Role of 18F-FDG PET/CT in the diagnosis and management of multiple myeloma and other plasma cell disorders: a consensus statement by the International Myeloma Working Group

Perspectives on the Risk-Stratified Treatment of Multiple Myeloma

The multiple myeloma treatment landscape has changed dramatically. This change, paralleled by an increase in scientific knowledge, has resulted in significant improvement in survival. However, heterogeneity remains in clinical outcomes, with a proportion of patients not benefiting from current approaches and continuing to have a poor prognosis. A significant proportion of the variability in outcome can be predicted on the basis of clinical and biochemical parameters and tumor-acquired genetic variants, allowing for risk stratification and a more personalized approach to therapy. This article discusses the principles that can enable the rational and effective development of therapeutic approaches for high-risk multiple myeloma.

Long-Term Responders After Autologous Stem Cell Transplantation in Multiple Myeloma

Introduction

Multiple myeloma (MM) is considered an incurable hematological neoplasm. For transplant-eligible patients, initial treatment includes an induction phase followed by an autologous stem cell transplantation (ASCT). Despite the introduction of several drugs in the past years, relapses still occur. Nevertheless, some patients achieve sustained responses after successful induction treatment and ASCT.

Methods

We retrospectively evaluated all patients diagnosed with MM in our institution who underwent induction treatment and ASCT between 1990 and 2015. The subset of patients who achieved a sustained response (any degree) for 5 or more years after ASCT without further treatment or signs of progression were distinguished as “long-term responders” (LTRs). In the non-LTR group, a cohort referred to as “prolonged responders” (PLRs) showed sustained response of at least 5 years after ASCT but eventually relapsed. We collected and analyzed clinical and laboratory data.

Results

Two hundred and fifty patients were diagnosed with MM and received induction treatment and ASCT at our institution in the study period. Among them, 54 (21.6%) patients met the criteria for LTR. Some diagnostic features such as a younger age, female gender, ECOG performance status of 0, lower International Staging System (ISS) stage, lower bone marrow plasma cell infiltration, and lower serum levels of calcium, C-reactive protein, and lactate dehydrogenase (LDH) were found to be more prevalent in LTR. Female gender, an ECOG performance status of 0, a localized Durie-Salmon stage, an ISS of I–II, the absence of bone disease, and an LDH within normal range were also predictive of longer progression-free survival (PFS) and overall survival (OS) in the whole cohort. The depth of the response achieved after induction and ASCT as well as the administration of an IMID-based maintenance regimen may play a role in the differences observed on PFS between cohorts. A detectable M-protein with a monoclonal gammopathy of undetermined significance (MGUS)-like behavior was detected in one-third of LTR after ASCT. Although relapses continue to occur in patients who achieve a 5-year treatment-free period after ASCT, a plateau is observed in the survival curves at approximately 21 years of follow-up.

[Extramedullary plasmacytoma of the larynx：a case report]

This paper reported a case of extramedullary plasmacytoma of the larynx. The patient presented with persistent hoarseness and foreign body sensation in pharynx for 5 months. Left anterior laryngeal mass, left epiglottis fold distention was found during laryngoscopy. Cervical image examination showed that the left side wall of the glottis was thickened and showed a lump-like change, part of which protrusion into the laryngeal cavity, the laryngeal chamber became narrow, and the growth of thyroid cartilage was broken outwards and reached the level of the hyoid bone. After completing the examination, the laryngeal tumor resection and biopsy were performed under the suspension laryngoscope. Pathologic findings showed that diffuse proliferation of small cells was observed in laryngeal subepithelial fibrous tissue, with local appearance of private, atypia and mitosis. Combined with immunohistochemical results, it was consistent with plasma cell tumor.

Molecular Signature of 18F-FDG PET Biomarkers in Newly Diagnosed Multiple Myeloma Patients: A Genome-Wide Transcriptome Analysis from the CASSIOPET Study

The International Myeloma Working Group recently fully incorporated ¹⁸F-FDG PET into multiple myeloma (MM) diagnosis and response evaluation. Moreover, a few studies demonstrated the prognostic value of several biomarkers extracted from this imaging at baseline. Before these ¹⁸F-FDG PET biomarkers could be fully endorsed as risk classifiers by the hematologist community, further characterization of underlying molecular aspects was necessary. Methods: Reported prognostic biomarkers (¹⁸F-FDG avidity, SUV_max, number of focal lesions, presence of paramedullary disease [PMD] or extramedullary disease) were extracted from ¹⁸F-FDG PET imaging at baseline in a group of 139 patients from CASSIOPET, a companion study of the CASSIOPEIA cohort (ClinicalTrials.gov identifier NCT02541383). Transcriptomic analyses using RNA sequencing were realized on sorted bone marrow plasma cells from the same patients. An association with a high-risk gene expression signature (IFM15), molecular classification, progression-free survival, a stringent clinical response, and minimal residual disease negativity were explored. Results:¹⁸F-FDG PET results were positive in 79.4% of patients; 14% and 11% of them had PMD and extramedullary disease, respectively. Negative ¹⁸F-FDG PET results were associated with lower levels of expression of hexokinase 2 (HK2) (fold change, 2.1; adjusted P = 0.04) and showed enrichment for a subgroup of patients with a low level of bone disease. Positive ¹⁸F-FDG PET results displayed 2 distinct signatures: either high levels of expression of proliferation genes or high levels of expression of GLUT5 and lymphocyte antigens. PMD and IFM15 were independently associated with a lower level of progression-free survival, and the presence of both biomarkers defined a group of "double-positive" patients at very high risk of progression. PMD and IFM15 were related neither to minimal residual disease assessment nor to a stringent clinical response. Conclusion: Our study confirmed and extended the association between imaging biomarkers and transcriptomic programs in MM. The combined prognostic value of PMD and a high-risk IFM15 signature may help define MM patients with a very high risk of progression.

Radiomic Analysis of Positron-Emission Tomography and Computed Tomography Images to Differentiate between Multiple Myeloma and Skeletal Metastases

Context

Multiple myeloma and extensive lytic skeletal metastases may appear similar on positron-emission tomography and computed tomography (PET-CT) in the absence of an obvious primary site or occult malignancy. Radiomic analysis extracts a large number of quantitative features from medical images with the potential to uncover disease characteristics below the human visual threshold.

Aim

This study aimed to evaluate the diagnostic capability of PET and CT radiomic features to differentiate skeletal metastases from multiple myeloma.

Settings and Design

Forty patients (20 histopathologically proven cases of multiple myeloma and 20 cases of a variety of bone metastases) underwent staging 18F-fluorodeoxyglucose PET-CT at our institute.

Methodology

A total of 138 PET and 138 CT radiomic features were extracted by manual semi-automatic segmentation and standardized. The original dataset was subject separately to receiver operating curve analysis and correlation matrix filtering. The former showed 16 CT and 19 PET parameters to be significantly related to the outcome at 5%, whereas the latter resulted in 16 CT and 14 PET features. Feature selection was done with 7 evaluators with stratified 10-fold cross-validation. The selected features of each evaluator were subject to 14 machine-learning algorithms. In view of small sample size, two approaches for model performance were adopted: The first using 10-fold stratified cross-validation and the second using independent random training and test samples (26:14). In both approaches, the highest area under the curve (AUC) values were selected for 5 CT and 5 PET features. These 10 features were combined and the same process was repeated.

Statistical Analysis Used

The quality of the performance of the models was assessed by MSE, RMSE, kappa statistic, AUC, area under the precision-recall curve, F-measure, and Matthews correlation coefficient.

Results

In the first approach, the highest AUC = 0.945 was seen with 5 CT parameters. In the second approach, the highest AUC = 0.9538 was seen with 4 CT and one PET parameter. CT neighborhood gray-level different matrix coarseness and CT gray-level run-length matrix LGRE were common parameters in both approaches. Comparison of AUC of the above models showed no significant difference (P = 0.9845). Feature selection by principal components analysis and feature classification by the multilayer perceptron machine-learning model using independent training and test samples yielded the overall highest AUC.

