Droplet Digital PCR for Minimal Residual Disease Detection in Mature Lymphoproliferative Disorders

Minimal residual disease (MRD) detection has a powerful prognostic relevance for response evaluation and prediction of relapse in hematological malignancies. Real-time quantitative PCR (qPCR) has become the settled and standardized method for MRD assessment in lymphoid disorders. However, qPCR is a relative quantification approach, since it requires a reference standard curve. Droplet digital^TM PCR (ddPCR^TM) allows a reliable absolute tumor burden quantification withdrawing the need for preparing, for each experiment, a tumor-specific standard curve. We have recently shown that ddPCR has a good concordance with qPCR and could be a feasible and reliable tool for MRD monitoring in mature lymphoproliferative disorders. In this chapter we describe the experimental workflow, from the detection of the clonal molecular marker to the MRD monitoring by ddPCR, in patients affected by multiple myeloma, mantle cell lymphoma and follicular lymphoma. However, standardization programs among different laboratories are needed in order to ensure the reliability and reproducibility of ddPCR-based MRD results.

ELDA qASO-PCR for High Sensitivity Detection of Tumor Cells in Bone Marrow and Peripheral Blood

A quantitative allele-specific polymerase chain reaction in combination with an extreme limiting dilution approach (ELDA qASO-PCR) enables the detection of tumor cells in patients with multiple myeloma (MM) in bone marrow (BM) samples and in peripheral blood (PB) with a sensitivity of <10^-6. The two-step procedure of patient-specific tumor cell identification via the immunoglobulin heavy chain (IgH) and kappa/lambda light chain (k/λ LC) locus, followed by tumor cells quantification by ELDA qASO-PCR allows for the application of this method to the majority of MM patients, including those with Bence Jones proteinuria.

Molecular detection of minimal residual disease in multiple myeloma

Despite the significantly higher complete remission rates and improved survival achieved in the last decade, multiple myeloma (MM) patients continue to relapse due to persistence of minimal residual disease (MRD). Generally, MRD refers to persistence of low levels of disease in the order of one tumour cell in ≥10⁵ normal cells. Currently, molecular and immunophenotypic techniques are employed for MRD detection. This review focuses on MRD detection by molecular techniques, including allele-specific oligonucleotide polymerase chain reaction (ASO-PCR), next-generation sequencing (NGS) and digital PCR (dPCR), in addition to a brief description of, and comparison with, multiparameter flow cytometry. The basic principles, technical advantages and limitations, and the clinical impact of all three molecular techniques are reviewed and compared. They all have a sensitivity of at least 10^-5 , among which ASO real-time quantitative PCR is the most well-standardized, and NGS carries the highest sensitivity and applicability, while dPCR is still under investigation. Furthermore, molecular MRD negativity is a favourable prognostic factor for survival of patients with MM. However, several challenges inherent to molecular detection of MRD still remain to be overcome, particularly false negativity and failure to detect extramedullary disease. Finally, detection of MRD from peripheral blood remains challenging.

BMT CTN Myeloma Intergroup Workshop on Minimal Residual Disease and Immune Profiling: Summary and Recommendations from the Organizing Committee

The Blood and Marrow Transplant Clinical Trials Network Myeloma Intergroup Workshop on Minimal Residual Disease and Immune Profiling was convened on December 1, 2016 at the American Society of Hematology meeting to discuss the emerging data and technologies for minimal residual disease assessment and immune profiling in myeloma. Particular emphasis was placed on developing strategies to incorporate these techniques into clinical trial design. This document reviews the literature, summarizes the topics discussed in the workshop, and provides recommendations for integration of these techniques into future clinical trial design.

Is molecular remission the goal of multiple myeloma therapy?

The increased number of effective therapies and the wider use of combinations that give deeper remissions have resulted in a reassessment of the goals of myeloma therapy. With the advent of new therapeutic strategies and diagnostic tools, achievement of minimal residual disease (MRD)-negative status has become increasingly important, with some even considering it as the primary endpoint for therapy. The level of MRD that is aimed for is a continuous, rather than an absolute variable, with studies in both transplant-eligible and -noneligible patients showing that the level of MRD achieved is predictive of progression-free survival and overall survival, with an improvement in survival of approximately 1 year for each log-depletion in MRD level. The most widely used methods to assess MRD status include flow cytometry and clonality detection, using next-generation sequencing technologies with sensitivity limits of 1:10^-3 to 1:10^-6 The timing of when to assess MRD depends on the treatment used, as well as the molecular and cytogenetic subgroup of the myeloma itself. It is also becoming clear that the level of MRD negativity, as well as microenvironmental factors, are important prognostically, including the regeneration of normal plasma cells, and the normalization of the immune repertoire. With advances in antibody-based therapy and immunotherapy, the achievement of stable MRD states is now possible for a significant proportion of patients, and is a prerequisite for myeloma cure.

