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

Value of Whole-body Magnetic Resonance Imaging Using the MET-RADS-P Criteria for Assessing the Response to Intensified Androgen Deprivation Therapy in Metastatic Hormone-naïve and Castration-resistant Prostate Cancer

BACKGROUND AND OBJECTIVES

We assessed the agreement between prostate-specific antigen (PSA) and imaging responses using whole-body magnetic resonance imaging (wbMRI). Our aim was to explore the potential prognostic value of PSA and wbMRI responses in metastatic hormone-naïve prostate cancer (mHNPC) and castration-resistant PC (mCRPC).

METHODS

wbMRI was prospectively performed in 37 patients with mHNPC and 51 with mCRPC before and after 6-12 mo of androgen deprivation therapy and an androgen receptor pathway inhibitor (ARPI). Imaging responses were defined according to the Metastasis Reporting and Data System for PC (MET-RADS-P) criteria. A PSA response was defined as PSA ≤0.2 ng/ml in mHNPC and a ≥50% decrease from the pretreatment level in mCRPC. Agreement between PSA and wbMRI responses was assessed using Cohen's κ. The association between time to subsequent treatment and overall survival (OS) was analyzed using Cox regression analysis.

KEY FINDINGS AND LIMITATIONS

Agreement between PSA and wbMRI responses was fair in mHNPC (κ = 0.30) but none to slight in mCRPC (κ = 0.15). In mHNPC, patients with a PSA or wbMRI response were less likely to receive subsequent treatments; wbMRI progression was associated with a significantly higher risk of death (hazard ratio 8.59; p = 0.002). In mCRPC, two-thirds of patients with a PSA response showed progression on wbMRI; neither PSA nor wbMRI progression changed the likelihood of starting a subsequent treatment or the risk of death.

CONCLUSIONS AND CLINICAL IMPLICATIONS

In mHNPC, wbMRI progression was associated with a higher risk of needing subsequent treatment and shorter OS.

PATIENT SUMMARY

We evaluated the agreement between routine PSA (prostate-specific antigen) test results and whole-body MRI (magnetic resonance imaging) scans for assessing the response of metastatic prostate cancer to treatment. There was disagreement between the PSA and MRI results, mainly for patients with cancer that was resistant to hormone-based treatment. Combining PSA with whole-body MRI might provide a more accurate picture of the response of advanced prostate cancer to treatment.

Fast (< 30 min) "All-in-One" whole-body MRI for TNM staging in high-risk prostate cancer (PCa): Feasibility and comparison to 68Ga-Prostate Specific Membrane Antigen (PSMA)-PET/CT

PURPOSE

Next-generation imaging techniques, including PSMA-PET/CT and whole-body MRI (WB-MRI), are disrupting the management of prostate cancer (PCa). This study aimed to build a fast "All-In-One" WB-MRI protocol and to compare it to 68Ga-PSMA-PET/CT for local (T), nodal (N), and distant staging (M1a, M1b, M1c).

METHODS

Fifty-two PCa patients at high-risk for metastases underwent a fast "All-in-One" WB-MRI (combining biparametric prostate assessment based on rapid T2-weighted and diffusion-weighted imaging (DWI) following the PI-RADS v2.1 guidelines and the MET-RADS-P guidelines). This WB-MRI prococol was compared to routinely performed PSMA-PET/CT read according to PSMA-RADS 1.0. Inter-technique agreement on staging and proportion differences in positive findings were assessed using Gwet's AC1 and Exact test.

RESULTS

Fast "All-in-One" WB-MRI better detected local tumors (T) (87 % vs 77 %, p = 0.063), while PSMA-PET/CT detected more nodes (40 % vs 29 %, p = 0.031) with a median small axis of 5 mm. No proportion difference was observed in the detection of extra nodal metastases (M1b) (p > 0.999). Inter-technique agreement ranged from good (AC1M1a = 0.68, AC1N = 0.79) to very good (AC1T = 0.86, AC1EPE = 0.89, AC1M1b = 0.93, AC1M1c = 0.96). Fewer oligometastatic patients were detected with PSMA-PET/CT (11 %) compared to WB-MRI (19 %).

