Is This the Time to Introduce Minimal Residual Disease in Multiple Myeloma Clinical Practice?

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Prognostic Significance of the Stage at Which an MRD-Negative Status Is Achieved for Patients With Multiple Myeloma Who Received ASCT

Objective

To explore the prognostic significance of the stage at which a minimal residual disease (MRD)-negative status is achieved for patients with newly diagnosed multiple myeloma (NDMM) who received autologous hematopoietic stem cell transplantation (ASCT).

Cases and Methods

A retrospective analysis of 186 NDMM patients who received "induction therapy-ASCT-maintenance therapy" in our center and achieved an MRD-negative status was performed. Patients were divided into three groups, A (induction therapy), B (3 months after ASCT), and C (maintenance therapy), according to the stage at which an MRD-negative status was achieved.

Results

The median time to progression (TTP) of 186 patients was not reached; the median overall survival (OS) was 113.8 months. The median TTP of the patients in three groups was not reached (P=0.013), and the median OS of the patients in three groups was not reached, not reached, and 71.2 months, respectively (P=0.026). Among patients with standard-risk cytogenetics, the median TTP of those in all three groups was not reached (P=0.121), and the median OS of the patients in three groups was not reached, not reached, and 99.6 months, respectively (P=0.091). Among patients with high-risk cytogenetics, the median TTP of those in three groups was not reached, 53.9 months, and 35.8 months (P=0.060), and the median OS was not reached, 71.2 months, and 60.2 months, respectively (P=0.625). Among patients with R-ISS stage I-II, the median TTP of those in three groups was not reached (P=0.174), and the median OS of the patients in three groups was not reached, not reached, and 99.6 months, respectively (P=0.186). Among the 29 patients with R-ISS stage III, the median TTP of those in the 3 groups were unreached, unreached, and 35.1 months (P<0.001), and the median OS was unreached, unreached, and 48.5 months, respectively (P=0.020). In all enrolled patients, the stage of reaching MRD-negative was an independent prognostic factor for TTP, rather than a prognostic factor for OS. The stage of reaching MRD-negative in patients with R-ISS III was an independent prognostic factor for OS.

Conclusion

For the same patients who are MRD-negative, the prognoses of those who achieve an MRD-negative status at different groups are different. The stage at which an MRD-negative status is achieved can predict the prognosis of patients with R-ISS stage III.

Plasma cell myeloma: role of histopathology, immunophenotyping, and genetic testing

Myeloma is a malignant neoplasm of plasma cells with complex pathogenesis. Diagnosis and risk stratification require the integration of histology, radiology, serology, and genetic data. Bone marrow biopsies are essential for myeloma diagnosis by providing material for histologic and cytologic assessment as well as immunophenotypic and genetic studies. Flow cytometry and genetic studies are, in particular, becoming increasingly important for diagnosis, risk stratification, and assessment of treatment response. Myeloma has traditionally been characterized by recurrent cytogenetic abnormalities that can be divided into two subtypes: hyperdiploid, characterized by trisomies, and non-hyperdiploid, characterized by translocations involving chromosome 14. These abnormalities are thought to be primary events, initiating a premalignant state, which progresses to myeloma through the acquisition of secondary mutations. The emergence of next-generation sequencing has led to the discovery of numerous mutations and gene fusions that comprise the heterogenous genomic landscape of myeloma. As the underlying pathogenesis of myeloma continues to be delineated, possible therapeutic targets have also emerged. Herein, we describe the importance of histology, immunophenotype, and mutational analysis in the assessment of myeloma.

