Magnetic resonance imaging pattern of bone marrow involvement as a new predictive parameter of disease progression in newly diagnosed patients with multiple myeloma eligible for autologous stem cell transplantation

Breaking through Multiple Myeloma: A Paradigm for a Comprehensive Tumor Ecosystem Targeting

Multiple myeloma (MM) is a cancerous condition characterized by the proliferation of plasma cells within the hematopoietic marrow, resulting in multiple osteolytic lesions. MM patients typically experience bone pain, kidney damage, fatigue due to anemia, and infections. Historically, MM was an incurable disease with a life expectancy of around three years after diagnosis. However, over the past two decades, the development of novel therapeutics has significantly improved patient outcomes, including response to treatment, remission duration, quality of life, and overall survival. These advancements include thalidomide and its derivatives, lenalidomide and pomalidomide, which exhibit diverse mechanisms of action against the plasma cell clone. Additionally, proteasome inhibitors such as bortezomib, ixazomib, and carfilzomib disrupt protein degradation, proving specifically toxic to cancerous plasma cells. Recent advancements also involve monoclonal antibodies targeting surface antigens, such as elotuzumab (anti-CS1) and daratumumab (anti-CD38), bispecific t-cell engagers such as teclistamab (anti-BCMA/CD3) and Chimeric antigen receptor T (CAR-T)-based strategies, with a growing focus on drugs that exhibit increasingly targeted action against neoplastic plasma cells and relevant effects on the tumor microenvironment.

Newly Diagnosed Multiple Myeloma Patients with Skeletal-Related Events and Abnormal MRI Pattern Have Poor Survival Outcomes: A Prospective Study on 370 Patients

Contemporary information is sparse on the frequency of skeletal-related events (SREs) in multiple myeloma (MM) patients at a population-based level in the era of novel agents. In this context, we conducted this single-center, prospective, observational study to determine the incidence of SREs among newly diagnosed MMs (NDMM) and to explore the possible correlations with disease characteristics, imaging finding, and patient prognosis. A total of 370 patients with available baseline MRIs were included. Among them, 208 (56%) presented with at least one SRE at diagnosis. Fractures were the most common reported SREs (48%). The incidence of SREs at diagnosis was higher in patients with osteolytic lesions, abnormal MRI pattern, hypercalcemia, and at least 60% bone marrow infiltration by plasma cells. Importantly, the patients with normal MRI pattern, who did not present with SREs at diagnosis, had statistically significant improved median OS in comparison with the patients who had abnormal MRI patterns and/or the presence of SREs at diagnosis (9.3 vs. 6.6 years, p = 0.048). Our data, which represent one of a few systematic reports on the incidence and characteristics of SREs in the era of novel agents, was indicative of a high incidence of SREs at the time of MM diagnosis. Early detection of myeloma bone disease and tailored patient management are essential to optimize patient outcomes.

Evaluation of Diffuse Bone Marrow Infiltration Pattern in Monoclonal Plasma Cell Diseases by Quantitative Whole-body Magnetic Resonance Imaging

RATIONALE AND OBJECTIVES

To analyze diffuse infiltration pattern in monoclonal plasma cell diseases by diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) and quantitative chemical-shift encoded MRI.

MATERIALS AND METHODS

Ninety-nine patients with monoclonal plasma cell diseases and 15 healthy control subjects were retrospectively analyzed. All patients underwent whole-body MRI (including DWIBS and mDIXON Quant) and were divided into three groups: monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and multiple myeloma (MM). Apparent diffusion coefficient (ADC), fat fraction (FF), and T2* values for each group were calculated then analyzed by one-way ANOVA and receiver operating characteristic curve. Correlations of ADC, FF, and T2* with clinical indices were analyzed with Spearman correlation test.

RESULTS

The ADC and T2* values of MM were significantly higher than those of the healthy control, MGUS and SMM (ADC: p = 0.003, p = 0.003, and p = 0.042; T2*: all with p < 0.001). The FF values of MM were significantly lower than those of the healthy control, MGUS and SMM (p < 0.001, p < 0.001 and p = 0.034). The ADC, FF, and T2* thresholds for recognizing MM and MGUS+SMM were 0.51 × 10^-3 mm²/s, 31.14%, and 10.53 ms, respectively. The ADC, FF, and T2* values were identified to be significantly associated with bone marrow plasma cells and hemoglobin in patients (all with p < 0.001).

CONCLUSION

ADC, FF, and T2* were significantly correlated with clinical indices related to monoclonal plasma cell diseases. MM with the diffuse infiltration pattern can be distinguished more objectively from MGUS and SMM by quantitative functional MRI parameters.

Optimization of whole-body 2-[18F]FDG-PET/MRI imaging protocol for the initial staging of patients with myeloma

OBJECTIVE

To determine the optimal 2-[¹⁸F]FDG-PET/MRI imaging protocol for the initial staging of patients with suspected or confirmed multiple myeloma.

