Comparison of the diagnostic performance and impact on management of 18F-FDG PET/CT and whole-body MRI in multiple myeloma

Role of Imaging in Multiple Myeloma: A Potential Opportunity for Quantitative Imaging and Radiomics?

Multiple myeloma (MM) is the second most prevalent hematologic malignancy, particularly affecting the elderly. The disease often begins with a premalignant phase known as monoclonal gammopathy of undetermined significance (MGUS), solitary plasmacytoma (SP) and smoldering multiple myeloma (SMM). Multiple imaging modalities are employed throughout the disease continuum to assess bone lesions, prevent complications, detect intra- and extramedullary disease, and evaluate the risk of neurological complications. The implementation of advanced imaging analysis techniques, including artificial intelligence (AI) and radiomics, holds great promise for enhancing our understanding of MM. The integration of advanced image analysis techniques which extract features from magnetic resonance imaging (MRI), computed tomography (CT), or positron emission tomography (PET) images has the potential to enhance the diagnostic accuracy for MM. This innovative approach may lead to the identification of imaging biomarkers that can predict disease prognosis and treatment outcomes. Further research and standardized evaluations are needed to define the role of radiomics in everyday clinical practice for patients with MM.

EANM guidelines on the use of [18F]FDG PET/CT in diagnosis, staging, prognostication, therapy assessment, and restaging of plasma cell disorders

We provide updated guidance and standards for the indication, acquisition, and interpretation of [18F]FDG PET/CT for plasma cell disorders. Procedures and characteristics are reported and different scenarios for the clinical use of [18F]FDG PET/CT are discussed. This document provides clinicians and technicians with the best available evidence to support the implementation of [18F]FDG PET/CT imaging in routine practice and future research.

Chemokine Receptor 4-Targeted PET/CT with [68Ga]pentixather in Newly Diagnosed Multiple Myeloma: a Comparative Study with [68Ga]pentixafor PET/CT

PURPOSE

This study aimed to compare the detection rate of [68Ga]pentixather PET/CT and [68Ga]pentixafor PET/CT in newly diagnosed multiple myeloma (NDMM) patients, and to explore the value of [68Ga]pentixather PET/CT for tumor load assessment.

METHODS

Nineteen NDMM Patients were prospectively recruited and underwent both [68Ga]pentixather PET/CT and [68Ga]pentixafor PET/CT. A positive PET scan was defined as the presence of PET-positive focal bone lesions, paraskeletal disease, extramedullary plasmacytoma, or diffuse bone marrow uptake. Lesion numbers, SUVmax and PET-related tumor burden values were compared. The correlations between PET-related tumor burden and clinical risk stratification were analyzed.

RESULTS

[68Ga]pentixather PET/CT showed a tendency of higher positive rate compared with [68Ga]pentixafor PET/CT [94.7% (18/19) vs. 78.9% (15/19), p > 0.05]. Among 14 patients with 151 matched focal bone lesions, [68Ga]pentixather PET detected more or equal number of lesions in 13 patients, and demonstrated higher uptake value than 68 Ga-pentixafor PET [SUVmax, 16.8 (9.0, 23.8) vs. 13.4 (6.5, 20.4), p < 0.001]. For PET related-tumor burden, positive correlations of total bone marrow uptake (TBmU) (r = 0.9540, p < 0.0001) and SUVmean of total bone marrow (r = 0.9632, p < 0.0001) in two PET scans were observed. Higher TBmU [7864.9 (5549.2, 11,616.2) vs. 5383.4(4102.7, 11,041.8), p < 0.001], SUVmean of total bone marrow [1.4 (1.1, 2.2) vs. 1.1 (0.7, 2.1), p < 0.001] were demonstrated on [68Ga]pentixather PET than [68Ga]pentixafor PET. And the level of TBmU in [68Ga]pentixather PET and [68Ga]pentixafor PET were both elevated in Durie-Salmon Staging (DSS) III than DSS I (p < 0.01).

CONCLUSIONS

[68Ga]pentixather PET/CT performed a non-inferior capability for tumor detection compared to [68Ga]pentixafor PET/CT in NDMM patients. [68Ga]pentixather PET/CT can assess tumor load in MM patients and depict a significantly higher PET-related total tumor burden than [68Ga]pentixafor PET/CT.

