Minimal Residual Disease After Autologous Stem-Cell Transplant for Patients With Myeloma: Prognostic Significance and the Impact of Lenalidomide Maintenance and Molecular Risk

Opportunities and challenges for MRD assessment in the clinical management of multiple myeloma

Measurable residual disease (MRD) assessment is, from the methodological point of view, ready for prime time in multiple myeloma (MM). Abundant evidence underscores the value of MRD status determined using highly sensitive next-generation flow cytometry and next-generation sequencing tests in evaluating response to treatment and, therefore, prognosis in patients with this disease. MRD response assessment and monitoring might present a range of opportunities for individualized patient management. Moreover, the considerable amounts of high-quality and standardized MRD data generated in clinical trials have led to the acceptance of MRD negativity as an early end point for accelerated regulatory approval of treatments for MM. The data leave no doubt that the efficacy of new regimens in inducing deeper and durable MRD-negative responses is connected with prolonged survival. Yet, several evidential, technical and practical challenges continue to limit the implementation of MRD-guided treatment strategies in routine practice, and the use of MRD as a surrogate end point remains controversial to some. In this Review, we draw on past and present research to propose opportunities for overcoming some of these challenges, and to accelerate the use of MRD assessment for improved clinical management of patients with MM.

Are we maintaining minimal residual disease in myeloma?

Minimal residual disease (MRD) has emerged as an important prognostic maker in patients with multiple myeloma at different stages of their treatment. Moreover, it is being increasingly incorporated as an endpoint in various clinical trials. Since maintenance therapy is an integral part of myeloma treatment, especially in the upfront setting post autologous transplantation, it is imperative to understand the role of MRD testing in the maintenance stetting. This review aims to examine the utility and dynamics of MRD testing in order to elucidate its prognostic role and possible incorporation in clinical decision making processes.

Sustained bone marrow and imaging MRD negativity for 3 years drives discontinuation of maintenance post-ASCT in myeloma

ABSTRACT

Discontinuation of lenalidomide maintenance after autologous stem cell transplantation is a burning question within the multiple myeloma (MM) community, especially after the inclusion of minimal residual disease (MRD) in the disease response criteria. In this prospective study, we evaluated the conversion to MRD positivity, the treatment-free survival (TFS), and the progression-free survival (PFS) in 52 patients with MM who discontinued lenalidomide maintenance after achieving sustained bone marrow and imaging MRD negativity for 3 years. Patients who developed MRD positivity after lenalidomide discontinuation restarted lenalidomide maintenance at the same dose. The median follow-up from lenalidomide discontinuation was 3 years. Overall, 12 (23%) patients obtained MRD positivity and restarted lenalidomide maintenance. Only 4 (7.6%) patients progressed; 3 had a biochemical progression and 1 had a clinical progression. The overall median PFS was not reached, whereas the 7-year PFS from diagnosis was 90.2%. The 1-, 2-, and 3-year TFS rates were 93.9%, 91.6%, and 75.8%, respectively, whereas the 1-, 2-, and 3-year landmark PFS rates from maintenance discontinuation (study entrance) were 96.0%, 96.0%, and 92.9%, respectively. There were no statistically significant associations among age, sex, Second Revision International Staging System, type of induction therapy, and use of consolidation therapy and the effect outcomes of PFS and TFS. We conclude that maintenance discontinuation after 3 years of sustained marrow and imaging MRD negativity is associated with low rates of MRD conversion and progressive disease. Thus, in the era of modern antimyeloma treatments, a subgroup of patients may remain treatment free while in complete remission without jeopardizing disease response.

Cytogenetic risk stratification combined with minimal residual disease status influences the therapeutic outcome and prognosis of multiple myelomas

To explore the value of cytogenetic risk stratification combined with minimal residual disease (MRD) status in predicting the therapeutic efficacy and prognosis for multiple myeloma (MM). From January 2017 to December 2023, 73 cases of newly diagnosed MM were recruited. Cytogenetic risks were stratified according to the results of fluorescence in situ hybridization (FISH); MRD status and clinical data were analyzed. The progression-free survival (PFS) and overall survival (OS), and their influencing factors were evaluated. During the median follow-up period of 30 (4-65) months, the median progression-free survival (PFS) and overall survival (OS) were 38 (95% CI 29.7, 46.3) months and 55 (95% CI 45.9, 64.1) months, respectively. In our cohort, the 3-year PFS rate was 51.0% and the 3-year OS rate was 71.0%. According to the MRD status, 31 MM patients were assigned to the MRD-positivity group and 42 to the MRD-negativity group. Significant differences were detected in the median PFS (30 months vs. 45 months, χ2 = 7.747, P = 0.005) and OS (34 months vs. 59 months, χ2 = 8.683, P = 0.003) between groups. Subgroup analyses based on the cytogenetic risk stratification (standard risk [SR] and high risk [HR]) showed that MM patients in the SR/MRD-negativity subgroup did not reach the median PFS and OS, and the median PFS (42 months vs. 33 months, P = 0.093) and OS (59 months vs. 42 months, P = 0.703) were similar between the SR/MRD-positivity and HR/MRD-negativity subgroups. In comparison to the HR/MRD-negativity subgroup, the median PFS (20 months vs. 33 months, P = 0.031) and OS (33 months vs. 42 months, P = 0.032) were significantly shorter in the HR/MRD-positivity group. Multivariate analysis showed that MRD-positivity was an independent risk factor for PFS (HR 2.874, 95% CI 1.452, 5.689; P = 0.008) and OS (HR 3.504, 95% CI 1.599, 7.676; P = 0.002) of MM. MRD status is a powerful prognostic indicator of PFS and OS in MM, but its performance is inferior to cytogenetic risk stratification. More high-risk cytogenetic abnormalities (HRCAs) indicate a worse prognosis of MM, while MRD-negativity improves HRCA-associated prognosis of MM. We recommend a risk stratification by assessing MRD status combined with HRCAs in MM patients, thus favoring the design of individualized treatment.

Minimal Residual Disease-Based End Point for Accelerated Assessment of Clinical Trials in Multiple Myeloma: A Pooled Analysis of Individual Patient Data From Multiple Randomized Trials

PURPOSE

Newly approved drugs and combinations treating multiple myeloma (MM) have resulted in substantial improvements in patients' survival. To deliver rapid access to newer therapies, an earlier end point to expedite clinical trials is needed. Our objective was to evaluate the minimal residual disease-negative complete response (MRD-CR) as an intermediate end point for progression-free survival (PFS) and overall survival (OS) in newly diagnosed (ND) transplant-eligible (NDTE) patients, ND transplant-ineligible (NDTinE) patients, and patients with relapsed/refractory (RR) MM.

PATIENTS AND METHODS

Individual patient data from 20 randomized multicenter trials were collected. Eleven studies (4,773 patients) with sufficient data were analyzed to evaluate whether 9- or 12-month MRD-CR classified at a 10-5 threshold could be reasonably likely to predict the clinical benefit of new agents regarding PFS and OS. Global odds ratio (OR) was estimated using the bivariate Plackett Copula model. Supportive evaluation included correlations of the treatment effects on MRD-CR end points and PFS/OS, evaluated by both linear regression (R2weighted least squared) and Copula (R2Copula) models.

RESULTS

The analysis demonstrated that both 9- and 12-month MRD-CR strongly correlated with PFS at patient level in NDTE patients, NDTinE patients, and patients with RRMM. Global ORs ranged from 3.06 to 16.24, all with 95% CIs excluding 1.0. Encouraging trial-level correlations (R2, 0.61-0.70) were observed by pooling three populations and were stronger (R2, 0.67-0.78) in the ND population. Similar results were observed for OS.

CONCLUSION

Our findings provided the support for use of MRD-CR classified at a 10-5 threshold at either 9 or 12 months after starting of the treatment, as an intermediate end point to support accelerated approvals, in future trials in NDTE patients, NDTinE patients, and patients with RRMM.

