Using MALDI-TOF mass spectrometry in peripheral blood for the follow up of newly diagnosed multiple myeloma patients treated with daratumumab-based combination therapy

Serum mass spectrometry for treatment monitoring in patients with multiple myeloma receiving ARI0002h CAR T-cells

Chimeric antigen receptor (CAR) T-cell therapies have increased the patients with relapsed/refractory multiple myeloma (RRMM) in whom standard electrophoretic techniques fail to detect the M-protein. Quantitative immunoprecipitation mass spectrometry (QIP-MS) can accurately measure serum M-protein with high sensitivity, and identify interferences caused by therapeutic monoclonal antibodies. Here, we investigate the outcome of QIP-MS in 33 patients treated with the academic BCMA-directed CAR T-cell ARI0002h (Cesnicabtagene Autoleucel). QIP-MS offered more detailed insights than serum immunofixation (sIFE), identifying glycosylated M-proteins and minor additional peaks. Moreover, the potential interferences owing to daratumumab or tocilizumab treatments were successfully detected. When analysing different assay platforms during patient's monitoring after ARI0002h administration, we observed that QIP-MS showed a high global concordance (78.8%) with sIFE, whereas it was only moderate (55.6%) with bone marrow (BM)-based next-generation flow cytometry (NGF). Furthermore, QIP-MS consistently demonstrated the lowest negativity rate across the different timepoints (27.3% vs. 60.0% in months 1 and 12, respectively). Patients with QIP-MS(+)/BM-based NGF(-) showed a non-significant shorter median progression free survival than those with QIP-MS(-)/BM-based NGF(-). In summary, we show the first experience to our knowledge demonstrating that QIP-MS could be particularly useful as a non-invasive technique when evaluating response after CAR T-cell treatment in MM.

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.

Improved Screening of Monoclonal Gammopathy Patients by MALDI-TOF Mass Spectrometry

Monoclonal gammopathies are a group of blood diseases characterized by presence of abnormal immunoglobulins in peripheral blood and/or urine of patients. Multiple myeloma and plasma cell leukemia are monoclonal gammopathies with unclear etiology, caused by malignant transformation of bone marrow plasma cells. Mass spectrometry with matrix-assisted laser desorption/ionization and time-of-flight detection is commonly used for investigation of the peptidome and small proteome of blood plasma with high accuracy, robustness, and cost-effectivity. In addition, mass spectrometry coupled with advanced statistics can be used for molecular profiling, classification, and diagnosis of liquid biopsies and tissue specimens in various malignancies. Despite the fact there have been fully optimized protocols for mass spectrometry of normal blood plasma available for decades, in monoclonal gammopathy patients, the massive alterations of biophysical and biochemical parameters of peripheral blood plasma often limit the mass spectrometry measurements. In this paper, we present a new two-step extraction protocol and demonstrated the enhanced resolution and intensity (>50×) of mass spectra obtained from extracts of peripheral blood plasma from monoclonal gammopathy patients. When coupled with advanced statistics and machine learning, the mass spectra profiles enabled the direct identification, classification, and discrimination of multiple myeloma and plasma cell leukemia patients with high accuracy and precision. A model based on PLS-DA achieved the best performance with 71.5% accuracy (95% confidence interval, CI = 57.1-83.3%) when the 10× repeated 5-fold CV was performed. In summary, the two-step extraction protocol improved the analysis of monoclonal gammopathy peripheral blood plasma samples by mass spectrometry and provided a tool for addressing the complex molecular etiology of monoclonal gammopathies.

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.

Detection of serum M-protein in acetonitrile precipitates by MALDI-TOF mass spectrometry: A novel, low-cost methodology

BACKGROUND

Several studies have demonstrated the analytical sensitivity of MALDI-TOF mass spectrometry (MALDI-TOF MS) by immunoenrichment for M-protein analysis. We report the results of a novel, low-cost, reagent-based extraction process using acetonitrile (ACN) precipitation to enrich for κ and λ light chains which can be analysed by MALDI-TOF MS.

METHODS

Institutional Ethics committee approval was obtained. Serum samples from patients with monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma (MM), plasmacytoma, AL amyloidosis and Waldenström macroglobulinemia (WM) underwent ACN precipitation. The images obtained were overlaid on apparently healthy donor serum samples to confirm the presence of M-protein. A sample was considered positive for M-protein if there was a sharp or broad peak within the κ or λ mass/charge (m/z) range: m/z- [M + 2H]2+: 11,550-12,300 Da and λ m/z- [M + 2H]2+: 11,100-11,500 Da. Images were acquired at a m/z range of 10,000-29,000 Da. Corresponding serum protein electrophoresis (SPEP), serum immunofixation electrophoresis (IFE) and serum free light chain (sFLC) assay by nephelometry were performed for all the samples.

RESULTS

Two-hundred-and-two serum samples were included in the study: MM- 184 (91%); AL amyloidosis- 2 (1%); plasmacytoma- 8 (4%); MGUS- 6 (3%) and WM- 2 (1%). All the SPEP positive samples were identified by MALDI-TOF MS. Out of 179 samples positive for M-protein by IFE, MALDI-TOF MS was positive in 176 samples (98%). Compared to IFE, the sensitivity and specificity of M-protein identification by MALDI-TOF MS were 98.3% and 52.2%, respectively.

CONCLUSIONS

This study demonstrates the feasibility of qualitatively identifying M-protein without the need for antibody-based immunoenrichment, making the technique cost-effective.

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.

Mass spectrometry vs immunofixation for treatment monitoring in multiple myeloma

EXENT&FLC-MS is more sensitive than IFE in detecting the M-protein of MM patients in serum, both at baseline and during treatment monitoring.

EXENT&FLC-MS is more accurate than IFE to predict patients’ outcome.

Monitoring of the monoclonal protein (M-protein) by electrophoresis and/or immunofixation (IFE) has long been used to assess treatment response in multiple myeloma (MM). However, with the use of highly effective therapies, the M-protein becomes frequently undetectable, and more sensitive methods had to be explored. We applied IFE and mass spectrometry (EXENT&FLC-MS) in serum samples from newly diagnosed MM patients enrolled in the PETHEMA/GEM2012MENOS65 obtained at baseline (n = 223), and after induction (n = 183), autologous stem cell transplantation (n = 173), and consolidation (n = 173). At baseline, the isotypes identified with both methods fully matched in 82.1% of samples; in the rest but 2 cases, EXENT&FLC-MS provided additional information to IFE with regards to the M-protein(s). Overall, the results of EXENT&FLC-MS and IFE were concordant in >80% of cases, being most discordances due to EXENT&FLC-MS⁺ but IFE⁻ cases. After consolidation, IFE was not able to discriminate 2 cohorts with different median progression-free survival (PFS), but EXENT&FLC-MS did so; furthermore, among IFE⁻ patients, EXENT&FLC-MS identified 2 groups with significantly different median PFS (P = .0008). In conclusion, compared with IFE, EXENT&FLC-MS is more sensitive to detect the M-protein of patients with MM, both at baseline and during treatment, and provides a more accurate prediction of patients’ outcome. This trial was registered at www.clinicaltrials.gov as #NCT01916252.