Conclusions

Machine-learning models using CT parameters were found to differentiate bone metastases from multiple myeloma better than models using PET parameters. Combined models using PET and CECT data showed better overall performance than models using only either PET or CECT data. Machine-learning models using independent training and test sets were performed on par with those using 10-fold stratified cross-validation with the former incorporating slightly more PET features. Certain first- and second-order CT and PET texture features contributed in differentiating these two conditions. Our findings suggested that, in general, metastases were finer in CT and PET texture and myelomas were more compact.

99mTc-CD3813: A Nanobody-Based Single Photon Emission Computed Tomography Radiotracer with Clinical Potential for Myeloma Imaging and Evaluation of CD38 Expression

Daratumumab (DARA) is an anti-CD38 monoclonal antibody for the treatment of multiple myeloma (MM). The tumor CD38 expression level is one of the important factors in determining the efficacy of DARA treatment. Therefore, there is an urgent clinical need for a noninvasive tool to evaluate the CD38 levels in cancer patients before, during, and after DARA treatment. In this study, we prepared a new molecular imaging probe ^99mTc-CD3813, the ^99mTc-labeled nanobody CD3813, for noninvasive imaging of CD38 expression by single photon emission computed tomography (SPECT). We evaluated ^99mTc-CD3813 for its CD38 affinity and specificity and its capacity to image the CD38 expression in the MM and lymphoma xenografts models. ^99mTc-CD3813 SPECT/CT is able to visualize subcutaneous/orthotopic myeloma lesions in animal models and has advantages over ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography. Excess DARA has less impact on its tumor uptake (3.14 ± 0.83 vs 2.29 ± 0.91 %ID/g, n.s.), strongly suggesting that there is no competition between ^99mTc-CD3813 and DARA in binding to CD38. ^99mTc-CD3813 SPECT/CT revealed significant reduction in CD38 expression in the Ramos-bearing mice under DARA treatment, as evidenced by their reduced tumor uptake (3.04 ± 0.70 vs 1.07 ± 0.28 %ID/cc, P < 0.001). ^99mTc-CD3813 SPECT/CT was also able to detect the increased tumor uptake (0.79 ± 0.29 vs 2.12 ± 0.12 %ID/cc, P < 0.001) due to the upregulation of CD38 levels caused by all-trans retinoic acid infection. ^99mTc-CD3813 is a promising SPECT radiotracer for imaging the CD38-positive tumors and has clinical potential as a molecular imaging tool for evaluation of the CD38 expression level in patients before, during, and after DARA treatment.

Case of non-secretory multiple myeloma eventually diagnosed by 18F-FDG PET/CT

Non-secretory multiple myeloma (NSMM) is a rare type of multiple myeloma characterized by the absence of the M protein, making its diagnosis challenging. Here, we report a 67-year-old female patient eventually diagnosed as NSMM with positron emission tomography-computed tomography (PET/CT) imaging as a clue.

A Rare Extramedullary Involvement Site in Patients With Multiple Myeloma: Stomach

ABSTRACT

Multiple myeloma (MM) is a hematologic malignancy associated with uncontrolled clonal proliferation of plasma cells. Extramedullary disease in MM is an aggressive entity with a poor prognosis. Moreover, involvement of the gastrointestinal tract is a rare aggressive biological sign. 18F-FDG PET/CT is an irreplaceable modality in the assessment of extramedullary disease. We present 2 cases with gastric involvement of MM that were shown by 18F-FDG PET/CT and confirmed as plasma cell infiltration pathologically. 18F-FDG PET/CT studies of MM patients should be interpreted carefully for gastrointestinal involvement, and it should be kept in mind that it can mimic other malignancies.

Comparison of MRI Features of Fat Fraction and ADC for Early Treatment Response Assessment in Participants with Multiple Myeloma

Background An imaging-based predictor of response could provide prognostic information early during treatment course in patients with multiple myeloma (MM). Purpose To investigate if very early changes in bone marrow relative fat fraction (rFF) and apparent diffusion coefficient (ADC) histogram metrics, occurring after one cycle of induction therapy in participants with newly diagnosed MM, could help predict overall best response status. Materials and Methods This prospective study included participants with MM who were enrolled between August 2014 and December 2017. Histogram metrics were extracted from ADC and rFF maps from MRI examinations performed before treatment and after the first treatment cycle. Participants were categorized into the very good partial response (VGPR) or better group and the less than VGPR group per the International Myeloma Working Group response criteria. ADC and rFF map metrics for predicting treatment response were compared using the Wilcoxon rank test, and the false discovery rate (FDR) was used to correct for multiple comparisons. Results A total of 23 participants (mean age, 65 years ± 11 [SD]; 13 men) were evaluated. There was no evidence of a difference in ADC metrics between the two responder groups after correcting for multiple comparisons. The rFF histogram changes between pretreatment MRI and MRI after the first treatment cycle (ΔrFF) that provided significant differences between the VGPR or better and less than VGPR groups were as follows: ΔrFF_10th Percentile (median, 0.5 [95% CI: 0, 1] vs -2.5 [95% CI: -5.1, 0.1], respectively), ΔrFF_90th Percentile (median, 2 [95% CI: 1, 6.8] vs -0.5 [95% CI: -1, 0]), ΔrFF_Mean (median, 3.4 [95% CI: 0.3, 7.6] vs -1.1 [95% CI: -1.8, -0.7]), and ΔrFF_Root Mean Squared (median, 3.2 [95% CI: 0.3, 6.1] vs -0.7 [95% CI: -1.3, -0.4]) (FDR-adjusted P = .03 for all), and the latter two also presented mean group increases in the VGPR or better group that were above the upper 95% CI limit for repeatability. Conclusion Very early changes in bone marrow relative fat fraction histogram metrics, calculated from MRI examination at baseline and after only one cycle of induction therapy, may help to predict very good partial response or better in participants with newly diagnosed multiple myeloma. © RSNA, 2022 Online supplemental material is available for this article.

18F-FDG-PET/CT in relapsed multiple myeloma: Are prognostic thresholds different from first-line therapy?

Purpose

While ¹⁸F-FDG PET/CT yields valuable prognostic information for patients in first-line therapy of multiple myeloma (MM), its prognostic relevance in relapse is not established. Available studies of relapsed MM describe prognostic thresholds for frequently used PET/CT parameters that are significantly higher than those identified in the first-line setting. The purpose of this study was to evaluate the prognostic role of PET/CT in relapsed MM, based on parameters used in the first-line setting.

Methods

Our retrospective study included 36 patients with MM who had received autologous or allogeneic stem cell transplantation, suffered at least one relapse, and underwent FDG-PET/CT at relapse. Number of focal bone lesions (FL), maximal standardised uptake value (SUVmax), and presence of PET-positive extramedullary lesions (EMD) were analysed.

Results

For the number of FLs, the prognostic value was demonstrated with a cut-off of > 3 (median OS 3.8 months vs. not reached, p = 0.003). Median OS of patients with SUVmax ≤ 4 was not reached, while it was 3.9 months in patients with SUVmax > 4 (p = 0.014). Presence of EMD was a significant prognostic parameter too, with median OS of 3.6 months versus not reached (p = 0.004). The above-mentioned parameters showed prognostic significance for PFS as well. Combination of higher ISS stage and PET/CT parameters identified patients with particularly short OS (3.7 months vs. not reached, p < 0.001) and PFS (3.6 vs. 11.7 months p < 0.001).

Conclusion

The PET/CT parameters SUVmax > 4, nFL > 3, and presence of EMD identify patients with poor prognosis not only in the first-line setting but also in relapsed MM.

