa statistics (K). Results The number of metastatic regions reported by the Senior Radiologist (249) and Resident Radiologist (251) was comparable. For the primary/dominant RAC pattern, the agreement between readers was excellent for the metastatic findings in cervical, dorsal, and lumbosacral spine, pelvis, limbs, lungs and other sites (K:0.81–1.0), substantial for thorax, retroperitoneal nodes, other nodes and liver (K:0.61–0.80), moderate for pelvic nodes (K:0.56), fair for primary soft tissue and not assessable for skull due to the absence of findings. For the secondary RAC pattern, agreement between readers was excellent for the metastatic findings in cervical spine (K:0.93) and retroperitoneal nodes (K:0.89), substantial for those in dorsal spine, pelvis, thorax, limbs and pelvic nodes (K:0.61–0.80), and moderate for lumbosacral spine (K:0.44). Conclusions We found inter-observer agreement between two readers of different expertise levels to be excellent in bone, but mixed in other body regions. Considering the importance of bone metastases in patients with APC, our results favor the use of MET-RADS-P in response to the growing clinical need for monitoring of metastasis in these patients.

Metastatic Diffusion Volume Based on Apparent Diffusion Coefficient as a Prognostic Factor in Castration‐Resistant Prostate Cancer

“…Twenty-eight patients (42%) underwent either radical prostatectomy or radiotherapy. The median number of received therapeutic lines was three (1)(2)(3)(4)(5)(6)(7)(8). Among the patients, 17 (26%) and 22 (33%) patients had a treatment history including taxane-based chemotherapy and new hormonal drugs, respectively.…”

“…6 Although high interreader agreement in the MET-RADS-P assessment has been shown, a simpler and more objective method is needed to make the evaluation more convenient. 7 On the other hand, objective quantitative analysis methods for WB-DWI are being explored, and Blackledge et al proposed a quantitative analysis method to evaluate the volume of the signal region as the total diffusion volume based on the apparent diffusion coefficient (ADC) value. 8 ADC values, which represent the extent of restricted water diffusion in tissues, have been reported to be useful as imaging biomarkers that reflect the histological and biological grades of various malignancies, including prostate cancer.…”

Semi-Automated Segmentation of Bone Metastases from Whole-Body MRI: Reproducibility of Apparent Diffusion Coefficient Measurements

“…The RECIST v1.1 criteria commonly used for evaluating response to treatment, however, are inappropriate for assessing the response of bone metastases, because bone-limited lesions are classified as “unmeasurable” [ 4 , 5 ]. Whole-body MRI (WB-MRI) that includes WB diffusion-weighted images (DWI) marks a paradigm shift in the assessment of treatment response of bone metastases [ 6 , 7 , 8 ]: indeed, beyond volume changes visible on conventional imaging, WB-MRI can also detect early functional changes via differences in apparent diffusion coefficient (ADC) [ 9 , 10 ], a quantitative index of water motility obtained from DWI [ 11 , 12 ]. Unlike soft tissue lesions [ 13 ], active bone lesions have higher ADC values than normal, fat-rich bone marrow [ 14 , 15 ], but ADC values tend to increase for both soft tissues and malignant bone lesions when there is substantial response to therapy due to an increased mobility of water molecules accompanying cell death [ 16 , 17 ].…”

Whole-body MRI: detecting bone metastases from prostate cancer

“…Since then, numerous reports have been published on the addition of DWI to WB-MRI for the detection of bone metastases in not only prostate cancer, but also breast cancer, lung cancer, and multiple myeloma [5,[38][39][40]. Moreover, this led many researchers to pay more attention to the field of prostate cancer [6,[41][42][43][44][45][46][47][48][49][50].…”