18 FDG-PET/CT for prognostic stratification of patients with multiple myeloma relapse after stem cell transplantation

Clinical impact of [18F]FDG-PET/CT in ARI0002h treatment, a CAR-T against BCMA for relapsed/refractory multiple myeloma

ABSTRACT

Multiple myeloma (MM) remains incurable, with poor outcomes in heavily pretreated patients. Chimeric antigen receptor (CAR) T-cell therapy has emerged as a promising treatment; however, outcomes after such therapy in patients with soft-tissue plasmacytomas and other bone lesions remain poorly understood. This study included 63 patients with relapsed/refractory MM treated either in the CARTBCMA-HCB-01 clinical trial (ARI0002h; academic B-cell maturation antigen [BCMA]-targeted CAR T-cell therapy) or in compassionate use. The aim was to evaluate the impact of soft-tissue involvement (extramedullary [EMD] and paraskeletal [PS] plasmacytomas) in response, survival and safety. Baseline [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) from 5 participating centers were reviewed centrally. Of 63 patients, 52.4% presented plasmacytomas at the time of inclusion (21 PS, exclusively; and 12 EMD). Per responses, there were no significant differences between patients with and without plasmacytomas. A correlation was present between International Myeloma Working Group responses and those obtained by [18F]FDG-PET/CT at day 100 (Bologna criteria). No differences were observed in progression-free survival (PFS) or overall survival (OS) between patients with or without plasmacytomas. However, both PFS and OS were significantly shorter in patients with EMD. Interestingly, [18F]FDG-PET/CT response assessed on day 100, in accordance with the Bologna criteria, was predictive of survival outcomes. A metabolic tumor volume of ≥25 cm3 at baseline [18F]FDG-PET/CT was associated with earlier disease progression and shorter OS. These results highlight the importance of EMD evaluation by [18F]FDG-PET/CT before and after CAR T-cell infusion. This trial was registered at www.ClinicalTrials.gov as #NCT04309981; and EudraCT, 2019-001472-11.

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

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

Prognostic value of 18F-FDG PET/CT in patients with relapsed multiple myeloma

This study aimed to assess the prognostic value of 18F-fluorodeoxyglucose positron emission tomography/computer tomography (18F-FDG PET/CT) in patients with relapsed multiple myeloma (MM). Fifty-one consecutive patients with relapsed MM were enrolled in this retrospective study. 18F-FDG parameters based on the Italian Myeloma Criteria for PET Use (IMPeTUs) and clinical data were analyzed for overall survival (OS) and progression-free survival (PFS). The Cox proportional risk model was used for univariate and multivariate analysis, and Kaplan-Meier survival curves were used for survival analysis. The median length of follow-up was 20 months (IQR, 5-29 months), the median PFS for the entire cohort was 8 months (IQR, 3-17 months) and the median OS was 21 months (IQR, 8-49 months). Multivariate survival analysis demonstrated that the Deauville score of BM > 3 [HR 2.900, 95% CI (1.011, 8.319), P = 0.048] and the presence of EMD [HR 3.134, 95% CI (1.245, 7.891), P = 0.015] were independent predictors of poor PFS. The presence of EMD [HR 12.777, 95% CI (1.825, 89.461), P = 0.010] and the reduced platelets count [HR 7.948, 95% CI (1.236, 51.099), P = 0.029] were adversely associated with OS. 18F-FDG PET/CT parameters based on IMPeTUs have prognostic significance in patients with relapsed MM.

Prognostic significance of extramedullary disease (EMD) detected on pre-transplant 18F-FDG PET/CT in patients with multiple myeloma: Results of PIPET-M trial

Background

It is difficult to prognosticate the post-Autologous Stem Cell Transplant (ASCT) responses in multiple myeloma (MM) with the currently available prognostication models. 18F-FDGPET/CT has numerous advantages to prognosticate the post-transplant responses by assessing extramedullary disease (EMD) in addition to the extent of active disease. We aimed at identifying the prognostic value of EMD in predicting progression-free survival (PFS) and overall survival (OS).

Methods

This is a single centre prospective study from western India during a study period of 2014-2022 (with a median follow-up of patients of 6 years). All ASCT patients underwent 18F-FDG-PET/CT as part of pre-transplant workup. The conditioning and treatment protocols were not modified based on PET/CT findings. EMD on PET/CT was correlated with pre-transplant biochemical markers and post-ASCT survival/ progression (as defined by revised IMWG criteria). Statistical analysis was done using SPSS ver. 20.

Results

Patients with pre-ASCT EMD had a hazard-ratio for post-transplant all-cause mortality of 5.46 (p-0.045). Pre-transplant β2M and LDH were significantly higher in patients with EMD (p-0.036). The 6-year median OS in patients with and without EMD were 57.1%, and 80.6% respectively. Kaplan-Meier analysis showed poorer OS in patients with EMD χ2 (1-0.496, p-0.481). There was no significant difference in clinical or biochemical EFS among patients with EMD.

Conclusion

EMD detected on 18F-FDG-PET/CT has a higher hazard for mortality and is significantly correlated with pre-transplant higher β2M and LDH levels. Thus, EMD by pre-transplant 18F-FDG-PET/CT has a significant prognostic role.