CT-derived relationship between low relative muscle mass and bone damage in patients with multiple myeloma undergoing stem cells transplantation

OBJECTIVE

Sarcopenia or low muscle mass is related to worse prognosis in cancer patients. We investigated whether muscle mass is related to bone damage on CT in patients with multiple myeloma (MM).

METHODS

Approval from the institutional review board was obtained. N = 74 consecutive patients (mean age, 60.8 years ± 9.24 [standard deviation]; range, 36-89 years) for MM who underwent transplant were included. Sarcopenia cut-off points defined as skeletal muscle index (SMI) used were<41 cm2/m2. To assess bone damage in MM the MSBDS (myeloma spine and bone damage score) was used. One-way analysis of variance and the X2 test were used. Kaplan-Meier analysis was performed to generate progression and survival curves according to SMI and MSBDS. The testing level was set at 0.05.

RESULTS

The median SMI was 47.1 ± 14.2 and according to SMI 18/74 (24%) had sarcopenia which was more prevalent in females (p.001). A strong and significant association between patients with low muscle mass and elevated bone damage (24/74, 32.4%) and patients with normal/non-low muscle mass low bone damage (30/74, 40.5%) was present. Multiple Logistic regression did not show any significant relationship or confounding influence among SMI and MSBDS regarding sex (p.127), cytogenetic status (p.457), staging (p.756) and relapse (.126). Neither SMI nor MSBDS resulted significantly related to overall survival as shown in Kaplan-Meier analysis.

CONCLUSION

Sarcopenia and bone damage affected MM patients undergoing stem cell transplantation and are significantly associated.

ADVANCES IN KNOWLEDGE

Quantitative measurement of sarcopenia and bone damage on CT resulted present in MM patients undergoing stem cell transplantation and are significantly associated.

A review of different methods used for quantification and assessment of FDG-PET/CT in multiple myeloma

The quantification of positron emission tomography/computed tomography (PET/CT) in multiple myeloma (MM) is challenging. Different methods of PET/CT quantification for assessment of fluorodeoxyglucose (FDG) uptake in myeloma patients have been suggested. This is the first review article that focuses on the advantages and disadvantages of each approach. Use of the maximum standardized uptake value (SUVmax) showed some promise in prognostic stratification of MM patients. However, it is affected by noise and time of flight and is subject to high variability. Volumetric PET metrics such as total lesion glycolysis and metabolic tumor volume are other proposed approaches. The high number of osteolytic lesions in MM patients makes this approach difficult in clinical practice. In addition, evaluation of small focal lesions is subject to partial volume correction. CT-based segmentation for assessment of FDG radiotracer is recently introduced. The methodologies are highly reproducible, but the clinical values of the approaches are unclear and still under investigation. We also discuss the Italian Myeloma criteria for PET Use (IMPeTUs), which is a qualitative approach, as a point of comparison. The reproducibility of IMPeTUs depends heavily on the level of user experience. We recommend further studies for assessing the prognostic significance of CT-threshold approaches in the assessment of MM patients.

Oligosecretory myeloma with gastrointestinal tract involvement: an unusual presentation and literature review

A woman in her 70s with vague gastrointestinal (GI) symptoms and unintentional weight loss was referred to endoscopy clinic for investigation and consideration of GI malignancy. CT of the thorax, abdomen and pelvis showed a suspicious mass in the oesophago-gastric junction with a lytic lesion on S1-S2 sacrum. A subsequent upper GI endoscopy revealed two raised, ulcerated tumours on the lesser curvature of the stomach. By the time an MRI of the whole spine was done which revealed multiple metastases involving thoracic, lumbar and sacral skeleton, she had developed leg weakness and paraesthesias, consistent with the imaging findings. A positron emission tomography/CT scan further confirmed the above findings. The initial working diagnosis was primary GI tumour with bony metastases. However, she was later referred to the haematology team after the immunohistochemistry of the tumour showed that it was of a plasma cell origin (CD138 positive) associated with lambda light chain deposits. Serum-free light chain showed a raised lambda light chain of 272 mg/L and kappa light chain of 11.3 mg/L and involved/uninvolved light chain ratio of 24. Bone marrow biopsy confirmed a plasma cell myeloma with moderate disease burden. Monoclonal lambda chains were demonstrated on immunofixation but negative on serum protein electrophoresis and hence a diagnosis of oligosecretory myeloma with GI involvement was made. Subsequent management involved physiotherapy, pain management and chemotherapy, where this woman was commenced on Velcade (generically known as bortezomib), thalidomide and dexamethasone and she continued to experience clinical and biochemical improvement.

Imaging for Plasma Cell Dyscrasias: What, When, and How?

Imaging plays a vital role in the diagnosis, response assessment, and follow-up of patients with plasma cell bone disease. The radiologic diagnostic paradigm has thus far evolved with developing technology and availability of better imaging platforms; however, the skewed availability of these imaging modalities in developed vis-à-vis the developing countries along with the lack of uniformity in reporting has led to a consensus on the imaging criteria for diagnosing and response assessment in plasma cell dyscrasia. Therefore, it is imperative for not only the radiologists but also the treating oncologist to be aware of the criteria and appropriate imaging modality to be used in accordance with the clinical question. The review will allow the treating oncologist to answer the following questions on the diagnostic, prognostic, and predictive abilities of various imaging modalities for plasma cell dyscrasia: a) What lesions can look like multiple myeloma (MM) but are not?; b) Does the patient have MM? To diagnose MM in a high-risk SMM patient with clinical suspicion, which modality should be used and why?; c) Is the patient responding to therapy on follow-up imaging once treatment is initiated?; d) To interpret commonly seen complications post-therapy, when is it a disease and when is the expected sequel to treatment? Fractures, red marrow reconversion?; and e) When is the appropriate time to flag a patient for further workup when interpreting MRI spine done for back pain in the elderly? How do we differentiate between commonly seen osteoporosis-related degenerative spine versus marrow infiltrative disorder?

Extramedullary disease in multiple myeloma: a systematic literature review

Extramedullary involvement (or extramedullary disease, EMD) represents an aggressive form of multiple myeloma (MM), characterized by the ability of a clone and/or subclone to thrive and grow independent of the bone marrow microenvironment. Several different definitions of EMD have been used in the published literature. We advocate that true EMD is restricted to soft-tissue plasmacytomas that arise due to hematogenous spread and have no contact with bony structures. Typical sites of EMD vary according to the phase of MM. At diagnosis, EMD is typically found in skin and soft tissues; at relapse, typical sites involved include liver, kidneys, lymph nodes, central nervous system (CNS), breast, pleura, and pericardium. The reported incidence of EMD varies considerably, and differences in diagnostic approach between studies are likely to contribute to this variability. In patients with newly diagnosed MM, the reported incidence ranges from 0.5% to 4.8%, while in relapsed/refractory MM the reported incidence is 3.4 to 14%. Available data demonstrate that the prognosis is poor, and considerably worse than for MM without soft-tissue plasmacytomas. Among patients with plasmacytomas, those with EMD have poorer outcomes than those with paraskeletal involvement. CNS involvement is rare, but prognosis is even more dismal than for EMD in other locations, particularly if there is leptomeningeal involvement. Available data on treatment outcomes for EMD are derived almost entirely from retrospective studies. Some agents and combinations have shown a degree of efficacy but, as would be expected, this is less than in MM patients with no extramedullary involvement. The paucity of prospective studies makes it difficult to justify strong recommendations for any treatment approach. Prospective data from patients with clearly defined EMD are important for the optimal evaluation of treatment outcomes.