METHODS

Radiologists and nuclear medicine specialists reviewed all PET/MRI exams of 104 patients with a monoclonal gammopathy (MG). The presence of focal and diffuse bone marrow involvement (BMI) was assessed using 4 different image datasets: WB-MRI, PET, WB-PET/MRI, and WB-DCE-PET/MRI. A reference standard was established by a panel review of all baseline and follow-up imaging, and biological and pathological information. The diagnostic performance for each image dataset to detect BMI was evaluated and compared (Fisher's exact test).

RESULTS

Sensitivity, specificity, and accuracy for focal BMI of WB-MRI was 87%, 97%, and 92%; of PET was 78%, 97%, and 95%; of WB-PET/MRI was 93%, 97%, and 95%; and of WB-DCE-PET/MRI was 93%, 97%, and 95%, respectively. WB-PET/MRI and WB-DCE-PET/MRI were statistically superior to PET (p = 0.036) without decreasing specificity. The sensitivity, specificity, and accuracy of WB-MRI for diffuse BMI detection was 91%, 80%, and 85%; of 3DT1-PET was 53%, 89%, and 74%; of WB-PET/MRI was 98%, 66%, and 79%; and of WB-DCE-PET/MRI was 98%, 59%, and 75%, respectively. PET lacked sensitivity compared to all other dataset studies (p < 0.0001). WB-MRI had the best accuracy without reaching statistical significance when compared to the other datasets.

CONCLUSION

The WB-PET/MRI dataset including T1 and T2 Dixon, WB-DWI, and PET images provides optimal diagnostic performance to detect both focal lesions and diffuse BMI, with limited added value of WB-DCE for baseline staging of patients with MG. Key Points • The combination of morphological and functional MRI sequences and metabolic (2-[¹⁸F]FDG-PET) images increases the diagnostic performance of PET/MRI to detect focal bone lesions. • The adjunction of dynamic contrast-enhanced sequences did not improve diagnostic performance.

Differentiation of Diffuse Infiltration Pattern in Multiple Myeloma From Hyperplastic Hematopoietic Bone Marrow: Qualitative and Quantitative Analysis Using Whole-Body MRI

BACKGROUND

The visual assessment used for diffuse infiltration of multiple myeloma (MM) is inadequate. It can be difficult to differentiate MM from hyperplastic hematopoietic bone marrow (HHBM) because the MRI signal characteristics overlap.

PURPOSE

To analyze the bone marrow diffuse signal changes on whole-body MRI caused by MM and HHBM.

STUDY TYPE

Retrospective.

SUBJECTS

Thirty Four patients with MM (21 men and 13 women), 22 patients with HHBM (9 men and 13 women), and 15 healthy controls (9 men and 6 women).

FIELD STRENGTH/SEQUENCE

A 3.0 T MRI; diffusion-weighted whole-body imaging with background body signal suppression (DWIBS), modified Dixon T1 fast field echo, and T2 STIR.

ASSESSMENT

Three radiologists analyzed the whole-body MRI alone and in combination with apparent diffusion coefficient (ADC) and fat fraction (FF) with qualitative and quantitative analysis. Normalized T1 and T2 signal intensities (nT1 and nT2) and signal-to-noise ratio (SNR) were obtained.

STATISTICAL TESTS

Kruskal-Wallis and chi-square tests.

RESULTS

The MM group had significantly higher ADC and significantly lower FF than HHBM and control groups. There was no significant difference in nT1, nT2 or SNR between MM and HHBM (P = 0.932, P = 0.097, and P = 0.110, respectively). Receiver operating characteristic (ROC) analysis using ADC and FF cut-off values of 0.47 × 10^-3  mm² /sec and 20.63%, respectively. The AUC was 0.866 for ADC and 0.886 for FF. The quantitative analysis yielded better specificity (observer 1: 81.8% vs. 27.3%; observer 2: 68.2% vs. 22.7%; and observer 3: 72.7% vs. 18.2%) and a higher diagnostic accuracy (observer 1: 82.1% vs. 51.8%; observer 2: 80.4% vs. 50.0%; observer 3: 76.8% vs. 44.6%) than the qualitative analysis.

DATA CONCLUSION

Whole-body MRI combined with DWIBS and mDIXON could be used to differentiate between MM and HHBM. Combining the quantitative ADC and FF with the whole-body MRI improved the specificity and accuracy in differentiating these conditions.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Bone marrow tracer uptake pattern of PET-CT in multiple myeloma: image interpretation and prognostic value

PURPOSE

To evaluate the prognostic value of bone marrow (BM) imaging pattern and other imaging findings assessed by ¹⁸F-FDG PET-CT in multiple myeloma(MM) and to find out the image interpretation cut-off to define different BM tracer uptake pattern.

MATERIALS AND METHODS

We retrospectively studied PET-CT examinations and clinical data of 100 healthy individuals and 172 newly diagnosed MM patients. A BM uptake > liver SUVmean was selected as the positivity cut-off of pathological uptake in BM after comparing BM uptake in normal control and MM patients. With this interpretation cut-off, we defined the BM FDG uptake pattern as four types: normal, focal, diffuse, and mixed. The clinical correlation and prognostic value of BM uptake pattern were evaluated. The findings were validated in an independent prospective cohort with 72 MM patients.