Minimal residual disease in multiple myeloma

Minimal Residual Disease (MRD) in multiple myeloma has emerged as a significant prognostic factor, guiding treatment strategies and enhancing patient outcomes. Despite advancements in therapies such as proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, CAR-T cell therapy, and bispecific antibodies, complete eradication of malignant plasma cells remains challenging. MRD refers to a small number of residual cancer cells that persist after treatment and require sensitive methods like next-generation flow cytometry (NGF) and next-generation sequencing (NGS) for detection. MRD negativity has been associated with improved progression-free survival (PFS) and overall survival (OS), making it a key marker in clinical trials. The clinical utility of MRD lies in its ability to predict outcomes, with sustained MRD negativity linked to prolonged survival. Furthermore, it will likely help in tailoring treatment approaches, such as therapy escalation for high-risk patients or de-escalation for those achieving MRD negativity. Despite its prognostic value, challenges remain in standardizing MRD testing, ensuring its widespread availability, and addressing variability in results based on different detection methods. Future research aims to refine MRD-guided treatment and explore novel detection techniques, such as liquid biopsies, to improve patient monitoring in multiple myeloma.

How First-Line Therapy is Changing in Transplant-Eligible Multiple Myeloma Patients

Multiple myeloma is a malignant haematological neoplasm characterised by the proliferation of plasma cells in the bone marrow. Each year, over 35,000 new cases are diagnosed in the United States, and nearly 13,000 patients die from the disease.1 The main cause of morbidity is bone disease, characterised by osteolytic lesions, which, unlike other malignancies that metastasise to bone, are not followed by new bone formation.2 Other major clinical manifestations include anaemia, hypercalcemia, renal failure, and an increased risk of infections. Approximately 1-2% of patients present with extramedullary disease (EMD) at the time of diagnosis, while 8% develop EMD later in the course of the disease.3 Although multiple myeloma remains incurable, its treatment continues to evolve rapidly. Approved therapies include immunomodulatory agents (IMiDs, such as thalidomide, lenalidomide, and pomalidomide), proteasome inhibitors (bortezomib, carfilzomib, and ixazomib), and monoclonal antibodies (mAb) targeting CD38 (especially daratumumab and isatuximab) and SLAMF7. New therapeutic avenues include bispecific antibodies and chimeric antigen receptor T-cell (CAR-T) therapy.4-5 The latest ESMO (European Society for Medical Oncology)6 and NCCN (National Comprehensive Cancer Network) guidelines7 have set the standard of care for patients with newly diagnosed multiple myeloma (NDMM) eligible for transplantation, particularly those in good general condition and < 70 years old. This approach is divided into four phases: induction therapy, hematopoietic stem cell collection, and autologous transplant, consolidation, and maintenance. The most significant differences between the guidelines occur during the induction phase, influenced by regulatory approvals in the United States and Europe. This article will focus on the changing landscape of therapies for newly diagnosed multiple myeloma (NDMM) in transplant-eligible.

Targeted Delivery of c(RGDfk)-Modified Liposomes to Bone Marrow Through In Vivo Hitchhiking Neutrophils for Multiple Myeloma Therapy

Multiple myeloma (MM) is a prevalent bone marrow disorder. The challenges in managing MM include selecting chemotherapy regimens that effectively modulate the myeloma microenvironment and delivering them to the bone marrow with high efficacy and minimal toxicity. Herein, a novel bone marrow targeting strategy using c(RGDfk) peptide-modified liposomes loaded with chemotherapeutics is developed, which can specifically recognize and hitchhike neutrophils following systemic administration, capitalizing on their natural aging process to facilitate precise drug delivery to the bone marrow, thus minimizing off-target effects. On the one hand, c(RGDfk)-functionalized liposomes containing carfilzomib (CRLPs) successfully transformed macrophages from M2 phenotype to M1 phenotype, enhancing immunotherapeutic responses. On the other hand, c(RGDfk)-functionalized liposomes encapsulating BMS-202 (BRLPs), a small molecule checkpoint inhibitor, interrupted the PD-1/PD-L1 axis and promoted the infiltration of cytotoxic T cells. The co-administration of CRLPs and BRLPs successfully delivered drugs to bone marrow, leading to significant modulation of the myeloma microenvironment, reduced tumor growth, and improved survival time of MM-bearing mouse models. These findings introduced an alternative approach to modulating the myeloma microenvironment and underscored the efficacy of hitchhiking neutrophils for bone marrow drug delivery. This strategy show advantages over traditional drug delivery methods in terms of improved efficacy and lowered toxicity.

Combination autologous stem cell transplantation with chimeric antigen receptor T-cell therapy for refractory/relapsed B-cell lymphoma: a single-arm clinical study

Autologous stem cell transplantation (ASCT) and chimeric antigen receptor T-cells (CAR-T) have been used as consolidation therapies for patients with refractory/relapsed B cell non-Hodgkin's lymphoma (R/R B-NHL) in remission after second-line chemotherapy or salvage therapy. However, patients with different pathological subtypes and remission states may benefit differently from ASCT or CAR-T cell therapy. Furthermore, consolidation treatment involving ASCT or CAR-T cells still poses a significant risk of disease relapse. We conducted a retrospective, single-arm study of 47 patients with R/R B-NHL, and found that the combination of ASCT and CAR-T therapy improved the 3-year progression-free survival (PFS) and overall survival (OS) rates to 66.04% (95%CI: 48.311-78.928) and 72.442% (95%CI: 53.46-84.708) respectively. Furthermore, the combination therapy has no serious adverse events. Thus, ASCT combined with CAR-T cell therapy is effective against multiple subtypes of R/R B-NHL, and can effectively prolong the long-term survival of patients.

Evidence-based Korean guidelines for the clinical management of multiple myeloma: addressing 12 key clinical questions

Multiple myeloma (MM), a hematological malignancy, is characterized by malignant plasma cell proliferation in the bone marrow. Recent treatment advances have significantly improved patient outcomes associated with MM. In this study, we aimed to develop comprehensive, evidence-based guidelines for the diagnosis, prognosis, and treatment of MM. We identified 12 key clinical questions essential for MM management, guiding the extensive literature review and meta-analysis of the study. Our guidelines provide evidence-based recommendations by integrating patient preferences with survey data. These recommendations include current and emerging diagnostic tools, therapeutic agents, and treatment strategies. By prioritizing a patient-centered approach and rigorous data analysis, these guidelines were developed to enhance MM management, both in Korea and globally.

Minimally Invasive Assessment of Peripheral Residual Disease During Maintenance or Observation in Transplant-Eligible Patients With Multiple Myeloma

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.In multiple myeloma (MM), measurable residual disease (MRD) is assessed in bone marrow (BM). However, less invasive evaluation of peripheral residual disease (PRD) in blood could be advantageous and less cumbersome. We investigated the prognostic value of PRD monitoring after 24 cycles of maintenance in 138 transplant-eligible patients with MM enrolled in the GEM2012MENOS65/GEM2014MAIN clinical trials. PRD was assessed using next-generation flow (NGF) and mass spectrometry (MS). Positive PRD by NGF in 16/138 (11.5%) patients was associated with a 13-fold increased risk of progression and/or death; median progression-free survival (PFS) and overall survival (OS) were 2.5 and 47 months, respectively. Considering patients' MRD status in BM as the reference, PRD detection using NGF showed positive and negative predictive values of 100% and 73%, respectively. Presence of PRD helped identifying patients at risk of imminent progression among those with positive MRD in BM. Patients with undetectable PRD according to both NGF and MS showed 2-year PFS and OS rates of 97% and 100%, respectively. In multivariate analyses including the Revised International Staging System and the complete remission status, only MRD in BM and PRD by NGF showed independent prognostic value for PFS. This study supports the use of less invasive PRD monitoring during maintenance or observation in transplant-eligible patients with MM.

Flow Cytometric MRD Detection in Selected Mature B-Cell Malignancies

The quantification of submicroscopic minimal residual disease (MRD) after therapy proved to have independent prognostic significance in many mature B-cell malignancies. With the advent of routine benchtop cytometers capable of simultaneously analyzing ≥8 colors and with improved standardization, flow cytometry has become the method of choice for MRD assessments in some lymphoma entities. Herein we describe general aspects of flow cytometric standardization. Chronic lymphocytic leukemia (CLL) and multiple myeloma (MM) are used as examples to explain the technical standardization of flow cytometry for MRD detection according to EuroFlow strategies. MRD data acquisition and detailed analysis in MM and CLL is a particular focus of this chapter.