Utility of PET/CT in Assessing Early Treatment Response in Patients With Newly Diagnosed Multiple Myeloma

Multiple Myeloma (MM) is a plasma cell malignancy characterized by diverse clinical presentations. While biochemical assessment of disease activity is commonly utilized to monitor treatment response, findings on magnetic resonance imaging and positron emission tomography/computed tomography (PET/CT), among other imaging modalities, have proven to harbor prognostic value. We sought to corroborate these findings by examining the prognostic significance of Fluorodeoxyglucose (FDG) PET/CT scanning in the setting of newly diagnosed MM. We retrospectively analyzed 195 patients with a PET/CT available both at diagnosis and at 6 months post-treatment to examine the value of PET/CT results as an adjuvant metric to conventional hematologic responses in terms of time to next treatment (TTNT) and overall survival (OS). The median TTNT and OS for the entire cohort were 24.6 (95% CI=20.4-29.1) and 79 (95% CI=63.1-119.1) months, respectively. When comparing PET/CT (-) with PET/CT (+) patients, we found significantly prolonged median TTNT (55.2 vs. 17.8 months, p<0.0001) and OS (unreached vs. 60.8 months, p<0.0001) for the PET/CT (-) group. We then examined the additive value of PET/CT on the hematologic response achieved at 6 months, and we found that PET/CT (-) is associated with significantly increased median TTNT and OS for both the very good partial response (VGPR) group and the less than VGPR group. Importantly, PET/CT retained prognostic significance after adjusting for multiple other predictive variables. We conclude that a PET/CT (-) at 6 months confers a significant prognostic advantage for newly diagnosed MM patients and adds significant value to the hematologic response assessment.

Molecular Imaging in Multiple Myeloma-Novel PET Radiotracers Improve Patient Management and Guide Therapy

Due to its proven value in imaging of multiple myeloma (MM), including staging, prognostication, and assessment of therapy response, 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET) is utilized extensively in the clinic. However, its accuracy is hampered by imperfect sensitivity (e.g., so-called FDG-negative MM) as well as specificity (e.g., inflammatory processes), with common pitfalls including fractures and degenerative changes. Novel approaches providing a read-out of increased protein or lipid membrane syntheses, such as [11C]methionine and [11C]choline or the C-X-C motif chemokine receptor 4-targeting radiotracer [68Ga]Pentixafor, have already been shown to be suitable adjuncts or alternatives to FDG. In the present focused review, those imaging agents along with their theranostic potential in the context of MM are highlighted.

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.

An Unusual Case of Multiple Myeloma with Light-Chain Cast Nephropathy Secondary to a Very Large Plasmacytoma without Bone Marrow Involvement

Here, we report a case of a patient who presented to Strong Memorial Hospital with new-onset renal failure and anemia and was found to have multiple myeloma with lambda light-chain cast nephropathy secondary to a very large (14 cm × 14 cm × 12 cm) plasmacytoma without bone marrow involvement. This case is notable as solitary plasmacytomas are almost never seen with concomitant myeloma-defining CRAB criteria or significantly elevated serum free light-chain ratios. Although solitary plasmacytomas are typically definitively treated with radiation, this case highlights that systemic treatment may be helpful in certain clinical scenarios.

Comparison of [68Ga]-FAPI PET/CT and [18F]-FDG PET/CT in Multiple Myeloma: Clinical Experience

Objective: In this study, we aimed to compare [68Ga]FAPI PET/CT and [18F]FDG PET/CT imaging to detect lesions in multiple myeloma. Methods: A total of 14 patients with multiple myeloma who underwent [68Ga]FAPI PET/CT and [18F]FDG PET/CT imaging were included in this retrospective study. SUVmax values of [68Ga]FAPI and [18F]FDG were compared according to lesion locations. Also, lesion localization ability of both imaging methods was compared on the patient basis. Results: In 4 of 14 patients, [68Ga]FAPI PET/CT and [18F]FDG PET/CT have not detected any bone lesions. In 8 of the remaining 10 patients [18F]FDG PET/CT detected bone lesions but in this group, 6 patients showed more higher SUVmax values than [18F]FDG PET/CT in [68Ga]FAPI PET/CT.In contrast, 2 of 8 patients showed more higher SUVmax values than [68Ga]FAPI PET/CT in [18F]FDG PET/CT. Moreover, [68Ga]FAPI PET/CT detected bone lesions in two patients, which werenot detected by [18F]FDG PET/CT. Also, in five patients, [68Ga]FAPI PET/CT showed more bone lesions in comparison with[18F]FDG PET/CT. Only one patient, [18F]FDG PET/CT showed more bone lesions. Three extramedullary involvements were observed in the following locations: lung, presacral lymph node, and soft tissue mass lateral to the right maxillary sinus. Among these involvements, higher SUVmax values were observed in the lung and presacral lymph node with [68Ga]FAPI compared to [18F]FDG. However, the soft tissue mass showed a higher SUVmax value in [18F]FDG than [68Ga]FAPI. Conclusions: No significant superiority was observed in [68Ga]FAPI PET/CT over [18F]FDG PET/CT in patients with MM. However, [68Ga]FAPI PET/CT can be utilized as a complementary imaging method to [18F]FDG PET/CT in some settings, especially in low-[18F]FDG affinity and inconclusive cases. Considering the favorable aspects of [68Ga]FAPI PET/CT in MM, such as low background activity, absence of non-specific bone marrow, and physiological brain involvement, further studies with a larger sample size should be conducted.

Initial evaluation of [18F]-FACBC for PET imaging of multiple myeloma

RATIONALE

Multiple myeloma (MM) cells synthesize large amounts of paraproteins, making radiolabeled amino acids promising candidates for PET imaging of MM patients.

METHODS

We compare tumor uptake of the two amino acid analogs [18F]-fluoroethyltyrosine and [18F]-FACBC in a MM xenograft model and show the feasibility of PET imaging with [18F]-FACBC in a MM patient.

RESULTS

Preclinically [18F]-FACBC showed superior performance, mainly due to the uptake via the ASC-system. In a subsequent proof-of-concept investigation [18F]-FACBC PET was performed in a MM patient. It allowed identification of both lesions with and without CT correlate (SUVmean 8.0 or 7.9) based on higher uptake compared to normal bone marrow (SUVmean 5.7). Bone signal was elevated compared to non-MM patients, and, thus [18F]-FACBC potentially allows the assessment of bone marrow infiltration.

CONCLUSION

The FDA/EMA approved PET agent [18F]-FACBC is promising for imaging MM and should be further evaluated in prospective clinical studies.

Machine Learning and Deep Learning Applications in Multiple Myeloma Diagnosis, Prognosis, and Treatment Selection

Simple Summary

Multiple myeloma is a malignant neoplasm of plasma cells with complex pathogenesis. With major progresses in multiple myeloma research, it is essential that we reconsider our methods for diagnosing and monitoring multiple myeloma disease. This fact needs the integration of serology, histology, radiology, and genetic data; therefore, multiple myeloma study has generated massive quantities of granular high-dimensional data exceeding human understanding. With improved computational techniques, artificial intelligence tools for data processing and analysis are becoming more and more relevant. Artificial intelligence represents a wide set of algorithms for which machine learning and deep learning are presently among the most impactful. This review focuses on artificial intelligence applications in multiple myeloma research, first illustrating machine learning and deep learning procedures and workflow, followed by how these algorithms are used for multiple myeloma diagnosis, prognosis, bone lesions identification, and evaluation of response to the treatment.

Abstract

Artificial intelligence has recently modified the panorama of oncology investigation thanks to the use of machine learning algorithms and deep learning strategies. Machine learning is a branch of artificial intelligence that involves algorithms that analyse information, learn from that information, and then employ their discoveries to make abreast choice, while deep learning is a field of machine learning basically represented by algorithms inspired by the organization and function of the brain, named artificial neural networks. In this review, we examine the possibility of the artificial intelligence applications in multiple myeloma evaluation, and we report the most significant experimentations with respect to the machine and deep learning procedures in the relevant field. Multiple myeloma is one of the most common haematological malignancies in the world, and among them, it is one of the most difficult ones to cure due to the high occurrence of relapse and chemoresistance. Machine learning- and deep learning-based studies are expected to be among the future strategies to challenge this negative-prognosis tumour via the detection of new markers for their prompt discovery and therapy selection and by a better evaluation of its relapse and survival.

