A prospective comparison of 18F-fluorodeoxyglucose positron emission tomography-computed tomography, magnetic resonance imaging and whole-body planar radiographs in the assessment of bone disease in newly diagnosed multiple myeloma

PET Imaging for Hematologic Malignancies

Hematologic malignancies are a broad category of cancers arising from the lymphoid and myeloid cell lines. The 2016 World Health Organization classification system incorporated molecular markers as part of the diagnostic criteria and includes more than 100 subtypes. This article focuses on the subtypes for which imaging with positron emission tomography/computed tomography (PET/CT) has become an integral component of the patient's evaluation, that is, lymphoma and multiple myeloma. Leukemia and histiocytic and dendritic cell neoplasms are also discussed as these indications for PET/CT are less common, but increasingly seen in clinic.

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.

Prognostic impact of posttransplant FDG PET/CT scan in multiple myeloma

Multiple myeloma (MM) is a heterogeneous disease that may be evaluated by a broad array of imaging and laboratory techniques to measure disease activity and predict prognosis. Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scanning has been shown to be predictive of patient outcomes throughout the disease course. We sought to corroborate these findings by examining the prognostic impact of PET/CT scanning in the posttransplant setting. We retrospectively analyzed PET/CT scans in 229 MM patients receiving an autologous stem cell transplant (ASCT) near day 100, and correlated these findings with time to progression(TTP) and overall survival (OS) to assess the impact of day 100 PET/CT scan findings as an independent prognostic factor. The median OS for the entire cohort was 61.5 months (95% confidence interval [CI], 49-75) and the median TTP was 18.5 months (95% CI, 15.4-21.8). Among patients with abnormal day 100 PET findings (PET+), median TTP was 12.4 months vs 24 months among those with normal PET findings (PET-) (P < .0001). The median OS in the PET+ group was 46 months compared with 99 months in the PET- group (P < .0001). We conclude that an abnormal PET/CT scan near day 100 post-ASCT is predictive of shorter TTP and OS, with prognostic significance retained after adjusting for disease response and other prognostic variables in MM.

Overview and recent advances in PET/CT imaging in lymphoma and multiple myeloma

Imaging in hematological diseases has evolved extensively over the past several decades. Positron emission tomography/computed tomography (PET/CT) with of 2-[18 F]-fluoro-2-deoxy-d-glucose ([18 F] FDG) is currently essential for accurate staging and for early and late therapy response assessment for all FDG-avid lymphoproliferative histologies. The widely adopted visual Deauville 5-point scale and Lugano Classification recommendations have recently standardized PET scans interpretation and improved lymphoma patient management. In addition [18 F] FDG-PET is routinely recommended for initial evaluation and treatment response assessment of Multiple Myeloma (MM) with significant contribution in risk-stratification and prognostication, although magnetic resonance imaging remains the Gold Standard for the assessment of bone marrow involvement. In this review, an overview of the role of [18 F] FDG-PET, in hematological malignancies is provided, particularly focusing on Hodgkin lymphoma (HL) and Diffuse Large B Cell Lymphoma (DLBCL), both in adult and pediatric populations, and MM, at each point of patient management. Potential alternative molecular imaging applications in this field, such as non-[18 F] FDG-tracers, whole body magnetic resonance imaging (WB-MRI), hybrid PET/MRI and emerging radiomics research are briefly presented.

Updates and Ongoing Challenges in Imaging of Multiple Myeloma: AJR Expert Panel Narrative Review

Advances in the understanding and treatment of multiple myeloma have led to the need for more sensitive and accurate imaging of intramedullary and extramedullary disease. This role of imaging is underscored by recently revised imaging recommendations of the International Myeloma Working Group (IMWG). This narrative review discusses these recommendations from the IMWG for different disease stages, focusing on advanced whole-body modalities, and addresses related challenges and controversies. In the recommendations, whole-body low-dose CT is central in initial patient assessment, replacing the conventional skeletal survey. Although the recommendations favor MRI for diagnosis because of its superior sensitivity and utility in identifying myeloma-defining events, FDG PET/CT is recommended as the modality of choice for assessing treatment response. Consensus opinions are offered regarding the role of imaging in multiple myeloma for characterization of disease distribution, determination of prognosis, and response evaluation.

Whole Body Low Dose Computed Tomography (WBLDCT) Can Be Comparable to Whole-Body Magnetic Resonance Imaging (WBMRI) in the Assessment of Multiple Myeloma

Aim of the study is to compare the agreement between whole-body low-dose computed tomography (WBLDCT) and magnetic resonance imaging (WBMRI) in the evaluation of bone marrow involvement in patients with multiple myeloma (MM). Patients with biopsy-proven MM, who underwent both WBLDCT and WBMRI were retrospectively enrolled. After identifying the presence of focal bone involvement (focal infiltration pattern), the whole skeleton was divided into five anatomic districts (skull, spine, sternum and ribs, pelvis, and limbs). Patients were grouped according to the number and location of the lytic lesions (<5, 5-20, and >20) and Durie and Salmon staging system. The agreement between CT and MRI regarding focal pattern, staging, lesion number, and distribution was assessed using the Cohen Kappa statistics. The majority of patients showed focal involvement. According to the distribution of the focal lesions and Durie Salmon staging, the agreement between CT and MRI was substantial or almost perfect (all κ > 0.60). The agreement increased proportionally with the number of lesions in the pelvis and spine (κ = 0.373 to κ = 0.564, and κ = 0.469-0.624), while for the skull the agreement proportionally decreased without reaching a statistically significant difference (p > 0.05). In conclusion, WBLDCT showed an almost perfect agreement in the evaluation of focal involvement, staging, lesion number, and distribution of bone involvement in comparison with WBMRI.

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

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

Quantitative, Dynamic 18F-FDG PET/CT in Monitoring of Smoldering Myeloma: A Case Report

We report on a 52-year-old patient with an initial diagnosis of smoldering myeloma (SMM), who was monitored by means of dynamic and static positron emission tomography/computed tomography (PET/CT) with the radiotracer ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). Baseline PET/CT revealed no pathological signs. Six months later, a transition to symptomatic, multiple myeloma (MM) was diagnosed. The transition was not accompanied by focal, hypermetabolic lesions on PET/CT. However, a diffusely increased ¹⁸F-FDG uptake in the bone marrow, accompanied by a marked increase of semi-quantitative (standardized uptake value, SUV) and quantitative, pharmacokinetic ¹⁸F-FDG parameters, was demonstrated. After successful treatment, including tandem autologous transplantation, the diffuse uptake in the bone marrow as well as the semi-quantitative and quantitative parameters showed a marked remission. This response was also confirmed by the clinical follow-up of the patient. These findings suggest that in MM a diffuse ¹⁸F-FDG uptake in the bone marrow may indeed reflect an actual bone marrow infiltration by plasma cells. Moreover, SUV values and kinetic parameters, not only from myeloma lesions but also from random bone marrow samples, may be used for MM monitoring. This could be particularly helpful in the follow-up of myeloma patients negative for ¹⁸F-FDG-avid focal lesions.