Evaluation of prognostic staging systems of multiple myeloma in the era of novel agents

This study aimed to evaluate the existing staging systems for multiple myeloma (MM) in the real world. From January 2010 to June 2019, we retrospectively analyzed 859 newly diagnosed MM patients from two institutions. Clinical data including laboratory findings, imaging examinations and staging system were obtained by reviewing medical records. Survival distributions were estimated using the Kaplan-Meier curve analysis, and Cox proportional hazards model were used to identified risk factors. The overall survival (OS) of eligible patients was 61.0 months. The Revised International Staging System (R-ISS) had a larger receiver operating characteristic curve area (0.603) than both the International Staging System (0.573) and the Durie Salmon staging system (0.567). In the group receiving immunomodulatory agents-based regimens, the median OS was 92.0 months in R-ISS I, 63.0 months in R-ISS II and 18.0 months in R-ISS III (p < 0.0001). In the group receiving proteasome inhibitors-based regimens, the median OS was 102.0 months in R-ISS I, 63.0 months in R-ISS II and 22.0 months in R-ISS III (p < 0.0001). In different subgroups grouped according to age, hemoglobin (HGB), creatinine, and Ca, R-ISS also had a good stratification effect. Patients in R-ISS II, which accounted for 69.9% of all patients, were further analyzed. Univariate and multivariate Cox analyses revealed that age >65 years (p = 0.001), HGB < 100 g/L (p < 0.001), elevated LDH (p = 0.001), and Ca (p = 0.010) were independent predictors of worse prognosis within R-ISS II. To conclusion, R-ISS remains a valuable staging system in the real world of the novel drug era. However, patients classified as R-ISS II still have great heterogeneity.

Minimal Residual Disease in Myeloma: Application for Clinical Care and New Drug Registration

The development of novel agents has transformed the treatment paradigm for multiple myeloma, with minimal residual disease (MRD) negativity now achievable across the entire disease spectrum. Bone marrow-based technologies to assess MRD, including approaches using next-generation flow and next-generation sequencing, have provided real-time clinical tools for the sensitive detection and monitoring of MRD in patients with multiple myeloma. Complementary liquid biopsy-based assays are now quickly progressing with some, such as mass spectrometry methods, being very close to clinical use, while others utilizing nucleic acid-based technologies are still developing and will prove important to further our understanding of the biology of MRD. On the regulatory front, multiple retrospective individual patient and clinical trial level meta-analyses have already shown and will continue to assess the potential of MRD as a surrogate for patient outcome. Given all this progress, it is not surprising that a number of clinicians are now considering using MRD to inform real-world clinical care of patients across the spectrum from smoldering myeloma to relapsed refractory multiple myeloma, with each disease setting presenting key challenges and questions that will need to be addressed through clinical trials. The pace of advances in targeted and immune therapies in multiple myeloma is unprecedented, and novel MRD-driven biomarker strategies are essential to accelerate innovative clinical trials leading to regulatory approval of novel treatments and continued improvement in patient outcomes.

Utility of Flow Cytometry and Fluorescence In Situ Hybridization in Follow-up Monitoring of Plasma Cell Myeloma

OBJECTIVES

We sought to investigate the clinical utility of flow cytometry (FC) and fluorescence in situ hybridization (FISH) in the workup of myeloma.

METHODS

We retrospectively reviewed the reports of bone marrow biopsies received for myeloma evaluation between October 2015 and January 2019.

RESULTS

A total of 1,708 biopsy specimens from 469 myeloma patients (mean age, 64.5 years [SD, 9.3]; female, 41.4%) were reviewed. Both FC and FISH had comparable detection rates at the time of initial diagnosis (97.6% vs 98.8%) and for follow-up cases (28.6% vs 28.2%). FC and FISH results were concordant in 98.8% of the initial diagnosis cases and 89.6% of the follow-up cases. The FISH-positive (FISH+)/FC-negative (FC-) discordance and FISH-/FC+ discordance occurred among 81 (5.0%) and 87 (5.4%) follow-up cases. In comparison with all concordant cases, FISH+/FC- discordant cases were more likely to have received treatment with daratumumab (P < .05).

CONCLUSIONS

Plasma cell-enriched FISH and FC have comparable abnormal plasma cell detection rates, and approximately 10% of the follow-up cases have discordant FISH and FC results in which residual disease is detected by only one of these modalities. FISH testing should be considered for cases with negative FC, especially in patients who have received treatment with daratumumab or in cases in which there is concern about specimen adequacy.