Advancements in Multiple Myeloma Research: High-Throughput Sequencing Technologies, Omics, and the Role of Artificial Intelligence

Multiple myeloma is a complex and challenging type of blood cancer that affects plasma cells in the bone marrow. In recent years, the development of advanced research techniques, such as omics approaches-which involve studying large sets of biological data like genes and proteins-and high-throughput sequencing technologies, has allowed researchers to analyze vast amounts of genetic information rapidly and gain new insights into the disease. Additionally, the advent of artificial intelligence tools has accelerated data analysis, enabling more accurate predictions and improved treatment strategies. This review aims to highlight recent research advances in multiple myeloma made possible by these novel techniques and to provide guidance for researchers seeking effective approaches in this field.

Symptomatic Myeloma: PET, Whole-Body MR Imaging with Diffusion-Weighted Imaging or Both

According to international guidelines, patients with suspected myeloma should primarily undergo low-dose whole-body computed tomography (CT) for diagnostic purposes. To optimize sensitivity and specificity and enable treatment response assessment, whole-body MR (WB-MR) imaging should include diffusion-weighted imaging with apparent diffusion coefficient maps and T1-weighted Dixon sequences with bone marrow Fat Fraction Quantification. At baseline WB-MR imaging shows greater sensitivity for the detecting focal lesions and diffuse bone marrow infiltration pattern than 18F-fluorodeoxyglucose PET-CT, which is considered of choice for evaluating response to treatment and minimal residual disease and imaging of extramedullary disease.

Advanced imaging for earlier diagnosis and morbidity prevention in multiple myeloma: A British Society of Haematology and UK Myeloma Society Good Practice Paper

This Good Practice Paper provides recommendations for the use of advanced imaging for earlier diagnosis and morbidity prevention in multiple myeloma. It describes how advanced imaging contributes to optimal healthcare resource utilisation by in newly diagnosed and relapsed myeloma, and provides a perspective on future directions of myeloma imaging, including machine learning assisted reporting.

MRI-based Zero Echo Time and Black Bone Pseudo-CT Compared with Whole-Body CT to Detect Osteolytic Lesions in Multiple Myeloma

Background MRI is highly sensitive for assessing bone marrow involvement in multiple myeloma (MM) but does not enable detection of osteolysis. Purpose To assess the diagnostic accuracy, repeatability, and reproducibility of pseudo-CT MRI sequences (zero echo time [ZTE], gradient-echo black bone [BB]) in detecting osteolytic lesions in MM using whole-body CT as the reference standard. Materials and Methods In this prospective study, consecutive patients were enrolled in our academic hospital between June 2021 and December 2022. Inclusion criteria were newly diagnosed MM, monoclonal gammopathy of undetermined significance at high risk for MM, or suspicion of progressive MM. Participants underwent ZTE and BB sequences covering the lumbar spine, pelvis, and proximal femurs as part of 3-T whole-body MRI examinations, as well as clinically indicated fluorine 18 fluorodeoxyglucose PET/CT examination within 1 month that included optimized whole-body CT. Ten bone regions and two scores (categorical score = presence/absence of osteolytic lesion; semiquantitative score = osteolytic lesion count) were assessed by three radiologists (two experienced and one unfamiliar with pseudo-CT reading) on the ZTE, BB, and whole-body CT images. The accuracy, repeatability, and reproducibility of categorical scores (according to Gwet agreement coefficients AC1 and AC2) and differences in semiquantitative scores were assessed at the per-sequence, per-region, and per-patient levels. Results A total of 47 participants (mean age, 67 years ± 11 [SD]; 27 male) were included. In experienced readers, BB and ZTE had the same high accuracy (98%) in the per-patient analysis, while BB accuracy ranged 83%-100% and ZTE accuracy ranged 74%-94% in the per-region analysis. An increase of false-negative (FN) findings in the spine ranging from +17% up to +23%, according to the lumbar vertebra, was observed using ZTE (P < .013). Regardless of the region (except coxal bones), differences in the BB score minus the ZTE score were positively skewed (P < .021). Regardless of the sequence or region, repeatability was very good (AC1 ≥0.87 for all), while reproducibility was at least good (AC2 ≥0.63 for all). Conclusion Both MRI-based ZTE and BB pseudo-CT sequences of the lumbar spine, pelvis, and femurs demonstrated high diagnostic accuracy in detecting osteolytic lesions in MM. Compared with BB, the ZTE sequence yielded more FN findings in the spine. ClinicalTrials.gov Identifier: NCT05381077 Published under a CC BY 4.0 license. Supplemental material is available for this article.