Elevated pre-transplant C-reactive protein identifies a high-risk subgroup in multiple myeloma patients undergoing delayed autologous stem cell transplantation

The significance of elevated C-reactive protein (CRP) prior to autologous stem cell transplantation (ASCT) in multiple myeloma (MM) has not been studied. We analyzed 1111 MM patients who underwent ASCT at Mayo Clinic from 2007 to 2015. A total of 840 patients (76%) received early ASCT (⩽12 months from diagnosis) and 271 patients (24%) received delayed ASCT (>12 months from diagnosis). Elevated CRP (> upper normal limit (8 mg/L)) was seen in 14% and 22% of patients undergoing early and delayed ASCT, respectively (P=0.003). There was no correlation of CRP with pre-transplant response, bone marrow plasma cell percentage or labeling index. Patients with an elevated CRP had a higher likelihood of having circulating plasma cells prior to ASCT (33 vs 19%; P<0.001). In the early ASCT cohort, the median overall survival (OS) in patients with normal and elevated CRP was not reached and 91 months respectively (P=0.011). In the delayed ASCT cohort, the median OS in respective groups were 73 and 30 months respectively (P<0.001), with elevated CRP being an independent prognostic marker on multivariate analysis (hazard ratio 2.0; 95% confidence interval, 1.0-3.8; P=0.045). Elevated pre-transplant CRP identifies a high-risk population especially in patients undergoing delayed ASCT and should be incorporated in the pre-transplant evaluation.

Prognostic value of antigen expression in multiple myeloma: a PETHEMA/GEM study on 1265 patients enrolled in four consecutive clinical trials

Persistence of minimal residual disease (MRD) after treatment for myeloma predicts inferior outcomes, but within MRD-positive patients there is great heterogeneity with both early and very late relapses. Among different MRD techniques, flow cytometry provides additional information about antigen expression on tumor cells, which could potentially contribute to stratify MRD-positive patients. We investigated the prognostic value of those antigens required to monitor MRD in 1265 newly diagnosed patients enrolled in the GEM2000, GEM2005MENOS65, GEM2005MAS65 and GEM2010MAS65 protocols. Overall, CD19^pos, CD27^neg, CD38^lo, CD45^pos, CD81^pos, CD117^neg and CD138^lo expression predicted inferior outcomes. Through principal component analysis, we found that simultaneous CD38^lowCD81^posCD117^neg expression emerged as the most powerful combination with independent prognostic value for progression-free survival (HR:1.69; P=0.002). This unique phenotypic profile retained prognostic value among MRD-positive patients. We then used next-generation flow to determine antigen stability throughout the course of the disease, and found that the expression of antigens required to monitor MRD is mostly stable from diagnosis to MRD stages, except for CD81 whose expression progressively increased from baseline to chemoresistant tumor cells (14 vs 28%). Altogether, we showed that the phenotypic profile of tumor cells provides additional prognostic information, and could be used to further predict risk of relapse among MRD-positive patients.

Minimal residual disease in multiple myeloma: Benefits of flow cytometry

Over the last 20 years, the approaches to the treatment of multiple myeloma (MM) have changed considerably, which led to an increase in remission rate. Using new diagnostic methods has made it possible to assess the response to treatment more reliably and forecast disease recurrence: allele-specific polymerase chain reaction, new-generation sequencing and multicolor flow cytometry enable minimal residual disease (MRD) detection of with sensitivity of 10^-5 to 10^-6 . MRD assessment with flow cytometry using is a rapidly developing area of research. The goal of multicenter groups that use flow cytometry as a tool to detect MRD in patients with MM is achieving standardization and increasing sensitivity and specificity of this method. This article provides data about the methods used for MRD monitoring and describes the advances in the field of flow cytometry.

Current applications of multiparameter flow cytometry in plasma cell disorders

Multiparameter flow cytometry (MFC) has become standard in the management of patients with plasma cell (PC) dyscrasias, and could be considered mandatory in specific areas of routine clinical practice. It plays a significant role during the differential diagnostic work-up because of its fast and conclusive readout of PC clonality, and simultaneously provides prognostic information in most monoclonal gammopathies. Recent advances in the treatment and outcomes of multiple myeloma led to the implementation of new response criteria, including minimal residual disease (MRD) status as one of the most relevant clinical endpoints with the potential to act as surrogate for survival. Recent technical progress led to the development of next-generation flow (NGF) cytometry that represents a validated, highly sensitive, cost-effective and widely available technique for standardized MRD evaluation, which also could be used for the detection of circulating tumor cells. Here we review current applications of MFC and NGF in most PC disorders including the less frequent solitary plasmocytoma, light-chain amyloidosis or Waldenström macroglobulinemia.

Minimal residual disease analysis in myeloma - when, why and where

The primary hurdle in the path to curing multiple myeloma (MM) is defining a validated minimal residual disease (MRD) and its utility in the therapeutic decision making. A better definition of MRD will aid in tailoring MM therapy further to address the clonal heterogeneity and genomic instability and overcome patient's ineffective immune surveillance. MRD analysis can define the logical endpoint for maintenance therapy, in addition also aids in providing a better clinical end point for studies comparing novel agents in myeloma. MRD is a surrogate for the survival in MM. Guidelines for global incorporation of MRD in myeloma are fraught with lack of standardization, universal availability and abridged physicians' understanding of MRD modalities. We aimed at addressing some of the frequently asked questions in the MRD assessment and will also place in perspective some arguments in favor of MRD assessment in routine practice and clinical trial scenario.

Phase II study of bortezomib, cyclophosphamide and dexamethasone as induction therapy in multiple myeloma: DSMM XI trial

We assessed the safety and efficacy of bortezomib, cyclophosphamide and dexamethasone (VCD) induction therapy in previously untreated multiple myeloma patients. A total of 414 patients received three 21-day cycles of VCD prior to autologous stem-cell transplantation (ASCT). Most common grade ≥3 adverse events were leucopenia (31·4%) and thrombocytopenia (6·8%). The overall response rate (ORR) by investigator-based assessment was 85·4%. Most patients (74%) underwent successful central laboratory-based molecular cytogenetic analysis. No clinically relevant differences in ORR post-induction were seen between patients with or without high-risk cytogenetic abnormalities (86·2% vs. 84·3%). Further follow-up data are available for 113 patients receiving ASCT who were included in a prospective consolidation trial (median follow-up, 55·5 months); median progression-free survival (PFS) was 35·3 months and median overall survival (OS) was not reached. In patients with high-risk versus standard-risk cytogenetics, median PFS was 19·9 vs. 43·6 months (P < 0·0001), and median OS was 54·7 months versus not reached (P = 0·0022). VCD is an effective and tolerable induction regimen; results suggest that VCD induces high response rates independently of cytogenetic risk status, but after long-term follow-up, cytogenetic high risk is associated with markedly reduced PFS and OS 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.