The impact of response kinetics for multiple myeloma in the era of novel agents

Rapid remission by induction therapy has long been recognized as an important predictor for long-time survival in acute leukemia. However, the impact of response kinetics on multiple myeloma (MM) seems to be different and remains unexplored. The relationship between response kinetics and outcome were assessed in 626 patients with newly diagnosed MM who were included in a prospective, nonrandomized clinical trial (BDH 2008/02). Patients were assigned to either immunomodulatory drug- or proteasome inhibitor-based therapy. The response depth, time to best response (T_BR) and duration of best response (D_BR) were collected. Depth of response was associated with superior outcomes, consistent with findings from other studies. However, the early responders (defined as T_BR ≤3 months) showed significantly worse survival compared with late responders. We found that patients with rapid complete remission experienced inferior survivals comparable to those attaining a gradual partial remission. Moreover, 4 distinct response kinetics patterns were identified. Patients with gradual and sustained remission ("U-valley" pattern) experienced superior outcomes, whereas poor outcomes were observed in rapid and transient responders ("roller coaster" pattern) (median overall survival, 126 vs 30 months). The effects of response patterns on survival were confirmed in patients at different stages of disease and cytogenetic risk, including transplant-eligible patients and those attaining different extents of response depth. Collectively, our data indicated that slow and gradual response is a favorable prognostic factor in MM. In addition to response depth, the kinetic pattern of response is a simple and powerful predictor for survival even in the era of novel agents.

The pharmacologic management of multiple myeloma in older adults

INTRODUCTION

Multiple myeloma is a disease predominately affecting older adults. Pivotal to treating older adults is understanding their physiologic differences compared to younger subjects and how the complexity of therapies has an impact upon this patient population.

AREAS COVERED

Herein, the authors address the efficacy of chemotherapy regimens, decision-making for older adults, chemotherapy-associated toxicity and the approach to management. This review focuses on the complex treatment of older multiple myeloma patients and management of treatment-related adverse events.

EXPERT OPINION

Balancing efficacy and managing toxicity is a challenge for older myeloma patients. This group is more susceptible to treatment toxicities due to a higher incidence of pre-existing comorbidities and underlying diminished physiologic reserve. Intensive therapies such as autologous hematopoietic cell transplant (AHCT), however, still should be considered for all multiple myeloma patients, including older adults. The continued development of novel therapies and increased use of multi-drug regimens has changed the treatment paradigms yet understanding the complexity of the aging adult in the context of various drugs is warranted.

[Role of minimal residual disease detection by multiparameter flow cytometry in newly diagnosed multiple myeloma: an analysis of 106 patients]

目的

探讨多参数流式细胞术（MFC）检测微小残留病（MRD）在我国初诊多发性骨髓瘤（MM）患者中的可行性及其预后意义。

方法

回顾性分析2013年6月至2015年6月106例采用MFC进行MRD检测连续收治的初诊MM患者的临床资料。

结果

①106例患者中48例（45.3%）MRD转为阴性，中位达MRD阴性时间为3个月。接受自体造血干细胞移植（ASCT）患者MRD转阴率显著高于未接受ASCT患者（62.2%对36.2%，χ²=6.536，P=0.011）。②48例完全缓解（CR）患者中7例（14.6%）MRD持续阳性，这7例患者中5例已疾病进展，中位无进展生存（PFS）时间为19个月，3例死亡，中位总生存（OS）时间为28个月，MRD持续阳性CR患者的PFS及OS时间均明显短于MRD转阴CR患者（P值均<0.05）。③中位随访38个月，MRD转阴患者的预后显著优于阳性患者，二者中位PFS时间分别为未达到和17个月（P<0.001），中位OS均未达到（P<0.001）。根据MRD水平将患者分为四组：≥1%、0.1%~<1%、0.01%~<0.1%和阴性，结果显示随着MRD水平的降低，患者PFS及OS时间有逐渐延长趋势。④多因素分析显示，MRD是影响MM患者PFS[HR=0.133（95% CI 0.062~0.288），P<0.001]和OS[HR=0.156（95% CI 0.050~0.484），P=0.001]的独立预后因素。根据MRD、细胞遗传学情况将患者分为4组，结果显示MRD转阴的高危患者预后（PFS及OS）明显好于MRD阳性的高危患者（P<0.05），而与MRD转阴的标危患者预后相近（P>0.05）。