Amino Acid and Proliferation PET/CT for the Diagnosis of Multiple Myeloma

Multiple myeloma (MM) is a hematologic malignancy characterized by infiltration of monoclonal plasma cells in the bone marrow (BM). The standard examination performed for the assessment of bone lesions has progressed from radiographic skeletal survey to the more advanced imaging modalities of computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT). The Durie-Salmon PLUS staging system (upgraded from the Durie-Salmon staging system) applies 2-[18F]-fluoro-2-deoxy-glucose (18F-FDG) PET/CT, and MRI findings to the staging of MM, and 18F-FDG PET/CT has been incorporated into the International Myeloma Working Group (IMWG) guidelines for the diagnosis and staging of MM. However, 18F-FDG PET/CT has significant limitations in the assessment of diffuse BM infiltration and in the differentiation of MM lesions from inflammatory or infectious lesions. The potential of several new PET tracers that exploit the underlying disease mechanism of MM has been evaluated in terms of improving the diagnosis. L-type amino acid transporter 1 (LAT1), a membrane protein that transports neutral amino acids, is associated with cell proliferation and has strong ability to represent the status of MM. This review evaluates the potential of amino acid and proliferation PET tracers for diagnosis and compares the characteristics and accuracy of non-FDG tracers in the management of patients with MM.

Imaging of treatment response and minimal residual disease in multiple myeloma: state of the art WB-MRI and PET/CT

Bone imaging has been intimately associated with the diagnosis and staging of multiple myeloma (MM) for more than 5 decades, as the presence of bone lesions indicates advanced disease and dictates treatment initiation. The methods used have been evolving, and the historical radiographic skeletal survey has been replaced by whole body CT, whole body MRI (WB-MRI) and [¹⁸F]FDG-PET/CT for the detection of bone marrow lesions and less frequent extramedullary plasmacytomas.Beyond diagnosis, imaging methods are expected to provide the clinician with evaluation of the response to treatment. Imaging techniques are consistently challenged as treatments become more and more efficient, inducing profound response, with more subtle residual disease. WB-MRI and FDG-PET/CT are the methods of choice to address these challenges, being able to assess disease progression or response and to detect "minimal" residual disease, providing key prognostic information and guiding necessary change of treatment.This paper provides an up-to-date overview of the WB-MRI and PET/CT techniques, their observations in responsive and progressive disease and their role and limitations in capturing minimal residual disease. It reviews trials assessing these techniques for response evaluation, points out the limited comparisons between both methods and highlights their complementarity with most recent molecular methods (next-generation flow cytometry, next-generation sequencing) to detect minimal residual disease. It underlines the important role of PET/MRI technology as a research tool to compare the effectiveness and complementarity of both methods to address the key clinical questions.

Role of FDG PET in the staging of multiple myeloma

¹⁸F-Fluorodeoxyglucose (FDG) PET has been used for staging of hematologic malignancies for years. In multiple myeloma, this imaging modality can be used in many different scenarios, including initial staging, evaluation of treatment response, and investigation of residual disease or early relapse. FDG PET-CT has excellent diagnostic performance, similar to other advanced imaging modalities such as whole-body CT and MRI, and it is particularly helpful for the assessment of extramedullary disease. It also offers important prognostic information on survival and risk of relapse, both at baseline and after therapy. This review will cover the main applications, advantages, and limitations of FDG PET-CT in multiple myeloma and related clonal plasma cell proliferative disorders, such as smoldering multiple myeloma and plasmacytoma.

Whole-Body MRI with an Ultrahigh b-Value of 2000 s/mm2 Improves the Specificity of Diffusion-Weighted Imaging in Patients with Plasma Cell Dyscrasias

RATIONALE AND OBJECTIVES

Our study compared sensitivity, specificity, and accuracy of whole-body diffusion-weighted imaging (WB-DWI) using a b-value of 2000 s/mm² with that of the commonly used b-value of 800 s/mm² for depiction of active tumor sites in patients with plasma cell diseases. We introduced an ultrahigh b-value to reduce interfering signals from benign and post-therapeutic inactive lesions by suppressing T2-shine-through effects.

MATERIALS AND METHODS

The prospective single-center study included patients when they went through a whole-body MRI (WB-MRI) staging or response evaluation procedure. The apparent diffusion coefficient (ADC) and morphologic appearance served as reference for classifying focal lesions on WB-DWI as vital or post-therapeutic. Additionally, we compared our classification with patients' serological markers of disease activity.

RESULTS

One hundred participants (65 ± 10 years, 58 men) underwent WB-DWI between June and October 2019. The detection rate of vital focal lesions was similar for both b-values with a sensitivity of 0.99 using b = 800 s/mm² and 0.98 using b = 2000 s/mm². By contrast, specificity and accuracy were 0.09 and 0.71 when using a b-value of 800 s/mm², and 0.96 and 0.98 when using a b-value of 2000 s/mm², respectively. The difference in specificity and accuracy was statistically significant (p < 0.001).

CONCLUSION

Using a b-value of 2000 s/mm² significantly improved the specificity of lesion detection with WB-DWI as compared to the commonly used b-value of 800 s/mm². The high b-value significantly reduced signal intensities of post-therapeutic or benign lesions and provided a significantly more accurate representation of active tumor load.

Whole-Body MRI Is an Effective Imaging Modality for Hematological Malignancy Treatment Response Assessment: A Systematic Review and Meta-Analysis

OBJECTIVES

To evaluate the diagnostic accuracy of whole-body MRI (WB-MRI) for assessment of hematological malignancies' therapeutic response.

METHODS

PubMed, Embase, and Web of Science were searched up to August 2021 to identify studies reporting the diagnostic performance of WB-MRI for the assessment of hematological malignancies' treatment response. A bivariate random-effects model was applied for the generation of the pooled diagnostic performance.

RESULTS

Fourteen studies with 457 patients with lymphoma, multiple myeloma, and sarcoma (very small proportion) were analyzed. Overall pooled sensitivity and specificity of WB-MRI were 0.88 (95% CI: 0.73-0.95) and 0.86 (95% CI: 0.73-0.93), respectively. Studies using whole-body diffusion-weighted imaging (WB-DWI) showed higher sensitivity than those that did not (0.94 vs. 0.55, p = 0.02). The pooled concordance rate of WB-MRI to assess hematological malignancies' treatment response with reference standard was 0.78 (95% CI: 0.59-0.96). WB-MRI and PET/CT showed similar diagnostic performance (sensitivity [0.83 vs. 0.92, p = 0.11] and specificity [0.87 vs. 0.76, p = 0.73]).

CONCLUSION

WB-MRI has high diagnostic performance for hematological malignancies' treatment response assessment. The adding of WB-DWI is strongly associated with increased sensitivity.

Oncologist perspective: role of imaging in myeloma

With major advancements in treatments for multiple myeloma (MM), it is critical that we evaluate our methods for both diagnosing MM and monitoring its progression over time. Imaging methods, such as conventional skeletal x-ray, low-dose whole-body CT, MRI, and PET-CT, provide valuable information that influences our clinical decision-making. In this review, we will evaluate the role of these imaging techniques throughout the MM disease course, from diagnosis to follow-up after therapy, and also provide appropriate recommendations.