Quantitative and qualitative assessment of plasma cell dyscrasias in dual-layer spectral CT

Objectives

Virtual non-calcium (VNCa) images could improve assessment of plasma cell dyscrasias by enhancing visibility of bone marrow. Thus, VNCa images from dual-layer spectral CT (DLCT) were evaluated at different calcium suppression (CaSupp) indices, correlating results with apparent diffusion coefficient (ADC) values from MRI.

Methods

Thirty-two patients with initial clinical diagnosis of a plasma cell dyscrasia before any chemotherapeutic treatment, who had undergone whole-body low-dose DLCT and MRI within 2 months, were retrospectively enrolled. VNCa images with CaSupp indices ranging from 25 to 95 in steps of 10, conventional CT images, and ADC maps were quantitatively analyzed using region-of-interests in the vertebral bodies C7, T12, L1-L5, and the iliac bone. Independent two-sample t-test, Wilcoxon-signed-rank test, Pearson’s correlation, and ROC analysis were performed.

Results

Eighteen patients had a non-diffuse, 14 a diffuse infiltration in conventional MRI. A significant difference between diffuse and non-diffuse infiltration was shown for VNCa-CT with CaSupp indices from 55 to 95, for conventional CT, and for ADC (each p < 0.0001). Significant quantitative correlation between VNCa-CT and MRI could be found with strongest correlation at CaSupp index 65 for L3 (r = 0.68, p < 0.0001) and averaged L1-L5 (r = 0.66, p < 0.0001). The optimum CT number cut-off point for differentiation between diffuse and non-diffuse infiltration at CaSupp index 65 for averaged L1-L5 was −1.6 HU (sensitivity 78.6%, specificity 75.0%).

Conclusion

Measurements in VNCa-CT showed the highest correlation with ADC at CaSupp index 65. VNCa technique may prove useful for evaluation of bone marrow infiltration if MRI is not feasible.

Key Points

• VNCa-CT images can support the evaluation of bone marrow infiltration in plasma cell dyscrasias.

• VNCa measurements of vertebral bodies show significant correlation with ADC in MRI.

• Averaging L1-L5 at CaSupp index 65 allowed quantitative detection of infiltration comparable to MRI ADC.

Management of patients with difficult-to-treat multiple myeloma

Newer treatments for multiple myeloma (MM) have improved response rates and survival for many patients. However, MM remains challenging to treat due to the propensity for multiple relapses, cumulative and emergent toxicities from prior therapies and increasing genomic complexity that arises due to clonal evolution. In particular, patients with relapsed/refractory MM often require increased complexity of treatment, yet still experience poorer outcomes compared with patients who are newly diagnosed. Additionally, several patient subgroups, including those with extramedullary disease and patients who are frail and/or have multiple comorbidities, have an unfavorable prognosis and remain undertreated. This review (based on an Updates-in-Hematology session at the 25th European Hematology Association Annual Congress 2020) discusses the management of these difficult-to-treat patients with MM.

Positron Emission Tomography (PET) Imaging of Multiple Myeloma in a Post-Treatment Setting

2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography/computed tomography (FDG PET/CT) has an established clinical value in the diagnosis and initial staging of multiple myeloma (MM). In the last ten years, a vast body of literature has shown that this tool can also be of high relevance for monitoring therapy responses, making it the recommended imaging approach in this field. Starting from the strengths and weaknesses of radiological imaging in MM, the present review aims to analyze FDG PET/CT's current clinical value focusing on therapy response assessment and objective interpretation criteria for therapy monitoring. Given the potential occurrence of patients with MM showing non-FDG-avid bone disease, new opportunities can be provided by non-FDG PET tracers. Accordingly, the potential role of non-FDG PET tracers in this setting has also been discussed.

PET/CT in Multiple Myeloma: Beyond FDG

Recent advances in the diagnosis and treatment of multiple myeloma (MM) have highlighted the importance of imaging methods, not only in the localization and extent of the disease but also in prognostic stratification and assessment of response to therapy. In this context, PET/CT, combining both morphological and functional information, is particularly useful in this pathology. The tracer mostly used is 18F-FDG, a glucose analog, which provides extremely accurate information with a sensitivity ranging from 80 to 100%. However, this tracer has some limitations, mostly related to the physiological uptake of FDG in the bone marrow and brain, which reduce its effectiveness. For this reason, some studies in the literature have evaluated the effectiveness of other PET tracers, which provide information on protein metabolism or the synthesis of metabolic plasma membranes, such as choline and methionine, as well as innovative radiopharmaceuticals, directed against receptors expressed by cells of myeloma, including tracers directed to the chemokine receptor. This review analyzes the characteristics and accuracy of non-FDG tracers in the management of patients with multiple myeloma.

F-18 FDG PET/CT and F-18 FLT PET/CT as predictors of outcome in patients with multiple myeloma. A pilot study

OBJECTIVES

We evaluated the prognostic significance of the combined use of F-18 FDG (FDG) and F-18 FLT (FLT) PET/CT (PET/CT) in patients (pts) with multiple myeloma (MM) suspected relapse after a first line chemotherapy.

METHODS

twenty-eight patients (57 ± 12 years) underwent both PET/CT scans over 2-4 weeks. Patients were grouped according to imaging results (FDG+/-; FLT+/-) and the findings compared to the event free survival (EFS).

RESULTS

five pts had FDG+; FLT+, 8 showed FDG+;FLT-, two had FDG-;FLT + and 13 presented FDG-;FLT-, mostly (87 %) of FDG+;FLT- pts had destructive lytic bone lesions. At Cox regression analysis the FDG PET/CT (HR 4.4, 95 % CI 1.3-15.4, p < 0.05) and FLT PET/CT (HR 5.8, 95 % CI 1.7-19.3, p < 0.01) were predictive of worst prognosis. The Kaplan-Meier analysis showed that FDG and FLT PET/CT independently influenced the survival. FDG-;FLT-patients had better EFS as compared to FDG+; FLT + pts and FDG-;FLT + pts, those of FDG+;FLT- group also had worsened EFS.

