Nuclear medicine imaging of multiple myeloma, particularly in the relapsed setting

Molecular imaging of bone metastasis

Recent advances in molecularly targeted modular designs for in vivo imaging applications has thrusted open possibilities of investigating deep molecular interactions non-invasively and dynamically. The shifting landscape of biomarker concentration and cellular interactions throughout pathological progression requires quick adaptation of imaging agents and detection modalities for accurate readouts. The synergy of state of art instrumentation with molecularly targeted molecules is resulting in more precise, accurate and reproducible data sets, which is facilitating investigation of several novel questions. Small molecules, peptides, antibodies and nanoparticles are some of the commonly used molecular targeting vectors that can be applied for imaging as well as therapy. The field of theranostics, which encompasses joint application of therapy and imaging, is successfully leveraging the multifunctional use of these biomolecules [[1], [2]]. Sensitive detection of cancerous lesions and accurate assessment of treatment response has been transformative for patient management. Particularly, since bone metastasis is one of the dominant causes of morbidity and mortality in cancer patients, imaging can be hugely impactful in this patient population. The intent of this review is to highlight the utility of molecular positron emission tomography (PET) imaging in the context of prostate and breast bone metastatic cancer, and multiple myeloma. Furthermore, comparisons are drawn with traditionally utilized bone scans (skeletal scintigraphy). Both these modalities can be synergistic or complementary for assessing lytic- and blastic- bone lesions.

Recent developments on the application of molecular probes in multiple myeloma: Beyond [18F]FDG

Multiple myeloma (MM) is a neoplastic plasma cell proliferative disorder characterized by various osteolytic bone destruction as a radiological morphological marker. Functional imaging, particularly nuclear medicine imaging, is a promising method to visualize disease processes before the appearance of structural changes by targeting specific biomarkers related to metabolism ability, tumor microenvironment as well as neoplastic receptors. In addition, by targeting particular antigens with therapeutic antibodies, immuno-PET imaging can support the development of personalized theranostics. At present, various imaging agents have been prepared and evaluated in MM at preclinical and clinical levels. A summary overview of molecular functional imaging in MM is provided, and commonly used radiotracers are characterized.

[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.

Comparison between tumour metabolism derived from 18F-FDG PET/CT and accurate cytogenetic stratification in newly diagnosed multiple myeloma patients

Background

¹⁸F-fluorodeoxyglucose positron emission tomography integrated with computed tomography (¹⁸F-FDG PET/CT) is a useful tool for baseline staging in newly diagnosed multiple myeloma (MM) but also for prognostic stratification. This monocentric retrospective study aimed at examining the relation between baseline tumour metabolism assessed by ¹⁸F-FDG PET/CT and linear predictor (LP) score, a new cytogenetic stratification score.

Methods

From March 2012 to March 2019, 57 patients with newly diagnosed MM addressed to our institution for baseline ¹⁸F-FDG PET/CT were included. LP score was determined on systematic iliac crest bone marrow samples. Obtained on CD138-sorted bone marrow plasma cells, this recent composite cytogenetic stratification is a 6-marker based weighted score using fluorescence in situ hybridization (FISH) ± single nucleotide polymorphism (SNP) arrays. We compared quantitative metabolic parameters and LP score using a Kruskal-Wallis test and visual suspicion of diffuse bone marrow involvement (DBI; based on hepatic background as threshold of positivity) and cytogenetic data using a Chi-squared test.

Results

The distribution of total metabolic tumour volume (TMTV) and total lesion glycolysis (TLG) values among the three LP score categories was almost stochastic, with no significant association (P=0.70). Additionally, no significant association between TMTV/TLG and any of the six cytogenetic abnormalities included in LP score calculation. A significant association was found between visual high suspicion of DBI and LP score (P=0.036), and between this visual parameter and the presence of 1q gain (P=0.049).

Conclusions

There is no significant association between quantitative metabolic parameters assessed with ¹⁸F-FDG PET/CT and LP score in patients with newly diagnosed MM, suggesting a potential complementarity of these biomarkers for prognostic stratification. A significant association was found between high visual suspicion of DBI and LP score.