Whole-body magnetic resonance imaging (WBMRI) versus whole-body computed tomography (WBCT) for myeloma imaging and staging

Myeloma-associated bone disease (MBD) develops in about 80-90% of patients and severely affects their quality of life, as it accounts for the majority of mortality and morbidity. Imaging in multiple myeloma (MM) and MBD is of utmost importance in order to detect bone and bone marrow lesions as well as extraosseous soft-tissue masses and complications before the initiation of treatment. It is required for determination of the stage of disease and aids in the assessment of treatment response. Whole-body low-dose computed tomography (WBLDCT) is the key modality to establish the initial diagnosis of MM and is now recommended as reference standard procedure for the detection of lytic destruction in MBD. In contrast, whole-body magnetic resonance imaging (WBMRI) has higher sensitivity for the detection of focal and diffuse plasma cell infiltration patterns of the bone marrow and identifies them prior to osteolytic destruction. It is recommended for the evaluation of spinal and vertebral lesions, while functional, diffusion-weighted MRI (DWI-MRI) is a promising tool for the assessment of treatment response. This review addresses the current improvements and limitations of WBCT and WBMRI for diagnosis and staging in MM, underlining the fact that both modalities offer complementary information. It further summarizes the corresponding radiological findings and novel technological aspects of both modalities.

[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.

[Radiological diagnosis of multiple myeloma : Role of imaging and the current S3 guideline]

CLINICAL ISSUE

Multiple myeloma is a clonal B‑lymphocyte neoplasm of terminally differentiated plasma cells and accounts for approximately 10% of all hematologic malignancies. Reduction of bone mass, seen on computed tomography (CT) as focal osteolysis, or general osteopenia is mainly caused by tumor-induced resorption of bone.

STANDARD RADIOLOGICAL METHODS

Imaging methods are used in multiple myeloma to record the extent of various dimensions of the disease manifestations (damage to bone substance, bone marrow infiltration, extramedullary involvement) and the disease course. The aim of this review article is to summarize and outline the recommendations of the S3 guideline "Diagnostics, therapy and follow-up care for patients with monoclonal gammopathy of unclear significance (MGUS) or multiple myeloma" in terms of radiographic imaging.

APPRAISAL AND PRACTICAL RECOMMENDATIONS

The use of the conventional X‑ray skeletal status (Paris scheme) is obsolete. When a patient with symptomatic multiple myeloma is initially diagnosed, a whole-body CT should be performed to determine the extent of skeletal damage. The S3 guideline also regards CT as the first imaging modality in relapse and progression.

Metabolic Volume Measurements in Multiple Myeloma

Multiple myeloma (MM) accounts for 10-15% of all hematologic malignancies, as well as 20% of deaths related to hematologic malignant tumors, predominantly affecting bone and bone marrow. Positron emission tomography/computed tomography with 18F-fluorodeoxyglucose (FDG-PET/CT) is an important method to assess the tumor burden of these patients. It is often challenging to classify the extent of disease involvement in the PET scans for many of these patients because both focal and diffuse bone lesions may coexist, with varying degrees of FDG uptake. Different metrics involving volumetric parameters and texture features have been proposed to objectively assess these images. Here, we review some metabolic parameters that can be extracted from FDG-PET/CT images of MM patients, including technical aspects and predicting MM outcome impact. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) are volumetric parameters known to be independent predictors of MM outcome. However, they have not been adopted in clinical practice due to the lack of measuring standards. CT-based segmentation allows automated, and therefore reproducible, calculation of bone metabolic metrics in patients with MM, such as maximum, mean and standard deviation of the standardized uptake values (SUV) for the entire skeleton. Intensity of bone involvement (IBI) is a new parameter that also takes advantage of this approach with promising results. Other indirect parameters obtained from FDG-PET/CT images, such as visceral adipose tissue glucose uptake and subcutaneous adipose tissue radiodensity, may also be useful to evaluate the prognosis of MM patients. Furthermore, the use and quantification of new radiotracers can address different metabolic aspects of MM and may have important prognostic implications.

Daratumumab, Carfilzomib, Lenalidomide, and Dexamethasone With Minimal Residual Disease Response-Adapted Therapy in Newly Diagnosed Multiple Myeloma

PURPOSE

The MASTER trial combined daratumumab, carfilzomib, lenalidomide, and dexamethasone (Dara-KRd) in newly diagnosed multiple myeloma (NDMM), using minimal residual disease (MRD) by next-generation sequencing (NGS) to inform the use and duration of Dara-KRd post-autologous hematopoietic cell transplantation (AHCT) and treatment cessation in patients with two consecutive MRD-negative assessments.

METHODS

This multicenter, single-arm, phase II trial enrolled patients with NDMM with planed enrichment for high-risk cytogenetic abnormalities (HRCAs). Patients received Dara-KRd induction, AHCT, and Dara-KRd consolidation, according to MRD status. MRD was evaluated by NGS at the end of induction, post-AHCT, and every four cycles (maximum of eight cycles) of consolidation. Primary end point was achievement of MRD negativity (< 10^-5). Patients with two consecutive MRD-negative assessments entered treatment-free MRD surveillance.

RESULTS

Among 123 participants, 43% had none, 37% had 1, and 20% had 2+ HRCA. Median age was 60 years (range, 36-79 years), and 96% had MRD trackable by NGS. Median follow-up was 25.1 months. Overall, 80% of patients reached MRD negativity (78%, 82%, and 79% for patients with 0, 1, and 2+ HRCA, respectively), 66% reached MRD < 10^-6, and 71% reached two consecutive MRD-negative assessments during therapy, entering treatment-free surveillance. Two-year progression-free survival was 87% (91%, 97%, and 58% for patients with 0, 1, and 2+ HRCA, respectively). Cumulative incidence of MRD resurgence or progression 12 months after cessation of therapy was 4%, 0%, and 27% for patients with 0, 1, or 2+ HRCA, respectively. Most common serious adverse events were pneumonia (6%) and venous thromboembolism (3%).

CONCLUSION

Dara-KRd, AHCT, and MRD response-adapted consolidation leads to high rate of MRD negativity in NDMM. For patients with 0 or 1 HRCA, this strategy creates the opportunity of MRD surveillance as an alternative to indefinite maintenance.

Smoldering multiple myeloma: evolving diagnostic criteria and treatment strategies

The adage for smoldering myeloma (SMM) has been to observe without treatment, until criteria for active multiple myeloma were satisfied. Definitions and risk stratification models have become more sophisticated, with prognostication tailored to include high-risk cytogenetics as per the most recent International Myeloma Working Group 2020 risk model. Moreover, progress in defining genomic evolution and changes in the bone marrow microenvironment through the monoclonal continuum have given insight into the complexities underlying the different patterns of progression observed in SMM. Given recent data showing improved progression-free survival with early intervention in high-risk SMM, the current dilemma is focused on how these patients should be treated. This case-based article maps the significant advancements made in the diagnosis and risk stratification of SMM. Data from landmark clinical trials will also be discussed, and ongoing trials are summarized. Ultimately, we outline our approach to SMM and hope to impart to the reader a sound concept of the current clinical management of SMM.

Identification of novel combined biomarkers in the diagnosis of multiple myeloma

PURPOSE

Multiple myeloma (MM) is a haematological malignant disease with a clonal proliferation of plasma cells, and timely surveillance is helpful to improve the survival rate of patients with MM. However, there is a lack of simple and effective biomarkers for the diagnosis, prognosis, and residual disease evaluation of MM.

MATERIAL & METHODS

In the detection cohort, we used the samples from six newly diagnosed MM patients and six control subjects. Plasma proteins were labelled with dimethyl reagents and enriched by lectin AANL6, then the deglycosylated peptides were identified by LC-MS/MS. Differentially expressed proteins were used for further exploration. In the validation cohort, we used 90 newly diagnosed patients with MM and 70 cases of unrelated diseases as controls. The diagnosis performance was analysed by ROC analysis using SPSS.

RESULTS

In this study, we show, using lectin blots with AANL6, that glycosylation levels were higher in MM patients than in controls. After AANL6 enrichment, we detected 58 differentially expressed proteins using quantitative proteomics. We further validated one candidate Fibulin-1 (FBLN1). Using an Elisa assay, we showed that FBLN1 expression was increased in plasma of 90 cases of MM, and which was significantly correlated with DKK1 expression. ROC analysis showed that these two markers had a 95.7% specificity for determining the diagnosis of MM.