CONCLUSIONS

results from the aggregate use of PET/CT FDG and FLT in MM represent a valuable prognostic indicator for identifying patients at higher risk of undue events and may help to correctly stratify the patients with suspected relapse.

Prognostic impact of 18F-FDG PET/CT in patients with multiple myeloma presenting with renal impairment

Renal insufficiency (RI) is a frequent manifestation of multiple myeloma (MM) at time of diagnosis but there is no reliable prognostic factor for patients with MM presenting with RI. This study investigated the prognostic impact of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in patients with MM with RI at diagnosis. The records of 209 patients with MM between June 2011 and November 2018 were retrospectively analyzed. PET/CT positivity was defined as the presence of more than three focal lesions or the presence of extramedullary disease. Of 209 patients, 90 (43.1%) had RI and showed similar survival outcomes to patients who had normal renal function. In total, 113 patients (54.0%) were PET/CT-positive, and 46.6% of patients with RI were PET/CT-positive at baseline. In patients with RI, those who were PET/CT-positive showed significantly inferior survival outcomes to those who were PET/CT-negative [progression-free survival (PFS), 12.7 vs. 34.0 months, P < 0.001; overall survival (OS), 42.2 months vs. not reached, P = 0.001]. On multivariate analysis, PET/CT positivity was significantly associated with PFS and OS in patients with RI. In conclusion, PET/CT is a reliable imaging technique for predicting survival outcomes in patients with MM with RI.

Assessment of naive indolent lymphoma using whole-body diffusion-weighted imaging and T2-weighted MRI: results of a prospective study in 30 patients

Background

We prospectively evaluated the diagnostic utility of whole-body diffusion-weighted imaging with background body signal suppression and T2-weighted short-tau inversion recovery MRI (WB-DWIBS/STIR) for the pretherapeutic staging of indolent lymphoma in 30 patients.

Methods

This prospective study included 30 treatment-naive patients with indolent lymphomas who underwent WB-DWIBS/STIR and conventional imaging workup plus biopsy. The pretherapeutic staging agreement, sensitivity, and specificity of WB-DWIBS/STIR were investigated with reference to the multimodality and multidisciplinary consensus review for nodal and extranodal lesions excluding bone marrow.

Results

In the pretherapeutic staging, WB-DWIBS/STIR showed very good agreement (κ = 0.96; confidence interval [CI], 0.88–1.00), high sensitivity (93.4–95.1%), and high specificity (99.0–99.4%) for the whole-body regions. These results were similar to those of ¹⁸F-FDG-PET/CT, except for the sensitivity for extranodal lesions. For extranodal lesions, WB-DWIBS/STIR showed higher sensitivity compared to ¹⁸F-FDG-PET/CT for the whole-body regions (94.9–96.8% vs. 79.6–86.3%, P = 0.058).

Conclusion

WB-DWIBS/STIR is an effective modality for the pretherapeutic staging of indolent lymphoma, and it has benefits when evaluating extranodal lesions, compared with ¹⁸F-FDG-PET/CT.

Management of acute spinal cord compression in multiple myeloma

Spinal cord compression (SCC) is a devastating complication of multiple myeloma and has the potential to cause loss of neurological function. The common symptoms of SCC are back pain, motor weakness, and sensory change. Once diagnosed, the patient should be managed as soon as possible to prevent permanent loss of neurological function. Currently, there have been a number of studies describing the mechanism and management experience of SCC in patients with myeloma. The clinical features, diagnostic strategies, and the roles of different therapeutic options are herein reviewed.

Virtual calcium-suppression in dual energy computed tomography predicts metabolic activity of focal MM lesions as determined by fluorodeoxyglucose positron-emission-tomography

PURPOSE

Recent studies showed that dual energy CT (DECT) allows for detection of bone marrow infiltration in multiple myeloma (MM) by obtaining virtual non-calcium (VNCa) images. This feasibility study investigated, if VNCa imaging might discriminate metabolically active, focal lesions in MM against avital lesions in MM patients, considering fluorodeoxyglucose positron-emission-tomography CT (FDG PET/CT) as the standard of reference.

METHOD

The study included 60 osteolytic lesions in 10 consecutive low-dose whole body CT scans of patients with MM, who underwent both FDG PET/CT and DECT at a tertiary care university hospital. Circular ROI measurements were performed in predefined lesions on the monoenergetic CT (MECT) and VNCa images by three blinded radiologists. Each lesion was rated vital or avital by a blinded specialist of nuclear medicine, based on their FDG metabolism.

RESULTS

Each of the three readers could separate FDG PET/CT negative and positive MM lesions when analyzing the VNCa images, while MECT did not show a significant difference. Best results were yielded by high calcium suppression with excellent inter-rater reliability (average sensitivity 0.91, specificity 0.88, cutoff -46.9 HU), followed by medium and low calcium suppression.

CONCLUSIONS

In contrast to MECT imaging, VNCa imaging in DECT appears to be feasible to assess metabolic activity of focal MM lesions as defined by the standard of reference, FDG PET/CT. Considering the higher cost and radiation exposure of FDG PET/CT, DECT VNCa imaging might develop to be the modality of choice to assess metabolic activity of focal MM lesions.

Whole-Body Functional MRI and PET/MRI in Multiple Myeloma

Simple Summary

Whole-body magnetic resonance imaging (MRI) is recognized as the most sensitive imaging technique for the detection of bone marrow infiltration, and was therefore, recently included in the new diagnostic myeloma criteria, as proposed by the International Myeloma Working Group. The use of diffusion-weighted MRI further improved the performances of whole-body MRI in the setting of multiple myeloma, and its systematic implementation in general clinical practice is now recommended. Whole-body, dynamic, contrast-enhanced MRI might provide further information on lesions vascularity and might help evaluate response to treatment. Hybrid PET/MRI might act as the optimal imaging modality, owing to the association of the best techniques for both detecting bone marrow involvement and evaluating treatment response, providing one-stop-shop imaging in a whole-body scale. This review provides an overview on the value of whole-body MRI, including diffusion-weighted and dynamic contrast-enhanced MRI and whole-body ¹⁸F-FDG PET/MRI in diagnosis, staging, and response evaluation in multiple myeloma.