High sensitivity blood-based M-protein detection in sCR patients with multiple myeloma

We assessed the ability of a mass spectrometry-based technique, called monoclonal immunoglobulin rapid accurate mass measurement (miRAMM), to extend the analytical range of M-protein detection in serum samples obtained from myeloma patients in stringent complete response (sCR) post-autologous stem cell transplant (ASCT). To aid the M-protein detection post ASCT, the accurate molecular mass of the M-protein light chain at diagnosis was determined in all patients (N=30) and used to positively identify clones in the sCR serum. Day 100 post-ASCT, sCR samples had miRAMM identifiable M-proteins in 81% of patients. Patients who had achieved only a partial remission (PR) pre-ASCT and those with IgG isotypes serum samples had the highest rate of M-protein detection by miRAMM. miRAMM positivity at single time points (day 100, 6 months or 12 months) did not correlate with progression-free survival (PFS). In contrast, sCR patients who did not decrease their miRAMM M-protein intensities in serial measurements had shorter PFS than those whose miRAMM intensities decreased (median 17.9 months vs 51.6 months; P<0.0017). miRAMM M-protein is a more sensitive blood-based test than traditional M-protein tests and could cost effectively aid in serially monitoring complete remission for continue response or biochemical relapse.

Consolidation and Maintenance Therapies for Newly Diagnosed Multiple Myeloma in the Era of Novel Agents

Advances in therapy in multiple myeloma have resulted in significant improvements in patient outcomes; however, relapse remains problematic. Strategies to improve outcomes following autologous stem cell transplantation (ASCT) include consolidation to intensify therapy and improve depth of response and maintenance therapy to achieve long-term disease control. Immunomodulatory drugs (IMiDs), including thalidomide and lenalidomide, are appealing as maintenance therapy given their oral administration; however, the cumulative toxicities of thalidomide have limited its efficacy in maintenance therapy. Maintenance lenalidomide is better tolerated, and multiple studies have demonstrated an improvement in progression-free survival (PFS), but its impact on overall survival (OS) remains controversial. Additional concerns regarding the risk of second primary malignancies and significant cost of long-term lenalidomide therapy have also been raised. Proteasome inhibitors, particularly, bortezomib have also been incorporated in consolidation and maintenance regimens alone or in combination with an IMiD. Preliminary studies have suggested bortezomib maintenance may benefit patients with adverse cytogenetics, including t(4;14) and deletion 17p. Determination of the optimal consolidation and maintenance regimen and duration of therapy post-transplantation is a focus of several ongoing randomized studies.

Updated analysis of CALGB (Alliance) 100104 assessing lenalidomide versus placebo maintenance after single autologous stem-cell transplantation for multiple myeloma: a randomised, double-blind, phase 3 trial

Background

CALGB 100104 (Alliance) studied lenalidomide vs. placebo following autologous stem cell transplant (ASCT) for newly diagnosed myeloma patients, demonstrating improved time to progression (TTP) and overall survival (OS), and an increase in second primary malignancies (SPM) for lenalidomide at 34-months median follow-up. Here we report an updated intent-to-treat analysis at 91-months median follow-up.

Methods

Patients were eligible if they had active myeloma, had received at most two induction regimens and had achieved stable disease or better in the first 100 days after ASCT. In this phase 3 study, 460 patients were randomised in a double-blind manner to either lenalidomide (n=231) or placebo (n=229) utilizing a permutated-block randomisation with fixed block size. Randomisation was stratified by three factors: normal or elevated β2-microglobulin level at registration (≤2·5 mg/L vs > 2·5 mg/L), prior use or nonuse of thalidomide during induction therapy, and prior use or nonuse of lenalidomide during induction therapy. The starting dose was 10 mg daily, escalated to 15 mg daily after three months. The primary endpoint was TTP (time of progressive disease or death from any cause) using intent-to-treat analysis. After three interim analyses, the study was unblinded at median follow-up of 18 months and 86/128 placebo patients without progressive disease chose to cross over to lenalidomide. This study is registered with ClinicalTrials.gov identifier NCT00114101; new patients are no longer being recruited, but some patients remain on treatment and in follow-up.

Findings

The median TTP for lenalidomide is 57·3 months (95% CI 44·2–73·3) and 28·9 months (95% CI 23·0–36·3) for placebo (hazard ratio (HR): 0·57, 95% CI 0·46–0·71, p<0·0001). The TTP benefit with lenalidomide was observed regardless of whether patients were in a complete response at time of randomisation or whether they had received thalidomide or lenalidomide induction therapy. The most common grade 3–4 adverse events were neutropenia (116 (50%) of 231 patients in the lenalidomide arm and 37 (16%) of 229 patients in the placebo arm) and thrombocytopenia (34 patients (15%) in the lenalidomide arm and 11 patients (4·8%) in the placebo arm. Eighteen haematological (7·8%) and 14 solid tumour (6·1%) SPMs have been diagnosed following randomisation and prior to disease progression in the lenalidomide arm vs. three haematological (1·3%) and nine solid tumour (3·9%) SPMs in the placebo arm. Of the placebo SPMs, three haematological and five of nine solid tumour SPMs were in the crossover subgroup.