CONCLUSION

These data suggest that the MM cases display increased glycosylation after AANL6 enrichment and that the combined expression of FBLN1 and DKK1 can be used as an effective diagnostic biomarker.

Development of a new risk stratification system for patients with newly diagnosed multiple myeloma using R-ISS and 18F-FDG PET/CT

In multiple myeloma (MM), a high number of focal lesions (FL) detected using positron emission tomography/computed tomography (PET/CT) was found to be associated with adverse prognosis. To design a new risk stratification system that combines the Revised International Staging System (R-ISS) with FL, we analyzed the data of 380 patients with newly diagnosed MM (NDMM) who underwent ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/CT upon diagnosis. The K-adaptive partitioning algorithm was adopted to define subgroups with homogeneous survival. The combined R-ISS with PET/CT classified NDMM patients into four groups: R-ISS/PET stage I (n = 31; R-ISS I with FL ≤ 3), stage II (n = 156; R-ISS I with FL > 3 and R-ISS II with FL ≤ 3), stage III (n = 162; R-ISS II with FL > 3 and R-ISS III with FL ≤ 3), and stage IV (n = 31; R-ISS III with FL > 3). The 2-year overall survival rates for stages I, II, III, and IV were 96.7%, 89.8%, 74.7%, and 50.3%. The 2-year progression-free survival rates were 84.1%, 64.7%, 40.8%, and 17.1%, respectively. The new R-ISS/PET was successfully validated in an external cohort. This new system had a remarkable prognostic power for estimating the survival outcomes of patients with NDMM. This system helps discriminate patients with a good prognosis from those with a poor prognosis more precisely.

AcidoCEST MRI Evaluates the Bone Microenvironment in Multiple Myeloma

PURPOSE

Multiple myeloma (MM) is an incurable disease of malignant plasma cells in the bone marrow (BM). Adaptive responses to hypoxia may be an essential element in MM progression and drug resistance. This metabolic adaptation involves a decrease in extracellular pH (pHe), and it depends on the upregulation of glucose transporters (GLUTs) that is common in hypoxia and in cancer cells. CEST MRI is an imaging technique that assesses pHe indirectly by the exchange rate of magnetic saturation transfer between labile protons on a solute and water. Thus, this study aimed to determine the feasibility of acidoCEST MRI for pHe measurement using an orthotopic mouse model of MM compared with GLUT1 immunofluorescence staining as a reference.

PROCEDURES

Orthotopic BM engrafted MM xenografts were established in NSG/NOD mice using the human RPMI8226 myeloma cell line. AcidoCEST MRI was performed approximately 6 weeks after intravenous challenge, before and after intravenous administration of iopamidol. BM pHe values were generated via fitting the CEST spectrum with the Bloch-McConnell equations. Samples were decalcified, sectioned, and immunostained for GLUT1 expression. Pearson's correlation was used to assess the relationship between pHe and [H3O+] versus GLUT1 expression.

RESULTS

Ten mice underwent acidoCEST MRI followed by immunofluorescent histologic analysis. A strong negative correlation was seen between pHe versus GLUT1 expression (r = - 0.75, p < 0.001). After transformation of pH to [H3O+], a strong positive correlation between [H3O+] and GLUT1 expression was observed (r = 0.8, p < 0.001).

CONCLUSIONS

AcidoCEST MRI can measure the extracellular pH of bone marrow affected by multiple myeloma. In this MM orthotopic mouse model, pHe measured by acidoCEST MRI showed strong correlations with the metabolic phenotype of BM tumor assessed by immunofluorescent histological assessment of GLUT1 overexpression.

Intensity of bone involvement: a quantitative 18F-FDG PET/CT evaluation for monitoring outcome of multiple myeloma

PURPOSE

The parameter intensity of bone involvement (IBI) was recently proposed to quantitatively assess patients with multiple myeloma using 18F-fluorodeoxyglucose-PET combined with computed tomography (18F-FDG PET/CT) images. Here, we aimed to calculate IBI variation (ΔIBI) between two consecutive PET/CT of the same patient and verified its relationship with a subjective visual analysis of the images and with clinical outcome.

METHODS

Consecutive whole-body 18F-FDG PET/CT performed to assess the outcomes of 29 patients diagnosed with multiple myeloma were retrospectively evaluated. ΔIBI was calculated after bone segmentation, using liver standardized uptake value as a threshold to determine metabolically active volumes in the skeleton. For each pair of consecutive PET/CTs, two nuclear medicine physicians classified visually the most recent image as PET-remission, PET-progression or PET-stable when compared to the previous examination.

RESULTS

The lowest ΔIBI was -1.27 and the highest was 0.29. PET-remission was related to ΔIBI <0 (median = -0.10; -1.27 to +0.03), while PET-progression was related to ΔIBI >0 (median = 0.02; -0.07 to +0.29). ΔIBI around zero was found in images classified as PET-stable (median = 0.00; -0.08 to +0.06). Significant difference in ΔIBI was found between the three groups. Multivariate stepwise analysis showed that IBI value at diagnostic PET/CT, serum calcium and percentage of plasma cells in the bone marrow are independent prognostic factors.

CONCLUSION

Delta IBI provides quantitative data for variations of 18F-FDG uptake in the bone marrow during the follow-up of the patients. In addition, higher IBI values at diagnosis are associated with a higher risk of patient's death.

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.

Annotating BCMA Expression in Multiple Myelomas

B cell maturation antigen (BCMA) is a promising theranostic target for multiple myeloma (MM). BCMA-targeted therapeutics, such as antibody-drug conjugates and chimeric antigen receptor T-cell immunotherapies, are rapidly reshaping the treatment landscape of MM. Along with the progress, a critical challenge is to noninvasively visualize the dynamic change of BCMA for a better-personalized prescription of the above-mentioned therapeutics. We aim to develop immuno-positron emission tomography (immunoPET) imaging strategies to visualize BCMA expression and realize target-specific diagnosis of MM in the work. A series of BCMA-targeting nanobodies were produced and two of them were successfully labeled with gallium-68 (⁶⁸Ga). MM models were established using MM.1S cell line and NOD-Prkdc^em26Cd52Il2rg^em26Cd22/Nju mice. The diagnostic efficacies of the developed probes (i.e., [⁶⁸Ga]Ga-NOTA-MMBC2 and [⁶⁸Ga]Ga-NOTA-MMBC3) were investigated in disseminated MM models by immunoPET imaging, region of interest analysis on PET images, biodistribution study, and histopathological staining study. [⁶⁸Ga]Ga-NOTA-MMBC2 and [⁶⁸Ga]Ga-NOTA-MMBC3 were developed with radiochemical purities of >99%. ImmunoPET imaging with either [⁶⁸Ga]Ga-NOTA-MMBC2 or [⁶⁸Ga]Ga-NOTA-MMBC3 precisely visualized BCMA expression and delineated MM lesions throughout the bone marrows. Moreover, [⁶⁸Ga]Ga-NOTA-MMBC3 immunoPET successfully detected remnant MM after treatment with daratumumab, a prescription medicine used to treat MM. The immunoPET imaging data correlated well with the biodistribution and immunohistochemistry staining results. The work successfully developed two state-of-the-art BCMA-targeted radiotracers for annotating BCMA expression and diagnosing MM. Translational studies interpreting the diagnostic efficacies of the immunoPET radiotracers are warranted.

[Benefits of radiotherapy for patients with solitary plasmacytoma or multiple myeloma]

BACKGROUND

Treatment options for patients with solitary plasmacytoma (SP) or multiple myeloma (MM) should be discussed in an interdisciplinary context. This systematic review focuses on the importance of radiotherapy in MM and SP.