结论

ASCT患者中MFC检测的MRD转阴率更高。MRD是MM患者的独立预后因素，根据MRD水平可以对患者预后进行分层。MRD转阴的细胞遗传学高危患者的预后与标危患者相近。MFC检测MRD值得在临床推广应用。

High-risk myeloma and minimal residual disease postautologous-HSCT predict worse outcomes

The aim of our study was to determine the impact of high-risk disease (HRD) and MRD on outcomes in myeloma patients receiving bortezomib-based induction followed by autologous hematopoietic stem cell transplant (auto-HSCT). HRD included t(4:14), t(14;16), del 17p, del 1p and/or amplification 1q by cytogenetics/FISH; all others were standard-risk disease (SRD). A subset of 165 newly diagnosed myeloma patients in a 2:1 ratio of HRD:SRD was generated using propensity score based nearest neighbor matching. Multiparametric flow cytometry (MFC) was used to detect MRD after auto-HSCT in select patients. MRD+ status at 3 months post auto-HSCT (hazard ratio (HR = 4.23, p = .028) and HRD (HR = 1.72, p = .026) were associated with a shorter PFS. Similarly, MRD+ 3 months post auto-HSCT (HR = 6.93, p = .08) and HRD (HR = 3.54, p < .001) and were associated with a shorter OS. Despite bortezomib-based induction, upfront auto-HSCT, and use of maintenance therapy, PFS and OS remained worse in MRD+ and HRD patients.

Minimal residual disease negativity using deep sequencing is a major prognostic factor in multiple myeloma

The introduction of novel agents has led to major improvements in clinical outcomes for patients with multiple myeloma. To shorten evaluation times for new treatments, health agencies are currently examining minimal residual disease (MRD) as a surrogate end point in clinical trials. We assessed the prognostic value of MRD, measured during maintenance therapy by next-generation sequencing (NGS). MRD negativity was defined as the absence of tumor plasma cell within 1 000 000 bone marrow cells (<10-6). Data were analyzed from a recent clinical trial that evaluated the role of transplantation in newly diagnosed myeloma patients treated with lenalidomide, bortezomib, and dexamethasone (RVD). MRD negativity was achieved at least once during maintenance in 127 patients (25%). At the start of maintenance therapy, MRD was a strong prognostic factor for both progression-free survival (adjusted hazard ratio, 0.22; 95% confidence interval, 0.15-0.34; P < .001) and overall survival (adjusted hazard ratio, 0.24; 95% confidence interval, 0.11-0.54; P = .001). Patients who were MRD negative had a higher probability of prolonged progression-free survival than patients with detectable residual disease, regardless of treatment group (RVD vs transplant), cytogenetic risk profile, or International Staging System disease stage at diagnosis. These results were similar after completion of maintenance therapy. Our findings confirm the value of MRD status, as determined by NGS, as a prognostic biomarker in multiple myeloma, and suggest that this approach could be used to adapt treatment strategies in future clinical trials.

Methods and role of minimal residual disease after stem cell transplantation

Relapse is the major cause of treatment failure after stem cell transplantation. Despite the fact that relapses occurred even if transplantation was performed in complete remission, it is obvious that minimal residual disease is present though not morphologically evident. Since adaptive immunotherapy by donor lymphocyte infusion or other novel cell therapies as well as less toxic drugs, which can be used after transplantation, the detection of minimal residual disease (MRD) has become a clinical important variable for outcome. Besides the increasing options to treat MRD, the most advanced technologies currently allow to detect residual malignant cells with a sensitivity of 10^-5 to 10^-6.Under the patronage of the European Society for Blood and Marrow Transplantation (EBMT) and the American Society for Blood and Marrow Transplantation (ASBMT) the 3rd workshop was held on 4/5 November 2016 in Hamburg/Germany, with the aim to present an up-to-date status of epidemiology and biology of relapse and to summarize the currently available options to prevent and treat post-transplant relapse. Here the current methods and role of minimal residual disease for myeloid and lymphoid malignancies are summarized.