National myeloma patient survey shows continuing inappropriate imaging and geographical inequalities

OBJECTIVE

To evaluate the provision of imaging at diagnosis of myeloma from the service user perspective with a specific focus on how the experiences of patients align with the National Institute for Health and Care Excellence (NICE) guidelines (NG35, 2016) on first-line imaging practice for myeloma in the United Kingdom.

METHODS

A national survey was performed to evaluate access to imaging from the patient's perspective. Patients with myeloma who received their diagnosis between 2017 and March 2022 were invited to participate. Data were collected using an online survey from 895 patients and carers between 4 and 14 March 2022.

RESULTS

Most patients had more than one imaging test. First-line MRI was used in 69.2% of respondents. First-line skeletal survey (SS, whole body X-rays) remained common (48.7% of respondents). 18F-fluorodexyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) was used least often (23.1% of respondents). SS was used more often in East England (57.9%) and Scotland (61.2%) than in South East England (36.3%).

CONCLUSIONS

Despite NICE recommendations, first-line MRI was not used in a third of patients surveyed, with geographical variation in imaging practice. Patients are still undergoing multiple imaging tests at diagnosis. Healthcare professionals should continue to emphasize the superiority of MRI compared to SS to drive for improvements in care.

ADVANCES IN KNOWLEDGE

Current recommendations on first-line imaging for myeloma are not provided consistently across the United Kingdom. There is a need to drive change and support healthcare professionals to deliver guidance-based recommendations to improve experience and outcomes for patients.

The role of conventional and novel PET radiotracers in assessment of myeloma bone disease

Over 80 % of patients with multiple myeloma (MM) experience osteolytic bone lesions, primarily due to an imbalanced interaction between osteoclasts and osteoblasts. This imbalance can lead to several adverse outcomes such as pain, fractures, limited mobility, and neurological impairments. Myeloma bone disease (MBD) raises the expense of management in addition to being a major source of disability and morbidity in myeloma patients. Whole-body x-ray radiography was the gold standard imaging modality for detecting lytic lesions. Osteolytic lesions are difficult to identify at an earlier stage on X-ray since the lesions do not manifest themselves on conventional radiographs until at least 30 % to 50 % of the bone mass has been destroyed. Hence, early diagnosis of osteolytic lesions necessitates the utilization of more complex and advanced imaging modalities, such as PET. One of the PET radiotracers that has been frequently investigated in MM is 18F-FDG, which has demonstrated a high level of sensitivity and specificity in detecting myeloma lesions. However, 18F-FDG PET/CT has several restrictions, and therefore the novel PET tracers that can overcome the limitations of 18F-FDG PET/CT should be further examined in assessment of MBD. The objective of this review article is to thoroughly examine the significance of both conventional and novel PET radiotracers in the assessment of MBD. The intention is to present the information in a manner that would be easily understood by healthcare professionals from diverse backgrounds, while minimizing the use of complex nuclear medicine terminology.

How do we image patients with multiple myeloma and precursor states?

Advances in morphological and functional imaging have led to superior detection of early bone disease, bone marrow infiltration, paramedullary and extramedullary involvement in multiple myeloma. The two functional imaging modalities that are most widely used and standardized are 18F-fluorodeoxyglucose-Positron emission tomography/computed tomography (FDG PET/CT) and whole-body magnetic resonance imaging with diffusion-weighted imaging (WB DW-MRI). Both prospective and retrospective studies have demonstrated that WB DW-MRI is more sensitive than PET/CT in the detection of baseline tumour burden and to assess response after therapy. In patients with smouldering multiple myeloma, WB DW-MRI is now the preferred imaging modality to rule out two or more unequivocal lesions which would be considered a myeloma-defining event by the updated international myeloma working group (IMWG) criteria. In addition to sensitive detection of baseline tumour burden, both PET/CT and WB DW-MRI have been successfully used for monitoring response to therapy and provide information that is complementary to IMWG response assessment and bone marrow minimal residual disease. In this article, we present 3 vignettes illustrating how we approach the use of modern imaging in the management of patients with multiple myeloma and precursor states, with a specific focus on recent data that have emerged since the publication of the IMWG consensus guideline on imaging. We have utilized data from prospective and retrospective studies to provide a rationale for our approach to imaging in these clinical scenarios and highlighted knowledge gaps requiring future investigation.