CONCLUSION

A fast (<30 min) "All-In-One" WB-MRI protocol can be implemented in clinical routine. It provides better anatomical characterization of the T2/T3 stage than 68Ga-PSMA-PET/CT, similar distant metastasis detection rate, but slightly inferior detection rate of nodal metastases.

The established chest MRI score for cystic fibrosis can be applied to contrast agent-free matrix pencil decomposition functional MRI: a multireader analysis

Background

Established morpho-functional chest magnetic resonance imaging (MRI) detects abnormalities in lung morphology and perfusion in people with cystic fibrosis (pwCF) using a dedicated scoring system. Functional assessment is performed using contrast-enhanced (CE) perfusion MRI. Novel matrix pencil decomposition MRI (MP-MRI) is a contrast agent-free alternative, but further validation of this technique is needed.

Objectives

The aim of this study was to evaluate the applicability of the validated morpho-functional chest MRI score for CE perfusion and MP perfusion MRI in a multireader approach.

Methods

Twenty-seven pwCF (mean age 20.8 years, range 8.4-45.7 years) underwent morpho-functional MRI including CE perfusion and MP perfusion MRI in the same examination. Nine blinded chest radiologists of different experience levels assessed lung perfusion and applied the validated chest MRI score to CE- and MP-MRI. Inter-reader agreement of perfusion scores in CE- and MP-MRI were compared with each other and with the MRI morphology score. Differences according to the readers' experience were also analyzed.

Results

The CE perfusion scores were overall lower than the MP perfusion scores (6.2 ± 3.3 vs. 6.9 ± 2.0; p < 0.05) with a strong correlation between both perfusion scores (r = 0.74; p < 0.01). The intraclass correlation coefficient (ICC) as measure for inter-reader agreement was good and significant for both perfusion scores, but higher for the CE perfusion score (0.75, p < 0.001) than for MP perfusion scores (0.61, p < 0.001). The Bland-Altman analysis revealed a difference in CE and MP perfusion scores with more extreme values in CE perfusion scores compared to MP perfusion scores (r = 0.62, p < 0.001). The morphology score showed a moderate to good correlation with the CE perfusion score (r = 0.73, p < 0.01) and the MP perfusion score (r = 0.55, p < 0.01). We did not find a difference in scoring according to the radiological experience level.

Conclusion

The established chest MRI score can be applied both to validated CE and novel MP perfusion MRI with a good interreader reliability. The remaining difference between CE and MP-MRI scores may be explained by a lack of routine in visual analysis of MP-MRI and may favor an automated analysis for use of MP-MRI as a noninvasive outcome measure.

The Whole-Body MRI Reporting and Data System Guidelines for Prostate Cancer (MET-RADS-P), Multiple Myeloma (MY-RADS), and Cancer Screening (ONCO-RADS)

Whole-body magnetic resonance imaging (WB-MRI) is being employed with increasing frequency to evaluate a broader spectrum of patients with diverse types of cancer and for cancer screening purposes. While clinical guidelines support its use, a standardized radiological approach is still lacking. To improve consistency in the acquisition, interpretation, and reporting of WB-MRI examinations, three reporting and data systems (RADSs) have been recently suggested: METastasis Reporting and Data System for Prostate Cancer (MET-RADS-P), Myeloma Response Assessment and Diagnosis System (MY-RADS), and Oncologically Relevant Findings Reporting and Data System (ONCO-RADS). MET-RADS-P was developed to stage and monitor men with advanced prostate cancer using WB-MRI. It has emerged as a reliable imaging biomarker for predicting metastatic disease progression and assessing treatment response. MY-RADS was developed to stage and monitor patients with multiple myeloma using WB-MRI, emerging as a prognostic imaging biomarker. However, the evidence regarding inter-reader agreement for MY-RADS is currently limited. ONCO-RADS was developed to standardize the use of WB-MRI for cancer screening in individuals with cancer predisposition syndromes and in the general population. While initial findings are promising, the evidence supporting its use remains limited. To further validate and expand upon these promising preliminary findings, additional large-scale, prospective, multicenter studies are necessary.