Allogeneic Hematopoietic Cell Transplantation for Myeloma: When and in Whom Does It Work

The growing list of available therapies for patients with multiple myeloma has resulted in tremendously high response rates and prolonged survival. However, the cure remains elusive. A continued effort at developing strategies to utilize all available treatment modalities in the most effective manner is needed. Allogeneic hematopoietic cell transplantation (allo-HCT) is a robust platform, associated with high response rates, and provides a unique foundation on which immune therapies and novel agents can be employed to improve clinical outcomes. Patients with high-risk myeloma and those relapsing after novel agent-based therapies or early after an autologous HCT should be considered for allo-HCT, ideally in a clinical trial setting. Results from several ongoing studies are expected to provide important information that will help determine the place of allo-HCT in the myeloma treatment algorithm.

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.

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.

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.

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.

Utilizing next-generation sequencing in the management of multiple myeloma

INTRODUCTION

Multiple myeloma (MM) is a bone marrow plasma cell malignancy characterized by wide clinical presentation and heterogeneous genetic background. Despite the recent advances in patient outcome, new markers are needed for improving risk prediction and choice of a more appropriate therapy. In this perspective, the genetic makeup of MM cells is being better characterized by means of next-generation sequencing (NGS) technologies. Areas covered: The authors discuss how the application of NGS has improved our knowledge of MM biology by discovering its mutational landscape, identifying the operating mutational processes, and revealing the clonal composition of tumors and the dynamics of its evolution; and how this can have important clinical implications in terms of prognostication, therapeutic choices, and response assessment. Finally, the authors provide a quick outlook of future applications of these technologies that could help in the management of the disease in the next years. Expert commentary: The clinical exploitation of NGS-based characterization of MM patients has as its ultimate goal the precision medicine. Considerable obstacles to its implementation in myeloma management exist; therefore, the concerted effort of all involved stakeholders is mandatory to ensure that it will become a reality in routine clinical practice in the next future.

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.

Multiple myeloma patients in long-term complete response after autologous stem cell transplantation express a particular immune signature with potential prognostic implication

The proportion of multiple myeloma patients in long-term complete response (LTCR-MM) for more than 6 years after autologous stem cell transplantation (ASCT) is small. To evaluate whether this LTCR is associated with a particular immune signature, peripheral blood samples from 13 LTCR-MM after ASCT and healthy blood donors (HBD) were analysed. Subpopulations of T-cells (naïve, effector, central memory and regulatory), B-cells (naïve, marginal zone-like, class-switched memory, transitional and plasmablasts) and NK-cells expressing inhibitory and activating receptors were quantified by multiparametric flow cytometry (MFC). Heavy/light chains (HLC) were quantified by nephelometry. The percentage of CD4⁺ T-cells was lower in patients, whereas an increment in the percentage of CD4⁺ and CD8⁺ effector memory T-cells was associated with the LTCR. Regulatory T-cells and NK-cells were similar in both groups but a particular redistribution of inhibitory and activating receptors in NK-cells were found in patients. Regarding B-cells, an increase in naïve cells and a corresponding reduction in marginal zone-like and class-switched memory B-cells was observed. The HLC values were normal. Our results suggest that LTCR-MM patients express a particular immune signature, which probably reflects a 'high quality' immune reconstitution that could exert a competent anti-tumor immunological surveillance along with a recovery of the humoral immunity.

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.

Role of Flow Cytometry in the Diagnosis and Prognosis of Plasma Cell Myeloma

This article provides an overview of the role of flow cytometry in the diagnosis and follow-up of plasma cell myeloma. A brief introduction to the general immunophenotypic features of normal and myeloma plasma cells is provided, followed by a discussion of technical issues as they relate to the application of flow cytometry in this entity. The prognostic and therapeutic utility of flow cytometric immunophenotyping in myeloma is also analyzed, with an emphasis on the growing role of minimal residual analysis as potential biomarker for evaluating treatment efficacy and for tailoring risk-adapted treatment, in prospective clinical trials.