New Developments in Myeloma Treatment and Response Assessment

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

Clinical Value of FDG-PET/CT in Multiple Myeloma: An Update

FDG-PET/CT is a standardized imaging technique that has reached a great importance in the management of patients affected by Multiple Myeloma. It is proved, in fact, that it allows a deep evaluation of therapy efficacy and provides several prognostic indexes both at staging and after therapy. For this reason, it is now recognised as a gold standard for therapy assessment. Beside this, in reacent years FDG-PET/CT contribution to the understanding of Multiple Myeloma has progressively grown. Papers have been published analyzing the prognostic value of active disease volume measurement and standardization issues, the meaning of FDG positive paramedullary and extrameduallary disease, the prognostic impact of FDG positive minimal residual disease, the relation between focal lesions and clonal eterogenity of this disease and the comparison with whole body DWI-MR in terms of detection and therapy assessment. These newer aspects not of clinical impact yet, of FDG-PET/CT in Multiple Myeloma will be presented and discussed in this review.

Deep Brain Stimulation in the Subthalamic Nucleus Can Improve Skilled Forelimb Movements and Retune Dynamics of Striatal Networks in a Rat Stroke Model

Recovery of upper limb (UL) impairment after stroke is limited in stroke survivors. Since stroke can be considered as a network disorder, neuromodulation may be an approach to improve UL motor dysfunction. Here, we evaluated the effect of high-frequency stimulation (HFS) of the subthalamic nucleus (STN) in rats on forelimb grasping using the single-pellet reaching (SPR) test after stroke and determined costimulated brain regions during STN-HFS using 2-[18F]Fluoro-2-deoxyglucose-([18F]FDG)-positron emission tomography (PET). After a 4-week training of SPR, photothrombotic stroke was induced in the sensorimotor cortex of the dominant hemisphere. Thereafter, an electrode was implanted in the STN ipsilateral to the infarction, followed by a continuous STN-HFS or sham stimulation for 7 days. On postinterventional day 2 and 7, an SPR test was performed during STN-HFS. Success rate of grasping was compared between these two time points. [18F]FDG-PET was conducted on day 2 and 3 after stroke, without and with STN-HFS, respectively. STN-HFS resulted in a significant improvement of SPR compared to sham stimulation. During STN-HFS, a significantly higher [18F]FDG-uptake was observed in the corticosubthalamic/pallidosubthalamic circuit, particularly ipsilateral to the stimulated side. Additionally, STN-HFS led to an increased glucose metabolism within the brainstem. These data demonstrate that STN-HFS supports rehabilitation of skilled forelimb movements, probably by retuning dysfunctional motor centers within the cerebral network.

Reduced splenic uptake on 68Ga-Pentixafor-PET/CT imaging in multiple myeloma - a potential imaging biomarker for disease prognosis

Beyond being a key factor for tumor growth and metastasis in human cancer, C-X-C motif chemokine receptor 4 (CXCR4) is also highly expressed by a number of immune cells, allowing for non-invasive read-out of inflammatory activity. With two recent studies reporting on prognostic implications of the spleen signal in diffusion-weighted magnetic resonance imaging in patients with plasma cell dyscrasias, the aim of this study was to correlate splenic ⁶⁸Ga-Pentixafor uptake in multiple myeloma (MM) with clinical parameters and to evaluate its prognostic impact.

Methods: Eighty-seven MM patients underwent molecular imaging with ⁶⁸Ga-Pentixafor-PET/CT. Splenic CXCR4 expression was semi-quantitatively assessed by peak standardized uptake values (SUV_peak) and corresponding spleen-to-bloodpool ratios (TBR) and correlated with clinical and prognostic features as well as survival parameters.

Results:⁶⁸Ga-Pentixafor-PET/CT was visually positive in all MM patients with markedly heterogeneous tracer uptake in the spleen. CXCR4 expression determined by ⁶⁸Ga-Pentixafor-PET/CT corresponded with advanced disease and was inversely associated with the number of previous treatment lines as compared to controls or untreated smouldering multiple myeloma patients (SUV_peakSpleen 4.06 ± 1.43 vs. 6.02 ± 1.16 vs. 7.33 ± 1.40; P < 0.001). Moreover, reduced splenic ⁶⁸Ga-Pentixafor uptake was linked to unfavorable clinical outcome. Patients with a low SUV_peakSpleen (<3.35) experienced a significantly shorter overall survival of 5 months as compared to 62 months in patients with a high SUV_peakSpleen >5.79 (P < 0.001). Multivariate Cox analysis confirmed SUV_peakSpleen as an independent predictor of survival (HR 0.75; P = 0.009).

Conclusion: These data suggest that splenic ⁶⁸Ga-Pentixafor uptake might provide prognostic information in pre-treated MM patients similar to what was reported for diffusion-weighted magnetic resonance imaging. Further research to elucidate the underlying biologic implications is warranted.

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.

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.