Interpretation

Despite an increase in haematological adverse events and SPMs, lenalidomide maintenance therapy following ASCT significantly improves TTP and can be considered a standard of care.

Lenalidomide Maintenance After Autologous Stem-Cell Transplantation in Newly Diagnosed Multiple Myeloma: A Meta-Analysis

Purpose Lenalidomide maintenance therapy after autologous stem-cell transplantation (ASCT) demonstrated prolonged progression-free survival (PFS) versus placebo or observation in several randomized controlled trials (RCTs) of patients with newly diagnosed multiple myeloma (NDMM). All studies had PFS as the primary end point, and none were powered for overall survival (OS) as a primary end point. Thus, a meta-analysis was conducted to better understand the impact of lenalidomide maintenance in this setting. Patients and Methods The meta-analysis was conducted using primary-source patient-level data and documentation from three RCTs (Cancer and Leukemia Group B 100104, Gruppo Italiano Malattie Ematologiche dell'Adulto RV-MM-PI-209, and Intergroupe Francophone du Myélome 2005-02) that met the following prespecified inclusion criteria: an RCT in patients with NDMM receiving ASCT followed by lenalidomide maintenance versus placebo or observation with patient-level data available and achieved database lock for primary efficacy analysis. Results Overall, 1,208 patients were included in the meta-analysis (605 patients in the lenalidomide maintenance group and 603 in the placebo or observation group). The median PFS was 52.8 months for the lenalidomide group and 23.5 months for the placebo or observation group (hazard ratio, 0.48; 95% CI, 0.41 to 0.55). At a median follow-up time of 79.5 months for all surviving patients, the median OS had not been reached for the lenalidomide maintenance group, whereas it was 86.0 months for the placebo or observation group (hazard ratio, 0.75; 95% CI, 0.63 to 0.90; P = .001). The cumulative incidence rate of a second primary malignancy before disease progression was higher with lenalidomide maintenance versus placebo or observation, whereas the cumulative incidence rates of progression, death, or death as a result of myeloma were all higher with placebo or observation versus lenalidomide maintenance. Conclusion This meta-analysis demonstrates a significant OS benefit and confirms the PFS benefit with lenalidomide maintenance after ASCT in patients with NDMM when compared with placebo or observation.

Utility of flow cytometry studies in the management of patients with multiple myeloma

PURPOSE OF REVIEW

Although the input of multiparameter flow cytometry (MFC) into the clinical management of multiple myeloma patients has faced some reluctance, continuously growing evidence supports the utility of MFC in this disease.

RECENT FINDINGS

MFC immunophenotyping of bone marrow and peripheral blood plasma cells affords cost-effective assessment of clonality, and provides prognostic information on the risk of progression in smoldering multiple myeloma, and the identification of active multiple myeloma patients with dismal outcome (e.g., high numbers of circulating tumor cells) or long-term survival despite suboptimal responses through the characterization of monoclonal gammopathy of undetermined significance-like phenotypes. Extensive data indicate that minimal residual disease (MRD) monitoring can be used as biomarker to evaluate treatment efficacy and act as surrogate for survival. The time has come to address within clinical trials the exact role of baseline risk factors and MRD monitoring for tailored therapy in multiple myeloma, which implies systematic usage of highly sensitive cost-effective, readily available, and standardized MRD techniques such as MFC.

SUMMARY

Next-generation MFC should be considered mandatory in the routine evaluation of multiple myeloma patients both at diagnosis and after therapy, and represents an attractive technique to integrate with high-throughput DNA and RNA-seq methods to help in understanding the mechanisms behind dissemination and chemoresistance of multiple myeloma.

Standardisation of minimal residual disease in multiple myeloma

The assessment of the effectiveness of chemotherapy in oncology cannot disregard the concept of minimal residual disease (MRD). In fact, the efforts of numerous scientific groups all over the world are currently focusing on this issue, with the sole purpose of defining sensitive, effective assessment criteria that are, above all, able to give acceptable, easily repeatable results worldwide. Regarding this issue, especially with the advent of new drugs, multiple myeloma is one of the haematologic malignancies for which a consensus has not yet been reached. In this review, we analyse various techniques that have been used to improve the sensitivity of response, aimed at reducing the cut-off values previously allowed, as well as serological values like serum-free light chain, or immunophenotypic tools on bone marrow or peripheral blood, like multi-parameter flow cytometry, or molecular ones such as allele-specific oligonucleotide (ASO)-qPCR and next-generation/high-throughput sequencing technologies (NGS). Moreover, our discussion makes a brief reference to promising techniques, such as mass spectrometry for identifying Ig light chain (LC) in peripheral blood, and the assessment of gene expression profile not only in defining prognostic risk at the diagnosis but also as a tool for evaluation of response.