RESULTS

In MM cohort, 34.9% patients had focal BM uptake pattern, 3.5% had diffuse pattern, 38.4% had mixed pattern, and 23.3% had normal BM uptake. Diffuse/mixed pattern was correlated with clinical and imaging parameters indicating high tumor burden, and inferior progression free survival (PFS; 3-year-PFS 26.8%) and overall survival (OS; 3-year-OS 50.6%). BM uptake pattern was an independent prognostic factor and diffuse/mixed pattern was associated with inferior OS (P = 0.037, HR 7.16) and PFS (P = 0.015, HR 7.77). The prognostic value of BM uptake pattern was also confirmed in validation set.

CONCLUSION

We propose an FDG uptake higher than liver as the positivity cut-off to discriminate between physiological and pathological uptake in BM and defined four BM FDG uptake pattern. BM FDG uptake pattern is a reliable prognostic predictor of MM.

Quantitative whole-body MR imaging for assessment of tumor burden in patients with multiple myeloma: correlation with prognostic biomarkers

Background

To assess the quantification of tumor burden in multiple myeloma (MM) patients using whole-body magnetic resonance imaging (MRI) and to identify the correlation between MRI parameters and prognostic biomarkers.

Methods

We retrospectively analyzed 95 newly diagnosed MM patients treated at our hospital from June 2018 to March 2020. All patients underwent whole-body MRI examination, including diffusion-weighted whole-body imaging with background body signal suppression (DWIBS), modified Dixon chemical-shift imaging (mDIXON), and short TI inversion recovery (STIR) sequences. The MRI presentation was used to determine MM infiltration patterns and calculate apparent diffusion coefficient (ADC) and a fat fraction (FF). The one-way ANOVA and Kruskal-Wallis test were used to compare the differences of these values between DS, ISS, and R-ISS stages in different MM infiltration patterns. Spearman correlation test was used for correlation analysis of ADC and FF against prognostic biomarkers, and two independent sample t-test was used to evaluate the differences of ADC and FF in different free light-chain ratio groups.

Results

The MRI presentation was classified into normal pattern (36 patients; 37.9%), diffuse (27 patients; 28.4%), and focal (32 patients; 33.7%) infiltration patterns. Statistically significant ADC and FF differences between different DS, ISS, and R-ISS stages were observed in normal/diffuse infiltration patterns but not in focal infiltration patterns. The ADC and FF of the normal/diffuse infiltration pattern showed correlations with hemoglobin, β2-microglobulin, bone marrow plasma cells, flow cytometry of bone marrow cells, and serum monoclonal protein. In contrast, ADC in focal infiltration patterns was negatively correlated with β2-microglobulin and C-reactive protein. The FF of patients with a normal/diffuse infiltration pattern was higher in the low free light-chain ratio group than that in the high free light-chain ratio group (P=0.023).

Conclusions

Our observations indicate that quantitative whole-body functional MRI examination may serve as an effective complement to imaging diagnosis based on morphology and provide further information on the tumor burden of patients with MM.

Analyzing Longitudinal wb-MRI Data and Clinical Course in a Cohort of Former Smoldering Multiple Myeloma Patients: Connections between MRI Findings and Clinical Progression Patterns

The purpose of this study was to analyze size and growth dynamics of focal lesions (FL) as well as to quantify diffuse infiltration (DI) in untreated smoldering multiple myeloma (SMM) patients and correlate those MRI features with timepoint and cause of progression. We investigated 199 whole-body magnetic resonance imaging (wb-MRI) scans originating from longitudinal imaging of 60 SMM patients and 39 computed tomography (CT) scans for corresponding osteolytic lesions (OL) in 17 patients. All FLs >5 mm were manually segmented to quantify volume and growth dynamics, and DI was scored, rating four compartments separately in T1- and fat-saturated T2-weighted images. The majority of patients with at least two FLs showed substantial spatial heterogeneity in growth dynamics. The volume of the largest FL (p = 0.001, c-index 0.72), the speed of growth of the fastest growing FL (p = 0.003, c-index 0.75), the DI score (DIS, p = 0.014, c-index 0.67), and its dynamic over time (DIS dynamic, p < 0.001, c-index 0.67) all significantly correlated with the time to progression. Size and growth dynamics of FLs correlated significantly with presence/appearance of OL in CT within 2 years after the respective MRI assessment (p = 0.016 and p = 0.022). DIS correlated with decrease of hemoglobin (p < 0.001). In conclusion, size and growth dynamics of FLs correlate with prognosis and local bone destruction. Connections between MRI findings and progression patterns (fast growing FL-OL; DIS-hemoglobin decrease) might enable more precise diagnostic and therapeutic approaches for SMM patients in the future.