New Developments in Myeloma Treatment and Response Assessment

Recent innovative strategies have dramatically redefined the therapeutic landscape for treating multiple myeloma patients. In particular, the development and application of immunotherapy and high-dose therapy have demonstrated high response rates and have prolonged remission duration. Over the past decade, new morphologic or hybrid imaging techniques have gradually replaced conventional skeletal surveys. PET/CT using 18F-FDG is a powerful imaging tool for the workup at diagnosis and for therapeutic evaluation allowing medullary and extramedullary assessment. The independent negative prognostic value for progression-free and overall survival derived from baseline PET-derived parameters such as the presence of extramedullary disease or paramedullary disease, as well as the number of focal bone lesions and SUVmax, has been reported in several large prospective studies. During therapeutic evaluation, 18F-FDG PET/CT is considered the reference imaging technique because it can be performed much earlier than MRI, which lacks specificity. Persistence of significant abnormal 18F-FDG uptake after therapy is an independent negative prognostic factor, and 18F-FDG PET/CT and medullary flow cytometry are complementary tools for detecting minimal residual disease before maintenance therapy. The definition of a PET metabolic complete response has recently been standardized and the interpretation criteria harmonized. The development of advanced PET analysis and radiomics using machine learning, as well as hybrid imaging with PET/MRI, offers new perspectives for multiple myeloma imaging. Most recently, innovative radiopharmaceuticals such as C-X-C chemokine receptor type 4-targeted small molecules and anti-CD38 radiolabeled antibodies have shown promising results for tumor phenotype imaging and as potential theranostics.

Hybrid simultaneous whole-body 2-[18F]FDG-PET/MRI imaging in newly diagnosed multiple myeloma: first diagnostic performance and clinical added value results

OBJECTIVES

Mixing diagnostic and prognostic data provided by whole-body MRI (WB-MRI) and 2-18F-fluorodeoxyglucose (2-[18F]FDG) positron emission tomography (2-[18F]FDG-PET) from a single simultaneous imaging technique for newly diagnosed multiple myeloma (NDMM) initial workup seems attractive. However, to date, the published data are scarce and this possibility has not been fully explored. In this prospective study, we aimed to explore the diagnostic performance and added clinical value of WB-2-[18F]FDG-PET/MRI imaging in NDMM.

METHODS

All patients with confirmed NDMM at the Nantes University Hospital were prospectively enrolled in this study and underwent WB-2-[18F]FDG-PET/MRI imaging on a 3-T Biograph mMR before receiving treatment. Before imaging, they were considered either as symptomatic or as smoldering MM (SMM). Diagnostic performance of global WB-2-[18F]FDG-PET/MRI imaging, as well as PET and MRI separately for FL and diffuse BMI detection, was assessed and compared in each group. PET-based (maximal standardized uptake value, SUVmax) and MRI-based (mean apparent diffusion coefficient value, ADCmean) quantitative features were collected for FL/para-medullary disease (PMD)/bone marrow and were compared.

RESULTS

A total of 52 patients were included in this study. PET and MRI were equally effective at detecting patients with FL (69% vs. 75%) and with diffuse BMI (62% for both) in the symptomatic MM group. WB-2-[18F]FDG-PET/MRI imaging detected FL in 22% of patients with SMM (with a higher diagnostic performance for MRI), resulting in a significant impact on clinical management in this population. SUVmax and ADCmean quantitative features were weakly or not correlated.

CONCLUSIONS

WB-2-[18F]FDG-PET/MRI could represent the next-generation imaging modality for MM.

KEY POINTS

• Whole-body 2-[18F]FDG-PET/MRI imaging detected at least one focal bone lesion in 75% of patients with symptomatic multiple myeloma, and PET and MRI were equally effective at identifying patients with a focal bone lesion. • Whole-body 2-[18F]FDG-PET/MRI imaging detected a focal bone lesion in 22% of patients with smoldering multiple myeloma (with a higher diagnostic performance for MRI). • MRI had a significant impact on clinical management of smoldering multiple myeloma.