Changes of cerebral network activity after invasive stimulation of the mesencephalic locomotor region in a rat stroke model

Motor deficits after stroke reflect both, focal lesion and network alterations in brain regions distant from infarction. This remote network dysfunction may be caused by aberrant signals from cortical motor regions travelling via mesencephalic locomotor region (MLR) to other locomotor circuits. A method for modulating disturbed network activity is deep brain stimulation. Recently, we have shown that high frequency stimulation (HFS) of the MLR in rats has restored gait impairment after photothrombotic stroke (PTS). However, it remains elusive which cerebral regions are involved by MLR-stimulation and contribute to the improvement of locomotion. Seventeen male Wistar rats underwent photothrombotic stroke of the right sensorimotor cortex and implantation of a microelectrode into the right MLR. 2-[¹⁸F]Fluoro-2-deoxyglucose ([¹⁸F]FDG)-positron emission tomography (PET) was conducted before stroke and thereafter, on day 2 and 3 after stroke, without and with MLR-HFS, respectively. [¹⁸F]FDG-PET imaging analyses yielded a reduced glucose metabolism in the right cortico-striatal thalamic loop after PTS compared to the state before intervention. When MLR-HFS was applied after PTS, animals exhibited a significantly higher uptake of [¹⁸F]FDG in the right but not in the left cortico-striatal thalamic loop. Furthermore, MLR-HFS resulted in an elevated glucose metabolism of right-sided association cortices related to the ipsilateral sensorimotor cortex. These data support the concept of diaschisis i.e., of dysfunctional brain areas distant to a focal lesion and suggests that MLR-HFS can reverse remote network effects following PTS in rats which otherwise may result in chronic motor symptoms.

Favorable Long-Term Outcomes with Autologous Stem Cell Transplantation for High-Risk Multiple Myeloma Patients with a Positive Result On 18F-FDG PET/CT at Baseline

BACKGROUND

18F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) is a useful tool for identifying high-risk features in patients with newly diagnosed multiple myeloma (NDMM). This study evaluated the role of autologous stem cell transplantation (ASCT) in patients presenting with positive results on PET/CT scans.

MATERIALS AND METHODS

The medical records of 210 patients who underwent PET/CT at diagnosis were retrospectively reviewed. Eligible patients for transplantation proceeded to upfront ASCT with high-dose chemotherapy (HDT) after induction therapy with novel agents.

RESULTS

The presence of a number of focal lesions (FL) >3 and extramedullary disease (EMD) occurred in 111 and 35 patients, respectively. ASCT was performed in 54 patients. Among patients with FL > 3, those treated with ASCT showed a prolonged 2-year progression-free survival (PFS) and overall survival (OS) rates compared to those not treated with ASCT (PFS, 60.2% vs. 23.5%, P < 0.001; OS, 91.7% vs. 63.6%, P = 0.005). In patients with FL ≤ 3, treatment by ASCT was associated with a higher 2-year PFS rate than no treatment by ASCT (74.0% vs. 54.9%, P = 0.040). The OS of patients treated with ASCT was not significantly longer than that of patients not treated with ASCT (P = 0.115). In multivariate analysis, FL > 3, Revised International Staging System (R-ISS), and upfront ASCT were independent prognostic factors for PFS and OS.

CONCLUSION

Presenting FL > 3 on baseline PET/CT represents a high-risk feature in patients with NDMM. Frontline ASCT with HDT prolonged the survival of patients with FL > 3.

Prognostic Value of FDG-PET/CT Parameters in Patients with Relapse/Refractory Multiple Myeloma before Anti-CD38 Based Therapy

Although anti-CD38 monoclonal antibodies have improved the prognosis of relapsed/refractory multiple myeloma (RRMM), some patients still experience early relapses with poor outcomes. This present study evaluated the predictive value of FDG PET/CT parameters for RRMM prior to initiating anti-CD38 treatment. We included 38 consecutive RRMM patients who underwent a PET/CT scan treated at our institution at relapse. The median PFS was 12.5 months and the median OS was not reached. 42% of the patients had an initial ISS score of 1, 37% of 2, and 21% of 3. The presence of >3 focal lesions (FLs, n = 19) and the ISS score were associated with inferior PFS (p = 0.0036 and p = 0.0026) and OS (p = 0.025 and p = 0.0098). Patients with >3 FLs had a higher initial ISS score (p = 0.028). In multivariable analysis, the ISS score and >3 FLs were independent prognostic factors for PFS (p = 0.010 and p = 0.025 respectively), and combined they individualized a high-risk group with a median PFS and OS of 3.1 months and 8.5 months respectively vs. not reached for the other patients. The presence of >3 FLs on PET was predictive of survival outcomes in patients with RRMM treated using CD38 targeted therapy. Combined with the initial ISS, an ultra-high-risk RRMM population can thus be identified.

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.