Whole-body MRI for staging prostate cancer: a narrative review

OBJECTIVE

To present a narrative review regarding the diagnostic accuracy of whole-body magnetic resonance imaging (WBMRI) in staging patients with high-risk prostate cancer (HRPCa) and compare it to established imaging modalities.

METHODS

A narrative review was carried out using PubMed using the following keywords: 'whole body', 'magnetic resonance imaging', 'MRI', 'prostate cancer', 'risk stratification', and 'staging'. Articles that evaluated WBMRI as the imaging modality to stage patients with HRPCa were included, while studies that solely assessed for biochemical recurrence or metastatic disease progression were excluded.

RESULTS

In the evaluation of lymphatic metastases, WBMRI has demonstrated a comparable, if not improved, sensitivity and specificity compared to conventional imaging of computed tomography (CT). Furthermore, WBMRI demonstrates improved sensitivity and specificity in detecting bone metastases compared to bone scintigraphy (BS). However, with advent of prostate-specific membrane antigen (PSMA) radioligands for positron emission tomography (PET), the diagnostic performance of WBMRI to detect metastatic disease appears inferior.

CONCLUSIONS

The diagnostic capabilities of WBMRI exceed that of conventional imaging of CT and BS in detecting metastatic disease in patients with HRPCa. However, WBMRI does not perform as well as PSMA PET/CT. Further study on cost comparisons between WBMRI and PSMA PET/CT are needed, as well as evaluations of combined PSMA PET/MRI are needed.

Prostate MRI for the detection of clinically significant prostate cancer: Update and future directions

PURPOSE OF REVIEW

In recent decades, there has been an increasing role for magnetic resonance imaging (MRI) in the detection of clinically significant prostate cancer (csPC). The purpose of this review is to provide an update and outline future directions for the role of MRI in the detection of csPC.

RECENT FINDINGS

In diagnosing clinically significant prostate cancer pre-biopsy, advances include our understanding of MRI-targeted biopsy, the role of biparametric MRI (non-contrast) and changing indications, for example the role of MRI in screening for prostate cancer. Furthermore, the role of MRI in identifying csPC is maturing, with emphasis on standardization of MRI reporting in active surveillance (PRECISE), clinical staging (EPE grading, MET-RADS-P) and recurrent disease (PI-RR, PI-FAB). Future directions of prostate MRI in detecting csPC include quality improvement, artificial intelligence and radiomics, positron emission tomography (PET)/MRI and MRI-directed therapy.

SUMMARY

The utility of MRI in detecting csPC has been demonstrated in many clinical scenarios, initially from simply diagnosing csPC pre-biopsy, now to screening, active surveillance, clinical staging, and detection of recurrent disease. Continued efforts should be undertaken not only to emphasize the reporting of prostate MRI quality, but to standardize reporting according to the appropriate clinical setting.

Personalizing approaches to the management of metastatic hormone sensitive prostate cancer: role of advanced imaging, genetics and therapeutics

PURPOSE

To summarize contemporary and emerging strategies for the diagnosis and management of metastatic hormone sensitive prostate cancer (mHSPC), focusing on diagnostic testing and therapeutics.

METHODS

Literature review using PUBMED-Medline databases as well as clinicaltrials.gov to include reported or ongoing clinical trials on treatment for mHSPC. We prioritized the findings from phase III randomized clinical trials, systematic reviews, meta-analyses and clinical practice guidelines.

RESULTS

There have been significant changes to the diagnosis and staging evaluation of mHSPC with the integration of increasingly accurate positron emission tomography (PET) imaging tracers that exceed the performance of conventional computerized tomography (CT) and bone scan. Germline multigene testing is recommended for the evaluation of patients newly diagnosed with mHSPC given the prevalence of actionable alterations that may create candidacy for specific therapies. Although androgen deprivation therapy (ADT) remains the backbone of treatment for mHSPC, approaches to first-line treatment include the integration of multiple agents including androgen receptor synthesis inhibitors (ARSI; abiraterone) Androgen Receptor antagonists (enzalutamide, darolutamide, apalautamide), and docetaxel chemotherapy. The combination of ADT, ARSI, and docetaxel chemotherapy has recently been evaluated in a randomized trial and was associated with significantly improved overall survival including in patients with a high burden of disease. The role of local treatment to the prostate with radiation has been evaluated in randomized trials with additional studies underway evaluating the role of cytoreductive radical prostatectomy.

