Redefining Non-measurable Multiple Myeloma Using Mass Spectrometry

Mass Spectrometry as Alternative Method to Identify and Monitor Non-Secretory Progressive Disease in Patients with Multiple Myeloma

INTRODUCTION

After receiving different lines of treatment, multiple myeloma patients tend to present with less secretory and more frequent extramedullary disease. These features make treatment monitoring and follow-up very complex since they have to be based on the use of imaging methods and/or bone marrow aspirations or biopsies.

OBJECTIVE

To present the case of a patient with myeloma progressing with non-secretory bone disease and to discuss the potential impact of mass spectrometry as a new highly sensitive method able to identify the monoclonal protein (MP) in the serum of these types of patients.

MATERIALS AND METHODS

Informed consent was signed by the patient prior to receiving each line of treatment. The clinical information and images were obtained from anonymized electronic files. The mass spectrometry was performed with the Immunoglobulin Isotypes (GAM) assay for the mass spectrometry EXENT® Analyser Technology from Binding Site, part of Thermofisher.

RESULTS

A 73-year-old male with IgG kappa multiple myeloma progressing with a new lytic lesion after receiving 14 cycles of Talquetamab as a third line of therapy who, due to the non-secretory nature of the disease at this point, could not be enrolled in a clinical trial, thus limiting his therapeutic options. The mass spectrometry was able to identify and quantify the presence of the patient's MP when the serum protein electrophoresis and immunofixation were still negative and therefore could have been used to confirm the progression, to permit the inclusion of the patient in a clinical trial and to further monitor the disease response.

CONCLUSIONS

The higher sensitivity of the mass spectrometry methods to detect the MP in patients with myeloma and other monoclonal gammopathies translates into better identification of the disease progression, permits the inclusion of more patients in clinical trials and facilitates treatment monitoring.

Progression free survival of myeloma patients who become IFE-negative correlates with the detection of residual monoclonal free light chain (FLC) by mass spectrometry

Deeper responses are associated with improved survival in patients being treated for myeloma. However, the sensitivity of the current blood-based assays is limited. Historical studies suggested that normalisation of the serum free light chain (FLC) ratio in patients who were negative by immunofixation electrophoresis (IFE) was associated with improved outcomes. However, recently this has been called into question. Mass spectrometry (MS)-based FLC assessments may offer a superior methodology for the detection of monoclonal FLC due to greater sensitivity. To test this hypothesis, all available samples from patients who were IFE negative after treatment with carfilzomib and lenalidomide-based induction and autologous stem cell transplantation (ASCT) in the Myeloma XI trial underwent FLC-MS testing. FLC-MS response assessments from post-induction, day+100 post-ASCT and six months post-maintenance randomisation were compared to serum FLC assay results. Almost 40% of patients had discordant results and 28.7% of patients with a normal FLC ratio had residual monoclonal FLC detectable by FLC-MS. FLC-MS positivity was associated with reduced progression-free survival (PFS) but an abnormal FLC ratio was not. This study demonstrates that FLC-MS provides a superior methodology for the detection of residual monoclonal FLC with FLC-MS positivity identifying IFE-negative patients who are at higher risk of early progression.

Performance Characteristics and Limitations of the Available Assays for the Detection and Quantitation of Monoclonal Free Light Chains and New Emerging Methodologies

Light chain measurements form an essential component of the testing strategy for the detection and monitoring of patients with suspected and/or proven plasma cell disorders. Urine-based electrophoretic assays remain at the centre of the international guidelines for response assessment but the supplementary role of serum-free light chain (FLC) assays in response assessment and the detection of disease progression due to their increased sensitivity has been increasingly recognised since their introduction in 2001. Serum FLC assays have also been shown to be prognostic across the spectrum of plasma cell disorders and are now incorporated into risk stratification scores for patients with monoclonal gammopathy of undetermined significance (MGUS), smouldering multiple myeloma, and light chain amyloidosis (AL amyloidosis), as well as being incorporated into the criteria for defining symptomatic multiple myeloma. There are now multiple different commercially available serum FLC assays available with differing performance characteristics, which are discussed in this review, along with the implications of these for patient monitoring. Finally, newer methodologies for the identification and characterisation of monoclonal FLC, including modifications to electrophoretic techniques, mass spectrometry-based assays and Amylite, are also described along with the relevant published data available regarding the performance of each assay.