Identifying CD38+ cells in patients with multiple myeloma: first-in-human imaging using copper-64-labeled daratumumab

18F-Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is one of the most widely used imaging techniques to detect multiple myeloma (MM). Intracellular FDG uptake depicts in vivo metabolic activity, which can be seen in both malignant and nonmalignant cells, resulting in limited sensitivity and specificity. Our group showed preclinically that tracing MM dissemination using a CD38-directed human antibody, daratumumab, that is radioconjugated with 64Cu via the chelator DOTA (64Cu-daratumumab), led to improved sensitivity and specificity over that of FDG. Here, we report the results of a phase 1 trial designed to (1) assess the safety and feasibility of 64Cu-daratumumab PET/CT and (2) preliminarily evaluate and characterize the ability of 64Cu-daratumumab to accurately detect or exclude MM lesions. A total of 12 daratumumab-naive patients were imaged. Prior to the injection of 15 mCi/5 mg of 64Cu-daratumumab, patients were treated with 0 (n = 3), 10 (n = 3), 45 (n = 3), or 95 mg (n = 3) of unlabeled daratumumab to assess its effect on image quality. No significant adverse events were observed from either unlabeled daratumumab or 64Cu-daratumumab. Of the dose levels tested, 45 mg unlabeled daratumumab was the most optimal in terms of removing background signal without saturating target sites. 64Cu-daratumumab PET/CT provided safe whole-body imaging of MM. A trial comparing the sensitivity and specificity of 64Cu-daratumumab PET/CT with that of FDG PET/CT is planned. This trial was registered at www.clinicaltrials.gov as #NCT03311828.

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.

99mTc-sestamibi SPECT/CT and 18F-FDG-PET/CT have similar performance but different imaging patterns in newly diagnosed multiple myeloma

PURPOSE

F-fluorodeoxiglucose (F-FDG)-PET/CT has been widely used to evaluate multiple myeloma. Tc-sestamibi (MIBI) scintigraphy has also been proposed for assessing multiple myeloma, but its use with state-of-the-art single-photon emission computed tomography/computed tomography (SPECT/CT) technology has not been fully evaluated.This study aimed to compare these two imaging modalities in multiple myeloma staging.

MATERIALS AND METHODS

Sixty-two patients with recently diagnosed multiple myeloma were submitted to whole-body F-FDG-PET/CT and whole-body MIBI scans plus SPECT/CT of the chest and abdomen/pelvis. Number of focal lesions, contiguous soft tissue involvement (CSTI), extramedullary lesions (EMLs) and diffuse bone marrow (BM) involvement were recorded.

RESULTS

PET/CT was positive in 59 patients (95%) and MIBI SPECT/CT in 58 (93%) (P = 0.69). MIBI detected more diffuse bone marrow involvement than PET/CT (respectively 78 vs. 58% of the patients), while PET/CT demonstrated more focal lesions than MIBI SPECT/CT (81 vs. 54% of the patients) (P = 0.002). PET/CT detected EMLs in four subjects and MIBI in one subject. CSTI was found in 28 (45%) and 23 (37%) patients on PET/CT and MIBI images, respectively (P = 0.36). Three patients with lytic lesions and no FDG uptake were MIBI positive, and two subjects with lytic lesions without MIBI uptake were FDG positive.

CONCLUSION

MIBI SPECT/CT performs similarly to F-FDG-PET/CT in identifying sites of active disease in multiple myeloma staging. MIBI is more efficient than FDG for detecting the diffuse involvement of bone marrow but less efficient for detecting focal lesions. Some patients presented a 'mismatch' pattern of FDG/MIBI uptake.

Fluorodeoxyglucose-avid focal lesions and extramedullary disease on 18F-FDG PET/computed tomography predict the outcomes of newly diagnosed symptomatic multiple myeloma patients

PURPOSE

To investigate whether the number of fluorodeoxyglucose (FDG)-avid focal lesions and the presence of extramedullary disease (EMD) on F-FDG PET/computed tomography (PET/CT) can predict the outcomes of newly diagnosed symptomatic multiple myeloma patients.

METHODS

We performed a meta-analysis to research the prognostic significance of focal lesions and EMD on F-FDG PET/CT for overall survival (OS) and progression-free survival (PFS) using a fix-effected model. The PubMed, EMBASE and Cochrane Library databases were searched. Manual searches were also conducted.

RESULTS

Of the 398 citations identified in the original search, 13 original studies with a total of 2823 patients met the inclusion criteria. The pooled hazard ratios of focal lesions were 1.63 [95% confidence interval (CI) 1.41-1.86, P = 0.442, I= 0%] for PFS and 2.15 (95% CI 1.74-2.57, P = 0.615, I= 0%) for OS. The pooled hazard ratios of EMD were 1.89 (95% CI 1.44-2.34, P = 0.497, I= 0%) for PFS and 1.91 (95% CI 1.08-2.73, P = 0.182, I= 29.6%) for OS. The results of the subgroup analysis showed the same trend. No significant heterogeneity was observed among studies.

CONCLUSION

This meta-analysis demonstrated that patients with a higher number of FDG-avid focal lesions and EMD on PET/CT may experience a higher risk for progression and a shorter survival time than those with a few focal lesions and no EMD.

The Link between Cytogenetics/Genomics and Imaging Patterns of Relapse and Progression in Patients with Relapsed/Refractory Multiple Myeloma: A Pilot Study Utilizing 18F-FDG PET/CT

Utilizing 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT), we performed this pilot study to evaluate the link between cytogenetic/genomic markers and imaging patterns in relapsed/refractory (RR) multiple myeloma (MM). We retrospectively analyzed data of 24 patients with RRMM who were treated at our institution between November 2018 and February 2020. At the last relapse/progression, patients had been treated with a median of three (range 1-10) lines of therapy. Six (25%) patients showed FDG avid extramedullary disease without adjacency to bone. We observed significantly higher maximum standardized uptake values (SUV_max) in patients harboring del(17p) compared with those without del(17p) (p = 0.025). Moreover, a high SUV_max of >15 indicated significantly shortened progression-free survival (PFS) (p = 0.01) and overall survival (OS) (p = 0.0002). One female patient exhibited biallelic TP53 alteration, i.e., deletion and mutation, in whom an extremely high SUV_max of 37.88 was observed. In summary, this pilot study suggested a link between del(17p)/TP53 alteration and high SUV_max on 18F-FDG PET/CT in RRMM patients. Further investigations are highly warranted at this point.