CONCLUSION

The staging and initial management of patients with mHSPC has undergone significant advances in the last decade with advancements in the diagnosis, treatment and sequencing of therapies.

Whole-Body MRI in Musculoskeletal Oncology: A Comprehensive Review with Recommendations

Whole-body (WB) MRI has emerged as an attractive method for oncologic evaluation, potentially replacing conventional imaging modalities and providing a one-step wide-coverage assessment of both the skeleton and soft tissues. In addition to providing anatomic information, WB MRI may also yield a functional analysis with the inclusion of diffusion-weighted imaging (DWI). DWI translates microstructural changes, resulting in an excellent alternative to fluorodeoxyglucose PET/CT. WB MRI (with DWI) offers comparable accuracy to PET/CT and has the advantage of avoiding ionizing radiation. Technological advances and the development of faster protocols have prompted greater accessibility of WB MRI, with growing applications in routine practice for the diagnosis, staging, and follow-up of cancer. This review discusses the technical considerations, clinical applications, and accuracy of WB MRI in musculoskeletal oncology. Keywords: Pediatrics, MR Imaging, Skeletal-Axial, Skeletal-Appendicular, Soft Tissues/Skin, Bone Marrow, Extremities, Oncology, Musculoskeletal Imaging © RSNA, 2023.

Analysis of interreader agreement in structured reports of pelvic multiparametric magnetic resonance imaging using the METastasis Reporting and Data System for Prostate Cancer guidelines

PURPOSE

To evaluate interreader agreement on pelvic multiparametric magnetic resonance imaging (mpMRI) interpretation among radiologists using a structured reporting tool based on the METastasis Reporting and Data System for Prostate Cancer (MET-RADS-P) guidelines.

METHODS

A structured report for follow-up pelvic mpMRI for advanced prostate cancer (APC) patients was formulated based on MET-RADS-P guidelines. In total, 163 paired pelvic mpMRI examinations were performed from December 2017 to February 2021 on 105 patients with APC. These were retrospectively reviewed by two senior and two junior radiologists for metastatic lesion detection and were categorized by these readers using primary/secondary response assessment categories (RACs), with and without the structured report. Interreader agreement regarding metastasis detection and RAC scores was evaluated with Cohen's kappa and weighted Cohen's kappa statistics (K), respectively.

RESULTS

The two senior radiologists showed higher agreement with the reference standard for metastasis detection using the structured report (S1: K = 0.83; S2: K = 0.73) compared with the conventional report (S1: K = 0.72; S2: K = 0.61). Junior radiologists showed similar results (J1: 0.66 vs. 0.59; J2: 0.65 vs. 0.57). The overall agreement between the two senior radiologists was excellent for the primary RAC pattern using the structured reports (K = 0.81) and was substantial for secondary RAC categorization (K = 0.75). The interreader agreement of the two junior radiologists was substantial for both primary and secondary RAC values (K = 0.76, 0.68).

CONCLUSION

Good interreader agreement was found for the follow-up assessment of APC patients between radiologists, where the pelvic mpMRI was reported using MET-RADS-P guidelines. This improvement applied to both metastatic lesion detection and qualitative RAC assessment.