Abstract

Bone disease is one of the major features of multiple myeloma (MM), and imaging has a pivotal role in both diagnosis and follow-up. Whole-body magnetic resonance imaging (MRI) is recognized as the gold standard for the detection of bone marrow involvement, owing to its high sensitivity. The use of functional MRI sequences further improved the performances of whole-body MRI in the setting of MM. Whole-body diffusion-weighted (DW) MRI is the most attractive functional technique and its systematic implementation in general clinical practice is now recommended by the International Myeloma Working Group. Whole-body dynamic contrast-enhanced (DCE) MRI might provide further information on lesions vascularity and help evaluate response to treatment. Whole Body PET/MRI is an emerging hybrid imaging technique that offers the opportunity to combine information on morphology, fat content of bone marrow, bone marrow cellularity and vascularization, and metabolic activity. Whole-body PET/MRI allows a one-stop-shop examination, including the most sensitive technique for detecting bone marrow involvement, and the most recognized technique for treatment response evaluation. This review aims at providing an overview on the value of whole-body MRI, including DW and DCE MRI, and combined whole-body ¹⁸F-FDG PET/MRI in diagnosis, staging, and response evaluation in patients with MM.

How we manage smoldering multiple myeloma

Smoldering myeloma (SMM) is an asymptomatic stage characterized by bone marrow plasma cells infiltration between 10-60% in absence of myeloma-defining events and organ damage. Until the revision of criteria of MM to require treatment, two main prognostic models, not overlapping each other, were proposed and used differently in Europe and in US. Novel manageable drugs, like lenalidomide and monoclonal antibodies, with high efficacy and limited toxicity, improvement in imaging and prognostication, challenge physicians to offer early treatment to highrisk SMM. Taking advantage from the debates offered by SOHO Italy, in this review we will update the evidence and consequent clinical practices in US and Europe to offer readers a uniform view of clinical approach at diagnosis, follow-up and supportive care in the SMM setting.

Prospective comparison of 18-FDG PET/CT and whole-body diffusion-weighted MRI in the assessment of multiple myeloma

Magnetic resonance imaging (MRI) and ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸FDG 18F-FDG PET-CT) are standard procedures for staging multiple myeloma (MM). Diffusion-weighted sequences applied to whole-body MRI (WB-DWI) improve its sensitivity. We compared the number of MM bone focal lesions (FLs) detected by ¹⁸F-FDG PET-CT and WB-DWI and evaluated the diagnostic performance of ¹⁸F-FDG PET-CT for diffuse infiltration. Thirty newly diagnosed MM patients prospectively underwent 18F-FDG PET-CT and WB-DWI. The criteria for skeletal region positivity were ≥ 1 focal bone lesions (FLs) and/or diffuse disease. MRI with the MY-RADS criteria was used as a reference standard for the diagnosis of diffuse infiltration. ¹⁸F-FDG PET-CT and WB-DWI were both interpreted as positive in 28/30 patients with an agreement of 1.00 (95% CI 0.77-1.00) between the two methods. The mean numbers of FLs were 16.7 detected by ¹⁸F-FDG PET-CT and 23.9 detected by WB-DWI (P = 0.028). WB-DWI detected more FLs in the skull (P = 0.001) and spine (P = 0.006). Agreement assessed using the prevalence and bias-corrected kappa index was moderate (0.40-0.60) for the spine, sternum-ribs and upper limbs and substantial (0.60-0.80) for the pelvis and lower limbs. As regards the diagnosis of diffuse bone marrow infiltration, the sensitivity, specificity and accuracy of ¹⁸F-FDG PET-CT were 0.75, 0.79 and 0.77, respectively. Although WB-DWI detected more FLs than did ¹⁸F-FDG PET-CT, there was no difference in the detection of bone disease on a per-patient basis. ¹⁸F-FDG PET-CT showed high performance, including for evaluation of diffuse infiltration.

Applications of PET in Diagnosis and Prognosis of Leukemia

As a malignant hematopoietic stem cell disease, leukemia remains life-threatening due to its increasing incidence rate and mortality rate. Therefore, its early diagnosis and treatment play a very important role. In the present work, we systematically reviewed the current applications and future directions of positron emission tomography (PET) in patients with leukemia, especially ¹⁸F-FDG PET/CT. As a useful imaging approach, PET significantly contributes to the diagnosis and treatment of different types of leukemia, especially in the evaluation of extramedullary infiltration, monitoring of leukemia relapse, detection of Richter’s transformation (RT), and assessment of the inflammatory activity associated with acute graft versus host disease. Future investigations should be focused on the potential of PET/CT in the prediction of clinical outcomes in patients with leukemia and the utility of novel radiotracers.

Multiple Myeloma: Role of Imaging in Diagnosis, Staging, and Treatment Response Assessment

Multiple myeloma is a common hematologic malignancy of plasma cells. Differentiating multiple myeloma from the precursor stages of monoclonal gammopathy of undetermined significance and smoldering multiple myeloma is very important because the treatment approach is different for each. The diagnosis is mainly clinical, while the role of imaging is confined to the staging process, assessing response to therapy, and monitoring for disease progression. In this article, we examine the role of different imaging modalities in patients with multiple myeloma.

Role of imaging in multiple myeloma

With rapid advancements in the diagnosis and treatment of multiple myeloma (MM), imaging has become instrumental in detection of intramedullary and extramedullary disease, providing prognostic information, and assessing therapeutic efficacy. Whole-body low dose computed tomography (WBLDCT) has emerged as the study of choice to detect osteolytic bone disease. Positron emission tomography/computed tomography (PET/CT) combines functional and morphologic information to identify MM disease activity and assess treatment response. Magnetic resonance imaging (MRI) has excellent soft-tissue contrast and is the modality of choice for bone marrow evaluation. This review focuses on the imaging modalities available for MM patient management, highlighting advantages, disadvantages, and applications of each.

Multiple Myeloma Associated Bone Disease

The lytic bone disease is a hallmark of multiple myeloma, being present in about 80% of patients with newly diagnosed MM, and in more during the disease course. The myeloma associated bone disease (MBD) severely affects the morbidity and quality of life of the patients. MBD defines treatment demanding MM. In recent years, knowledge of the underlying pathophysiology has increased, and novel imaging technologies, medical and non-pharmaceutical treatments have improved. In this review, we highlight the major achievements in understanding, diagnosing and treating MBD. For diagnosing MBD, low-dose whole-body CT is now recommended over conventional skeletal survey, but also more advanced functional imaging modalities, such as diffusion-weighted MRI and PET/CT are increasingly important in the assessment and monitoring of MBD. Bisphosphonates have, for many years, played a key role in management of MBD, but denosumab is now an alternative to bisphosphonates, especially in patients with renal impairment. Radiotherapy is used for uncontrolled pain, for impeding fractures and in treatment of impeding or symptomatic spinal cord compression. Cement augmentation has been shown to reduce pain from vertebral compression fractures. Cautious exercise programs are safe and feasible and may have the potential to improve the status of patients with MM.