Clinical significance of complete remission and measurable residual disease in relapsed/refractory multiple myeloma patients treated with T-cell redirecting immunotherapy

The impact of measurable residual disease (MRD) in relapse/refractory multiple myeloma (RRMM) patients treated with T-cell redirecting immunotherapy is uncertain. We analyzed MRD dynamics using next-generation flow in 201 patients treated in clinical trials with chimeric antigen receptor (CAR) T cells and T-cell engagers (TCE). Achieving MRD negativity at 10-6 was associated with 89% reduction in the risk of progression and/or death. Survival outcomes were improved in patients with sustained versus transient MRD negativity and were dismal in those who remained MRD positive. The intent-to-treat MRD negative rates were higher in patients treated with CAR T cells versus TCE. However, among patients achieving MRD negativity, there were no differences in survival outcomes when stratified according to treatment with CAR T cells versus TCE. In multivariate analysis including the number of prior lines of treatment, International Staging System, cytogenetic risk, extramedullary disease and type of T-cell redirecting immunotherapy, only the complete remission (CR) and MRD statuses showed independent prognostic value for progression-free and overall survival. In conclusion, our study shows that deep and sustained MRD negative CR is the most relevant prognostic factor and should be considered as the treatment endpoint in RRMM patients treated with CAR T cells and TCE.

Busulfan and cyclophosphamide for autologous stem cell transplantation in patients with multiple myeloma after proteasome inhibitor and/or immunomodulatory drug treatment

High-dose melphalan at 200 mg/m2 (MEL-200) is the standard conditioning regimen before autologous stem cell transplantation (ASCT) in patients with multiple myeloma (MM). Busulfan (BU) and cyclophosphamide (CY) can be used as alternatives when MEL is unavailable. However, most studies on BU/CY conditioning regimens were conducted before proteasome inhibitors (PIs) and immunomodulatory drugs (IMIDs) were available. This non-interventional comparative cohort study compared progression-free survival (PFS) between the MEL-200 and BU/CY in patients with MM treated with PIs and/or IMIDs. A total of 137 patients were analyzed (MEL-200,113 patients; BU/CY, 24 patients). The BU/CY group had a higher rate of PI and/or IMID use and very good partial response (VGPR) or complete remission (CR) at ASCT and post-ASCT maintenance. Median PFS was 29.7 and 46.8 months in the MEL-200 and BU/CY groups, respectively. In the multivariate analysis, PFS was significantly better in the BU/CY group. International Staging System Stage I and VGPR or CR at ASCT were significantly associated with longer PFS. No treatment-related mortality was observed in either group by day 100. The BU/CY conditioning regimen may be a viable alternative to the MEL-200 regimen in patients with MM who undergo ASCT after treatment with PIs and/or IMIDs.

Dynamics of minimal residual disease and its clinical implications in multiple myeloma: A retrospective real-life analysis

BACKGROUND

Minimal residual disease (MRD) testing is a promising approach to tailor the treatment of multiple myeloma (MM). However, several major concerns remain to be addressed before moving it into daily practice, most of which stem from the dynamic nature of the MRD status. Thus, it is crucial to understand the MRD dynamics and propose its clinical implications.

METHODS

We retrospectively analysed the data of patients with newly diagnosed MM (NDMM) who had flow cytometry-based MRD tests at multiple time points after initiation of therapy. The impact of undetectable MRD (including attainment, duration and loss) on clinical outcomes was analysed.

RESULTS

In a cohort of 220 patients with NDMM, attainment of MRD- offered favourable outcomes (P < 0.0001 for both progression-free survival (PFS) and overall survival (OS)), regardless of baseline risk factors. Notably, MRD- duration ≥12 months was associated with an 83 % (95 % confidence interval (CI), 0.09-0.34; P < 0.0001) or 69 % (95 % CI, 0.13-0.76; P = 0.0098) reduction in risk of progression/death or death, while the longer MRD- was sustained, the better the outcome was. Loss of MRD- led to poor PFS (hazard ratio (HR) 0.01, 95 % CI 0-0.06, P < 0.0001) and OS (HR 0.03, 95 % CI 0-0.24, P = 0.0008). Most patients (70 %) who lost MRD- status carried high-risk cytogenetic abnormalities (HRCAs). While MRD- was temporally inconsistent with conventional therapeutic responses (eg ≥ complete remission or very good partial response), it predicted disease progression or recurrence more robustly than the latter. Last, the predictive value of the MRD status was independent of baseline risk factors (eg high-risk cytogenetic abnormality, International Staging System (ISS) or Revised (R-)ISS staging).

CONCLUSIONS

Longitudinal assessment of MRD during the treatment course and follow-up is required for monitoring disease progression or relapse, to guide treatment decisions. Accordingly, a prospective study is currently ongoing to investigate the feasibility and benefit of the MRD-tailored therapy according to the longitudinal changes of the MRD status.

Clinical implications of residual normal plasma cells within bone marrow across various disease stages in multiple myeloma

Residual normal plasma cells (NPCs), which compete with tumor plasma cells, play an important role in multiple myeloma. However, large-scale cohort studies investigating residual NPCs, especially at the minimal residual disease (MRD) phase, are currently lacking. In this study, we conducted a comprehensive investigation into the clinical significance of residual NPCs throughout the entire disease course in 1363 myeloma patients from the NICHE cohort (NCT04645199). Our results revealed that myeloma patients with high baseline NPCs ratio (≥5%) exhibited distinct indolent features, characterized by lower tumor burden, reduced frequencies of cytopenia, immunoparesis, and high-risk cytogenetics. Importantly, high residual NPCs ratio at diagnosis or relapse was independently associated with favorable survival. High absolute percentages of NPCs at undetectable MRD were related with superior clinical benefit and immune reconstitution. At MRD-positive phases, grouping based on NPCs ratio (<50%, 50-90%, ≥90%) demonstrated better risk stratification compared to residual tumor log levels. Based on the time-dependent NPCs ratio trend, we developed a dynamic MRD model that classifies patients into three groups with diverse longitudinal trends, leading to distinct prognoses. Collectively, residual NPCs serves not only as a valuable complementary biomarker for risk stratification but also provides valuable insights on reclassifications and kinetics of MRD.

MRD dynamics during maintenance therapy in 259 patients with nontransplant eligible multiple myeloma

This study explored the impact of different maintenance therapies on survival outcomes in patients with multiple myeloma (MM), focusing on changes in minimal residual disease (MRD) during maintenance. Conducted at a single center, this retrospective study included 259 newly diagnosed MM patients who did not undergo autologous stem cell transplantation (ASCT). The results indicated that patients receiving lenalidomide as maintenance therapy showed significantly better progression-free survival (PFS) and overall survival (OS) compared to those treated with bortezomib or no maintenance therapy. However, bortezomib proved more effective in high-risk MM cases. Patients who were MRD-negative prior to starting maintenance therapy had a better prognosis than MRD-positive patients. Notably, lenalidomide was the most effective regimen irrespective of MRD status. Patients maintaining or achieving MRD-negativity within the first year of lenalidomide treatment exhibited improved prognoses, confirming lenalidomide as the optimal maintenance choice.

Measurable Residual Disease Testing in Multiple Myeloma Following T-Cell Redirecting Therapies

Several novel T-cell-based therapies have recently become available for multiple myeloma (MM). These T-cell redirecting therapies (TRTs) include chimeric antigen receptor T-cells (CAR-T) and bispecific antibodies (BiAbs). In both clinical trial and real-world data, these therapies have demonstrated high rates of deep clinical response, and some are now approved for second-line treatment for relapsed MM. The deep and sustained clinical responses these therapies are capable of inducing will require sophisticated response monitoring to provide meaningful information for patient care. Obtaining measurable residual disease (MRD) negativity has been validated as an independent positive prognostic marker for progression-free survival (PFS) and overall survival (OS) in both newly diagnosed and relapsed refractory patients with multiple myeloma. Assessment for MRD negativity was performed in all of the trials for FDA-approved TRT. Here, we summarize pertinent data for MRD assessment following TRT in MM and provide a rationale and structured framework for conducting MRD testing post TRT.