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.

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.

18F-FDG and 11C-Methionine PET/CT in Newly Diagnosed Multiple Myeloma Patients: Comparison of Volume-Based PET Biomarkers

¹¹C-methionine (¹¹C-MET) is a new positron emission tomography (PET) tracer for the assessment of disease activity in multiple myeloma (MM) patients, with preliminary data suggesting higher sensitivity and specificity than ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). However, the value of tumor burden biomarkers has yet to be investigated. Our goals were to corroborate the superiority of ¹¹C-MET for MM staging and to compare its suitability for the assessment of metabolic tumor burden biomarkers in comparison to ¹⁸F-FDG. Twenty-two patients with newly diagnosed, treatment-naïve symptomatic MM who had undergone ¹¹C-MET and ¹⁸F-FDG PET/CT were evaluated. Standardized uptake values (SUV) were determined and compared with total metabolic tumor volume (TMTV) for both tracers: total lesion glycolysis (TLG) and total lesion ¹¹C-MET uptake (TLMU). PET-derived values were compared to Revised International Staging System (R-ISS), cytogenetic, and serologic MM markers such as M component, beta 2 microglobulin (B2M), serum free light chains (FLC), albumin, and lactate dehydrogenase (LDH). In 11 patients (50%), ¹¹C-MET detected more focal lesions (FL) than FDG (p < 0.01). SUVmax, SUVmean, SUVpeak, TMTV, and TLMU were also significantly higher in ¹¹C-MET than in ¹⁸F-FDG (p < 0.05, respectively). ¹¹C-MET PET biomarkers had a better correlation with tumor burden (bone marrow plasma cell infiltration, M component; p < 0.05 versus p = n.s. respectively). This pilot study suggests that ¹¹C-MET PET/CT is a more sensitive marker for the assessment of myeloma tumor burden than ¹⁸F-FDG. Its implications for prognosis evaluation need further investigation.

Comparison of 11C-Choline and 11C-Methionine PET/CT in Multiple Myeloma

PURPOSE

PET/CT with both C-choline and C-methionine has recently been reported to offer advantages over F-FDG for imaging in multiple myeloma (MM). The aim of this study was to directly compare the diagnostic performance of both non-FDG radiotracers in MM patients.

METHODS

Nineteen patients with a history of MM (n = 18) or solitary bone plasmacytoma (n = 1) underwent both C-choline and C-methionine PET/CT for diagnostic imaging. In this retrospective analysis, scans were compared on a patient and on a lesion basis. In 12 patients, respective tracer uptake in the iliac crest was correlated with the extent of malignant bone marrow plasma cell infiltration.

RESULTS

C-methionine detected more intramedullary MM lesions in 8 (42.1%) of 19 patients. In the remainder (11/19 [57.9%]), both C-choline and C-methionine provided equal results. C-methionine demonstrated higher lesion-to-muscle ratios (P = 0.0001). In the 12 patients in whom a recent bone marrow biopsy was available, SUVmean as well as SUVmax correlated significantly with the degree of malignant plasma cell infiltration for both C-methionine (SUVmean: r = 0.85, P < 0.001; SUVmax: r = 0.82, P = 0.001) and C-choline (SUVmean: r = 0.72, P < 0.008; SUVmax: r = 0.73; P = 0.006).

CONCLUSIONS

Our data suggest that C-methionine PET/CT might be more sensitive than C-choline PET/CT for the detection of active MM lesions.

Value of low-dose whole-body CT in the management of patients with multiple myeloma and precursor states

OBJECTIVE

To determine the value of low-dose whole-body CT (WBCT) in the management of patients with multiple myeloma (MM) and precursor states.

MATERIALS AND METHODS

The study group comprised 116 patients (mean age: 68 ± 11 years, 48% women) who underwent WBCT for the work-up or surveillance of MM or MM precursor disease. WBCTs were reviewed for the presence of MM-related bone disease and incidental findings requiring therapy. The medical records, results from bone marrow aspirations and biopsies and follow-up imaging studies were reviewed to assess the influence of WBCT on patient management.

RESULTS

Whole-body CT led to a change in management in 32 patients (28%). Of those, 17 patients with MM precursor disease were found to have MM-related bone disease, 13 patients had progression of MM, requiring a change in treatment, in one patient hepatocellular carcinoma was diagnosed, requiring a change in therapy, and one patient had a rib lesion requiring intervention. In 65 patients (56%), WBCT was performed for surveillance of MM precursor disease or stable treated MM, and did not detect new lesions, thereby providing reassurance to the hematologist on disease status and management. In 15 patients (13%) WBCT was performed as a new baseline before a change or new therapy. In 4 patients (3%), WBCT was performed for a change in symptoms, but did not detect lesions that would lead to a change in management.