Agreement Between 18F-FDG PET/CT and Whole-Body Magnetic Resonance Compared With Skeletal Survey for Initial Staging and Response at End-of-Treatment Evaluation of Patients With Multiple Myeloma

PURPOSE

To compare the agreement between whole-body (WB) magnetic resonance (MR) imaging, 18F-FDG PET/CT, and skeletal survey (SS) in patients with multiple myeloma (MM) for diagnosis, initial staging, response evaluation, and early detection of complications.

METHODS

This is a retrospective cohort study including MM patients who were diagnosed, treated, and followed in 2 institutions. These patients were studied with SS, WB-MR, and/or 18F-FDG PET/CT. We studied bone lesions by anatomical locations and analyzed the concordance between SS and a tomographic technique (WB-MR or 18F-FDG PET/CT) and between both tomographic techniques (WB-MR and PET/CT).

RESULTS

Forty-four MM patients with a mean age of 62.6 years (range, 38-85 years) were included from January 2012 to February 2016. Whole-body MR and 18F-FDG PET/CT found more lesions than SS in every location except in the skull. Concordance between WB-MR and 18F-FDG PET/CT was either good or excellent in most of the locations and in plasmacytoma studies. However, WB-MR was better than 18F-FDG PET/CT in the study of complications (medullar compression and vascular necrosis).

CONCLUSIONS

Our results suggest the study of MM patients should include WB-MR and/or 18F-FDG PET/CT, whereas SS is only useful for the skull. Whole-body MR and 18F-FDG PET/CT are complementary techniques, because both of them show good concordance in almost every location. It is still necessary to individualize the indication of each technique according to patient characteristics.

Expression and pathogenesis of VCAM-1 and VLA-4 cytokines in multiple myeloma

Objective

The objective of this study is to investigate the expression of Vascular cell adhesion molecule-1 (VCAM-1) and very late appearing antigen-4 (VLA-4) cytokines in MM (multiple Myeloma).

Method

Forty patients with MM are selected as the experimental group and 30 healthy persons as the control group. Flow cytometry is used to detect the expression of VCAM-1 (CD106), VLA-4 (CD49d), CD38 and CD138 antigens in experimental group and control group. ELISA (Enzyme Linked Immunosorbent Assay) is used to detect the concentration of VCAM-1 in serum of experimental group and control group. RT-PCR is used to detect the expression of VCAM-1.

Results

The positive rate and antigen expression rate of VACM-1 antigen in the experimental group were significantly higher than those in the control group (P < 0.05). There were statistical differences of VLA-4 and VCAM-1 antigens between the initial diagnosis group and the relapse/refractory group, and between the relapse/refractory group and the platform stage group (P < 0.05). There were significant differences between VLA-4 antigen and VACM-1 antigen, phase I and phase II, and between phase I and phase III (P < 0.05). The concentration of VCAM-1 and the expression of VCAM-1 mRNA in the experimental group were significantly higher than (P < 0.01). In the different stages of ISS (International Staging System) and different disease groups in the experimental group, the concentration of VCAM-1 and the expression level of VCAM-1 mRNA are significantly different among the three groups of stage I, II and III (P < 0.01). There is a significant difference between the initial diagnosis group, the relapse/refractory group and the platform group (P < 0.05).

Conclusion

There are abnormal expressions of adhesion molecules VCAM-1 and VLA-4 in multiple myeloma patients, which are related to ISS staging.

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.

Imaging Characteristics of Coexisting Primary Pulmonary Carcinoid Tumor and Multiple Myeloma on 18F-FDG and 68Ga-DOTATATE PET/CT

A 69-year-old man with recurrent multiple myeloma underwent FDG PET/CT evaluation. A pulmonary nodule without higher-than-background FDG avidity was later biopsied as a low-grade neuroendocrine tumor. On further Ga-DOTATATE PET/CT evaluation of patient's neuroendocrine tumor, the lytic myeloma lesions revealed only mild DOTATATE avidity while the primary pulmonary neuroendocrine tumor showed intense DOTATATE uptake. The distinct imaging characteristics of different primary malignancies correlated with their underlying different pathology.