Prolonged survival with a longer duration of maintenance lenalidomide after autologous hematopoietic stem cell transplantation for multiple myeloma

BACKGROUND

Although lenalidomide maintenance therapy has demonstrated improved outcomes after autologous hematopoietic stem cell transplantation (auto-HCT) for patients with multiple myeloma (MM), the impact of the duration of this therapy is not clearly known.

METHODS

This study retrospectively analyzed all MM patients who were placed on maintenance lenalidomide after auto-HCT between January 2007 and December 2013. Progression-free survival (PFS) and overall survival (OS) were analyzed in multivariate Cox proportional hazards regression models that included the duration of maintenance as a time-dependent covariate.

RESULTS

Of the 464 patients identified, 46% initiated therapy early (<4 months after auto-HCT). The median PFS and OS were 38 and 78 months, respectively. Improvements in PFS (hazard ratio [HR], 0.13; 95% confidence interval [CI], 0.04-0.38; P < .001) and OS (HR, 0.09; 95% CI, 0.03-0.26; P < .001) were seen for those on maintenance for >2 years versus those on maintenance for ≤2 years. For those on maintenance for >3 versus those on maintenance for ≤3 years, this trend continued with improvements seen in PFS (HR, 0.02; 95% CI, 0.00-0.44; P = .012) and OS (HR, 0.05; 95% CI, 0.00-0.83; P = .037). The incidence of second primary malignancies (SPMs) in the entire cohort was 3%. No differences were seen in survival between early and late initiators of maintenance lenalidomide.

CONCLUSIONS

A longer duration of maintenance therapy was associated with longer survival. The incidence of SPMs was low, and they were not associated with the duration of maintenance. The timing of the initiation of maintenance had no effect on survival. Cancer 2016;122:3831-3837. © 2016 American Cancer Society.

Minimal residual disease monitoring and immune profiling in multiple myeloma in elderly patients

The value of minimal residual disease (MRD) in multiple myeloma (MM) has been more frequently investigated in transplant-eligible patients than in elderly patients. Because an optimal balance between treatment efficacy and toxicity is of utmost importance in patients with elderly MM, sensitive MRD monitoring might be particularly valuable in this patient population. Here, we used second-generation 8-color multiparameter-flow cytometry (MFC) to monitor MRD in 162 transplant-ineligible MM patients enrolled in the PETHEMA/GEM2010MAS65 study. The transition from first- to second-generation MFC resulted in increased sensitivity and allowed us to identify 3 patient groups according to MRD levels: MRD negative (<10(-5); n = 54, 34%), MRD positive (between <10(-4) and ≥10(-5); n = 20, 12%), and MRD positive (≥10(-4); n = 88, 54%). MRD status was an independent prognostic factor for time to progression (TTP) (hazard ratio [HR], 2.7; P = .007) and overall survival (OS) (HR, 3.1; P = .04), with significant benefit for MRD-negative patients (median TTP not reached, 70% OS at 3 years), and similar poorer outcomes for cases with MRD levels between <10(-4) and ≥10(-5) vs ≥10(-4) (both with a median TTP of 15 months; 63% and 55% OS at 3 years, respectively). Furthermore, MRD negativity significantly improved TTP of patients >75 years (HR, 4.8; P < .001), as well as those with high-risk cytogenetics (HR, 12.6; P = .01). Using second-generation MFC, immune profiling concomitant to MRD monitoring also contributed to identify patients with poor, intermediate, and favorable outcomes (25%, 61%, and 100% OS at 3 years, respectively; P = .01), the later patients being characterized by an increased compartment of mature B cells. Our results show that similarly to transplant candidates, MRD monitoring is one of the most relevant prognostic factors in elderly MM patients, irrespectively of age or cytogenetic risk. This trial was registered at www.clinicaltrials.gov as #NCT01237249.

Is it possible to cure myeloma without allogeneic transplantation?