Minimal Residual Disease in Multiple Myeloma: State of the Art and Future Perspectives

Minimal residual disease (MRD) detection represents a sensitive tool to appropriately measure the response obtained with therapies for multiple myeloma (MM). The achievement of MRD negativity has superseded the conventional complete response (CR) and has been proposed as a surrogate endpoint for progression-free survival and overall survival. Several techniques are available for the detection of MRD inside (next-generation sequencing, flow cytometry) and outside (PET/CT, magnetic resonance) the bone marrow, and their complementary use allows a precise definition of the efficacy of anti-myeloma treatments. This review summarizes MRD data and results from previous clinical trials, highlights open issues related to the role of MRD in MM and discusses how MRD could be implemented in clinical practice to inform on patient prognosis and drive therapeutic decisions.

Solitary Plasmacytoma: a Review of Diagnosis and Management

PURPOSE OF REVIEW

Solitary plasmacytoma is a rare plasma cell dyscrasia, classified as solitary bone plasmacytoma or solitary extramedullary plasmacytoma. These entities are diagnosed by demonstrating infiltration of a monoclonal plasma cell population in a single bone lesion or presence of plasma cells involving a soft tissue mass, respectively. Both diseases represent a single localized process without significant plasma cell infiltration into the bone marrow or evidence of end organ damage. Clinically, it is important to classify plasmacytoma as having completely undetectable bone marrow involvement versus minimal marrow involvement. Here, we discuss the diagnosis, management, and prognosis of solitary plasmacytoma.

RECENT FINDINGS

There have been numerous therapeutic advances in the treatment of multiple myeloma over the last few years. While the treatment paradigm for solitary plasmacytoma has not changed significantly over the years, progress has been made with regard to diagnostic tools available that can risk stratify disease, offer prognostic value, and discern solitary plasmacytoma from quiescent or asymptomatic myeloma at the time of diagnosis. Despite various studies investigating the use of systemic therapy or combined modality therapy for the treatment of plasmacytoma, radiation therapy remains the mainstay of therapy. Much of the recent advancement in the management of solitary plasmacytoma has been through the development of improved diagnostic techniques.

FDG-PET/CT, a Promising Exam for Detecting High-Risk Myeloma Patients?

Multiple myeloma (MM) is a haematological neoplasm characterized by a clonal proliferation of malignant plasma cells in the bone marrow. MM is associated with high morbidity and mortality and variable survival, which can be very short for some patients but over 10 years for others. These differences in survival are explained by intra- and inter-tumoral heterogeneity and demonstrate the potential benefits of adapting the treatment course for high-risk patients with a poorer prognosis. Indeed, identification of these high-risk patients is necessary and is based on the identification of high-risk biomarkers including clinical variables, genomics and imaging results. Positron emission tomography combined with computed tomography using 18F-deoxyfluoroglucose (FDG-PET/CT) is a reliable technique for the initial staging of patients with symptomatic multiple myeloma (MM), and has been included in the IMWG (International Myeloma Working Group) recommendations in 2019. According to clinical studies, FDG-PET/CT characteristics could be used to define high-risk patients at initial diagnosis of symptomatic MM. The goal of this review is to demonstrate the prognostic value of FDG-PET in symptomatic MM patients, particularly in identifying high-risk patients, and thus, to best adapt therapeutic management in the future.

Choline PET/CT in Multiple Myeloma

The field of multiple myeloma (MM) imaging has evolved. The International Myeloma Working Group recently recommended performing 18F-fluorodeoxyglucose glucose (18FDG) positron emission tomography/computed tomography (PET/CT) with the aim of staging MM patients at baseline and evaluating response to therapy. Novel oncological radiotracers such as 11C-Choline and 18F-Fluorocholine, have been studied in comparison with 18FDG, mostly in MM patients presenting with refractory disease or suspected relapse. Choline-based tracers may overcome some limitations of 18FDG, which include a lack of sensitivity in depicting skull lesions and the fact that 10% of MM patients are FDG-negative. The majority of MM lesions display a higher uptake of Choline than FDG. Also, in many situations, Choline may offer better lesion visualization, with a higher tumor to background ratio; however, various patterns of Choline and FDG uptake have been observed in MM and some limitations, notably as regards liver lesions, should be recognized. Overall, Choline may provide additional detection of up to 75% more lesions. This article aims to provide a comprehensive review of the potential role of Choline in multiple myeloma, as compared to FDG, encompassing Choline physiopathology as well as data from clinical studies.

Positron Emission Tomography (PET) Radiopharmaceuticals in Multiple Myeloma

Multiple myeloma (MM) is a plasma cell disorder, characterized by clonal proliferation of malignant plasma cells in the bone marrow. Bone disease is the most frequent feature and an end-organ defining indicator of MM. In this context, imaging plays a pivotal role in the management of the malignancy. For several decades whole-body X-ray survey (WBXR) has been applied for the diagnosis and staging of bone disease in MM. However, the serious drawbacks of WBXR have led to its gradual replacement from novel imaging modalities, such as computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT). PET/CT, with the tracer ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG), is now considered a powerful diagnostic tool for the detection of medullary and extramedullary disease at the time of diagnosis, a reliable predictor of survival as well as the most robust modality for treatment response evaluation in MM. On the other hand, ¹⁸F-FDG carries its own limitations as a radiopharmaceutical, including a rather poor sensitivity for the detection of diffuse bone marrow infiltration, a relatively low specificity, and the lack of widely applied, established criteria for image interpretation. This has led to the development of several alternative PET tracers, some of which with promising results regarding MM detection. The aim of this review article is to outline the major applications of PET/CT with different radiopharmaceuticals in the clinical practice of MM.