ImmunoPET imaging of CD38 in murine lymphoma models using 89Zr-labeled daratumumab

PURPOSE

CD38 is considered a potential biomarker for multiple myeloma (MM) and has shown a strong link with chronic lymphocytic leukemia due to high and uniform expression on plasma cells. In vivo evaluation of CD38 expression may provide useful information about lesion detection and prognosis of treatment in MM. In this study, immunoPET imaging with ⁸⁹Zr-labeled daratumumab was used for differentiation of CD38 expression in murine lymphoma models to provide a potential non-invasive method for monitoring CD38 in the clinic.

METHODS

Daratumumab was radiolabeled with ⁸⁹Zr (t_1/2 = 78.4 h) via conjugation with desferrioxamine (Df). After Western blot (WB) was used to screen CD38 expression in five lymphoma cell lines, flow cytometry and cellular binding assays were performed to test the binding ability of labeled or conjugated daratumumab with CD38 in vitro. PET imaging and biodistribution studies were performed to evaluate CD38 expression after injection of ⁸⁹Zr-Df-daratumumab. ⁸⁹Zr-Df-IgG was also evaluated as a non-specific control group in the Ramos model. Finally, CD38 expression in tumor tissues was verified by histological analysis.

RESULTS

Using WB screening, the Ramos cell line was found to express the highest level of CD38 while the HBL-1 cell line had the lowest expression. Df-conjugated and ⁸⁹Zr-labeled daratumumab displayed similar high binding affinities with Ramos cells. PET imaging of ⁸⁹Zr-Df-daratumumab showed a high tumor uptake of up to 26.6 ± 8.0 %ID/g for Ramos at 120 h post-injection, and only up to 6.6 ± 2.9 %ID/g for HBL-1 (n = 4). Additionally, ⁸⁹Zr-Df-IgG demonstrated a low tumor uptake in the Ramos model (only 4.3 ± 0.8 %ID/g at 120 h post-injection). Ex vivo biodistribution studies showed similar trends with imaging results. Immunofluorescence staining of tumor tissues verified higher CD38 expression of Ramos than that of HBL-1.

CONCLUSIONS

The role of ⁸⁹Zr-Df-daratumumab was investigated for evaluating CD38 expression in lymphoma models non-invasively and was found to be to a promising imaging agent of CD38-positive hematological diseases such as MM in future clinical applications.

The Critical Role of Imaging in the Management of Multiple Myeloma

Multiple myeloma (MM) is characterized by abnormal proliferation of plasma cells in the bone marrow leading to symptoms of anemia, renal failure, hypercalcemia, and bone lesions. Bone imaging is critical for the diagnosis, staging, assessment for the presence and extent of bone lesions, and initial treatment of MM. Skeletal survey is the preferred initial imaging modality due to its availability and low cost. However, it has poor sensitivity and patients with occult myeloma may escape detection, delaying their diagnosis and treatment. New cross-sectional imaging modalities such as low-dose whole body CT, MRI, and PET-CT have high sensitivity and specificity for detecting lytic lesions and extramedullary relapse in MM. The combined use of cross-sectional imaging may provide complimentary information for staging, prognosis, and disease monitoring. In this review, we will discuss commonly used imaging modalities and their advantages and disadvantages in the management of MM.

Multiple Extramedullary Plasmacytoma in a Setting of Complete Bone Marrow Remission: Food for Thought

Extramedullary plasmacytoma as a mode of relapse in multiple myeloma (MM) is unusual. Current recommendations do not incorporate the routine use of 18-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET/CT) imaging prior to haematopoietic stem cell transplant (HSCT) in MM. We report a case of relapsed MM with complete remission as per IMWG criteria. In the interim period, before the HSCT, the patient had localizing neurological signs and symptoms attributed to multiple extramedullary plasmacytomas. The uniqueness of this case is that this patient after complete marrow remission with no obvious external masses had unexpected, symptomatic multiple extramedullary plasmacytomas. This case illustrates the need for integration of FDG PET/CT imaging into routine pre-HSCT investigations in relapsed MM to prevent missing any asymptomatic extramedullary plasmacytomas.