Whole-Body Low-Dose CT in Multiple Myeloma: Diagnostic Value of Appendicular Medullary Patterns of Attenuation

OBJECTIVE. The purpose of this article is to analyze whole-body low-dose CT-detected appendicular medullary patterns of attenuation in patients with newly diagnosed multiple myeloma and to determine the diagnostic performance of whole-body low-dose CT in detecting diffuse marrow infiltration. MATERIALS AND METHODS. A total of 76 patients with myeloma who underwent whole-body low-dose CT and spinal MRI at initial assessment were retrospectively analyzed. The medullary cavities of femurs and humeri were evaluated qualitatively and quantitatively on CT. Medullary attenuation and SD-to-mean attenuation ratio were recorded for each long bone. The pattern of marrow involvement on spinal MRI was used as reference. The chi-square test was used to evaluate the relationship between the CT-based appendicular medullary cavity pattern and the MRI pattern, and ROC analysis was performed to assess the diagnostic accuracy of CT attenuation measurements for the differentiation between diffuse and mixed CT-based appendicular medullary cavity patterns. RESULTS. Medullary attenuation differed significantly among mixed, nodular, and diffuse CT-based appendicular medullary cavity patterns in the femurs (mean, 34.23 HU and range, 15-61 HU; mean, 66.26 HU and range, 26-104 HU; mean, 92.80 HU and range, 53-127 HU, respectively) and humeri (mean, 22.18 HU and range, 9-41; mean, 61.18 HU and range, 23-93 HU; mean, 77.50 and range, 25-105 HU, respectively). To discriminate between diffuse and mixed CT-based appendicular medullary cavity patterns, optimal cutoff attenuation values were 63 HU (sensitivity, 97.7%; specificity, 100.0%) for the femurs, and 52 HU (sensitivity, 97.4%; specificity, 100.0%) for the humeri. A total of 24 of 30 (80.0%) patients with a diffuse MRI pattern showed a diffuse CT-based appendicular medullary cavity pattern on whole-body low-dose CT, and all patients with a diffuse CT-based appendicular medullary cavity pattern also showed a diffuse pattern on MRI. CONCLUSION. According to analysis of peripheral medullary patterns of attenuation, whole-body low-dose CT can identify patients with multiple myeloma with diffuse marrow involvement.

Longitudinal monitoring of apparent diffusion coefficient (ADC) in myeloma patients with lower M-gradient levels undergoing systemic treatment and whole-body MRI monitoring

OBJECTIVES

Longitudinal assessment of changes in apparent diffusion coefficient (ADC)-values in multiple myeloma (MM) patients and their potential role for classifying disease activity.

METHODS

Retrospective analysis of whole-body-MRI data in 73 stage III MM patients undergoing systemic treatment. Bone marrow involvement was evaluated using a standardized unenhanced 4-sequences whole-body-MRI protocol. We measured ADC-values in focal lesions (FL) and diffusely involved bone marrow (DIBM) areas. Response to treatment was based on the course of hematologic parameters. The time points of MRI-examinations were baseline, 1st (mean, 3 months), 2nd (mean, 10 months), and 3rd (mean, 18 months) follow up (FU).

RESULTS

Mean IgG and IgA serum values at baseline were 2.1 mg/dl and 1.8 mg/dl, respectively. Patients were classified into responders (n = 59) and non-responders (n = 34). Some patients were re-enrolled for new treatment regimens as they became therapy-refractory. Patterns of medullary involvement were focal (n = 44), diffuse (n = 61) and mixed (n = 30). In FL, a subgroup of myeloma patients undergoing short-term 1st FU experienced a significant increase in ADC in responders (p = 0.001), but not in non-responders (p = 0.9). In the further course of the study, ADC levels decreased continuously in responders (p = 0.02) and increased slightly in non-responders (p = 0.8). In patients with DIBM, ADC values decreased in the responders (p < 0.001) and in the non-responders (p = 0.78). An ADC cut-off value of 0.5-0.6 × 10^-3  mm²/s for diagnosing inactive disease at follow-up proved unreliable.

CONCLUSIONS

In myeloma-patients with lower tumor burden, the longitudinal course of ADC-values is predictable only for FL whereas for DIBM ADC-changes considerably overlap between responders and non-responders and are not indicative for assessment of the disease activity.

Role of computed tomography texture analysis using dual-energy-based bone marrow imaging for multiple myeloma characterization: comparison with histology and established serologic parameters

Objective

To identify textural features on dual-energy CT (DECT)–based bone marrow images in myeloma which correlate with serum markers of myeloma activity and the degree of medullary involvement.

Methods

A total of 110 patients (63.0 ± 11.0 years, 51 female) who underwent unenhanced whole-body DECT between September 2015 and February 2019 were retrospectively included, which was approved by our institutional ethics committee with a waiver of the informed consent requirement. All patients had current hematologic laboratory tests. Using DECT post-processing, non-calcium bone marrow images were reconstructed. The vertebral bodies T10–L5 were segmented for quantification of textural features, which were compared with serologic parameters and myeloma stages by the Mann-Whitney U test. In a subgroup of 56/110 patients with current bone marrow biopsies, textural features were correlated with the degree of bone marrow infiltration.