Identification of Therapy-Induced Clonal Evolution and Resistance Pathways in Minimal Residual Clones in Multiple Myeloma through Single-Cell Sequencing

PURPOSE

In multiple myeloma (MM), therapy-induced clonal evolution is associated with treatment resistance and is one of the most important hindrances toward a cure for MM. To further understand the molecular mechanisms controlling the clonal evolution of MM, we applied single-cell RNA sequencing (scRNA-seq) to paired diagnostic and posttreatment bone marrow (BM) samples.

EXPERIMENTAL DESIGN

scRNA-seq was performed on 38 BM samples from patients with monoclonal gammopathy of undetermined significance (n = 1), MM patients at diagnosis (n = 19), MM posttreatment (n = 17), and one healthy donor (HD). The single-cell transcriptome data of malignant plasma cells (PC) and the surrounding immune microenvironment were analyzed.

RESULTS

Profiling by scRNA-seq data revealed three primary trajectories of transcriptional evolution after treatment: clonal elimination in patients with undetectable minimal residual disease (MRD-) and clonal stabilization and clonal selection in detectable MRD (MRD+) patients. We noted a metabolic shift toward fatty acid oxidation in cycling-resistant PCs, whereas selective PCs favored the NF-κB pathway. Intriguingly, when comparing the genetic and transcriptional dynamics, we found a significant correlation between genetic and nongenetic factors in driving the clonal evolution. Furthermore, we identified variations in cellular interactions between malignant PCs and the tumor microenvironment. Selective PCs showed the most robust cellular interactions with the tumor microenvironment.

CONCLUSIONS

These data suggest that MM cells could rapidly adapt to induction treatment through transcriptional adaptation, metabolic adaptation, and specialized immune evasion. Targeting therapy-induced resistance mechanisms may help to avert refractory disease in MM.

Prognostic value of the "dynamic" R2-ISS in patients with multiple myeloma undergoing anti-CD38 antibody-based triplet therapies

To retrospectively analyze whether the second revision of the international staging system (R2-ISS) influenced prognosis at treatment initiation in patients with multiple myeloma (MM) receiving anti-CD38 antibody-based triplet treatments. High-risk chromosomal abnormalities were examined from diagnosis to treatment initiation and considered positive if detected once. R2-ISS was recalculated at the initiation of treatment and defined as "dynamic R2-ISS." Data from 150 patients who underwent the defined treatments were analyzed. The median progression-free survival (PFS) was 19.5 months, and the median overall survival (OS) was 36.5 months. Dynamic R2-ISS significantly stratified prognoses for both PFS and OS. The median PFS for patients with dynamic R2-ISS IV was 3.3 months, and the median OS was 11.7 months, indicating extremely poor outcomes. Although the Revised International Staging System (R-ISS) calculated at the initiation of treatment significantly stratified treatment outcomes, the patients classified as R-ISS could be further stratified by R2-ISS to provide better prognostic information. Dynamic R2-ISS showed potential as a prognostic tool in patients with MM who are treated with anti-CD38 antibody-based triplet therapies.

Minimal Residual Disease Status in Multiple Myeloma 1 Year After Autologous Hematopoietic Cell Transplantation and Lenalidomide Maintenance Are Associated With Long-Term Overall Survival

PURPOSE

Prognostic Immunophenotyping in Myeloma Response (PRIMeR) is an ancillary study of minimal residual disease (MRD) assessment for multiple myeloma by next-generation multiparameter flow cytometry (MFC). Patients were enrolled on a three-arm randomized control trial (Blood and Marrow Transplants Clinical Trials Network 0702 Stem Cell Transplant for Myeloma in Combination of Novel Agents [STaMINA]; ClinicalTrials.gov identifier: NCT01109004).

METHODS

Four hundred and thirty-five patients consented to the MRD panel, which included 10 monoclonal antibodies measured via six-color MFC. MRD was measured at baseline/preautologous hematopoietic cell transplant (BL/preAutoHCT), premaintenance (PM), and 1 year (Y1) after AutoHCT with a sensitivity of 10-5 to 10-6. The primary objective was to assess MRD-negative (MRDneg) at 1 year after AutoHCT and progression-free survival and overall survival (PFS/OS).

RESULTS

Similar to the STaMINA results, at a median follow-up of 70 months, there was no significant difference in PFS/OS by treatment arm in the PRIMeR patients. MRDneg at all three time points was associated with significantly improved PFS, and MRDneg at Y1 had significantly longer OS. Multivariate analysis of PFS, adjusting for disease risk and treatment arm, demonstrated hazard ratios (HRs) in MRD-positive patients compared with MRDneg patients at BL, PM, and Y1 of 1.55 (P = .0074), 1.83 (P = .0007), and 3.61 (P < .0001), respectively. Corresponding HRs for OS were 1.19 (P = .48), 0.88 (P = .68), and 3.36 (P < .001). Patients with sustained MRDneg or who converted to MRDneg by Y1 had similar PFS/OS.

CONCLUSION

To our knowledge, this first, prospective US cooperative group, multicenter study demonstrates that MRDneg at Y1 after AutoHCT with lenalidomide maintenance is prognostic for improved 6-year PFS and OS. Serial MRD measurements may direct trials to test how further therapy may improve long-term PFS and OS.

Risk factors of early disease progression and decreased survival for multiple myeloma patients after upfront autologous stem cell transplantation

Multiple myeloma (MM) stands as the second most prevalent hematological malignancy, constituting approximately 10% of all hematological malignancies. Current guidelines recommend upfront autologous stem cell transplantation (ASCT) for transplant-eligible MM patients. This study seeks to delineate factors influencing post-ASCT outcomes in MM patients. Our cohort comprised 150 MM patients from Taipei Veterans General Hospital, with progression-free survival (PFS) as the primary endpoint and overall survival (OS) as the secondary endpoint. A Cox proportional hazards model was employed to discern potential predictive factors for survival. ASCT age ≥ 65 (hazard ratio [HR] 1.94, 95% confidence interval [CI] 1.08-3.47) and the presence of extramedullary disease (HR 2.53, 95% CI 1.53-4.19) negatively impacted PFS. Conversely, treatment response ≥ VGPR before ASCT (HR 0.52, 95% CI 0.31-0.87) and total CD34+ cells collected ≥ 4 × 106 cells/kg on the first stem cell harvesting (HR 0.52, 95% CI 0.32-0.87) were positively associated with PFS. For OS, patients with ISS stage III (HR 2.06, 95% CI 1.05-4.04), the presence of extramedullary disease (HR 3.92, 95% CI 2.03-7.58), light chain ratio ≥ 100 before ASCT (HR 7.08, 95% CI 1.45-34.59), post-ASCT cytomegalovirus infection (HR 9.43, 95% CI 3.09-28.84), and a lower conditioning melphalan dose (< 140 mg/m2; HR 2.75, 95% CI 1.23-6.17) experienced shorter OS. In contrast, post-ASCT day + 15 absolute monocyte counts (D15 AMC) > 500/µl (HR 0.36, 95% CI 0.17-0.79) and post-ASCT day + 15 platelet counts (D15 PLT) > 80,000/µl (HR 0.48, 95% CI 0.24-0.94) were correlated with improved OS. Significantly, early PLT and AMC recovery on day + 15 predicting longer OS represents a novel finding not previously reported. Other factors also align with previous studies. Our study provides real-world insights for post-ASCT outcome prediction beyond clinical trials.

High-risk multiple myeloma: Redefining genetic, clinical, and functional high-risk disease in the era of molecular medicine and immunotherapy

Multiple myeloma (MM) exhibits significant heterogeneity in its presentation, genetics, and treatment response. Despite therapeutic advances, some patients continue to relapse early (ER, <18-months) and rapidly cycle through therapies. Myriad prognostic factors have been identified and incorporated into risk stratification models; however, these produce discordant, often three-tiered outputs that fail to identify many patients destined for ER. Treatment strategies are increasingly focused on disease biology and trials enriched for high-risk (HR)MM, but consensus on the minimum required testing and a succinct, specific, and clinically meaningful definition for HRMM remains elusive. We review the risk-factors, definitions, and future directions for HRMM.

Minimal Residual Disease-Adapted Therapy in Multiple Myeloma: Current Evidence and Opinions

PURPOSE OF REVIEW

Multiple myeloma (MM) is a biologically heterogeneous malignancy with relatively uniform treatment paradigms. This review aims to assess the growing role of Minimal Residual Disease (MRD) assessment in facilitating response-adapted therapeutic decision making to individualize therapy in MM.