CONCLUSION

Whole-body CT provides important information for disease monitoring and detection of incidental findings, thereby improving the management of patients with MM.

Fluorodeoxyglucose-PET/Computed Tomography as a Predictor of Prognosis in Multiple Myeloma

Fluorodeoxyglucose-PET/CT is a valuable tool for the work-up of patients with newly diagnosed and relapsed/refractory multiple myeloma, because it assesses bone damage with high sensitivity and specificity and detects extramedullary sites of proliferating clonal plasma cells (extramedullary diseases). PET/CT provides valuable prognostic data at diagnosis and at restaging during the course of the disease. Consistencies between independent studies confirm the negative prognostic value of extramedullary disease and greater than 3 focal lesions, whereas the role of standardized uptake value is more conflicting. Standardization of the technique is ongoing.

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.

Imaging in multiple myeloma: How? When?

Bone disease is the most frequent feature of multiple myeloma (MM) and represents a marker of end-organ damage; it is used to establish the diagnosis and to dictate the immediate need for therapy. For this reason, imaging plays a significant role in the management of MM patients. Although conventional radiography has traditionally been the standard imaging modality, its low sensitivity in detecting osteolytic lesions and inability to evaluate response to therapy has called for the use of more sophisticated techniques, such as whole-body low-dose computed tomography (WBLDCT), whole-body magnetic resonance imaging, and ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (PET/CT). In this review, the advantages, indications of use, and applications of the 3 techniques in the management of patients with MM in different settings will be discussed. The European Myeloma Network and the European Society for Medical Oncology guidelines have recommended WBLDCT as the imaging modality of choice for the initial assessment of MM-related lytic bone lesions. Magnetic resonance imaging is the gold-standard imaging modality for detection of bone marrow involvement, whereas PET/CT provides valuable prognostic data and is the preferred technique for assessment of response to therapy. Standardization of most of the techniques is ongoing.

18F-FDG PET/CT is useful for determining survival outcomes of patients with multiple myeloma classified as stage II and III with the Revised International Staging System

PURPOSE

This study evaluated the prognostic role of ¹⁸F-FDG PET/CT at baseline in patients with newly diagnosed multiple myeloa (MM) and evaluated the prognostic relevance of ¹⁸F-FDG PET/CT for each stage according to the Revised International Staging System (R-ISS).

METHOD

We retrospectively analyzed the records of 167 patients with newly diagnosed MM. ¹⁸F-FDG PET/CT was performed prior to induction therapy in patients with newly diagnosed MM.

RESULTS

In the total cohort, the presence of more than three hypermetabolic focal lesions (FLs) or extramedullary disease (EMD) on baseline PET/CT was associated with significantly inferior progression-free survival (PFS) and overall survival (OS) than other patients. Because most patients (91%) with EMD had more than three FLs, PET/CT positivity was defined as the presence of more than three FLs or the presence of EMD. In multivariate analyses, PET/CT positivity was an independent predictor of PFS and OS in all patients. Fifty-five patients (46.1%) with R-ISS II were PET/CT-positive at baseline and had significantly shorter PFS and OS. PET/CT positivity was also correlated with poor PFS and OS in patients with R-ISS III.

CONCLUSION

¹⁸F-FDG PET/CT was an independent predictor of survival outcomes in patients with newly diagnosed MM. In addition, performing ¹⁸F- FDG PET/CT at diagnosis may be useful for determining the survival outcomes of MM patients with R-ISS II and III.

European Myeloma Network recommendations on tools for the diagnosis and monitoring of multiple myeloma: what to use and when

The diagnosis of multiple myeloma can be challenging, even for experienced physicians, and requires close collaboration between numerous disciplines (orthopedics, radiology, nuclear medicine, radiation therapy, hematology and oncology) before the final diagnosis of myeloma is made. The definition of multiple myeloma is based on the presence of clinical, biochemical, histopathological, and radiological markers of disease. Specific tests are needed both at presentation and during follow-up in order to reach the correct diagnosis and characterize the disease precisely. These tests can also serve prognostic purposes and are useful for follow-up of myeloma patients. Molecular analyses remain pivotal for defining high-risk myeloma and are used in updated patient stratifications, while minimal residual disease assessment via flow cytometry, molecular techniques and radiological approaches provides additional prognostic information on patients' long-term outcome. This pivotal information will guide our future treatment decisions in forthcoming clinical trials. The European Myeloma Network group updated their guidelines on different diagnostic recommendations, which should be of value to enable appropriate use of the recommendations both at diagnosis and during follow-up.

Predictive value of 18 F-FDG PET/CT scanning in combination with clinical parameters in patients with newly diagnosed multiple myeloma

OBJECTIVE

To evaluate the association of ¹⁸ F-2'-deoxy 2'-fluorodeoxyglucose (¹⁸ F-FDG) PET/CT with clinical parameters in predicting patients with newly diagnosed multiple myeloma (MM).

METHODS

A total of 120 MM patients undergoing ¹⁸ F-FDG PET/CT scanning were analyzed in a retrospective cohort study.