Results

First-order features were higher in patients with advanced stage of myeloma (p < .02), whereas the 2nd-order “gray-level co-occurrence matrix (GLCM) cluster prominence” was lower (p < .04). In patients with elevated serum-free light chains (SFLC) or kappa/lambda SFLC ratio above 1.56, the “entropy” and 2nd-order GLCM features were lower (p < .03). The degree of bone marrow infiltration correlated with 1st-order features (e.g., “uniformity”; r_P = 0.49; p < .0001), whereas “entropy” and 2nd-order GLCM features were negatively correlated (e.g., “difference entropy”; r_P = − 0.54; p < .0001).

Conclusions

CT textural features applied on non-calcium bone marrow images correlate well with myeloma-related serologic parameters and histology showing a more uniform tissue structure and higher attenuation with increasing medullary infiltration and could therefore be used as additional imaging biomarkers for non-invasive assessment of medullary involvement.

Key Points

• Texture analysis applied on dual-energy reconstructed non-calcium bone marrow images provides information about marrow structure and attenuation.

• Myeloma-related serologic parameters and the degree of myeloma cell infiltration correlate with 1st- and 2nd-order features which could be useful as additional imaging biomarkers for non-invasive assessment of medullary involvement.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-07320-8) contains supplementary material, which is available to authorized users.

Mid-term response assessment in multiple myeloma using a texture analysis approach on dual energy-CT-derived bone marrow images - A proof of principle study

PURPOSE

To identify textural features on dual-energy CT (DECT)-generated virtual non calcium (VNC) bone marrow images in a small group of patients with multiple myeloma undergoing systemic treatment which could potentially help for mid-term response assessment.

METHODS

44 patients (59.1 ± 11.2 yr.) with multiple myeloma who underwent unenhanced whole-body reduced-dose DECT before and after systemic therapy were evaluated. All patients had current hematologic laboratory tests including serum levels of immunoglobulins, albumin, and total proteins. Using DECT post-processing, bone marrow images of the axial skeleton were reconstructed. The vertebral bodies T10-L5 were segmented for quantification of 1st order (n = 18) and 2nd order Gray Level Co-occurrence Matrix (GLCM) textural features (n = 23) based on an open-source radiomics library (Pyradiomics), which were then compared with the hematologic response category to treatment. Five patients underwent only active surveillance at intervals after previous successful therapy.

RESULTS

According to hematologic diagnosis, 29 patients were classified as complete response (CR), 10 as partial response (PR) and 5 as stable disease (SD). We observed a significant drop of the 1st order textural features "10th percentile" (p = 0.009), "median" (p = 0.01), and "minimum" (p < 0.0001) after treatment, whereas the 1st order feature "range" (p = 0.0004) and the 2nd order GLCM feature "difference variance" (p = 0.007) significantly increased in patients experiencing CR. A similar trend, however, without statistical significance, could be observed in patients achieving PR after treatment. 2nd order GLCM feature "difference variance" proved to be a significant discriminator (p = 0.01) between patients with CR and PR (sensitivity 0.93, specificity 0.70) for a cut-off value of -0.28. In patients classified CR, both the mean serum protein and the beta-2 microglobulin decreased after treatment, whereas the serum albumin increased (p < 0.01). The same trend without significance could be observed in patients classified PR.

CONCLUSIONS

Changes in textural features applied on VNC bone marrow images in the pre- and posttreatment settings correlate well with myeloma-specific hematologic parameters and provide complementary information for the assessment of the late effects of treatment on the bone marrow.

Extended Texture Analysis of Non-Enhanced Whole-Body MRI Image Data for Response Assessment in Multiple Myeloma Patients Undergoing Systemic Therapy