Heavy+light chain monitoring correlates with clinical outcome in multiple myeloma patients

Novel anti-myeloma agents have improved patient response rates, which are historically based on reductions of the M-protein. These methods can be inaccurate for quantifying M-proteins at low concentrations. We compared the consistency and clinical impact of response assignment by electrophoretic and heavy+light chain (HLC) immunoassays post-consolidation in 463 newly diagnosed patients. The two methods gave similar assignments in patients with partial (PR; 79% agreement) or complete response (⩾CR; 92%). However, in patients achieving very good PR (VGPR) there was poor concordance between methods (45%). Median progression-free survival (PFS) for standard VGPR patients was 34.5 months; HLC responses stratified these patients further into PR, VGPR and ⩾CR, with median PFS of 21.3, 28.9 months and not reached, respectively; P<0.001. At this time, abnormal HLC ratios had better concordance with multiparametric flow cytometry (sensitivity 10⁻⁴) (37 and 34% positive, respectively), compared to immunofixation (62% positive). In addition, HLC-pair suppression was identified in 38% of patients and associated with shorter PFS (30.6 months vs not reached; P<0.001). We conclude that HLC monitoring could augment electrophoretic assessments in patients achieving VGPR. The prognostic significance of HLC responses might partly depend on the patients’ ability to recover their immune system, as determined by normalisation of HLC measurements.

High-throughput sequencing for noninvasive disease detection in hematologic malignancies

Noninvasive monitoring of minimal residual disease (MRD) has led to significant advances in personalized management of patients with hematologic malignancies. Improved therapeutic options and prolonged survival have further increased the need for sensitive tumor assessment that can inform treatment decisions and patient outcomes. At diagnosis or relapse of most hematologic neoplasms, malignant cells are often easily accessible in the blood as circulating tumor cells (CTCs), making them ideal targets to noninvasively profile the molecular features of each patient. In other cancer types, CTCs are generally rare and noninvasive molecular detection relies on circulating tumor DNA (ctDNA) shed from tumor deposits into circulation. The ability to precisely detect and quantify CTCs and ctDNA could minimize invasive procedures and improve prediction of clinical outcomes. Technical advances in MRD detection methods in recent years have led to reduced costs and increased sensitivity, specificity, and applicability. Among currently available tests, high-throughput sequencing (HTS)-based approaches are increasingly attractive for noninvasive molecular testing. HTS-based methods can simultaneously identify multiple genetic markers with high sensitivity and specificity without individual optimization. In this review, we present an overview of techniques used for noninvasive molecular disease detection in selected myeloid and lymphoid neoplasms, with a focus on the current and future role of HTS-based assays.

International Myeloma Working Group consensus criteria for response and minimal residual disease assessment in multiple myeloma

Treatment of multiple myeloma has substantially changed over the past decade with the introduction of several classes of new effective drugs that have greatly improved the rates and depth of response. Response criteria in multiple myeloma were developed to use serum and urine assessment of monoclonal proteins and bone marrow assessment (which is relatively insensitive). Given the high rates of complete response seen in patients with multiple myeloma with new treatment approaches, new response categories need to be defined that can identify responses that are deeper than those conventionally defined as complete response. Recent attempts have focused on the identification of residual tumour cells in the bone marrow using flow cytometry or gene sequencing. Furthermore, sensitive imaging techniques can be used to detect the presence of residual disease outside of the bone marrow. Combining these new methods, the International Myeloma Working Group has defined new response categories of minimal residual disease negativity, with or without imaging-based absence of extramedullary disease, to allow uniform reporting within and outside clinical trials. In this Review, we clarify several aspects of disease response assessment, along with endpoints for clinical trials, and highlight future directions for disease response assessments.

Depth of Response in Multiple Myeloma: A Pooled Analysis of Three PETHEMA/GEM Clinical Trials

Purpose To perform a critical analysis on the impact of depth of response in newly diagnosed multiple myeloma (MM). Patients and Methods Data were analyzed from 609 patients who were enrolled in the GEM (Grupo Español de Mieloma) 2000 and GEM2005MENOS65 studies for transplant-eligible MM and the GEM2010MAS65 clinical trial for elderly patients with MM who had minimal residual disease (MRD) assessments 9 months after study enrollment. Median follow-up of the series was 71 months. Results Achievement of complete remission (CR) in the absence of MRD negativity was not associated with prolonged progression-free survival (PFS) and overall survival (OS) compared with near-CR or partial response (median PFS, 27, 27, and 29 months, respectively; median OS, 59, 64, and 65 months, respectively). MRD-negative status was strongly associated with prolonged PFS (median, 63 months; P < .001) and OS (median not reached; P < .001) overall and in subgroups defined by prior transplantation, disease stage, and cytogenetics, with prognostic superiority of MRD negativity versus CR particularly evident in patients with high-risk cytogenetics. Accordingly, Harrell C statistics showed higher discrimination for both PFS and OS in Cox models that included MRD (as opposed to CR) for response assessment. Superior MRD-negative rates after different induction regimens anticipated prolonged PFS. Among 34 MRD-negative patients with MM and a phenotypic pattern of bone marrow involvement similar to monoclonal gammopathy of undetermined significance at diagnosis, the probability of "operational cure" was high; median PFS was 12 years, and the 10-year OS rate was 94%. Conclusion Our results demonstrate that MRD-negative status surpasses the prognostic value of CR achievement for PFS and OS across the disease spectrum, regardless of the type of treatment or patient risk group. MRD negativity should be considered as one of the most relevant end points for transplant-eligible and elderly fit patients with MM.