Relation of whole-body metabolic tumor volume and total lesion glycolysis on fluorodeoxyglucose PET/computed tomography with clinical and laboratory parameters in newly diagnosed multiple myeloma

OBJECTIVE

This study aims to evaluate the relationships of metabolic fluorodeoxyglucose PET/computed tomography (FDG PET/CT) parameters such as whole-body metabolic tumor volume (WB MTV), WB-total lesion glycolysis (TLG), and bone marrow (BM)-mean standard uptake value (SUVmean) with clinical stage and other prognostic biomarkers in newly diagnosed multiple myeloma (MM) patients.

METHODS

Patients who underwent pretreatment PET/CT with the diagnosis of MM were evaluated retrospectively. The number of focal lesions, WB MTV, WB TLG, and BM SUVmean values were measured on FDG PET/CT images. Clinical stages and prognostic laboratory parameters were recorded the pretreatment period.

RESULTS

WB MTV and WB TLG values were significantly higher in patients with more than three focal lesions on FDG PET/CT scan (all P < 0.001). According to the Revised International Staging System (R-ISS), all WB MTV, WB TLG, and BM SUVmean values are significantly higher in patients with stage 3 disease than in stages 1-2 ( P = 0.027, P = 0.019, P = 0.001, respectively). Serum creatinine level is positively correlated with WB MTV, WB TLG, and BM SUVmean values ( P = 0.020, P = 0.004, P < 0.001, respectively). In addition, the β2 microglobulin level, an essential biochemical prognostic parameter, was positively correlated with the BM SUVmean value ( P = 0.013).

CONCLUSION

The BM SUVmean, WB MTV, and WB TLG values, which reflect FDG avid WB tumor burden, are associated with prognostic biomarkers and R-ISS stage in newly diagnosed MM patients. It contributes to the identification of high-risk patients at the pretreatment staging.

The potential role of mass spectrometry for the identification and monitoring of patients with plasma cell disorders: Where are we now and which questions remain unanswered?

Mass spectrometry (MS) techniques provide a highly sensitive methodology for the assessment and monitoring of paraproteins compared to standard electrophoretic techniques. The International Myeloma Working Group (IMWG) recently approved the use of intact light chain matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in lieu of immunofixation in the clinical assessment of patients and the assessment of patients enrolled on clinical trials. The increased sensitivity of these assays may help to detect and monitor monoclonal proteins (MP) in many patients with previously non-measurable disease, will reduce complete response (CR) rates and increase detection of low-level MP. The ability to track the unique mass or amino acid sequence of the MP also eliminates interference from therapeutic monoclonal antibodies (tmAbs) in most patients with IgG kappa myeloma. The intact light chain assays also provide structural information about the monoclonal light chain, including the presence of N-linked glycosylation, which has been shown to be commoner on amyloidogenic light chains and may have prognostic significance in monoclonal gammopathy of undetermined significance (MGUS). In this review, we discuss these issues alongside differences in the analytical and practical aspects related to the different MS assays under development and the challenges for MS.

18 F-FDG PET/CT and MRI in the Management of Multiple Myeloma: A Comparative Review

During the last two decades, the imaging landscape of multiple myeloma (MM) has evolved with whole-body imaging techniques such as fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) and MRI replacing X-ray skeletal survey. Both imaging modalities have high diagnostic performance at the initial diagnosis of MM and are key players in the identification of patients needing treatment. Diffusion-weighted MRI has a high sensitivity for bone involvement, while 18F-FDG PET/CT baseline parameters carry a strong prognostic value. The advent of more efficient therapeutics, such as immunomodulatory drugs and proteasome inhibitors, has called for the use of sensitive imaging techniques for monitoring response to treatment. Diffusion-weighted MRI could improve the specificity of MRI for tumor response evaluation, but questions remain regarding its role as a prognostic factor. Performed at key time points of treatment in newly diagnosed MM patients, 18F-FDG PET/CT showed a strong association with relapse risk and survival. The deployment of minimal residual disease detection at the cellular or the molecular level may raise questions on the role of these imaging techniques, which will be addressed. This review summarizes and outlines the specificities and respective roles of MRI and 18F-FDG PET/CT in the management of MM.

[Positron emission tomography/computed tomography (PET/CT) in multiple myeloma]

BACKGROUND

Imaging plays a pivotal role in the management of multiple myeloma (MM). Besides morphological imaging methods, such as whole-body X‑ray, computed tomography (CT) and magnetic resonance imaging (MRI), the hybrid modality positron emission tomography/CT (PET/CT) using the glucose analogue ¹⁸F‑fluorodeoxyglucose (¹⁸F‑FDG) as radiotracer is increasingly used.