Identifying MRI-based radiomics features capable to assess response to systemic treatment in multiple myeloma (MM) patients. Retrospective analysis of whole-body MR-image data in 67 consecutive stage III MM patients (40 men; mean age, 60.4 years). Bone marrow involvement was evaluated using a standardized MR-imaging protocol consisting of T1w-, short-tau inversion recovery- (STIR-) and diffusion-weighted-imaging (DWI) sequences. Ninety-two radiomics features were evaluated, both in focally and diffusely involved bone marrow. Volumes of interest (VOI) were used. Response to treatment was classified according to International Myeloma Working Group (IMWG) criteria in complete response (CR), very-good and/or partial response (VGPR + PR), and non-response (stable disease (SD) and progressive disease (PD)). According to the IMWG-criteria, response categories were CR (n = 35), VGPR + PR (n = 19), and non-responders (n = 13). On apparent diffusion coefficient (ADC)-maps, gray-level small size matrix small area emphasis (Gray Level Size Zone (GLSZM) small area emphasis (SAE)) significantly correlated with CR (p < 0.001), whereas GLSZM non-uniformity normalized (NUN) significantly (p < 0.008) with VGPR/PR in focal medullary lesions (FL), whereas in diffuse involvement, 1st order root mean squared significantly (p < 0.001) correlated with CR, whereas for VGPR/PR Log (gray-level run-length matrix (GLRLM) Short Run High Gray Level Emphasis) proved significant (p < 0.003). On T1w, GLRLM NUN significantly (p < 0.002) correlated with CR in FL, whereas gray-level co-occurrence matric (GLCM) informational measure of correlation (Imc1) significantly (p < 0.04) correlated with VGPR/PR. For diffuse myeloma involvement, neighboring gray-tone difference matrix (NGTDM) contrast and 1st order skewness were significantly associated with CR and VGPR/PR (p < 0.001 for both). On STIR-images, CR correlated with gray-level co-occurrence matrix (GLCM) Informational Measure of Correlation (IMC) 1 (p < 0.001) in FL and 1st order mean absolute deviation in diffusely involved bone marrow (p < 0.001). VGPR/PR correlated at best in FL with GSZLM size zone NUN (p < 0.019) and in all other involved medullary areas with GLSZM large area low gray level emphasis (p < 0.001). GLSZM large area low gray level emphasis also significantly correlated with the degree of bone marrow infiltration assessed histologically (p = 0.006). GLCM IMC 1 proved significant throughout T1w/STIR sequences, whereas GLSZM NUN in STIR and ADC. MRI-based texture features proved significant to assess clinical and hematological response (CR, VPGR, and PR) in multiple myeloma patients undergoing systemic treatment.

Assessment of early treatment response on MRI in multiple myeloma: Comparative study of whole-body diffusion-weighted and lumbar spinal MRI

Objectives

To compare remission status at completion of chemotherapy for multiple myeloma (MM) with changes in total diffusion volume (tDV) calculated from whole-body diffusion-weighted imaging (WB-DWI) and fat fraction (FF) of lumbar bone marrow (BM) by modified Dixon Quant (mDixon Quant) soon after induction of chemotherapy, and to assess the predictive value of MRI.

Methods

Fifty patients (mean age, 66.9 ± 10.5 years) with symptomatic myeloma were examined before and after two cycles of chemotherapy. From WB-DWI data, tDV was obtained with the threshold for positive BM involvement. Mean FF was calculated from lumbar BM using the mDixon Quant sequence. At the completion of chemotherapy, patients were categorized into a CR/very good PR (VGPR) group (n = 15; mean age, 67.6 ± 10.3 years) and a PR, SD or PD group (n = 35; mean age, 69.1 ± 8.6 years). ROC curves were plotted to assess performance in predicting achievement of CR/VGPR.

Results

At second examination, serum M protein, β₂-microglobulin, and tDV were significantly decreased and hemoglobin, mean ADC, and FF were significantly increased in the CR/VGPR group and serum M protein was significantly increased in the PR/SD/PD group. The general linear model demonstrated that percentage changes in FF and M protein contributed significantly to achieving CR/VGPR (P = 0.02, P = 0.04, respectively). AUCs of ROC curves were 0.964 for FF and 0.847 for M protein.

Conclusions

Early change in FF of lumbar BM and serum M protein soon after induction of chemotherapy contributed significantly to prediction of CR/VGPR.

Applications of PET-MRI in musculoskeletal disease

New integrated PET-MRI systems potentially provide a complete imaging modality for diagnosis and evaluation of musculoskeletal disease. MRI is able to provide excellent high-resolution morphologic information with multiple contrast mechanisms that has made it the imaging modality of choice in evaluation of many musculoskeletal disorders. PET offers incomparable abilities to provide quantitative information about molecular and physiologic changes that often precede structural and biochemical changes. In combination, hybrid PET-MRI can enhance imaging of musculoskeletal disorders through early detection of disease as well as improved diagnostic sensitivity and specificity. The purpose of this article is to review emerging applications of PET-MRI in musculoskeletal disease. Both clinical applications of malignant musculoskeletal disease as well as new opportunities to incorporate the molecular capabilities of nuclear imaging into studies of nononcologic musculoskeletal disease are discussed. Lastly, we discuss some of the technical considerations and challenges of PET-MRI as they specifically relate to musculoskeletal disease.

LEVEL OF EVIDENCE

5 TECHNICAL EFFICACY: Stage 3 J. Magn. Reson. Imaging 2018;48:27-47.

Functional and molecular MRI of the bone marrow in multiple myeloma

MRI plays an important role in the management of patients with plasma cell neoplasms and has been recognized as a biomarker of malignancy in the novel criteria for the diagnosis of multiple myeloma. Functional and molecular MRI techniques such as diffusion-weighted imaging (spinal or whole body), intravoxel incoherent motion, and dynamic contrast enhanced MRI, provide additional information related to tumor cellularity and angiogenesis, which may have prognostic implications for patients with smoldering and symptomatic myeloma. These non-invasive functional techniques are also being evaluated as imaging biomarkers for response assessment in myeloma patients. The purpose of this article is to provide a comprehensive critical review on the current use and potential future applications of these advanced MRI techniques in multiple myeloma. In addition, we will address the technologies involved and describe the qualitative and quantitative characteristics of normal bone marrow with these techniques.