RECENT FINDINGS

MRD has been repeatedly demonstrated to provide strong prognostic information, superseding traditional IMWG response criteria. The use of MRD to modulate therapy remains controversial. Here, we review the existing landscape of MRD-adapted trial designs in both induction/consolidation and maintenance settings, including recent data from influential studies and retrospective analyses. We navigate existing data, leverage the increased resolution of longitudinal MRD assessments, and comment on trials in progress to explain our current utilization of MRD in the clinic. MRD transcends traditional response assessments by providing a window into disease-treatment interaction over time. As a strong patient-level surrogate, MRD has limited current use in individualizing treatment, but is poised to comprehensively shape treatment strategies at many key points in a patient's MM course.

Multiple myeloma patients with a long remission after autologous hematopoietic stem cell transplantation

Autologous stem cell transplantation (autoHCT) is considered standard of care for newly diagnosed multiple myeloma (MM). Although most patients eventually progress after autoHCT, a small proportion achieve a durable response. In this retrospective study we included 1576 patients, 244 (15%) of whom were long-term responders (LTR), defined as having a progression-free survival (PFS) of ≥8 years after transplant. Patients in the LTR group were younger than the non-LTR group (median age 58.4 vs. 59.5 years; p = 0.012), less likely to have high-risk cytogenetics (4% vs. 14%; p < 0.001), more often had <50% bone marrow plasma cells (67% vs. 58%; p = 0.018) and R-ISS stage I disease (43% vs. 34%). More patients in the LTR group received post-transplant maintenance (63% vs. 52%; p = 0.002). Patients in the LTR group had higher rates of complete response (CR) at day100 (41% vs. 27%; p < 0.001) and at best post-transplant response (70% vs. 37%; p < 0.001), compared to the non-LTR group. Patients in the LTR groups had a median PFS of 169.3 months and the median overall survival (OS) had not been reached. The leading cause of death in the LTR was disease progression. In conclusion, 15% of patients in the cohort were LTR after upfront autoHCT, with distinct characteristics and a median PFS of more than 14 years.

Impact of pretransplant minimal residual disease in patients with multiple myeloma and a very good partial response or better receiving autologous hematopoietic stem cell transplantation

BACKGROUND

The prognostic significance of minimal residual disease (MRD) status before autologous hematopoietic stem cell transplantation (autoHCT) in patients with multiple myeloma (MM) has not been clearly elucidated.

METHODS

Retrospective single-center study of adult MM patients who achieved ≥very good partial response (VGPR) after induction therapy from 2015 to 2021 received upfront autoHCT and had available pretransplant MRD status by next-generation flow cytometry. The cohort was divided into pretransplant MRD-negative (MRDneg) and MRD-positive (MRDpos) groups.

RESULTS

A total of 733 patients were included in our analysis; 425 were MRDneg and 308 MRDpos at autoHCT. In the MRDpos group, more patients had high-risk cytogenetic abnormalities (48% vs. 38%, respectively; p = .025), whereas fewer patients achieved ≥CR before autoHCT (14% vs. 40%; p < .001). At day 100 after autoHCT, 37% of the MRDpos versus 71% of the MRDneg achieved ≥CR, and at best posttransplant response 65% versus 88% achieved ≥CR, respectively. After a median follow-up of 27.6 months (range, 0.7-82.3), the median PFS was significantly shorter for patients in the MRDpos group compared to the MRDneg group: 48.2 months (95% confidence interval [CI], 0.3-80.5) versus 80.1 months (95% CI, 0.5-80.1), respectively (p < .001). There was no significant difference in overall survival between the two groups (p = .41). Pretransplant MRDpos status was predictive of shorter PFS in multivariate analysis (hazard ratio, 1.80; 95% CI, 1.31-2.46; p < .001). The impact of pretransplant MRD status was retained in most of the examined subgroups.

CONCLUSIONS

In patients achieving ≥VGPR to induction, pretransplant MRDpos status was associated with a lower CR rate after autoHCT and a shorter PFS.

The role of maintenance therapy following autologous stem cell transplantation in newly diagnosed multiple myeloma: Considerations on behalf of the Chronic Malignancies Working Party of the EBMT

Recent treatment advancements in multiple myeloma have led to significant improvements in patient outcomes. Maintenance therapy following autologous haematopoietic stem cell transplantation (AHCT) is now standard of care and has been demonstrated to prolong and deepen treatment responses. Currently, lenalidomide remains the single agent that has been approved for maintenance post-AHCT in Europe and the USA which, if tolerated, is continued until disease progression. The treatment landscape is rapidly expanding however, and the optimal personalised maintenance approach for a patient is becoming more complex. Treatment outcomes for patients with high-risk disease remain poor and choice of maintenance in this population also remains unclear. This review article evaluates up-to-date literature regarding established maintenance approaches. It further analyses ongoing studies exploring maintenance regimens using combination and novel agents, approaches to maintenance in patients with cytogenetic high-risk disease and minimal residual disease response-adapted strategies that reflect the current evolving treatment paradigm.

Monitoring Minimal Residual Disease in Patients with Multiple Myeloma by Targeted Tracking Serum M-Protein Using Mass Spectrometry (EasyM)

PURPOSE

We investigated both the clinical utilities and the prognostic impacts of the clonotypic peptide mass spectrometry (MS)-EasyM, a blood-based minimal residual disease (MRD) monitoring protocol in multiple myeloma.

EXPERIMENTAL DESIGN

A total of 447 sequential serum samples from 56 patients with multiple myeloma were analyzed using EasyM. Patient-specific M-protein peptides were sequenced from diagnostic samples; sequential samples were quantified by EasyM to monitor the M-protein. The performance of EasyM was compared with serum immunofixation electrophoresis (IFE), bone marrow multiparameter flow cytometry (MFC), and next-generation flow cytometry (NGF) detection. The optimal balance of EasyM sensitivity/specificity versus NGF (10-5 sensitivity) was determined and the prognostic impact of MS-MRD status was investigated.

RESULTS

Of the 447 serum samples detected and measured by EasyM, 397, 126, and 92 had time-matching results for comparison with serum IFE, MFC-MRD, and NGF-MRD, respectively. Using a dotp >0.9 as the MS-MRD positive, sensitivity was 99.6% versus IFE and 100.0% versus MFC and NGF. Using an MS negative cutoff informed by ROC analysis (<1.86% of that at diagnosis), EasyM sensitivity remained high versus IFE (88.3%), MFC (85.1%), and NGF (93.2%), whereas specificity increased to 90.4%, 55.8%, and 93.2%, respectively. In the multivariate analysis, older diagnostic age was an independent predictor for progression-free survival [PFS; high risk (HR), 3.15; 1.26-7.86], the best MS-MRD status (MS-MRD negative) was independent predictor for both PFS (HR, 0.25; 0.12-0.52) and overall survival (HR, 0.16; 0.06-0.40).

CONCLUSIONS

EasyM is a highly sensitive and minimal invasive method of MRD monitoring in multiple myeloma; MS-MRD had significant predictive ability for survival outcomes.

A Risk Stratification System in Myeloma Patients with Autologous Stem Cell Transplantation

Autologous stem cell transplantation (ASCT) has been a mainstay in myeloma treatment for over three decades, but patient prognosis post-ASCT varies significantly. In a retrospective study of 5259 patients with multiple myeloma (MM) at the University of Arkansas for Medical Sciences undergoing ASCT with a median 57-month follow-up, we divided the dataset into training (70%) and validation (30%) subsets. Employing univariable and multivariable Cox analyses, we systematically assessed 29 clinical variables, identifying crucial adverse prognostic factors, such as extended duration between MM diagnosis and ASCT, elevated serum ferritin, and reduced transferrin levels. These factors could enhance existing prognostic models. Additionally, we pinpointed significant poor prognosis markers like high serum calcium and low platelet counts, though they are applicable to a smaller patient population. Utilizing seven easily accessible high-risk variables, we devised a four-stage system (ATM4S) with primary stage borders determined through K-adaptive partitioning. This staging system underwent validation in both the training dataset and an independent cohort of 514 ASCT-treated MM patients from the University of Iowa. We also explored cytogenetic risk factors within this staging system, emphasizing its potential clinical utility for refining prognostic assessments and guiding personalized treatment approaches.