Correlation Between Uptake of 18F-FDG During PET/CT and Ki-67 Expression in Patients Newly Diagnosed With Multiple Myeloma Having Extramedullary Involvement

The aim of this study was to evaluate the relationship of prognosis of patients with multiple myeloma having extramedullary involvement (EMM) with the ¹⁸F- fluorodeoxyglucose(18F-FDG) maximum standardized uptake value and the expression of Ki-67 in biopsy samples. Sixty-five patients were newly diagnosed with multiple myeloma presenting with EMM at our hospital from January 2005 to January 2015. Of these 65 patients, 20 were enrolled in this study. Over the last decade, both the maximum standardized uptake value and Ki-67 expression in these extramedullary lesions significantly correlated with progression-free survival, respectively (P= .039, P =.009). After combining—the maximum standardized uptake value and the Ki-67 expression as an integral—there was a significant correlation between both the overall survival (P = .027) and progression-free survival (P= .014). Patients have poor outcomes when EMM is detected at presentation. Both the maximum standardized uptake value and Ki-67 expression could aid in accurately evaluating EMM patient prognosis.

MRI versus 18F-FDG-PET/CT for detecting bone marrow involvement in multiple myeloma: diagnostic performance and clinical relevance

PURPOSE

To compare the diagnostic performance of MRI and ¹⁸F-FDG-PET/CT in detecting bone marrow involvement (BMI) in patients with multiple myeloma (MM).

MATERIALS AND METHODS

This retrospective study was approved by our Institutional Review Board. Two radiologists and two nuclear medicine specialists independently and blindly reviewed 84 pairs of MRI and PET/CT scans obtained in 73 MM patients. Readers assessed the presence and patterns of BMI. The best valuable comparator (BVC) for BMI was established by a panel review of all baseline and follow-up imaging, and biological and pathological information. Intra- and inter-reader agreement and correlation between MRI and PET/CT were assessed using the prevalence-adjusted bias-adjusted kappa (k) coefficient. Diagnostic performance of MRI and PET/CT in detecting BMI was evaluated from ROC characteristics. Association between imaging and biological, pathological, and clinical findings was assessed using Wilcoxon rank-sum and chi-square tests.

RESULTS

Intra- and inter-reader agreement was very good for MRI (k = 0.90 [0.81; 1.00] and 0.88 [0.78; 0.98]). Intra- and inter-reader agreement was good for PET/CT (k = 0.80 [0.69; 0.91] and 0.71 [0.56; 0.86]). The sensitivity of MRI to detect BMI (97% [90%; 100%]) was significantly superior to that of PET/CT (76% [64%; 85%]) (p < 0.001). The specificity of MRI (86% [57%; 98%]) was lower than that of PET/CT (93% [66%; 100%]), without reaching statistical significance (p = 0.32). There was a strong correlation between decisions regarding patient management and PET/CT findings (p < 0.001).

CONCLUSION

MRI is significantly more sensitive than PET/CT to detect BMI in MM. Patient management is more strongly correlated with PET/CT findings.

KEY POINTS

• MRI and PET/CT have very close diagnostic value for the detection of bone marrow involvement in multiple myeloma. • MRI has a significantly higher sensitivity and better reproducibility. • PET/CT findings appear to have a higher impact on clinical decisions.

Chemokine receptor-4 targeted PET/CT with 68Ga-Pentixafor in assessment of newly diagnosed multiple myeloma: comparison to 18F-FDG PET/CT

PURPOSE

¹⁸F-FDG PET/CT has some limitations in the evaluation of multiple myeloma (MM). Since chemokine receptor-4 is overexpressed in MM, we perform a prospective cohort study to compare the performance of ⁶⁸Ga-Pentixafor and ¹⁸F-FDG PET/CT in newly diagnosed MM.

METHODS

Thirty patients with newly diagnosed MM were recruited. All patients underwent ⁶⁸Ga-Pentixafor and¹⁸F-FDG PET/CT within 1 week after enrollment. A positive PET/CT was defined as the presence of focal PET-positive lesions in bone marrow or diffuse bone marrow patterns (uptake > liver). Bone marrow uptake values in ⁶⁸Ga-Pentixafor and¹⁸F-FDG PET/CT (total bone marrow glycolysis [TBmG_FDG], total bone marrow uptake with ⁶⁸Ga-Pentixafor [TBmU_CXCR4], total bone marrow volume [TBmV], SUVmean, and SUVmax) were obtained by drawing total bone marrow volume of interest on PET/CT. The positive rates of the PET/CT scans were statistically compared, and the correlation between quantitative bone marrow uptake values and clinical characteristics, laboratory findings, and staging was analyzed.

RESULTS

⁶⁸Ga-Pentixafor PET/CT had a higher positive rate than ¹⁸F-FDG PET/CT in recruited patients (93.3 vs. 53.3%, p = 0.0005). In quantitative analysis, bone marrow uptake values in ⁶⁸Ga-Pentixafor (TBmU_CXCR4, SUVmax, and SUVmean) were positively correlated with end organ damage, staging, and laboratory biomarkers related to tumor burden including serum β2-microglobulin, serum free light chain, and 24-h urine light chain (p < 0.05). In ¹⁸F-FDG PET/CT, only the SUVmean of total bone marrow was positively correlated with serum free light chain and 24-h urine light chain (p < 0.05).

CONCLUSIONS

⁶⁸Ga-Pentixafor PET/CT is promising in assessment of newly diagnosed MM.

TRIAL REGISTRATION NUMBER

NCT03436342.

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.

Imaging and bone marrow assessments improve minimal residual disease prediction in multiple myeloma

The value of minimal residual disease (MRD) status by bone marrow and imaging analysis as independent prognostic factors has been well established in multiple myeloma (MM). Nevertheless data about their potential complementarity for a more accurate assessment are limited. With this aim, we retrospectively analyzed the prediction of outcome with the combination of PET-CT and MRD, assessed by multiparameter flow cytometry (MFC) in 103 patients with newly diagnosed MM. We confirmed the benefit in terms of progression-free survival (PFS), linked to the achievement of negativity by MFC (hazard ratio [HR] 0.53; 95% confidence interval [CI]: 0.28-0.98), and PET-CT (HR 0.18; 95% CI: 0.09-0.36) individually. By combining both techniques, patients who became MRD-/PET-, with a median of PFS 92 months, had significant prolonged median PFS (P < .001). This is compared with MRD+/PET- and PET+ patients (median PFS of 45 and 28 months, respectively). We observed a significant difference (P = .003) in overall survival (OS) outcomes between MRD-/PET- and MRD+/PET- patients (4-year OS 94.2% and 100%, respectively), vs PET+ patients (4-year OS 73.8%). All survival results were confirmed in a conditional landmark analysis. These findings support the potential complementarity between PET-CT and MFC, and highlight their better predictive capability when improving sensitivity.

Long-term clinical outcomes in a cohort of patients with solitary plasmacytoma treated in the modern era

BACKGROUND

The risk of recurrence of solitary plasmacytoma (SP)/progression to MM is well established, but patient, imaging and treatment factors influencing risk of progression require further evaluation.

