Detection of minimal residual disease in patients with multiple myeloma using clonotype-specific PCR primers designed from DNA extracted from archival bone marrow slides

Outcomes of poor peripheral blood stem cell mobilizers with multiple myeloma at the first mobilization: A multicenter retrospective study in Japan

Autologous stem cell transplantation (ASCT) remains an important therapeutic strategy for multiple myeloma; however, a proportion of patients fail to mobilize a sufficient number of peripheral blood stem cells (PBSCs) to proceed to ASCT. In the present study, we aimed to clarify the characteristics and outcomes of poor mobilizers. Clinical data on poorly mobilized patients who underwent PBSC harvest for almost 10 years were retrospectively collected from 44 institutions in the Japanese Society of Myeloma (JSM). Poor mobilizers were defined as patients with less than 2 × 106/kg of CD34+ cells harvested at the first mobilization. The proportion of poor mobilization was 15.1%. A sufficient dataset including overall survival (OS) was evaluable in 258 poor mobilizers. Overall, 92 out of 258 (35.7%) poor mobilizers did not subsequently undergo ASCT, mainly due to an insufficient number of PBSCs. Median OS from apheresis was longer for poor mobilizers who underwent ASCT than for those who did not (86.0 vs. 61.9 mon., p = 0.02). OS from the diagnosis of poor mobilizers who underwent ASCT in our cohort was similar to those who underwent ASCT in the JSM database (3y OS rate, 86.8% vs. 85.9%). In this cohort, one-third of poor mobilizers who did not undergo ASCT had relatively poor survival. In contrast, the OS improved in poor mobilizers who underwent ASCT. However, the OS of extremely poor mobilizers was short irrespective of ASCT.

Minimal residual disease detection in multiple myeloma: comparison between BML single-tube 10-color multiparameter flow cytometry and EuroFlow multiparameter flow cytometry

Minimal residual disease (MRD)-negative status in multiple myeloma (MM) is associated with favorable outcomes. Although EuroFlow next-generation flow (NGF) is a global standard for MRD detection, its operating cost is high. Therefore, it is desirable to develop a less expensive method with equivalent sensitivity to that of EuroFlow-NGF. In this study, we compared the analytical ability of our BML 10-color multiparameter flow cytometry (MFC) to that of EuroFlow-NGF. Bone marrow samples collected from 51 patients with MM were subjected to MRD detection using BML 10-color-MFC and EuroFlow-NGF. Our antibody panel consisted of CD38 multiepitope, CD138, CD45, CD56, CD19, CD27, CD81, CD117, cytoplasmic immunoglobulin (cIg) κ, and cIgλ in a single tube. The median percentages of total plasma cells, as per 10-color-MFC and EuroFlow-NGF, were 0.2148% and 0.2200%, respectively, with a good correlation between the methods (r = 0.950). The median percentages of myeloma cells determined via 10-color-MFC and EuroFlow-NGF were 0.0012% and 0.0007%, respectively, with a strong correlation (r = 0.954). Our 10-color-MFC demonstrated high sensitivity to detect MRD; the results showed a good correlation with those obtained using EuroFlow-NGF. Therefore, our cost-effective single-tube MFC (approximately 100 USD/sample) is a promising alternative method for the detection of MRD in patients with MM.

Minimal Residual Disease in Multiple Myeloma: Current Landscape and Future Applications With Immunotherapeutic Approaches

The basic principle that deeper therapeutic responses lead to better clinical outcomes in cancer has emerged technologies capable of detecting rare residual tumor cells. The need for ultra-sensitive approaches for minimal residual disease (MRD) detection is particularly evident in Multiple Myeloma (MM), where patients will ultimately relapse despite the achievement of complete remission, which is commonplace due to remarkable therapeutic advances. Consequently, current response criteria on MM have been amended based on MRD status and MRD negativity is now considered the most dominant prognostic factor and the most valuable indicator for a subsequent relapse. However, there are particular limitations and several aspects for MRD assessment that remain open. This review summarizes current data on MRD in the clinical management of MM, highlights open issues and discusses the challenges and the endless opportunities arising for both patients and clinicians. Furthermore, it focuses on the current status of MRD in clinical trials, its dynamics in addressing debatable aspects in the clinical handling and its potential role as the prevailing factor for future MRD-driven tailored therapies.

Minimal Residual Disease Assessment Within the Bone Marrow of Multiple Myeloma: A Review of Caveats, Clinical Significance and Future Perspectives

There is an increasing clinical interest in the measure and achievement of minimal residual disease (MRD) negativity in the bone marrow of Multiple Myeloma (MM) patients, as defined equally either by Multicolor Flow Cytometry (MFC) or by Next Generation Sequencing (NGS) technologies. At present, modern technologies allow to detect up to one on 104 or on 105 or even on 106 cells, depending on their throughput. MFC approaches, which have been progressively improved up to the so-called Next Generation Flow (NGF), and NGS, which proved clear advantages over ASO-PCR, can detect very low levels of residual disease in the BM. These methods are actually almost superimposable, in terms of MRD detection power, supporting the lack of unanimous preference for either technique on basis of local availability. However, some technical issues are still open: the optimal assay to use to detect either phenotype (e.g., next generation multidimensional flow cytometry, imaging) or genotype aberrations (e.g., ASO-RQ PCR, digital droplet PCR, NGS) and their standardization, the sample source (BM or peripheral blood, PB) and its pre-processing (red-cell lysis vs. Ficoll, fresh vs. frozen samples, requirement of CD138+ cells enrichment). Overall, MRD negativity is considered as the most powerful predictor of favorable long-term outcomes in MM and is likely to represent the major driver of treatment strategies in the near future. In this manuscript, we reviewed the main pitfalls and caveats of MRD detection within bone marrow in MM patients after front-line therapy, highlighting the improving of the currently employed technology and describing alternative methods for MRD testing in MM, such as liquid biopsy.