MRD detection in multiple myeloma: comparison between MSKCC 10-color single-tube and EuroFlow 8-color 2-tube methods

In patients with multiple myeloma, obtaining posttreatment minimal residual disease (MRD) negativity is associated with longer progression-free survival and overall survival. Here, we compared the diagnostic performance of a single 10-color tube with that of a EuroFlow 8-color 2-tube panel for MRD testing. Bone marrow samples from 41 multiple myeloma patients were tested in parallel using the 2 approaches. Compared with the sum of the cells from the EuroFlow two 8-color tubes, the Memorial Sloan Kettering Cancer Center (MSKCC) single 10-color tube had a slight reduction in total cell number with a mean ratio of 0.85 (range, 0.57-1.46; P < .05), likely attributable to permeabilization of the cells. Percent of plasma cells showed a high degree of concordance (r² = 0.97) as did normal plasma cells (r² = 0.96), consistent with no selective plasma cell loss. Importantly, concordant measurement of residual disease burden was seen with abnormal plasma cells (r² = 0.97). The overall concordance between the 2 tests was 98%. In 1 case, there was a discrepancy near the limit of detection of both tests in favor of the slightly greater theoretical sensitivity of the EuroFlow 8-color 2-tube panel (analytical sensitivity limit of MSKCC single 10-color tube: 6 cells in 1 million with at least 3 million cell acquisitions; EuroFlow 8-color 2-tube panel: 2 cells in 1 million with the recommended 10 million cell acquisitions).

The Role of Minimal Residual Disease Testing in Myeloma Treatment Selection and Drug Development: Current Value and Future Applications

Treatment of myeloma has benefited from the introduction of more effective and better tolerated agents, improvements in supportive care, better understanding of disease biology, revision of diagnostic criteria, and new sensitive and specific tools for disease prognostication and management. Assessment of minimal residual disease (MRD) in response to therapy is one of these tools, as longer progression-free survival (PFS) is seen consistently among patients who have achieved MRD negativity. Current therapies lead to unprecedented frequency and depth of response, and next-generation flow and sequencing methods to measure MRD in bone marrow are in use and being developed with sensitivities in the range of 10^-5 to 10^-6 cells. These technologies may be combined with functional imaging to detect MRD outside of bone marrow. Moreover, immune profiling methods are being developed to better understand the immune environment in myeloma and response to immunomodulatory agents while methods for molecular profiling of myeloma cells and circulating DNA in blood are also emerging. With the continued development and standardization of these methodologies, MRD has high potential for use in gaining new drug approvals in myeloma. The FDA has outlined two pathways by which MRD could be qualified as a surrogate endpoint for clinical studies directed at obtaining accelerated approval for new myeloma drugs. Most importantly, better understanding of MRD should also contribute to better treatment monitoring. Potentially, MRD status could be used as a prognostic factor for making treatment decisions and for informing timing of therapeutic interventions. Clin Cancer Res; 23(15); 3980-93. ©2017 AACR.

Lenalidomide, Bortezomib, and Dexamethasone with Transplantation for Myeloma

BACKGROUND

High-dose chemotherapy plus autologous stem-cell transplantation has been the standard treatment for newly diagnosed multiple myeloma in adults up to 65 years of age. However, promising data on the use of combination therapy with lenalidomide, bortezomib, and dexamethasone (RVD) in this population have raised questions about the role and timing of transplantation.

METHODS

We randomly assigned 700 patients with multiple myeloma to receive induction therapy with three cycles of RVD and then consolidation therapy with either five additional cycles of RVD (350 patients) or high-dose melphalan plus stem-cell transplantation followed by two additional cycles of RVD (350 patients). Patients in both groups received maintenance therapy with lenalidomide for 1 year. The primary end point was progression-free survival.

RESULTS

Median progression-free survival was significantly longer in the group that underwent transplantation than in the group that received RVD alone (50 months vs. 36 months; adjusted hazard ratio for disease progression or death, 0.65; P<0.001). This benefit was observed across all patient subgroups, including those stratified according to International Staging System stage and cytogenetic risk. The percentage of patients with a complete response was higher in the transplantation group than in the RVD-alone group (59% vs. 48%, P=0.03), as was the percentage of patients in whom minimal residual disease was not detected (79% vs. 65%, P<0.001). Overall survival at 4 years did not differ significantly between the transplantation group and the RVD-alone group (81% and 82%, respectively). The rate of grade 3 or 4 neutropenia was significantly higher in the transplantation group than in the RVD-alone group (92% vs. 47%), as were the rates of grade 3 or 4 gastrointestinal disorders (28% vs. 7%) and infections (20% vs. 9%). No significant between-group differences were observed in the rates of treatment-related deaths, second primary cancers, thromboembolic events, and peripheral neuropathy.

CONCLUSIONS

Among adults with multiple myeloma, RVD therapy plus transplantation was associated with significantly longer progression-free survival than RVD therapy alone, but overall survival did not differ significantly between the two approaches. (Supported by Celgene and others; IFM 2009 Study ClinicalTrials.gov number, NCT01191060 .).

Posttransplant maintenance therapy in multiple myeloma: the changing landscape

Transplant-eligible patients with multiple myeloma (MM) now have extended survival after diagnosis owing to effective modern treatment strategies that include new agents in induction therapy, autologous stem cell transplant (ASCT), consolidation therapy and posttransplant maintenance therapy. Standard of care for newly diagnosed, fit patients includes ASCT and, often nowadays, posttransplant maintenance. Several large studies have shown the efficacy of maintenance with thalidomide, lenalidomide and bortezomib in the treatment scheme of MM with regards to prolonging progression-free survival and, to a lesser degree, overall survival. Herein we discuss the data currently available to support the use of maintenance therapy in patients after ASCT as well as the newer available agents that may be a part of its changing landscape in the years to come.

Should minimal residual disease negativity be the end point of myeloma therapy?

Publisher's Note: This article has a companion Counterpoint by Sonneveld. Publisher's Note: Join in the discussion of these articles at Blood Advances Community Conversations.

Should minimal residual disease negativity not be the end point of myeloma therapy?

Publisher's Note: This article has a companion Point by Anderson. Publisher's Note: Join in the discussion of these articles at Blood Advances Community Conversations.