Real-world prognostic significance of attaining minimal residual disease negativity in newly diagnosed multiple myeloma

The aim of the study was to evaluate the prognostic impact of minimal residual disease (MRD) in the real-world setting and the interaction between MRD and molecular risk, clinical response and autologous stem-cell transplant (ASCT). A retrospective analysis of 275 newly diagnosed multiple myeloma (NDMM) patients who achieved very good partial remission (VGPR) or better before maintenance were involved. We examined MRD status by multiparameter flow cytometry (MFC). At a median follow-up of 37 months (4-88 months), In patients who achieved ≥ VGPR, those with MRD negativity had significantly longer PFS (51 vs. 26 months; P < 0.001) and OS (Not reached: NR vs. 62 months, P < 0.001) than those with MRD positivity. MRD positivity was the independent prognostic factor for PFS with hazard ratios of 2.650 (95% CI 1.755-4.033, P < 0.001) and OS with hazard ratios of 2.122 (95% CI 1.155-3.899, P = 0.015). Achieving MRD negativity was able to ameliorate a poor prognosis associated with genetic high risk. MRD negativity was associated with better PFS regardless of ASCT treatment. MRD status was more predictable for clinical outcome than conventional clinical responses. Moreover, Sustained MRD negativity ≥ 12 or ≥ 24 months improved both PFS and OS. Patients with NDMM who achieved MRD-negative status or sustained MRD negativity had deep remission and improved clinical outcomes regardless of high-risk cytogenetics, ASCT and clinical responses in a real-world setting.

Predictors of unsustained measurable residual disease negativity in transplant-eligible patients with multiple myeloma

ABSTRACT

The role of measurable residual disease (MRD) negativity as a biomarker to stop treatment is being investigated in transplant-eligible patients with multiple myeloma (MM). Thus, it is important to identify risk factors of MRD resurgence and/or progressive disease (PD) among patients achieving undetectable MRD to avoid undertreating them. Here, we studied 267 newly diagnosed transplant-eligible patients with MM enrolled in the GEM2012MENOS65 and GEM2014MAIN clinical trials who achieved MRD negativity by next-generation flow cytometry. After a median follow-up of 73 months since the first MRD negative assessment, 111 of the 267 (42%) patients showed MRD resurgence and/or PD. The only prognostic factors at diagnosis that predicted MRD resurgence and/or PD were an International Staging System (ISS) 3 and the presence of ≥0.01% circulating tumor cells (CTCs). Failure to achieve MRD negativity after induction also predicted higher risk of MRD resurgence and/or PD. Patients having 0 vs 1 vs ≥2 risk factors (ISS 3, ≥0.01% CTCs, and late MRD negativity) showed 5-year rates of MRD resurgence and/or PD of 16%, 33%, and 57%, respectively (P < .001). Thus, these easily measurable risk factors could help refine the selection of patients for whom treatment cessation after MRD negativity is being investigated in clinical trials. This trial was registered at www.clinicaltrials.gov as NCT01916252 and NCT02406144.

Longitudinal genetically detectable minimal residual disease by fluorescence in situ hybridization confers a poor prognosis in myeloma

Background

Deeper depth of response (DpR) after induction therapy, especially gain of negative minimal residual disease (MRD), has been linked to prolonged survival in multiple myeloma (MM). However, flow-MRD examination focuses on the numbers but not on the biological characteristics of residual plasma cells (PCs).

Objectives

To explore whether the genetic features of residual tumor cells affect the survival time of patients with MM.

Design

A retrospective cohort study.

Methods

We investigated the clonality of cytogenetic abnormalities (CAs) of the residual PCs using interphase fluorescence in situ hybridization (iFISH) in the National Longitudinal Cohort of Hematological Diseases in China (NCT04645199). Here, a longitudinal cohort of 269 patients with patient-paired diagnostic and post-induction iFISH results was analyzed.

Results

Persistent CAs after induction therapy were detected in about half of the patients (118/269, 43%), and patients with undetectable CAs showed significantly improved survival compared with those with genetically detectable MRD [median progression-free survival (mPFS): 59.7 versus 35.7 months, p < 0.001; median overall survival (mOS): 97.1 versus 68.8 months, p = 0.011]. In addition, different patterns of therapy-induced clonal evolution were observed by comparing the clonal structure of residual PCs with paired baseline samples. Patients who maintained at a high risk during follow-up had the worst survival (mPFS: 30.5 months; mOS: 54.4 months), while those who returned to lower risk or had iFISH- at both time points had the best survival (mPFS: 62.0 months, mOS: not reached).

Conclusion

These findings highlighted the prognostic value of genetic testing in residual tumor cells, which may provide a deep understanding of clonal evolution and guide clinical therapeutic strategies.

Contribution of post-transplantation therapy to sustained MRD negativity in multiple myeloma: a retrospective analysis

Post-transplantation therapy is commonly performed in patients with myeloma and can prolong progression-free survival (PFS). However, whether post-transplantation therapy contributes to achieving and continuing MRD-negativity remains controversial. This retrospective analysis aimed to evaluate the clinical impact of post-transplantation therapy, including tandem autologous stem cell transplantation (ASCT), in myeloma patients. The subjects were 79 patients (median age: 62 years) who received induction therapy, including bortezomib and/or lenalidomide, of whom 58 underwent post-transplantation therapy. At the median follow-up time of 50 months, the 4-year PFS rate was significantly higher in patients who underwent post-transplantation therapy than those who did not (60.6% vs. 28.6%, P = 0.012). Multivariate analysis revealed post-transplantation therapy to be a significant prognostic factor for long PFS. Tandem ASCT followed by consolidation and/or maintenance therapies improved PFS and OS. The minimal residual disease (MRD)-negative rate was significantly higher in patients who underwent post-transplantation therapy than those who did not (50.9% vs. 16.7%, P = 0.006). Post-transplantation therapy contributed to sustained MRD-negativity, which predicted long PFS and overall survival. Patients frequently discontinued post-transplantation therapy due to adverse events within 4 months. In conclusion, post-transplantation therapy improved PFS and contributed to sustained MRD-negativity in myeloma patients.

The prognostic utility of dynamic risk stratification at disease progression in patients with multiple myeloma

OBJECTIVES

There may be a shift in risk stratification at progression compared to that at diagnosis in patients with multiple myeloma (MM). We aimed to evaluate whether re-staging and stage migration is of prognostic impact.

METHODS

Real-world data from the National Longitudinal Cohort of Hematologic Diseases-multiple myeloma were collected; 263 consecutive patients demonstrating disease progression were finally included. Staging at diagnosis and re-staging at progression were performed using the International Staging System (ISS) and Revised International Staging System (RISS).

RESULTS

Based on ISS re-staging, the median post-progression survival (mPPS) of patients with stage I, II, and III was 44.2, 21.7, and 11.6 months, respectively (P < 0.0001). Based on RISS re-staging, the mPPS of patients with stage I, II, and III was 50.3, 22.2, and 11.4 months, respectively (P < 0.0001). The mPPS in patients with improved, maintained, and deteriorated ISS stage migration from diagnosis was 33.6, 20.9, and 16 months, respectively (P = 0.0051) and that with improved, maintained, and deteriorated RISS stage migration was 48.4, 23.1, and 13.9 months, respectively (P < 0.001). Compared to patients with maintained or improved disease stage, those with deteriorated ISS/RISS migration showed significantly higher incidence of Del(17P) at progression and worse PPS. Multivariate analyses indicated both re-staging and stage migration by ISS/RISS at progression were independent predictors for PPS.

CONCLUSIONS

We demonstrated that ISS/RISS re-staging showed superior prognostic utility over ISS/RISS staging in predicting PPS. Patients with deteriorated stage migration or maintained advanced stage at progression may need more individualized treatment.

Minimal residual disease status is the prognostic determinant following high-dose treatment for patients with multiple myeloma

BACKGROUND

The presence of minimal residual disease (MRD+) following autologous stem cell transplantation (ASCT) in multiple myeloma represents a poor prognostic factor for progression-free survival (PFS) and overall survival (OS).

METHODS

At our department, we recommend lenalidomide maintenance for patients who are MRD+ after ASCT, while MRD-negative (MRD-) patients, after information about the national guidelines, were not advised to follow this regimen.