Laboratory practice is central to earlier myeloma diagnosis: Utilizing a primary care diagnostic tool and laboratory guidelines integrated into haematology services

Treatment advances have greatly improved survival, but myeloma is among the worst of all cancers for delayed diagnosis, causing serious morbidities and early deaths. This delay is largely because the symptom profile of myeloma has very low specificity, and in primary care, myeloma is rare. However, initiating the journey to diagnosis simply requires considering myeloma and sending blood to test for monoclonal immunoglobulin. Laboratory tests reliably detect monoclonal immunoglobulin, which is present in 99% of myeloma cases, so why do health care systems have such a problem with delayed diagnosis? The Myeloma UK early diagnosis programme has brought together diverse expertise to investigate this problem, and this article was prepared by the programme's working group for laboratory best practice. It reviews evidence for test requesting, analysis and reporting, for which there is large variation in practice across the United Kingdom. It presents a 'GP Myeloma diagnostic tool' and how it can be integrated into laboratory practice alongside a laboratory best practice tool. It proposes improved requesting and integration with haematology services for reporting and interpretation. Here the laboratory has a central role in creating efficient and cost-effective pathways for appropriate and timely bone marrow examination for myeloma diagnosis.

M-protein detection by mass spectrometry for minimal residual disease in multiple myeloma

Multiple myeloma (MM) is characterized by excessive production of monoclonal immunoglobulins (M proteins). Routine screening methods for M proteins to assess prognosis are unable to detect low levels of M proteins produced by residual tumor cells, ie, minimal residual disease (MRD). Assessment of MRD can be conducted by examining residual tumor cells in bone marrow or circulating M proteins. Advances in mass spectrometry have enabled reliable and highly sensitive detection of low abundance serum biomarkers making it a viable and significantly less invasive approach. Mass spectrometry can achieve dynamic monitoring of MRD and identify therapeutic monoclonal antibodies as well as oligoclonal proteins. In this review we summarize mass spectrometry methods in M protein detection and their applications of MRD detection in MM.

Measurable residual disease in peripheral blood in myeloma: dream or reality

PURPOSE OF REVIEW

Therapeutic advancements in multiple myeloma have led to increasingly deeper and more durable responses, creating a need for highly sensitive and applicable techniques for measurable residual disease (MRD) assessment. Bone marrow assays can deeply assess for MRD, but it is not conducive to performing frequent and dynamic evaluations, which may be needed for MRD-adapted treatment approaches. Recently, numerous techniques for MRD assessment in peripheral blood have come under investigation, and their integration into routine clinical practice is eagerly anticipated.

RECENT FINDINGS

The identification of circulating tumor cells (CTCs), evaluation of cell-free DNA, and measuring monoclonal protein concentration with mass spectrometry are promising research areas for assessing myeloma in peripheral blood. CTCs assessment and cell-free DNA may carry prognostic significance, but they lack the sensitivity of bone marrow-based techniques. Mass spectrometry has already been implemented in clinical practice in certain centers, but its full potential has yet to be fully realized. This review focuses on recent developments in these fields, emphasizing the potential future roles of these assessments.

SUMMARY

MRD assessment in peripheral blood is still in the development stage but holds promise for not only complementing bone marrow based evaluations but also potential for improving sensitivity.

Determination of the target of monoclonal immunoglobulins: a novel diagnostic tool for individualized MGUS therapy, and prevention and therapy of smoldering and multiple myeloma

Subsets of patients diagnosed with a monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM) or multiple myeloma (MM), present with a monoclonal immunoglobulin (Ig) specific for an infectious pathogen, including hepatitis C and B viruses (HCV, HBV), Helicobacter pylori and several Herpesviruses. Such cases are likely initiated by infection, since in the context of HCV- or HBV-infected patients, antiviral therapy can lead to the disappearance of antigenic stimulation, control of clonal plasma cells, and reduced or suppressed monoclonal Ig production. Complete remission has been obtained with anti-HCV therapy in refractory MM with a HCV-specific monoclonal Ig, and antiviral treatments significantly improved the probability of survival of MM patients infected with HCV or HBV prior to the diagnosis of MM. Monoclonal Igs may also target glucolipids, particularly glucosylsphingosine (GlcSph), and GlcSph-reducing therapy can lead to complete remission in SMM and MM patients presenting with a GlcSph-specific monoclonal Ig. The present review describes the importance of determining the target of the monoclonal Ig of MGUS, SMM and MM patients, and discusses the efficacy of target-reducing treatments in the management of MGUS, SMM and MM cases who present with a monoclonal Ig reactive against a treatable infectious pathogen or GlcSph.