The future of PSMA PET and WB MRI as next-generation imaging tools in prostate cancer

Radiolabelled prostate-specific membrane antigen (PSMA)-based PET-CT has been shown in numerous studies to be superior to conventional imaging in the detection of nodal or distant metastatic lesions. ⁶⁸Ga-PSMA PET-CT is now recommended by many guidelines for the detection of biochemically relapsed disease after radical local therapy. PSMA radioligands can also function as radiotheranostics, and Lu-PSMA has been shown to be a potential new line of treatment for metastatic castration-resistant prostate cancer. Whole-body (WB) MRI has been shown to have a high diagnostic performance in the detection and monitoring of metastatic bone disease. Prospective, randomized, multicentre studies comparing ⁶⁸Ga-PSMA PET-CT and WB MRI for pelvic nodal and metastatic disease detection are yet to be performed. Challenges for interpretation of PSMA include tracer trapping in non-target tissues and also urinary excretion of tracers, which confounds image interpretation at the vesicoureteral junction. Additionally, studies have shown how long-term androgen deprivation therapy (ADT) affects PSMA expression and could, therefore, reduce tracer uptake and visibility of PSMA⁺ lesions. Furthermore, ADT of short duration might increase PSMA expression, leading to the PSMA flare phenomenon, which makes the accurate monitoring of treatment response to ADT with PSMA PET challenging. Scan duration, detection of incidentalomas and presence of metallic implants are some of the major challenges with WB MRI. Emerging data support the wider adoption of PSMA PET and WB MRI for diagnosis, staging, disease burden evaluation and response monitoring, although their relative roles in the standard-of-care management of patients are yet to be fully defined.

Whole-body MRI: detecting bone metastases from prostate cancer

Whole-body magnetic resonance imaging (WB-MRI) is currently used worldwide for detecting bone metastases from prostate cancer. The 5-year survival rate for prostate cancer is > 95%. However, an increase in survival time may increase the incidence of bone metastasis. Therefore, detecting bone metastases is of great clinical interest. Bone metastases are commonly located in the spine, pelvis, shoulder, and distal femur. Bone metastases from prostate cancer are well-known representatives of osteoblastic metastases. However, other types of bone metastases, such as mixed or inter-trabecular type, have also been detected using MRI. MRI does not involve radiation exposure and has good sensitivity and specificity for detecting bone metastases. WB-MRI has undergone gradual developments since the last century, and in 2004, Takahara et al., developed diffusion-weighted Imaging (DWI) with background body signal suppression (DWIBS). Since then, WB-MRI, including DWI, has continued to play an important role in detecting bone metastases and monitoring therapeutic effects. An imaging protocol that allows complete examination within approximately 30 min has been established. This review focuses on WB-MRI standardization and the automatic calculation of tumor total diffusion volume (tDV) and mean apparent diffusion coefficient (ADC) value. In the future, artificial intelligence (AI) will enable shorter imaging times and easier automatic segmentation.

Current Opinion on the Use of Magnetic Resonance Imaging in Staging Prostate Cancer: A Narrative Review

Accurate staging is critical for treatment planning and prognosis in men with prostate Cancer. Prostate magnetic imaging resonance (MRI) may aid in the staging evaluation by verifying organ-confined status, assessing the status of the pelvic lymph nodes, and establishing the local extent of the tumor in patients being considered for therapy. MRI has a high specificity for diagnosing extracapsular extension, and therefore may impact the decision to perform nerve sparing prostatectomy, along with seminal vesicle invasion and lymph node metastases; however, its sensitivity remains limited. Current guidelines vary significantly regarding endorsing the use of MRI for staging locoregional disease. For high-risk prostate cancer, most guidelines recommend cross sectional imaging, including MRI, to evaluate for more extensive disease that may merit change in radiation field, extended androgen deprivation therapy, or guiding surgical planning. Although MRI offers reasonable performance characteristics to evaluate bone metastases, guidelines continue to support the use of bone scintigraphy. Emerging imaging technologies, including coupling positron emission tomography (PET) with MRI, have the potential to improve the accuracy of prostate cancer staging with the use of novel radiotracers.

Recent Advancements in CT and MR Imaging of Prostate Cancer

CT and MRI are both commonly used in prostate cancer (PCa) management, which includes a large spectrum from screening positive pre-diagnosis phase to metastatic disease. CT and MRI have continually evolved to meet the changing demands for PCa management. For CT, novel techniques such as dual energy CT and photon counting CT show promising results for tissue characterization and quantification. For MRI, the detection, staging, and management of prostate cancer has been significantly improved by the development of multiparametric, biparametric, and whole-body MRI techniques. Additionally, research on ultrasmall superparamagnetic particles of iron oxide contrast-enhanced MRI has revealed promising results for nodal staging of PCa. In this manuscript we aim to outline the current status and recent advancements of CT and MRI in PCa imaging.