RESULTS

Out of the total 228 patients, 175 received ASCT following first-line induction (MRD- 92 (53%), MRD+ 83 (47%), at 2 months post-ASCT), while 53 underwent ASCT after second-line treatment (MRD- 27 (51%), MRD+ 26 (49%), at the same time point). Comparatively, MRD- patients who did not receive maintenance demonstrated better OS than MRD+ patients who received upfront ASCT and maintenance treatment (96% vs. 86%, p = 0.030, at 3 years). However, nonsignificant difference was found in PFS (76% vs. 62%, at 3 years). Furthermore, second-line ASCT, MRD- non-maintained patients exhibited significantly better PFS than MRD+ (71% vs. 27%, p > 0.001, at 3 years). However, OS was better but nonsignificant (96% vs. 76%, at 3 years). Fluorescence in situ hybridization (FISH) analysis was performed on 141 out of the 228 patients. Of these, 85 (60%) patients were deemed standard risk (SR), and 56 (40%) were classified as high risk (HR). In the SR cohort, MRD- patients exhibited better PFS and OS than MRD+ patients (71% vs. 59% and 100% vs. 85%, respectively). In the HR cohort, the MRD- patients showed superior PFS but similar OS compared to MRD+ patients (66% vs. 42% and 81% vs. 80%, respectively).

CONCLUSIONS

Our results indicate that being MRD- is a more crucial prognostic factor for the 3-year PFS and OS than the presence of high-risk cytogenetic markers or undergoing maintenance treatment. The latter appears insufficient, particularly for MRD+ patients following ASCT in the second-line setting, suggesting that these patients may require a more intensive treatment approach.

Intensifying treatment in PET-positive multiple myeloma patients after upfront autologous stem cell transplantation

18F-Fluorodeoxyglucose positron emission tomography/computed tomography (PET) positivity after first-line treatment with autologous stem cell transplantation (ASCT) in multiple myeloma is strongly correlated with reduced progression-free and overall survival. However, PET-positive patients who achieve PET negativity after treatment seem to have comparable outcomes to patients who were PET negative at diagnosis. Hence, giving PET-positive patients additional treatment may improve their outcome. In this phase II study, we screened first-line patients with very good partial response (VGPR) or better after ASCT with PET. PET-positive patients received four 28-day cycles of carfilzomib-lenalidomide-dexamethasone (KRd). Flow cytometry-based minimal residual disease (MRD) analysis was performed before and after treatment for correlation with PET. Overall, 159 patients were screened with PET. A total of 53 patients (33%) were PET positive and 57% of PET-positive patients were MRD negative, demonstrating that these response assessments are complementary. KRd consolidation converted 33% of PET-positive patients into PET negativity. MRD-negative patients were more likely to convert than MRD-positive patients. In summary, PET after ASCT detected residual disease in a substantial proportion of patients in VGPR or better, even in patients who were MRD negative, and KRd consolidation treatment changed PET status in 33% of patients.

Single-agent lenalidomide maintenance after upfront autologous stem cell transplant for newly diagnosed multiple myeloma: The MD Anderson experience

The optimal duration of lenalidomide (Len) maintenance for patients with multiple myeloma (MM) after autologous stem cell transplantation (autoHCT) is unknown. We conducted a retrospective single-center analysis of adult MM patients that received upfront autoHCT between 2005 and 2021, followed by single-agent Len maintenance. A total of 1167 patients were included with a median age of 61.4 (range 25.4-82.3) years, and high-risk chromosomal abnormalities in 19%. Median duration of maintenance was 22.3 (range 0.03-139.6) months. After a median follow-up of 47.9 (range 2.9-171.7) months, median PFS and OS for the entire cohort were 56.6 (95% CI 48.2-61.4) months and 111.3 (95% CI 101.7-121.5) months, respectively. In MVA, high-risk cytogenetics was associated with a worse PFS (HR 1.91) and OS (HR 1.73) (p < .001 for both). Use of KRD induction and achievement of MRD-negative ≥ VGPR before autoHCT were associated with an improved PFS (HR 0.53 and HR 0.57, respectively; p < .001 for both). Longer maintenance duration, even with a 5-year cutoff, was associated with superior PFS and OS (HR 0.17 and 0.12, respectively; p < .001 for both). A total of 106 patients (9%) developed a second primary malignancy (SPM), mostly solid tumors (39%) and myeloid malignancies (30%). Longer maintenance duration was associated with a higher risk of SPM, reaching statistical significance after >2 years (odds ratio 2.25; p < .001). In conclusion, outcomes with Len maintenance were comparable to those reported in large clinical trials. Longer duration of maintenance, even beyond 5 years, was associated with improved survival.

Clinical Benefit of Autologous Stem Cell Transplantation for Patients with Multiple Myeloma Achieving Undetectable Minimal Residual Disease after Induction Treatment

Attaining undetectable minimal residual disease (MRD) is the current therapeutic goal for multiple myeloma. But there is a current lack of data regarding the clinical benefit of autologous stem cell transplantation (ASCT) for patients with myeloma achieving early MRD-negative status after induction treatment, in addition to the interaction of longitudinal MRD status with ASCT. The current study included 407 patients with transplant-eligible multiple myeloma with available MRD status from the National Longitudinal Cohort of Hematological Diseases in China (NCT04645199), of whom 147 (34.4%) achieved early undetectable MRD and 182 (44.7%) received ASCT. Early MRD-negative status was associated with a lower risk of disease progression [HR = 0.447; 95% confidence interval (CI), 0.333-0.600; P < 0.001] and death (HR = 0.473; 95% CI, 0.320-0.700; P < 0.001). Of note, patients who achieved undetectable MRD early still benefitted from ASCT, with a remarkable improvement in the median MRD-negative duration (33.5-58.0 months, P < 0.001), progression-free survival (PFS; 46.0-88.3 months, P < 0.001), and overall survival (OS; 76.4 months to not reached, P = 0.003). These clinical benefits were more pronounced in patients with aggressive features (high-risk cytogenetic abnormalities or high tumor burden) compared with standard-risk patients. Similar results were observed in patients with detectable MRD after induction treatment. In addition, we identified four MRD-status transformation patterns following ASCT, which were strongly correlated with diverse survival outcomes (P < 0.001). Our study revealed the enhanced clinical significance of ASCT in patients with transplant-eligible myeloma, regardless of early MRD status, particularly for high-risk patients. Subsequent prospective trials are essential to validate these observations.

Significance

Achieving and maintaining undetectable MRD is the current treatment goal for multiple myeloma. Our results emphasized the remarkable clinical benefit of ASCT on MRD-negative duration, PFS, and OS in patients with multiple myeloma regardless of early MRD status. These favorable impacts were more evident in patients with aggressive features. Importantly, dynamic MRD monitoring among ASCT could facilitate personalized stratification of therapeutic approaches.

Flow Cytometry in Diagnosis, Prognostication, and Monitoring of Multiple Myeloma and Related Disorders

Flow cytometry plays a critical role in the diagnosis, prognostication, therapy response evaluation, and clinical management of plasma cell neoplasms. The review summarizes how flow cytometry is used in the initial evaluation to distinguish primary and secondary clonal plasma cell populations from each other and from reactive plasma cells. We further illustrate the kinds of prognostic information the assessment can provide at diagnosis and disease follow-up of primary plasma cell neoplasms. Technical requirements for MRD assays and their use in therapy efficacy assessment and clinical decision-making in multi-myeloma are discussed.

Measurable Residual Disease Testing in Multiple Myeloma Routine Clinical Practice: A Modified Delphi Study

We used a modified Delphi approach to establish areas of consensus and nonconsensus regarding the utility of determining measurable residual disease (MRD) to assess multiple myeloma (MM) treatment response, which may inform disease management and design of future clinical trials. This modified Delphi study incorporated 2 iterative rounds of surveys to evaluate the opinions of an expert panel of 61 practicing hematological oncologists from across 14 countries in Europe concerning the use of MRD testing in MM management. Survey 1 assessed experts' opinions on MRD testing in different clinical situations and associated challenges. Survey 2 focused on the lack of consensus areas identified in survey 1. Consensus to an individual question was defined a priori as 75% agreement or disagreement by the panel. From the 2 rounds of surveys, the experts reached consensus agreement that MRD testing should be performed in newly diagnosed or relapsed patients who achieved complete response (CR) or better after transplantation. In transplant-ineligible patients, experts recommended MRD testing in those who are ≤70 years old and in CR. If a patient was previously positive on positron-emission tomography and computed tomography (PET/CT), both MRD and PET/CT should be assessed at CR. MRD testing should be performed ≤6 months after transplantation and every 6-12 months in continuously treated patients in CR. There was no consensus on making treatment decisions based on MRD status. MRD testing is an important component of clinical management in MM. Additional data will further clarify the role of MRD in guiding treatment decisions.