Race for the Cure: From the Oldest to the Newest Monoclonal Antibodies for Multiple Myeloma Treatment

Multiple myeloma is characterized by a wide clinical heterogeneity due to an intricate network of interactions between bone marrow-resident clonal plasma cells and the microenvironment. Over the last years, dramatic improvement in the understanding of these pathways led to the introduction of novel drugs with immune-mediated mechanisms of action. Some of these compounds, such as the anti-cd38 daratumumab and isatuximab, the anti-slamf-7 elotuzumab, and the antibody-drug conjugate belantamab-mafodotin, have been tested in large clinical trials and have now fully entered the real-life management. The bispecific T-cell engagers are under investigation with promising results, and other satisfactory data is expected from the application of nanotechnologies. The perfect timing to introduce these drugs in the sequence of treatment and their adverse events represent new challenges to be addressed, and further experience is required to improve their use.

Proceedings from the Blood and Marrow Transplant Clinical Trials Network Myeloma Intergroup Workshop on Immune and Cellular Therapy in Multiple Myeloma

The Blood and Marrow Transplant Clinical Trials Network (BMT CTN) Myeloma Intergroup conducted a workshop on Immune and Cellular Therapy in Multiple Myeloma on January 7, 2022. This workshop included presentations by basic, translational, and clinical researchers with expertise in plasma cell dyscrasias. Four main topics were discussed: platforms for myeloma disease evaluation, insights into pathophysiology, therapeutic target and resistance mechanisms, and cellular therapy for multiple myeloma. Here we provide a comprehensive summary of these workshop presentations.

Investigating the utility of saliva immunoglobulins for the detection of myeloma and using myeloma proteins to clarify partition between oral and systemic immunity

OBJECTIVES

Myeloma is characterised by the presence of monoclonal immunoglobulin (M-protein) and the free light chain (FLC) in blood. We investigated whether these M-proteins and FLC are detectable in myeloma patients' saliva to evaluate its utility for non-invasive screening and monitoring of haematological malignancies.

METHODS

A total of 57 patients with monoclonal gammopathy and 26 age-matched healthy participants provided paired serum and saliva samples for immunoglobulin characterisation and quantification.

RESULTS

Myeloma patients had IgG or IgA M-protein levels ranging up to five times and FLC levels up to a thousand times normal levels of polyclonal immunoglobulins. Despite these highly elevated levels, only two IgG and no IgA M-proteins or FLC could be detected in paired saliva samples. Most patients had reduced levels of serum polyclonal immunoglobulins, but all had normal levels of salivary IgA.

CONCLUSIONS

Immunoglobulin transfer from blood is not determined by levels in the systemic circulation and more likely dictated by periodontal inflammation and the integrity of the oral epithelium. Immunoglobulins secreted by bone marrow plasma cells do not substantially enter saliva, which represents a poor medium for myeloma diagnosis. These findings, along with normal salivary IgA levels despite systemic immunoparesis, support a strong partitioning of oral from systemic humoral immunity.

The potential role of mass spectrometry for the identification and monitoring of patients with plasma cell disorders: Where are we now and which questions remain unanswered?

Mass spectrometry (MS) techniques provide a highly sensitive methodology for the assessment and monitoring of paraproteins compared to standard electrophoretic techniques. The International Myeloma Working Group (IMWG) recently approved the use of intact light chain matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in lieu of immunofixation in the clinical assessment of patients and the assessment of patients enrolled on clinical trials. The increased sensitivity of these assays may help to detect and monitor monoclonal proteins (MP) in many patients with previously non-measurable disease, will reduce complete response (CR) rates and increase detection of low-level MP. The ability to track the unique mass or amino acid sequence of the MP also eliminates interference from therapeutic monoclonal antibodies (tmAbs) in most patients with IgG kappa myeloma. The intact light chain assays also provide structural information about the monoclonal light chain, including the presence of N-linked glycosylation, which has been shown to be commoner on amyloidogenic light chains and may have prognostic significance in monoclonal gammopathy of undetermined significance (MGUS). In this review, we discuss these issues alongside differences in the analytical and practical aspects related to the different MS assays under development and the challenges for MS.

Bringing mass spectrometry into the care of patients with multiple myeloma

Serum protein electrophoresis methods are widely employed to detect, quantify and isotype M-proteins for multiple myeloma patients. Increasing clinical demands to detect residual disease and interferences from new therapeutic monoclonal antibody treatments have stretched electrophoretic methods to their analytical limits. Newer techniques to detect M-proteins using mass spectrometry (MS) are emerging with improved clinical and analytical performance. These techniques are beginning to gain traction within the routine clinical lab testing. This review describes these MS methods with attention to the current and future roles such testing could play in the care of multiple myeloma patients.