Prognostic value of sequencing-based minimal residual disease detection in patients with multiple myeloma who underwent autologous stem-cell transplantation

Background

Most patients with multiple myeloma (MM) are considered to be incurable, and relapse owing to minimal residual disease (MRD) is the main cause of death among these patients. Therefore, new technologies to assess deeper response are required.

Patients and methods

We retrospectively analyzed 125 patients with MM who underwent high-dose melphalan plus autologous stem-cell transplantation (ASCT) to detect MRD in autograft/bone marrow (BM) cells using a next-generation sequencing (NGS)-based method and allele-specific oligonucleotide-polymerase chain reaction (ASO-PCR).

Results

NGS-based method was applicable to 90% and this method had at least one to two logs greater sensitivity compared to ASO-PCR. MRD negative by NGS [MRD^NGS(−)] (defined as <10⁻⁶) in post-ASCT BM cases (n = 26) showed a significantly better progression-free survival (PFS) (96% at 4 years, P < 0.001) and overall survival (OS) (100% at 4 years, P =0.04) than MRD^NGS(+) in post-ASCT BM cases (n = 25). When restricting the analysis to the 39 complete response cases, patients who were MRD^NGS(−) (n = 24) showed a significantly better PFS than those that were MRD^NGS(+) (n = 15) (P =0.02). Moreover, MRD^NGS(−) in post-ASCT BM cases (n = 12) showed significantly a better PFS than MRD^NGS(+) cases (n = 7) where MRD was not detected by ASO-PCR (P = 0.001). Patients whose autografts were negative by NGS-based MRD assessment (<10⁻⁷) (n = 19) had 92% PFS and 100% OS at 4 years post-ASCT. Conversely, the NGS-based MRD positive patients who received post-ASCT treatment using novel agents (n = 49) had a significantly better PFS (P = 0.001) and tended to have a better OS (P= 0.214) than those that were untreated (n = 33).

Conclusions

Low level MRD detected by NGS-based platform but not ASO-PCR has significant prognostic value when assessing either the autograft product or BM cells post-ASCT.

Comparison of Minimal Residual Disease Detection by Multiparameter Flow Cytometry, ASO-qPCR, Droplet Digital PCR, and Deep Sequencing in Patients with Multiple Myeloma Who Underwent Autologous Stem Cell Transplantation

Multiple myeloma (MM) is a hematological malignancy with a poor prognosis, characterized by clonal proliferation of plasma cells in the bone marrow (BM). Relapse due to undetected minimal residual disease (MRD) is the leading cause of death among patients with MM. This review summarizes the methods and prognostic value of MRD assessment in BM and autografts from MM patients who underwent autologous stem cell transplantation (ASCT) by multiparameter flow cytometry (MFC), allele-specific oligonucleotide real-time quantitative PCR (ASO-qPCR), droplet digital PCR (ddPCR), and next-generation sequencing (NGS)-based detection methods. MRD assessment using NGS-based approaches has clear prognostic value and better sensitivity compared to traditional methods.

Quantitative polymerase chain reaction analysis with allele-specific oligonucleotide primers for individual IgH VDJ regions to evaluate tumor burden in myeloma patients

Quantitative polymerase chain reaction (PCR) with patient-specific, allele-specific oligonucleotide (ASO) primers for individual immunoglobulin H VDJ region (ASO-PCR) amplification was performed using several sources of clinical material, including mRNA from peripheral blood cells (PBMNCs), whole bone marrow cells (BMMNCs), and the CD20+ CD38- B-cell population in bone marrow, as well as cell-free DNA from the sera of patients with multiple myeloma (MM). We designed the ASO primers and produced sufficient PCR fragments to evaluate tumor burden in 20 of 30 bone marrow samples at diagnosis. Polymerase chain reaction amplification efficiency depended on primer sequences because the production of ASO-PCR fragments did not correlate with serum M-protein levels. However, the ASO-PCR levels in BMMNCs showed statistically significant correlations with those in PBMNCs and CD20+ CD38- B-cells. The good association between the BMMNC and PBMNC data indicated that PBMNCs could be a suitable source for monitoring minimal residual disease (MRD). In the case of cell-free DNA, ASO-PCR levels showed a unique pattern and remained high even after treatment. Because the sequence information for each ASO-PCR product was identical to the original, the cell-free DNA might also be useful for evaluating MRD. Moreover, the ASO-PCR products were clearly detected in 17 of 22 mRNA samples from CD20+ CD38- populations, suggesting that MM clones might exist in relatively earlier stages of B cells than in plasma cells. Thus, ASO-PCR analysis using various clinical materials is useful for detecting MRD in MM patients as well as for clarifying MM pathogenesis.