Guidelines for the use of imaging in the management of patients with myeloma

The role of imaging in myeloma has gained increasing importance over the past few years. The recently revised definition of myeloma from the International Myeloma Working Group (IMWG) includes cross sectional imaging as a method to define bone disease and also incorporates its use in the disease definition for patients with suspected smouldering myeloma. The National Institute for Health and Care Excellence myeloma guidelines also recommend cross sectional imaging for patients with suspected myeloma. There is also increasing use of imaging in disease assessments and the International Myeloma Working Group has recently incorporated imaging in defining new response categories of minimal residual disease negativity, with or without imaging-based evidence of disease. Plain X-rays have previously been the standard imaging modality included in a myeloma work up at presentation but evidence is mounting for use of cross-sectional modalities such as computed tomography (CT), magnetic resonance imaging (MRI) and 18 fluoro-deoxyglucose (18 F-FDG) positron emission tomography (PET)/CT. Funding and therefore availability of newer imaging techniques remains a barrier. Here, we propose an evidence-based approach to the use and technical application of the latest imaging modalities at diagnosis and in the follow-up of patients with myeloma and plasmacytoma.

The Role of Imaging in the Treatment of Patients With Multiple Myeloma in 2016

The novel criteria for the diagnosis of symptomatic multiple myeloma have revealed the value of modern imaging for the management of patients with myeloma. Whole-body low-dose CT (LDCT) has increased sensitivity over conventional radiography for the detection of osteolytic lesions, and several myeloma organizations and institutions have suggested that whole-body LDCT should replace conventional radiography for the work-up of patients with myeloma. MRI is the best imaging method for the depiction of marrow infiltration by myeloma cells. Whole-body MRI (or at least MRI of the spine and pelvis if whole-body MRI is not available) should be performed for all patients with smoldering multiple myeloma with no lytic lesions to look for occult disease, which may justify treatment. In addition, MRI accurately illustrates the presence of plasmacytomas, spinal cord, and/or nerve compression for surgical intervention or radiation therapy; it is also recommended for the work-up of solitary bone plasmacytoma, and it may distinguish malignant from benign fractures (which is very important in cases of patients in biochemical remission with no other signs of progression). Diffusion weighted imaging (DWI) seems to improve MRI diagnosis in patients with myeloma. PET/CT is a functional imaging technique, more sensitive than conventional radiography for the detection of lytic lesions, which probably allows better definition of complete response and minimal residual disease compared with all other imaging methods. PET/CT has shown the best results in the follow-up of patients with myeloma and has an independent prognostic value both at diagnosis and following treatment. PET/CT can also be used for the work-up of solitary bone plasmacytoma and nonsecretory myeloma.

Quantitative Diffusion-weighted Imaging of the Bone Marrow: An Adjunct Tool for the Diagnosis of a Diffuse MR Imaging Pattern in Patients with Multiple Myeloma

Purpose To evaluate the apparent diffusion coefficients (ADCs) of magnetic resonance (MR) imaging patterns in the bone marrow of patients with multiple myeloma (MM) and to determine a threshold ADC that may help distinguish a diffuse from a normal pattern with high accuracy. Materials and Methods This prospective study was approved by the ethics review board, and informed consent was obtained. Ninety-nine patients with newly diagnosed, untreated MM and 16 healthy control subjects underwent spinal MR imaging including diffusion-weighted imaging, and bone marrow ADCs were calculated. Pattern assignment was based on visual assessment of conventional MR images. The Kruskal-Wallis H test, the Mann-Whitney test, and the one-way analysis of variance were used to compare ADCs between patient subsets and control subjects, and a receiver operating characteristic analysis was performed. Results Mean ADCs ± standard deviation in patients with MM for the normal, focal, and diffuse MR imaging patterns were 0.360 × 10^-3 mm²/sec ± 0.110, 1.046 × 10^-3 mm²/sec ± 0.232, and 0.770 × 10^-3 mm²/sec ± 0.135, respectively. There were significant differences in ADCs between diffuse and normal (P < .001), diffuse and focal (P < .001), and focal and normal (P < .001) patterns. Patients with a diffuse pattern had more features of advanced disease, higher international staging system score, increased incidence of high-risk cytogenetics, and higher revised international staging system score. ADCs greater than 0.548 × 10^-3 mm²/sec showed 100% sensitivity (26 of 26) and 98% specificity (48 of 49) for the diagnosis of a diffuse (vs normal) MR imaging pattern, whereas an ADC greater than 0.597 × 10^-3 mm²/sec showed 96% sensitivity (25 of 26) and 100% specificity (49 of 49). Conclusion ADCs of MR imaging patterns in patients with MM differ significantly. A diffuse MR imaging pattern can be distinguished more objectively from a normal MR imaging pattern by adding quantitative diffusion-weighted imaging to standard MR imaging protocols. ^© RSNA, 2016 Online supplemental material is available for this article.