RESULTS

Based on multivariate analysis, β2M, LDH, number of focal lesions (FLs), and SUVmax were significantly correlated with OS. These 4 variables were used to construct a new staging system (NSS) based on the number of risk factors. NSS provided a better discrimination of risk between stages III and II than International staging system (ISS) (P < .001 vs P = .086). For OS, there was no significant difference among risk groups in Durie-Salmon (DS) stage (P > .05). Based on Spearman correlation analysis, the presence of lesions in appendicular skeleton, number of FLs, and SUVmax appeared to indicate advanced stage of MM. ROC curves which showed the combination of β2M with calcium got a specificity of 96.3% for lesions in appendicular skeleton, and LDH alone had 100% specificity in predicting the number of FLs, although the sensitivity was only 50%.

CONCLUSIONS

¹⁸ F-FDG PET/CT in combination with clinical parameters provided an accurate and simple method for risk stratification of patients with newly diagnosed MM.

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

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

11C-Methionine-PET in Multiple Myeloma: A Combined Study from Two Different Institutions

¹¹C-methionine (MET) has recently emerged as an accurate marker of tumor burden and disease activity in patients with multiple myeloma (MM). This dual-center study aimed at further corroboration of the superiority of MET as positron emission tomography (PET) tracer for staging and re-staging MM, as compared to ¹⁸F-2`-deoxy-2`-fluoro-D-glucose (FDG).

78 patients with a history of solitary plasmacytoma (n=4), smoldering MM (SMM, n=5), and symptomatic MM (n=69) underwent both MET- and FDG-PET/computed tomography (CT) at the University Centers of Würzburg, Germany and Navarra, Spain. Scans were compared on a patient and on a lesion basis. Inter-reader agreement was also evaluated. In 2 patients, tumor biopsies for verification of discordant imaging results were available.

MET-PET detected focal lesions (FL) in 59/78 subjects (75.6%), whereas FDG-PET/CT showed lesions in only 47 patients (60.3%; p<0.01), accordingly disease activity would have been missed in 12 patients. Directed biopsies of discordant results confirmed MET-PET/CT results in both cases.

MET depicted more FL in 44 patients (56.4%; p<0.01), whereas in two patients (2/78), FDG proved superior. In the remainder (41.0%, 32/78), both tracers yielded comparable results. Inter-reader agreement for MET was higher than for FDG (κ = 0.82 vs κ = 0.72).

This study demonstrates higher sensitivity of MET in comparison to standard FDG to detect intra- and extramedullary MM including histologic evidence of FDG-negative, viable disease exclusively detectable by MET-PET/CT. MET holds the potential to replace FDG as functional imaging standard for staging and re-staging of MM.

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

The International Myeloma Working Group consensus aimed to provide recommendations for the optimal use of ¹⁸fluorodeoxyglucose (¹⁸F-FDG) PET/CT in patients with multiple myeloma and other plasma cell disorders, including smouldering multiple myeloma and solitary plasmacytoma. ¹⁸F-FDG PET/CT can be considered a valuable tool for the work-up of patients with both newly diagnosed and relapsed or refractory multiple myeloma because it assesses bone damage with relatively high sensitivity and specificity, and detects extramedullary sites of proliferating clonal plasma cells while providing important prognostic information. The use of ¹⁸F-FDG PET/CT is mandatory to confirm a suspected diagnosis of solitary plasmacytoma, provided that whole-body MRI is unable to be performed, and to distinguish between smouldering and active multiple myeloma, if whole-body X-ray (WBXR) is negative and whole-body MRI is unavailable. Based on the ability of ¹⁸F-FDG PET/CT to distinguish between metabolically active and inactive disease, this technique is now the preferred functional imaging modality to evaluate and to monitor the effect of therapy on myeloma-cell metabolism. Changes in FDG avidity can provide an earlier evaluation of response to therapy compared to MRI scans, and can predict outcomes, particularly for patients who are eligible to receive autologous stem-cell transplantation. ¹⁸F-FDG PET/CT can be coupled with sensitive bone marrow-based techniques to detect minimal residual disease (MRD) inside and outside the bone marrow, helping to identify those patients who are defined as having imaging MRD negativity.

PET Imaging for Initial Staging and Therapy Assessment in Multiple Myeloma Patients

Multiple myeloma (MM) is a hematological neoplasm characterized by the clonal proliferation of malignant plasma cells in the bone marrow. MM results in diffuse or focal bone infiltration and extramedullary lesions. Over the past two decades, advances have been made with regard to the diagnosis, staging, treatment, and imaging of MM. Computed tomography (CT) and magnetic resonance imaging (MRI) are currently recommended as the most effective imaging modalities at diagnostic. Yet, recent data from the literature suggest that positron emission tomography combined with computed tomography (PET/CT) using 18F-deoxyglucose (FDG) is a promising technique for initial staging and therapeutic monitoring in this pathology. This paper reviews the recent advances as well as the potential place of a more specific radiopharmaceutical in MM.