METHODS

This is a retrospective analysis of 66 SP patients (23 UK, 43 Brazil) diagnosed 1989-2016. Patient baseline characteristics were recorded. The incidence of progression to MM was calculated, including biochemical and imaging findings and the treatment modality received. Survival estimates were determined by Kaplan-Meier analyses.

RESULTS

With a median follow-up of 53.6 months the 5 year overall survival (OS) was 90.7% (95%CI 79-96%). The median progression free survival (PFS) from diagnosis was 61 months. Cumulative incidence of progression to MM was 49.9% at 5 years (95% CI 35.6-62.6%) and was significantly higher with bone plasmacytoma (47.2%, 95%CI 31.9-61.1%), than an extramedullary location (8.3%, 95%CI 0.4-32.3%, Gray test p = 0.0095)). The majority of patients with solitary bony plasmacytoma (SBP) received radiotherapy (RT) (51/53, 96.2%) whereas most extramedullary cases were treated with surgical resection (7/13, 53.8%). A small proportion of SBP patients received additional upfront chemotherapy, with 5/6 in remission after a median follow-up (FU) of 10 years. The diagnostic yield of surveillance functional FU imaging without other indications of relapse/progression was low. The positive predictive value of functional FU imaging was high but with a low negative predictive value, especially in cases of suspected relapse/progression.

CONCLUSION

Our data suggests functional imaging should be used if clinical suspicion of relapse/progression, rather than a routine surveillance tool, and upfront adjuvant chemotherapy is worthy of prospective evaluation.

[PET/CT with 18F-fluorodeoxyglucose and 11C-methionine after autologous stem cell transplantation in multiple myeloma patients]

AIM

to compare the results of tumor visualization when using 18F-FDG and 11C-methionine PET/CT after auto-HSCT in MM patients.

MATERIALS AND METHODS

A prospective study included 27 MM patients subjected to 18F-FDG and 11C-methionine PET/CT on day 100 after auto-HSCT. Obtained images were visually and semi - quantitatively analyzed. Focal areas of increased uptake for every radiopharmaceutical agent (hypermetabolic foci) not associated with its physiological distribution were registered. Maximum Standardized Uptake Values (SUVmax) in pathological foci were automatically calculated for every radiopharmaceutical agent separately. PET/CT findings were compared to antitumor response achieved after auto-HSCT according to International MM Working Group criteria.

RESULTS

After auto-HSCT, the majority of patients (16/60%) achieved a complete response. Abnormal 18F-FDG uptake was registered in 37% (n=10) of patients, negative PET findings were obtained in 63% (n=17) of patients. 11C-methionine PET/CT revealed hypermetabolic foci in 67% (n=18) of patients, and there was no 11C-methionine uptake in 33% (n=9). Pathological foci of radiopharmaceutical agent uptake were 1.8 times more frequently revealed using PET/CT with 11C-methionine (p.

Outcome of paraosseous extra-medullary disease in newly diagnosed multiple myeloma patients treated with new drugs

Extramedullary disease is relatively frequent in multiple myeloma, but our knowledge on the subject is limited and mainly relies on small case series or single center experiences. Little is known regarding the role of new drugs in this setting. We performed a meta-analysis of eight trials focused on the description of extramedullary disease characteristics, clinical outcome, and response to new drugs. A total of 2,332 newly diagnosed myeloma patients have been included; 267 (11.4%) had extramedullary disease, defined as paraosseous in 243 (10.4%), extramedullary plasmocytoma in 12 (0.5%), and not classified in 12 (0.5%) patients. Median progression-free survival was 25.3 months and 25.2 in extramedullary disease and non-extramedullary disease patients, respectively. In multivariate analysis the presence of extramedullary disease did not impact on progression-free survival (hazard ratio 1.15, P=0.06), while other known prognostic factors retained their significance. Patients treated with immunomodulatory drugs, mainly lenalidomide, or proteasome inhibitors had similar progression-free survival and progression-free survival-2 regardless of extramedullary disease presence. Median overall survival was 63.5 months and 79.9 months (P=0.01) in extramedullary and non-extramedullary disease patients, respectively, and in multivariate analysis the presence of extramedullary disease was associated with a reduced overall survival (hazard ratio 1.41, P<0.001), in line with other prognostic factors. With the limits of the use of low sensitivity imaging techniques, that lead to an underestimation of extramedullary disease, we conclude that in patients treated with new drugs the detrimental effect of extramedullary disease at diagnosis is limited, that lenalidomide is effective as are proteasome inhibitors, and that these patients tend to acquire a more aggressive disease in later stages. (EUDRACT2005-004714-32, NCT01063179 NCT00551928, NCT01091831, NCT01093196, NCT01190787, NCT01346787, NCT01857115).

18F-fluoro-ethyl-tyrosine (18F-FET) PET/CT as a potential new diagnostic tool in multiple myeloma: a preliminary study

Aim of the study

The aim of this study was to analyse the diagnostic accuracy of ^“18F-fluoro-ethyl-tyrosine (¹⁸F-FET) PET/CT tracer in multiple myeloma.

Material and methods

The analysed group included: patients with newly diagnosed active myeloma (eight patients); in very good partial remission or complete remission (VGPR or CR) after treatment (nine patients); and with active disease after relapse (15 patients).

Results

In patients with newly diagnosed myeloma, 64 lesions were found using CT and 83 lesions using ¹⁸F-FET. In six patients, the number of lesions using CT and ¹⁸F-FET was the same, and two had more lesions with the ¹⁸F-FET than with the CT. Patients in VGPR or CR had no FET-positive lesions. Fourteen out of 15 patients with active relapsed myeloma had 47 FET-positive lesions, CT assessment of the same group showed 282 lesions. In one patient with relapse soft tissue mass was found with ¹⁸F-FET but not with CT.

Conclusions

¹⁸F-FET can be a promising alternative to ¹⁸F-FDG PET/CT for myeloma-related bone disease diagnosis.

Extramedullary disease in multiple myeloma - controversies and future directions

Extramedullary disease of multiple myeloma (EM) remains a treatment challenge even in the era of new drugs. While many reports analyzing various aspects of EM have been published, mechanism of EM development has not been clarified yet. This review summarizes current knowledge about this clinical entity, including its history, diagnostics, imaging methods, incidence, prognosis, current treatment options, risk factors and known molecular mechanisms that might be involved in pathogenesis of EM.