Bone Metastases Are Measurable: The Role of Whole-Body MRI and Positron Emission Tomography

Metastatic tumor deposits in bone marrow elicit differential bone responses that vary with the type of malignancy. This results in either sclerotic, lytic, or mixed bone lesions, which can change in morphology due to treatment effects and/or secondary bone remodeling. Hence, morphological imaging is regarded unsuitable for response assessment of bone metastases and in the current Response Evaluation Criteria In Solid Tumors 1.1 (RECIST1.1) guideline bone metastases are deemed unmeasurable. Nevertheless, the advent of functional and molecular imaging modalities such as whole-body magnetic resonance imaging (WB-MRI) and positron emission tomography (PET) has improved the ability for follow-up of bone metastases, regardless of their morphology. Both these modalities not only have improved sensitivity for visual detection of bone lesions, but also allow for objective measurements of bone lesion characteristics. WB-MRI provides a global assessment of skeletal metastases and for a one-step "all-organ" approach of metastatic disease. Novel MRI techniques include diffusion-weighted imaging (DWI) targeting highly cellular lesions, dynamic contrast-enhanced MRI (DCE-MRI) for quantitative assessment of bone lesion vascularization, and multiparametric MRI (mpMRI) combining anatomical and functional sequences. Recommendations for a homogenization of MRI image acquisitions and generalizable response criteria have been developed. For PET, many metabolic and molecular radiotracers are available, some targeting tumor characteristics not confined to cancer type (e.g. 18F-FDG) while other targeted radiotracers target specific molecular characteristics, such as prostate specific membrane antigen (PSMA) ligands for prostate cancer. Supporting data on quantitative PET analysis regarding repeatability, reproducibility, and harmonization of PET/CT system performance is available. Bone metastases detected on PET and MRI can be quantitatively assessed using validated methodologies, both on a whole-body and individual lesion basis. Both have the advantage of covering not only bone lesions but visceral and nodal lesions as well. Hybrid imaging, combining PET with MRI, may provide complementary parameters on the morphologic, functional, metabolic and molecular level of bone metastases in one examination. For clinical implementation of measuring bone metastases in response assessment using WB-MRI and PET, current RECIST1.1 guidelines need to be adapted. This review summarizes available data and insights into imaging of bone metastases using MRI and PET.

Effects of Sex and Age on Fat Fraction, Diffusion-Weighted Image Signal Intensity and Apparent Diffusion Coefficient in the Bone Marrow of Asymptomatic Individuals: A Cross-Sectional Whole-Body MRI Study

We aimed to describe the relationships between the relative fat fraction (%FF), muscle-normalized diffusion-weighted (DW) image signal intensity and water apparent diffusion coefficient (ADC), sex and age for normal bone marrow, in the normal population. Our retrospective cohort consisted of 100 asymptomatic individuals, equally divided by sex and 10-year age groups, who underwent whole-body MRI at 1.5 T for early cancer detection. Semi-automated segmentation of global bone marrow volume was performed using the DW images and the resulting segmentation masks were projected onto the ADC and %FF maps for extraction of parameter values. Differences in the parameter values between sexes at age ranges were assessed using the Mann–Whitney and Kruskal–Wallis tests. The Spearman correlation coefficient r was used to assess the relationship of each imaging parameter with age, and of %FF with ADC and normalized DW signal intensity values. The average %FF of normal bone marrow was 65.6 ± 7.2%, while nSI_b50, nSI_b900 and ADC were 1.7 ± 0.5, 3.2 ± 0.9 and 422 ± 67 μm²/s, respectively. The bone marrow %FF values increased with age in both sexes (r = 0.63 and r = 0.64, respectively, p < 0.001). Values of nSI_b50 and nSI_b900 were higher in younger women compared to men of the same age groups (p < 0.017), but this difference decreased with age. In our cohort of asymptomatic individuals, the values of bone marrow relative %FF, normalized DW image signal intensity and ADC indicate higher cellularity in premenopausal women, with increasing bone marrow fat with aging in both sexes.