OBJECTIVE

Summary of local radio-oncological treatment options for patients with SP and MM.

MATERIALS AND METHODS

Based on a systematic literature search, the current evidence on the topic was analyzed and summarized.

RESULTS

Patients with SP should be primarily treated with radiotherapy with or without surgery. Irradiation concepts may vary depending on risk factors and manifestation (solitary bone plasmacytoma vs. solitary extramedullary plasmacytoma). Although local control rates are high after radiotherapy, progression to multiple myeloma frequently occurs. In patients with MM, radiation is mainly used in palliative settings for pain relief, prevention of fractures or in patients who suffer from neurological symptoms due to spinal cord compression. Irradiation dose and fractionation should be selected based on treatment indication and general condition of the patient.

CONCLUSION

Although most patients receive systemic treatment at initial diagnosis, approximately 40% of patients with MM will require radiation during the course of their disease. While radiation is mainly used for palliation in patients with MM, it represents the primary and curative treatment option in patients with SP.

2021 European Myeloma Network review and consensus statement on smoldering multiple myeloma: how to distinguish (and manage) Dr. Jekyll and Mr. Hyde

According to the updated International Myeloma Working Group criteria, smoldering multiple myeloma (SMM) is an asymptomatic plasma cell disorder characterized by an M-component >3 g/dL, bone marrow plasma cell infiltration >10% and <60%, and absence of any myeloma-defining event. Active multiple myeloma is preceded by SMM, with a median time to progression of approximately 5 years. Cases of SMM range from the extremes of "monoclonal gammopathy of undetermined significance-like", in which patients never progress during their lifetimes, to "early multiple myeloma", in which transformation into symptomatic disease, based on genomic evolution, may be rapid and devastating. Such a "split personality" makes the prognosis and management of individual patients challenging, particularly with regard to the identification and possible early treatment of high-risk SMM. Outside of clinical trials, the conventional approach to SMM generally remains close observation until progression to active multiple myeloma. However, two prospective, randomized trials have recently demonstrated a significant clinical benefit in terms of time to progression, and of overall survival in one of the two studies, for some patients with higher-risk SMM treated with lenalidomide ± dexamethasone, raising the question of whether such an approach should be considered a new standard of care. In this paper, experts from the European Myeloma Network describe current biological and clinical knowledge on SMM, focusing on novel insights into its molecular pathogenesis, new prognostic scoring systems proposed to identify SMM patients at higher risk of early transformation, and updated results of completed or ongoing clinical trials. Finally, some practical recommendations for the real-life management of these patients, based on Delphi consensus methodology, are provided.

[18F](2S,4R)-4-Fluoroglutamine as a New Positron Emission Tomography Tracer in Myeloma

The high glycolytic activity of multiple myeloma (MM) cells is the rationale for use of Positron Emission Tomography (PET) with ¹⁸F-fluorodeoxyglucose ([¹⁸F]FDG) to detect both bone marrow (BM) and extramedullary disease. However, new tracers are actively searched because [¹⁸F]FDG-PET has some limitations and there is a portion of MM patients who are negative. Glutamine (Gln) addiction has been recently described as a typical metabolic feature of MM cells. Yet, the possible exploitation of Gln as a PET tracer in MM has never been assessed so far and is investigated in this study in preclinical models. Firstly, we have synthesized enantiopure (2S,4R)-4-fluoroglutamine (4-FGln) and validated it as a Gln transport analogue in human MM cell lines, comparing its uptake with that of ³H-labelled Gln. We then radiosynthesized [¹⁸F]4-FGln, tested its uptake in two different in vivo murine MM models, and checked the effect of Bortezomib, a proteasome inhibitor currently used in the treatment of MM. Both [¹⁸F]4-FGln and [¹⁸F]FDG clearly identified the spleen as site of MM cell colonization in C57BL/6 mice, challenged with syngeneic Vk12598 cells and assessed by PET. NOD.SCID mice, subcutaneously injected with human MM JJN3 cells, showed high values of both [¹⁸F]4-FGln and [¹⁸F]FDG uptake. Bortezomib significantly reduced the uptake of both radiopharmaceuticals in comparison with vehicle at post treatment PET. However, a reduction of glutaminolytic, but not of glycolytic, tumor volume was evident in mice showing the highest response to Bortezomib. Our data indicate that [¹⁸F](2S,4R)-4-FGln is a new PET tracer in preclinical MM models, yielding a rationale to design studies in MM patients.

Imaging of patients with multiple myeloma and associated plasma cell disorders: consensus practice statement by the Medical Scientific Advisory Group to Myeloma Australia

Imaging modalities for multiple myeloma (MM) have evolved to enable earlier detection of disease. Furthermore, the diagnosis of MM requiring therapy has recently changed to include disease prior to bone destruction, specifically the detection of focal bone lesions. Focal lesions are early, abnormal areas in the bone marrow, which may signal the development of subsequent lytic lesions that typically occur within the next 18-24 months. Cross-sectional imaging modalities are more sensitive for the detection and monitoring of bone and bone marrow disease and are now included in the International Myeloma Working Group current consensus criteria for initial diagnosis and treatment response assessment. The aim of this consensus practice statement is to review the evidence supporting these modalities. A more detailed Position Statement can be found on the Myeloma Australia website.

Minimal residual disease in multiple myeloma: current status

Multiple myeloma (MM) is a treatable plasma cell cancer with no cure. Clinical evidence shows that the status of minimal residual disease (MRD) after treatment is an independent prognostic factor of MM. MRD indicates the depth of post-therapeutic remission. In this review article, we outlined the major clinical trials that have determined the prognostic value of MRD in MM. We also reviewed different methods that were used for MM MRD assessment. Most important, we reviewed our current understanding of MM MRD biology. MRD studies strongly indicate that MRD is not a uniform declination of whole MM tumor population. Rather, MM MRD exhibits unique signatures of cytogenetic aberration and gene expression profiles, unlike those of MM cells before therapy. Diagnostic high-risk MM and low-risk MM exhibited a diversity of MRD features. Clonal evaluation may occur at the MRD stage in MM. The dynamics from the diagnostic MM to MRD correlate with the disease prognosis. Lastly, on the aspect of omics, we performed data-based analysis to address the biological features underlying the course of diagnostic-to-MRD MM. To summarize, the MRD stage of disease represents a critical step in MM pathogenesis and progression. Demonstration of MM MRD biology should help us to deal with the curative difficulties.

What are the roles of global DNA and APC 2 gene promotor hypermethylation in multiple myeloma?

Background

In today's practice, gene-based approaches come to the fore in the determination of prognosis and treatment preferences of multiple myeloma (MM). DNA methylation is one of the new approach parameters. DNA methylation occurs by the addition of a methyl group to cytosines in CpG dinucleotides. In this study, besides comparing the global DNA and APC 2 gene promotor hypermethylation between our patients with MM and healthy control group, we aimed to demonstrate the effect of hypermethylation on MM treatment responses and survival.

Methods and results

38 patients diagnosed with MM between January 2016 and January 2020 and 50 healthy controls were included in the study. The initial hypermethylation of the patients and the healthy control group were statistically analyzed. In addition, the increase in hypermethylation in the MM group before and after the first series of treatments were analyzed within themselves. There is a significant difference between the patients with MM diagnosis and the healthy control group in terms of the initial global hypermethylation (P = 0.001). In patients with MM, hypermethylation was significantly higher. Global hypermethylation in the post-treatment measurements was significantly increased in comparison to the pre-treatment state (P = 0.012). In terms of APC 2 promotor gene-specific hypermethylation, no significant differences were detected between pre- and post-treatment values (P = 0.368).

Conclusions

This study represents valuable data with the initial global DNA hypermethylation results in the MM patient group and the increase in hypermethylation post-treatment. it will shed light on future studies.