OBJECTIVES

Aim of this review article is to outline the major applications of PET/CT in the diagnosis and management of MM, and to provide hints on the reading and interpretation.

MATERIALS AND METHODS

Background knowledge and guideline recommendations on imaging of MM are outlined and complemented by recent study results.

RESULTS

Although ¹⁸F‑FDG PET/CT is not currently considered a standard method for the diagnosis of MM, it is a very powerful diagnostic tool for the detection of medullary and extramedullary disease, a reliable predictor of survival and the most robust modality for treatment response evaluation. Moreover, it plays a significant role in minimal residual disease (MRD) assessment. On the other hand, practical considerations on local availability and costs limit the widespread use of PET/CT. In addition, false-negative and the seldom false-positive results and the heterogeneity of MM presentation inevitably make interpretation of PET/CT images challenging.

CONCLUSIONS

PET/CT has a high value in the diagnosis, prognosis, and assessment of treatment response in patients with MM. Therefore, the role of the modality in the management of the disease is expected to increase in the near future.

Association of loss of spleen visualization on whole-body diffusion-weighted imaging with prognosis and tumor burden in patients with multiple myeloma

This study investigated the clinical significance of loss of spleen visualization (LSV) on whole-body diffusion-weighted imaging (WB-DWI) in patients with multiple myeloma (MM). The WB-DWI of 96 patients with newly diagnosed MM (NDMM) and 15 patients with smoldering MM (sMM) were retrospectively reviewed. LSV was observed in 56 patients with NDMM (58.3%) and 1 patient with sMM (6.7%). Patients with NDMM with LSV had a higher median infiltration of bone marrow plasma cells (80.0% vs. 50.0%, p < 0.001) and median total diffusion volume (median; 540.2 vs. 137.0 mL, p = 0.003) than patients without LSV. Patients with LSV had a lower spleen-to-spinal cord ratio (0.36 vs. 0.96, p < 0.001) and worse 2-year overall survival (OS) (84.6% vs. 100%, p = 0.032). Patients who did not recover spleen visualization during treatment had a worse prognosis, even when they obtained very good partial response (median progression-free survival: 13.2 months). Spleen histopathological findings revealed higher cellularity and diffuse myeloma cell infiltration in a patient with LSV and splenic amyloidosis without extramedullary hematopoiesis in a patient without LSV. Therefore, LSV indicates worse prognosis for patients with MM, even when the patient responds to treatment. Further studies are warranted to clarify the immunological role of spleen in MM.

Comparative Performance of Whole Body MRI and 18F-FDG PET/CT in Evaluation of Response to Treatment of Multiple Myeloma: Meta-analysis and Systematic Review

Background: Traditional approaches for evaluating multiple myeloma (MM) treatment response have low sensitivity for residual disease. Recent studies highlight utility of whole-body MRI or FDG PET/CT in evaluating treatment response, with increasing emphasis on DWI. Objective: This systematic review was conducted to assess the diagnostic accuracy of whole-body MRI and FDG PET/CT for treatment response assessment in MM. Evidence Acquisition: Studies using whole-body MRI or FDG PET/CT to evaluate MM treatment response were identified through search of PubMed and EMBASE databases through June 30, 2021. Pooled sensitivity and specificity for detecting response were calculated by bivariate modeling. Diagnostic performance of whole-body MRI and FDG PET/CT were compared. Subgroup analyses assessed studies comparing both modalities and studies in which whole-body MRI included DWI. Evidence Synthesis: Twelve studies comprising 373 patients were included: six evaluated both modalities, four evaluated whole-body MRI only, and two evaluated FDG PET/CT only; of studies with MRI, five used DWI. Pooled sensitivity and specificity were 87% (95% CI, 75%-93%) and 57% (95% CI, 37%-76%) for whole-body MRI, versus 64% (95% CI, 45%-79%) and 82% (95% CI, 75%-88%) for FDG PET/CT (sensitivity: p = .29; specificity: p = .01). For studies directly comparing the modalities, pooled sensitivity and specificity were 90% (95% CI, 80%-100%) and 56% (95% CI, 44%-68%) for whole-body MRI, versus 66% (95% CI, 47%-85%) and 81% (95% CI, 72%-90%) for FDG PET/CT (sensitivity: p = .18; specificity: p < .001). Sensitivity and specificity were 93% (95% CI, 75%-98%) and 57% (95% CI, 21%-87%) for DWI, versus 74% (95% CI, 60%-85%) and 56% (95% CI, 38%-73%) for whole-body MRI without DWI (sensitivity: p = .27; specificity: p = .99). AUC was 0.84 for whole-body MRI, 0.83 for FDG PET/CT, and 0.92 for DWI. Conclusion: FDG PET/CT had significantly higher specificity, whereas whole-body MRI had higher sensitivity (though non-significant). DWI may contribute to the high sensitivity of whole-body MRI. Clinical Impact: This meta-analysis suggests potential complementary roles of whole-body MRI and FDG PET/CT in MM treatment response assessment. Future studies should explore their combination through PET/MRI.