The Assessment of CD56 and CD117 Expressions at the Time of the Diagnosis in Multiple Myeloma Patients

Objective:

The purpose of this study is to investigate the relationship between the CD56 and CD117 expressions and the clinical and laboratory findings in multiple myeloma (MM) patients.

Materials and Methods:

Analyses of multiparametric flow cytometry data obtained from the diagnostic bone marrow aspirations of a total of 34 newly diagnosed MM patients were assessed retrospectively. CD56 and CD117 expressions of the patients were compared with their stages and clinical parameters. The staging was performed according to the International Staging System (ISS).

Results:

Of the patients, 58.8% had ISS stage 1-2 MM while 41.2% had stage 3 MM. The number of CD56-positive patients was 29, whereas the number of CD117-positive patients was 13. There was no statistical difference between the CD56 and CD117 expressions and extramedullary involvement and lytic bone lesions. The median beta-2 microglobulin level was higher in the CD117-negative group (p=0.047). CD56 and CD117 expression levels were found to be lower in advanced-stage patients than in early-stage ones (p=0.026 and p=0.017). The lactate dehydrogenase (LDH) levels were high in advanced-stage patients, and an inverse relationship was found between LDH level and CD117 expression.

Conclusion:

Our findings that the CD56 and CD117 expression levels are lower in advanced stages than earlier stages and that LDH level and CD117 expression have an inverse relationship in patients with newly diagnosed MM suggest that CD56 and CD117 expressions may be prognostic markers for MM.

The Evolution of Prognostic Factors in Multiple Myeloma

Multiple myeloma (MM) is a heterogeneous hematologic malignancy involving the proliferation of plasma cells derived by different genetic events contributing to the development, progression, and prognosis of this disease. Despite improvement in treatment strategies of MM over the last decade, the disease remains incurable. All efforts are currently focused on understanding the prognostic markers of the disease hoping to incorporate the new therapeutic modalities to convert the disease into curable one. We present this comprehensive review to summarize the current standard prognostic markers used in MM along with novel techniques that are still in development and highlight their implications in current clinical practice.

Association of Minimal Residual Disease With Superior Survival Outcomes in Patients With Multiple Myeloma: A Meta-analysis

Importance

Numerous studies have evaluated the prognostic value of minimal residual disease (MRD) in patients with multiple myeloma (MM). Most studies were small and varied in terms of patient population, treatment, and MRD assessment methods.

Objective

To evaluate the utility of MRD detection in patients with newly diagnosed MM.

Data Sources

A Medline search was conducted for articles published in English between January 1990 and January 2016.

Study Selection

Eligible studies reported MRD status and progression-free survival (PFS) or overall survival (OS) in 20 or more patients following treatment. Among 405 articles identified, 21 met the initial eligibility criteria and were included in the analysis.

Data Extraction and Synthesis

Information on patient characteristics, treatment, MRD assessment, and outcomes were extracted using a standard form.

Main Outcomes and Measures

The impact of MRD status on PFS and OS was assessed by pooling data from relevant trials. Data were adjusted to allow for different proportions of patients with MRD in different studies, and analyzed using the Peto method. Forest plots were created based on Cox model analysis. Other prespecified research questions were addressed qualitatively.

Results

Fourteen studies (n = 1273) provided data on the impact of MRD on PFS, and 12 studies (n = 1100) on OS. Results were reported specifically in patients who had achieved conventional complete response (CR) in 5 studies for PFS (n = 574) and 6 studies for OS (n = 616). An MRD-negative status was associated with significantly better PFS overall (hazard ratio [HR], 0.41; 95% CI, 0.36-0.48; P < .001) and in studies specifically looking at CR patients (HR, 0.44; 95% CI, 0.34-0.56; P < .001). Overall survival was also favorable in MRD-negative patients overall (HR, 0.57; 95% CI, 0.46-0.71; P < .001) and in CR patients (HR, 0.47; 95% CI, 0.33-0.67; P < .001). Tests of heterogeneity found no significant differences among the studies for PFS and OS.

Conclusions and Relevance

Minimal residual disease-negative status after treatment for newly diagnosed MM is associated with long-term survival. These findings provide quantitative evidence to support the integration of MRD assessment as an end point in clinical trials of MM.

VTD-melphalan is well tolerated and results in very high rates of stringent CR and MRD-negative status in multiple myeloma

The addition of cytotoxic drugs to high-dose melphalan as a preparative regimen for autologous stem cell transplantation in multiple myeloma has not resulted in superior activity. Although novel agents have significantly improved outcome in multiple myeloma, their role in preparative regimens remains largely unknown. We have evaluated the toxicity and efficacy of combining bortezomib, thalidomide, and dexamethasone with high-dose melphalan. An institutional review board-approved retrospective analysis was performed on 100 consecutive patients receiving 153 transplants; 53 had tandem transplants; 64 patients received early transplants; and 36 had salvage transplantation. Endpoints were treatment-related toxicity and mortality, and quality of response post-transplantation with assessment of stringent complete remission (sCR) and minimal residual disease (MRD) status. Median age was 61 years, and median follow-up was 16.2 months. At 6 months, sCR was attained in 56% of patients and CR in 20%. An MRD status, assessed by sensitive (10⁻⁴) multiparameter flow cytometry, was achieved in 85%. The 100-day mortality rate was 2.6% (4/153); 1.8% for early transplants and 4.5% for salvage transplants. Grade 3–5 non-hematologic toxicities were mainly related to metabolism/nutrition; gastrointestinal and infectious problems. Median time to absolute neutrophil count of >500/µL was 12 days for both early and salvage transplantations. No significant differences in quality of response were observed between early and salvage transplantation or between single and tandem autologous stem cell transplantation. Since both sCR and MRD are excellent early surrogate markers for progression-free and overall survival, this regimen will likely be superior to melphalan alone, but it needs to be formally assessed in a randomized study.