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

BACKGROUND

Whole-body diffusion-weighted MRI (WB-DWI) is useful for assessing disease activity in castration-resistant prostate cancer (CRPC). MET-RADS-P is a subjective assessment-based reporting system proposed to standardize the interpretation of WB-DWI. However, a quantitative evaluation of WB-DWI has not been fully investigated.

PURPOSE

To investigate the validity, and analyze the prognostic value, of quantitative evaluation of WB-DWI based on apparent diffusion coefficient (ADC) values for CRPC.

STUDY TYPE

Retrospective.

POPULATION

Sixty-six patients with CRPC. The median age was 75 years. During the median follow-up period of 25.2 months, 23 of 66 patients (34.8%) died of prostate cancer.

FIELD STRENGTH/SEQUENCE

A 1.5 T WB-DWI was used with two b-values (0 s/mm² -1000 s/mm² ). A single-shot echo-planar imaging sequence was used.

ASSESSMENT

WB-DWI were evaluated by three readers according to MET-RADS-P scoring system. Using imaging software, Attractive BDScore, tumor diffusion volume (mDV) and ADC value of metastatic lesion (mADC) was calculated by two readers. The mDV was calculated with ADC values (×10^-3  mm² /sec) of 0.4-0.9 (mDV_0.4-0.9 ), 0.9-1.4 (mDV_0.9-1.4 ), and 1.4-1.8 (mDV_1.4-1.8 ), respectively.

STATISTICAL TESTS

Spearman's rank correlation coefficient was used to assess the correlation. The relationships between the variables with cancer-specific survival (CSS) were evaluated. Multivariate analysis was performed using the Cox proportional hazards model.

RESULTS

mDVs showed a strong positive correlation with MET-RADS-P scores (r = 0.90/0.87, P < 0.05 for both). mDV showed a statistically significant association with CSS (hazard ratio [HR]: 1.01, P < 0.05). When the mDVs calculated based on the ADC values were included, mDV_0.4-0.9 (HR: 1.02, P < 0.05) and the number of therapeutic lines (HR: 1.35, P < 0.05) were significant independent indicators of CSS shortening.

CONCLUSION

Assessment of metastatic tumor volume based on ADC values can be used in the prognostic evaluation of patients with CRPC. WB-DWI might be a potential prognostic imaging biomarker for CRPC.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 2.

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

Using semi-automated software simplifies quantitative analysis of the visible burden of disease on whole-body MRI diffusion-weighted images. To establish the intra- and inter-observer reproducibility of apparent diffusion coefficient (ADC) measures, we retrospectively analyzed data from 20 patients with bone metastases from breast (BCa; n = 10; aged 62.3 ± 14.8) or prostate cancer (PCa; n = 10; aged 67.4 ± 9.0) who had undergone examinations at two timepoints, before and after hormone-therapy. Four independent observers processed all images twice, first segmenting the entire skeleton on diffusion-weighted images, and then isolating bone metastases via ADC histogram thresholding (ADC: 650–1400 µm²/s). Dice Similarity, Bland-Altman method, and Intraclass Correlation Coefficient were used to assess reproducibility. Inter-observer Dice similarity was moderate (0.71) for women with BCa and poor (0.40) for men with PCa. Nonetheless, the limits of agreement of the mean ADC were just ±6% for women with BCa and ±10% for men with PCa (mean ADCs: 941 and 999 µm²/s, respectively). Inter-observer Intraclass Correlation Coefficients of the ADC histogram parameters were consistently greater in women with BCa than in men with PCa. While scope remains for improving consistency of the volume segmented, the observer-dependent variability measured in this study was appropriate to distinguish the clinically meaningful changes of ADC observed in patients responding to therapy, as changes of at least 25% are of interest.