Prospective Evaluation of Whole-Body MRI versus FDG PET/CT for Lesion Detection in Participants with Myeloma

Purpose To compare disease detection of myeloma using contemporary whole-body (WB) MRI and fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT protocols and to correlate imaging with laboratory estimates of disease burden, including molecular characteristics. Materials and Methods In this observational, prospective study, participants were recruited from November 2015 to March 2018 who had a diagnosis of myeloma, who were planned to undergo chemotherapy and autologous stem cell transplantation, and who underwent baseline WB-MRI and FDG PET/CT (ClinicalTrials.gov identifier NCT02403102). Baseline clinical data, including genetics, were collected. Paired methods were used to compare burden and patterns of disease. Results Sixty participants (mean age, 60 years ± 9 [standard deviation]; 35 men) underwent baseline WB-MRI and FDG PET/CT. WB-MRI showed significantly higher detection for focal lesions at all anatomic sites (except ribs, scapulae, and clavicles) and for diffuse disease at all sites. Two participants presented with two or more focal lesions smaller than 5 mm only at WB-MRI but not FDG PET/CT. Participants with diffuse disease at MRI had higher plasma cell infiltration (percentage of nucleated cells: median, 60% [interquartile range {IQR}, 50%-61%] vs 15% [IQR, 4%-50%]; P = .03) and paraprotein levels (median, 32.0 g/L [IQR, 24.0-48.0 g/L] vs 20.0 g/L [IQR, 12.0-22.6 g/L]; P = .02) compared with those without diffuse disease. All genetically high-risk tumors showed diffuse infiltration at WB-MRI. Conclusion WB-MRI helped detect a higher number of myeloma lesions than FDG PET/CT, and diffuse disease detected at WB-MRI correlated with laboratory measures of disease burden and molecular markers of risk. Keywords: MR-Imaging, Skeletal-Appendicular, Skeletal-Axial, Bone Marrow, Hematologic Diseases, Oncology Clinical trial registration no. NCT02403102. Supplemental material is available for this article. © RSNA, 2021.

Comparison of [18F]FDG PET/CT and MRI for Treatment Response Assessment in Multiple Myeloma: A Meta-Analysis

The present study was designed to assess the additional value of 2-deoxy-2[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) to magnetic resonance imaging (MRI) in the treatment response assessment of multiple myeloma (MM). We performed a meta-analysis of all available studies to compare the detectability of treatment response of [¹⁸F]FDG PET/CT and MRI in treated MM. We defined detecting a good therapeutic effect as positive, and residual disease as negative. We determined the sensitivities and specificities across studies, calculated the positive and negative likelihood ratios (LR), and made summary receiver operating characteristic curves (SROC) using hierarchical regression models. The pooled analysis included six studies that comprised 278 patients. The respective performance characteristics (95% confidence interval (CI)) of [¹⁸F]FDG PET/CT and MRI were as follows: sensitivity of 80% (56% to 94%) and 25% (19% to 31%); specificity of 58% (44% to 71%) and 83% (71% to 91%); diagnostic odds ratio (DOR) of 6.0 (3.0-12.0) and 1.7 (0.7-2.7); positive LR of 1.8 (1.3-2.4) and 1.4 (0.7-2.7); and negative LR of 0.33 (0.21-0.53) and 0.81 (0.62-1.1). In the respective SROC curves, the area under the curve was 0.77 (SE, 0.038) and 0.59 (SE, 0.079) and the Q* index was 0.71 and 0.57. Compared with MRI, [¹⁸F]FDG PET/CT had higher sensitivity and better DOR and SROC curves. Compared with MRI, [¹⁸F]FDG PET/CT had greater ability to detect the treatment assessment of MM.