Next Generation Flow for highly sensitive and standardized detection of minimal residual disease in multiple myeloma

Flow cytometry has become a highly valuable method to monitor minimal residual disease (MRD) and evaluate the depth of complete response (CR) in bone marrow (BM) of multiple myeloma (MM) after therapy. However, current flow-MRD has lower sensitivity than molecular methods and lacks standardization. Here we report on a novel next generation flow (NGF) approach for highly sensitive and standardized MRD detection in MM. An optimized 2-tube 8-color antibody panel was constructed in five cycles of design-evaluation-redesign. In addition, a bulk-lysis procedure was established for acquisition of ⩾10⁷ cells/sample, and novel software tools were constructed for automatic plasma cell gating. Multicenter evaluation of 110 follow-up BM from MM patients in very good partial response (VGPR) or CR showed a higher sensitivity for NGF-MRD vs conventional 8-color flow-MRD -MRD-positive rate of 47 vs 34% (P=0.003)-. Thus, 25% of patients classified as MRD-negative by conventional 8-color flow were MRD-positive by NGF, translating into a significantly longer progression-free survival for MRD-negative vs MRD-positive CR patients by NGF (75% progression-free survival not reached vs 7 months; P=0.02). This study establishes EuroFlow-based NGF as a highly sensitive, fully standardized approach for MRD detection in MM which overcomes the major limitations of conventional flow-MRD methods and is ready for implementation in routine diagnostics.

Myeloma in Elderly Patients: When Less Is More and More Is More

Multiple myeloma is a plasma cell malignancy that occurs among older adults and accounts for 15% of all hematologic malignancies in the United States. Thirty-five percent of patients are diagnosed at age 75 or older. Novel therapeutics and routine use of autologous stem cell transplantation (ASCT) have led to substantial improvements in patient survival, although improvements have been more impressive among patients younger than age 65. Finding the balance between under- and overtreating elderly patients is one of the biggest challenges specific to them as a subgroup of patients with MM. Decision making about which therapies and their dose intensity and duration should be influenced by a patient's functional status, personal preferences, disease characteristics, and ability to tolerate therapy. ASCT should be considered for all patients younger than age 80, assuming that they are not frail. The attainment of a stringent complete response and minimal residual disease negativity is associated with improved progression-free and overall survival. Again, consideration of quality of life for these patients is paramount. Although there is a growing list of tools to sort through these issues, a fully integrated approach has not yet been finely tuned, leaving additional work to be done for the treatment of elderly patients with MM.

Association between complete response and outcomes in transplant-eligible myeloma patients in the era of novel agents

OBJECTIVES

Achieving complete response (CR) has been linked to improved progression-free (PFS) and overall (OS) survival in myeloma. A meta-analysis was conducted to investigate whether this holds true in the era of novel agents (bortezomib, lenalidomide, thalidomide).

METHODS

A total of 24 studies in newly diagnosed patients undergoing autologous stem cell transplantation (ASCT) that reported associations between responses and long-term outcomes (PFS/OS rates post-ASCT by response, or hazard ratios with 95% confidence intervals from Cox models) were identified and analyzed.

RESULTS

Achievement of CR vs. <CR post-ASCT reduced risk of progression/death by 38% [risk ratio (RR): 0.62, P < 0.0001]; risk of death was 41% lower (RR: 0.59, P < 0.0001). Subgroup meta-analyses showed significant PFS risk reduction with CR post-ASCT with novel (RR: 0.32, P < 0.006) and non-novel (RR: 0.72, P < 0.0001) agents, and corresponding OS risk reduction with novel (RR: 0.33, P = 0.0013) and non-novel (RR: 0.64, P < 0.0001) agents. Risk reduction was greater with novel vs. non-novel agents (PFS: P = 0.047; OS: P = 0.058).

CONCLUSIONS

Achieving CR during first-line therapy remains important in the novel-agent era; magnitude of association between achieving CR and outcomes appears higher for CR obtained using novel vs. non-novel agents.

Second malignancies in the context of lenalidomide treatment: an analysis of 2732 myeloma patients enrolled to the Myeloma XI trial

We have carried out the largest randomised trial to date of newly diagnosed myeloma patients, in which lenalidomide has been used as an induction and maintenance treatment option and here report its impact on second primary malignancy (SPM) incidence and pathology. After review, 104 SPMs were confirmed in 96 of 2732 trial patients. The cumulative incidence of SPM was 0.7% (95% confidence interval (CI) 0.4–1.0%), 2.3% (95% CI 1.6–2.7%) and 3.8% (95% CI 2.9–4.6%) at 1, 2 and 3 years, respectively. Patients receiving maintenance lenalidomide had a significantly higher SPM incidence overall (P=0.011). Age is a risk factor with the highest SPM incidence observed in transplant non-eligible patients aged >74 years receiving lenalidomide maintenance. The 3-year cumulative incidence in this group was 17.3% (95% CI 8.2–26.4%), compared with 6.5% (95% CI 0.2–12.9%) in observation only patients (P=0.049). There was a low overall incidence of haematological SPM (0.5%). The higher SPM incidence in patients receiving lenalidomide maintenance therapy, especially in advanced age, warrants ongoing monitoring although the benefit on survival is likely to outweigh risk.