Fludeoxyglucose F 18 PET/Computed Tomography Evaluation of Therapeutic Response in Multiple Myeloma

Multiple myeloma is a malignancy of terminally differentiated plasma cells representing the second most common hematological malignancy. The recognition that disease outside the marrow can significantly influence the outcome of patients has highlighted the importance of imaging to define presence of tumor. Recent studies have demonstrated an added value of using imaging to assess presence of disease both inside and outside the marrow. To this end, the response criteria have been revised to include PET/computed tomography to be used in conjunction with bone marrow assessment to determine minimal residual disease status.

PET with Fluorodeoxyglucose F 18/Computed Tomography as a Staging Tool in Multiple Myeloma

In the past decade novel treatment options have dramatically prolonged the survival of patients with multiple myeloma. PET combined with computed tomography (CT) is a sensitive and reliable functional imaging tool that enables diagnosis and assessment of response to chemotherapy/radiotherapy, and combines high sensitivity in identifying both lytic lesions and extramedullary soft-tissue masses with the ability to provide reliable prognostic information in the management of patients with myeloma. This review comprises a comprehensive overview of PET with fluorodeoxyglucose F 18/CT imaging in combination with other convenient imaging procedures, and attempts at standardization with emphasis on post-therapy findings in patients with myeloma.

Interest of Pet Imaging in Multiple Myeloma

The interest of 18Fluoro-deoxyglucose (FDG) positron emission tomography (PET) imaging in the management of patients with multiple myeloma (MM) for the workup at diagnosis and for therapeutic evaluation has recently been demonstrated. FDG-PET is a powerful imaging tool for bone lesions detection at initial diagnosis with high sensitivity and specificity values. The independent pejorative prognostic value on progression-free survival (PFS) and overall survival (OS) of baseline PET-derived parameters (presence of extra-medullary disease (EMD), number of focal bone lesions (FLs), and maximum standardized uptake values [SUV_max]) has been reported in several large independent prospective studies. During therapeutic evaluation, FDG-PET is considered as the reference imaging technique, because it can be performed much earlier than MRI which lacks specificity. Persistence of significant FDG uptake after treatment, notably before maintenance therapy, is an independent pejorative prognostic factor, especially for patients with a complete biological response. So FDG-PET and medullary flow cytometry are complementary tools for detection of minimal residual disease before maintenance therapy. However, the definition of PET metabolic complete response should be standardized. In patients with smoldering multiple myeloma, the presence of at least one hyper-metabolic lytic lesions on FDG-PET may be considered as a criterion for initiating therapy. FDG-PET is also indicated for initial staging of a solitary plasmacytoma so as to not disregard other bone or extra-medullary localizations. Development of nuclear medicine offer new perspectives for MM imaging. Recent PET tracers are willing to overcome limitations of FDG. (11)C-Methionine, which uptake reflects the increased protein synthesis of malignant cells seems to correlate well with bone marrow infiltration. Lipid tracers, such as Choline or acetate, and some peptide tracers, such as (68) Ga-Pentixafor, that targets CXCR4 (chemokine receptor-4, which is often expressed with high density by myeloma cells), are other promising PET ligands. 18F-fludarabine and immuno-PET targeting CD138 and CD38 also showed promising results in preclinical models.

Dual-tracer PET/CT scan after injection of combined [18 F]NaF and [18 F]FDG outperforms MRI in the detection of myeloma lesions

The detection rates of whole-body combined [¹⁸ F]NaF/[¹⁸ F]FDG positron emission tomography combined with computed tomography (PET/CT), CT alone, whole-body magnetic resonance imaging (WB-MRI), and X-ray were prospectively studied in patients with treatment-requiring plasma cell disorders The detection rates of imaging techniques were compared, and focal lesions were classified according to their anatomic location. Twenty-six out of 30 initially included patients were assessable. The number of focal lesions detected in newly diagnosed patients (n = 13) and in relapsed patients (n = 13) were 296 and 234, respectively. The detection rate of PET/CT was significantly higher than those of WB-MRI (P < 0.05) and CT (P < 0.0001) both in patients with newly diagnosed and in those with relapsed multiple myeloma (MM). The X-ray detection rate was significantly lower than those of all other techniques, while CT detected more lesions compared with WB-MRI at diagnosis (P = 0.025). With regard to the infiltration patters, relapsed patients presented more diffuse patterns, and more focal lesions located in the limbs compared with newly diagnosed patients. In conclusion, the detection rate of [¹⁸ F]NaF/[¹⁸ F]FDG PET/CT was significantly higher than those of CT, MRI, and X-ray, while the detection rate of X-rays was significantly lower than those of all other imaging techniques except for focal lesions located in the skull.

Combination bone marrow imaging using positron emission tomography (PET)-MRI in plasma cell dyscrasias: correlation with prognostic laboratory values and clinicopathological diagnosis

Objective

This prospective observational study of positron emission tomography (PET)-MRI findings in 16 consecutive newly diagnosed patients with a plasma cell dyscrasia describes and compares MRI-detected myeloma lesions with ¹⁸F-fludeoxyglucose PET-avid myeloma lesions, and correlates quantitative imaging findings to a range of biochemical and prognostic parameters.

Methods

Simultaneously acquired whole body PET and MRI images were evaluated qualitatively for the presence of focal or generalised abnormalities of bone marrow (BM) on either modality. Quantitative analysis comprised mean standardised uptake values (SUVmean) and fractional water content of the BM measured from PET and chemical shift MRI images of the second to fourth lumbar vertebrae.

Results

Final diagnoses comprised symptomatic myeloma (n = 10), asymptomatic myeloma (n = 4) and monoclonal gammopathy of uncertain significance (n = 2). 8/10 patients with symptomatic myeloma demonstrated BM abnormalities on qualitative assessment of MRI compared to 4/10 on PET. BM SUVmean inversely correlated with serum albumin (r = 0.57, p = 0.017). BM water fraction correlated with trephine cellularity and blood platelet count (r = 0.78, p = 0.00039 and r = 0.61, p = 0.0013 respectively). BM water fraction correlated with SUVmean in patients with low plasma cell burden (r = 0.91, p = 0.0015) but not in patients with high plasma cell burden (r = 0.18, p = 0.61).

Conclusion

PET-MRI shows promise in both morphological and functional multiparametric quantitative assessment of myeloma.

Advances in knowledge

For the first time, multiparametric imaging in myeloma has been shown to predict BM abnormalities and correlate with known biochemical prognostic markers, moving PET-MRI beyond simple diagnostic applications into potential prognostic and treatment selection applications.