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

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

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

Multiple myeloma (MM) is characterized by a monoclonal plasma cell population in the bone marrow. Lytic lesions occur in up to 90 % of patients. For many years, whole-body X-ray (WBX) was the method of choice for detecting skeleton abnormalities. However, the value of WBX in relapsing disease is limited because lesions persist post-treatment, which restricts the capacity to distinguish between old, inactive skeletal lesions and new, active ones. Therefore, alternative techniques are necessary to visualize disease activity. Modern imaging techniques such as magnetic resonance imaging, positron emission tomography and computed tomography offer superior detection of myeloma bone disease and extramedullary manifestations. In particular, the properties of nuclear imaging enable the identification of disease activity by directly targeting the specific cellular properties of malignant plasma cells. In this review, an overview is provided of the effectiveness of radiopharmaceuticals that target metabolism, surface receptors and angiogenesis. The available literature data for commonly used nuclear imaging tracers, the promising first results of new tracers, and our pilot work indicate that a number of these radiopharmaceutical applications can be used effectively for staging and response monitoring of relapsing MM patients. Moreover, some tracers can potentially be used for radio immunotherapy.

11C-Methionine-PET: a novel and sensitive tool for monitoring of early response to treatment in multiple myeloma

Multiple myeloma (MM) remains an essentially incurable hematologic malignancy. However, new treatment modalities and novel drugs have been introduced and thus additional tools for therapy monitoring are increasingly needed. Therefore, we evaluated the radiotracers 11C-Methionine (paraprotein-biosynthesis) and 18F-FDG (glucose-utilization) for monitoring response to anti-myeloma-therapy and outcome prediction. Influence of proteasome-inhibition on radiotracer-uptake of different MM cell-lines and patient-derived CD138+ plasma cells was analyzed and related to tumor-biology. Mice xenotransplanted with MM.1S tumors underwent MET- and FDG-μPET. Tumor-to-background ratios before and after 24 h, 8 and 15 days treatment with bortezomib were correlated to survival. Treatment reduced both MET and FDG uptake; changes in tracer-retention correlated with a switch from high to low CD138-expression. In xenotransplanted mice, MET-uptake significantly decreased by 30-79% as early as 24 h after bortezomib injection. No significant differences were detected thus early with FDG. This finding was confirmed in patient-derived MM cells. Importantly, early reduction of MET- but not FDG-uptake correlated with improved survival and reduced tumor burden in mice. Our results suggest that MET is superior to FDG in very early assessment of response to anti-myeloma-therapy. Early changes in MET-uptake have predictive potential regarding response and survival. MET-PET holds promise to individualize therapies in MM in future.

PET-CT in the UK: current status and future directions

Combined positron-emission tomography and computed tomography (PET-CT) has taken the oncological world by storm since being introduced into the clinical domain in the early 21(st) century and is firmly established in the management pathway of many different tumour types. Non-oncological applications of PET-CT represent a smaller but steadily growing area of interest. PET-CT continues to be the focus of a large number of research studies and keeping up-to-date with the literature is important but represents a challenge. Consequently guidelines recommending PET-CT usage need to be revised regularly to encompass new developments. The purpose of this article is twofold: first, it provides a detailed review of the evidence-base underpinning the major uses of PET-CT in clinical practice, which may be of value to a wide-range of individuals, including those directly involved with PET-CT and to a much larger group with limited exposure, but for whom a précis of the current state-of-play may help inform other radiology and multidisciplinary team (MDT) work; the second purpose is as a companion to revised guidelines on evidence-based indications for PET-CT in the UK (being published concurrently) providing a detailed commentary on new indications with a summary of emerging data supporting these additional clinical uses of the technique.

11C-Methionine-PET in Multiple Myeloma: Correlation with Clinical Parameters and Bone Marrow Involvement

Multiple myeloma (MM) remains an essentially incurable hematologic malignancy originating from clonal plasma cells. This study evaluated the usefulness of the radiotracers ¹¹C-methionine (MET) and ¹⁸F-2`-deoxy-2`-fluorodeoxyglucose (FDG) for staging and re-staging in MM.

43 patients with MM underwent both MET- and FDG-PET/CT for staging or re-staging within 3±2 days. Scans were compared on a patient and on a lesion basis. Tracer uptake was correlated with the degree of bone marrow (BM) involvement and standard clinical parameters of disease activity. Additionally, BM samples were stained for L-type amino acid transporter 1 (LAT1) expression in 15 patients. MET-PET detected focal lesions (FL) in 39/43 subjects (90.7%), whereas 10 patients were missed in FDG-PET/CT (detection rate, 33/43; 76.7%; p<0.05). MET depicted more FL in 28/43 patients (65.1%; p<0.001), whereas in the remainder (34.9%, n=15) both tracers yielded comparable results. LAT1 was highly expressed on the cell surface of myeloma cells. Both FDG and MET uptake correlated significantly with biopsy-proven BM involvement (p<0.001), with MET demonstrating a stronger correlation (SUV_mean, r=0.9 vs r=0.6; SUV_max, r=0.88 vs r=0.58). Abnormal beta-2-microglobulin and free light chain levels correlated with the presence of focal intramedullary lesions detected in MET- or FDG-PET/CT (MET, p=0.006 and p=0.01, respectively; FDG, p=0.02 and p=0.01). MET appears to be superior to FDG for staging and re-staging of both intra- and extramedullary MM lesions. Tracer uptake correlates with BM involvement, β2m and FLC levels and appears to be a more accurate marker of tumor burden and disease activity.