Minimal Residual Disease in Multiple Myeloma: Past, Present, and Future

Responses to treatment have improved over the last decades for patients with multiple myeloma. This is a consequence of the introduction of new drugs that have been successfully combined in different clinical contexts: newly diagnosed, transplant-eligible or ineligible patients, as well as in the relapsed/refractory setting. However, a great proportion of patients continue to relapse, even those achieving complete response, which underlines the need for updated response criteria. In 2014, the international myeloma working group established new levels of response, prompting the evaluation of minimal residual disease (MRD) for those patients already in complete or stringent complete response as defined by conventional serological assessments: the absence of tumor plasma cells in 100,000 total cells or more define molecular and immunophenotypic responses by next-generation sequencing and flow cytometry, respectively. In this review, we describe all the potential methods that may be used for MRD detection based on the evidence found in the literature, paying special attention to their advantages and pitfalls from a critical perspective.

Adaptation of a multiple myeloma minimal residual disease multicolor flow cytometry assay for real-world practice

BACKGROUND

Achieving minimal residual disease (MRD) negativity following treatment for multiple myeloma (MM) is associated with improved progression free and overall survival. In the UK, MRD assessments in MM are not incorporated into routine clinical use outside trials. Widely used in other haematological malignancies, there is a role for widening the availability of myeloma MRD assays to laboratories outside larger treating centers.

METHODS

We set up and assessed concordance of a multicolor flow cytometry (MCF) assay for MM MRD in collaboration with a reference center including validity following delayed processing of samples using an optimized fixation step. We then conducted a real-world snapshot of MRD results in a cohort of newly diagnosed transplant-eligible patients treated with UK standard induction therapies at the time of analysis.

RESULTS

43 MCF MRD samples run in parallel with a reference center showed high correlation and minimal bias. 24 samples were split and processed in duplicate both fixed and fresh, with strong correlation, minimal bias, and no change in plasma cell phenotype by flow markers confirming a 6-day delay in processing did not affect assay performance. A real-world snapshot found 17% (10/58) of patients were MRD-negative post-bortezomib-based triplet induction therapy.

CONCLUSIONS

We successfully adopted a reference MCF MM MRD method which was stable for up to 6 days following sample collection potentially allowing broader access of this assay to smaller laboratories which would facilitate further investigation of the prognostic value and clinical utility of MRD assessments outside the trial setting in real-world practice.

Current Main Topics in Multiple Myeloma

Multiple Myeloma (MM) remains a difficult to treat disease mainly due to its biological heterogeneity, of which we are more and more knowledgeable thanks to the development of increasingly sensitive molecular methods that allow us to build better prognostication models. The biological diversity translates into a wide range of clinical outcomes from long-lasting remission in some patients to very early relapse in others. In NDMM transplant eligible (TE) patients, the incorporation of mAb as daratumumab in the induction regimens, followed by autologous stem cell transplantation (ASCT) and consolidation/maintenance therapy, has led to a significant improvement of PFS and OS.; however, this outcome remains poor in ultra-high risk MM or in those who did not achieve a minimal residual disease (MRD) negativity. Several trials are exploring cytogenetic risk-adapted and MRD-driven therapies in these patients. Similarly, quadruplets-containing daratumumab, particularly when administered as continuous therapies, have improved outcome of patients not eligible for autologous transplant (NTE). Patients who become refractory to conventional therapies have noticeably poor outcomes, making their treatment a difficult challenge in need of novel strategies. In this review, we will focus on the main points regarding risk stratification, treatment and monitoring of MM, highlighting the most recent evidence that could modify the management of this still incurable disease.

Lenalidomide Maintenance and Measurable Residual Disease in a Real-World Multiple Myeloma Transplanted Population Receiving Different Treatment Strategies Guided by Access to Novel Drugs in Brazil

Despite recent advances in multiple myeloma (MM), the incorporation of novel agents and measurable residual disease (MRD) monitoring in low-income countries remains a challenge. Although lenalidomide maintenance (M-Len) after autologous stem cell transplantation (ASCT) has been associated with improved outcomes and MRD has refined the prognosis of complete response (CR) cases, until now, there have been no data on the benefits of these approaches in Latin America. Here, we evaluate the benefits of M-Len and MRD using next-generation flow cytometry (NGF-MRD) at Day + 100 post-ASCT (n = 53). After ASCT, responses were evaluated based on the International Myeloma Working Group criteria and NGF-MRD. MRD was positive in 60% of patients with a median progression-free survival (PFS) of 31 months vs. not reached (NR) for MRD-negative cases (p = 0.05). The patients who received M-Len continuously had a significantly better PFS and overall survival (OS) than those without M-Len (median PFS: NR vs. 29 months, p = 0.007), with progression in 11% vs. 54% of cases after a median follow-up of 34 months, respectively. In a multivariate analysis, MRD status and M-Len therapy emerged as independent predictors of PFS (median PFS of M-Len/MRD^- vs. no M-Len/MRD⁺ of NR vs. 35 months, respectively; p = 0.01). In summary, M-Len was associated with improved survival outcomes in our real-world MM cohort in Brazil, with MRD emerging as a useful reproducible tool to identify patients at an earlier risk of relapse. The inequity in drug access remains a hurdle in countries with financial constraints, with a negative impact on MM survival.

MRD dynamics during maintenance for improved prognostication of 1280 patients with myeloma in the TOURMALINE-MM3 and -MM4 trials

Measurable residual disease (MRD) evaluation may help to guide treatment duration in multiple myeloma (MM). Paradoxically, limited longitudinal data exist on MRD during maintenance. We investigated the prognostic value of MRD dynamics in 1280 transplant-eligible and -ineligible patients from the TOURMALINE-MM3 and -MM4 randomized placebo-controlled phase 3 studies of 2-year ixazomib maintenance. MRD status at randomization showed independent prognostic value (median progression-free survival [PFS], 38.6 vs 15.6 months in MRD- vs MRD+ patients; HR, 0.47). However, MRD dynamics during maintenance provided more detailed risk stratification. A 14-month landmark analysis showed prolonged PFS in patients converting from MRD+ to MRD- status vs those with persistent MRD+ status (76.8% vs 27.6% 2-year PFS rates). Prolonged PFS was observed in patients with sustained MRD- status vs those converting from MRD- to MRD+ status (75.0% vs 34.2% 2-year PFS rates). Similar results were observed at a 28-month landmark analysis. Ixazomib maintenance vs placebo improved PFS in patients who were MRD+ at randomization (median, 18.8 vs 11.6 months; HR, 0.65) or at the 14-month landmark (median, 16.8 vs 10.6 months; HR, 0.65); no difference was observed in patients who were MRD-. This is the largest MM population undergoing yearly MRD evaluation during maintenance reported to date. We demonstrate the limited prognostic value of a single-time point MRD evaluation, because MRD dynamics over time substantially impact PFS risk. These findings support MRD- status as a relevant end point during maintenance and confirm the increased progression risk in patients converting to MRD+ from MRD- status. These trials were registered at www.clinicaltrials.gov as #NCT02181413 and #NCT02312258.

The burden of myeloma: novel approaches to disease assessment

Novel therapies in multiple myeloma (MM) have increased the rates of conventional complete remission (CR) in patients. However, patients in CR can have highly heterogeneous outcomes. Novel and more sensitive methods of assessing residual disease burden after therapy will help prognosticate this group better and, ideally, allow individualized therapy adjustments based on response depth in the future. Here, we review novel bone marrow, peripheral blood, and imaging methods for assessing myeloma burden and discuss the opportunities and limitations of incorporating these in everyday clinical practice.