Vertebral lesion distribution in multiple myeloma--assessed by reduced-dose whole-body MDCT

OBJECTIVE

To observe the distribution and potential distribution patterns of osteolytic and sclerotic vertebral involvement in a representative collective of multiple myeloma patients.

MATERIALS AND METHODS

A total of 66 consecutive patients with a diagnosis of multiple myeloma at initial diagnosis or during follow-up were examined by multidetector reduced-dose computed tomography to evaluate the distribution of bone lesions along the spine with focus on size, location, and lesion character. Confirmation of diagnosis was performed by comparison to follow-up computed tomography or magnetic resonance tomography. If >50% of all detected malignant lesions occurred in one spinal segment, the distribution pattern was called cervical, thoracic, lumbar, or sacral, otherwise a "mixed" pattern was classified.

RESULTS

Of a total number of 933 osseous spine lesions, 632 (67.7%) were classified as malignant (98.9% of them osteolytic) and 293 (31.5%) as benign. The distribution pattern analysis yielded two patients (3.8%) with a cervical, 26 (50%) with a thoracic, 4 (7.7%) with a lumbar, one (1.9%) with a sacral pattern, and 19 cases (36.6%) showed a mixed distribution pattern. Segment-wise, the mean lesion size was 6.52 ± 2.76 mm (cervical), 8.97 ± 5.43 mm (thoracic), 11.97 ± 7.11 mm (lumbar), and 17.5 ± 16.465 (sacral), whilst, related to the vertebra size, the lesion/vertebra size ratio is decreasing through the whole spine beginning from the top.

CONCLUSIONS

Multiple myeloma bone lesions occur preferably and are larger in the thoracic and lumbar spine. Moreover, a specific distribution pattern is present in about 60%.

Clonotypic Light Chain Peptides Identified for Monitoring Minimal Residual Disease in Multiple Myeloma without Bone Marrow Aspiration

BACKGROUND

Analytically sensitive techniques for measuring minimal residual disease (MRD) in multiple myeloma (MM) currently require invasive and costly bone marrow aspiration. These methods include immunohistochemistry (IHC), flow cytometry, quantitative PCR, and next-generation sequencing. An ideal MM MRD test would be a serum-based test sensitive enough to detect low concentrations of Ig secreted from multifocal lesions.

METHODS

Patient serum with abundant M-protein before treatment was separated on a 1-dimensional SDS-PAGE gel, and the Ig light-chain (LC) band was excised, trypsin digested, and analyzed on a Q Exactive mass spectrometer by LC-MS/MS. We used the peptide's abundance and sequence to identify tryptic peptides that mapped to complementary determining regions of Ig LCs. The clonotypic target tryptic peptides were used to monitor MRD in subsequent serum samples with prior affinity enrichment.

RESULTS

Sixty-two patients were tested, 20 with no detectable disease by IHC and 42 with no detectable disease by 6-color flow cytometry. A target peptide that could be monitored was identified in 57 patients (91%). Of these 57, detectable disease by LC-MS/MS was found in 52 (91%).

CONCLUSIONS

The ability to use LC-MS/MS to measure disease in patients who are negative by bone marrow-based methodologies indicates that a serum-based approach has more analytical sensitivity and may be useful for measuring deeper responses to MM treatment. The method requires no bone marrow aspiration.

Role of Magnetic Resonance Imaging in the Management of Patients With Multiple Myeloma: A Consensus Statement

Purpose

The aim of International Myeloma Working Group was to develop practical recommendations for the use of magnetic resonance imaging (MRI) in multiple myeloma (MM).

Methods

An interdisciplinary panel of clinical experts on MM and myeloma bone disease developed recommendations for the value of MRI based on data published through March 2014.

Recommendations

MRI has high sensitivity for the early detection of marrow infiltration by myeloma cells compared with other radiographic methods. Thus, MRI detects bone involvement in patients with myeloma much earlier than the myeloma-related bone destruction, with no radiation exposure. It is the gold standard for the imaging of axial skeleton, for the evaluation of painful lesions, and for distinguishing benign versus malignant osteoporotic vertebral fractures. MRI has the ability to detect spinal cord or nerve compression and presence of soft tissue masses, and it is recommended for the workup of solitary bone plasmacytoma. Regarding smoldering or asymptomatic myeloma, all patients should undergo whole-body MRI (WB-MRI; or spine and pelvic MRI if WB-MRI is not available), and if they have > one focal lesion of a diameter > 5 mm, they should be considered to have symptomatic disease that requires therapy. In cases of equivocal small lesions, a second MRI should be performed after 3 to 6 months, and if there is progression on MRI, the patient should be treated as having symptomatic myeloma. MRI at diagnosis of symptomatic patients and after treatment (mainly after autologous stem-cell transplantation) provides prognostic information; however, to date, this does not change treatment selection.