During the last decades, a better understanding of the biology of multiple myeloma (MM) has led to the application of novel treatment strategies for MM patients. The new anti-myeloma regimens produce higher incidence of durable and of better quality responses and they improve overall survival, challenging the dogma of incurable disease, outside the context of allogeneic transplantation. This review presents all these strategies that aim to cure MM, including continuous treatment i.e. induction, consolidation and maintenance, treatment of asymptomatic MM and monitoring minimal residual disease using modern techniques, such as multi-parameter flow cytometry, molecular assays and advanced imaging.

Minimal Residual Disease by Next-Generation Sequencing: Pros and Cons

The wealth of data recently generated highlights that minimal residual disease (MRD)-negative status can be achieved in a large proportion of patients. These studies, in addition to a meta-analysis, clearly suggest significant improvement in both event-free survival (EFS) and overall survival (OS) among those patients achieving MRD-negative status, especially with sensitivity of one cell in 1 million bone marrow cells. There is an evolving consensus that achieving MRD-negative status should become the ultimate goal of therapeutic intervention. Further future efforts should now be directed at determining how MRD status can be used to guide and personalize further therapy including type of consolidation and maintenance therapy.

Multiple Myeloma Minimal Residual Disease

Assessment of minimal residual disease (MRD) is becoming standard diagnostic care for potentially curable neoplasms such as some acute leukemias as well as chronic myeloid and lymphocytic leukemia. Although multiple myeloma (MM) remains as an incurable disease, around half of the patients achieve complete remission (CR), and recent data suggests increasing rates of curability with "total-therapy-like" programs. This landscape is likely to be improved with the advent of new antibodies and small molecules. Therefore, conventional serological and morphological techniques have become suboptimal for sensitive evaluation of highly effective treatment strategies. Although, existing data suggests that MRD could be used as a biomarker to evaluate treatment efficacy, help on therapeutic decisions, and act as surrogate for overall survival, the role of MRD in MM is still a matter of extensive debate. Here, we review the different levels of remission used to define depth of response in MM and their clinical significance, as well as the prognostic value and unique characteristics of MRD detection using immunophenotypic, molecular, and imaging techniques. Key facts The higher efficacy of new treatment strategies for MM demand the incorporation of highly sensitive techniques to monitor treatment efficacy MRD could be used as a more potent surrogate biomarker for survival than standard CR We need to understand the pros and cons of the different MRD techniques The time has come to incorporate highly sensitive, cost-effective, readily available, and standardized MRD techniques into clinical trials to assess its role in therapeutic decisions.

New Perspectives Offered by Nuclear Medicine for the Imaging and Therapy of Multiple Myeloma

The management of multiple myeloma has fundamentally changed over the years and imaging techniques able to match the therapeutic advances are now much needed. Although many patients now achieve complete response after first-line treatment, relapse is common. Therefore, it would be important to improve the initial prognostic stratification and to detect minimal residual disease after treatment. (18)F-FDG-PET/CT is a useful imaging tool which has a high prognostic value at baseline evaluation and can effectively differentiate active from inactive lesions during induction treatment or after autologous stem-cell transplantation. In combination with biological data, it improves the prediction of relapse. Other PET tracers may soon enter clinical practice and overcome some of the limitations of (18)F-FDG, such as the low sensitivity in detecting early bone marrow infiltration. Excellent results with (11)C-Methionine are reported by Lapa and colleagues in this issue of the Journal. (11)C-Methionine uptake reflects the increased protein synthesis of malignant plasmocytes and correlates well with bone marrow infiltration. Other promising PET ligands include lipid tracers, such as (11)C-Choline or (11)C-acetate, and some peptide tracers, such as (68)Ga-Pentixafor, that targets CXCR4 (chemokine receptor-4), which is often expressed with high density by myeloma cells. Malignant plasma cells are radiosensitive and thus potentially amenable to systemic radionuclide therapy. Indeed, excellent preclinical results were obtained with radioimmunotherapy targeting CD38. Also, preliminary clinical results with peptides targeting CXCR4 (e.g. (177)Lu- or (90)Y-Pentixather) are encouraging. Multiple myeloma may represent a renewal of the already strong partnership between hematologists and nuclear medicine physicians.

Mcl-1 downregulation leads to the heightened sensitivity exhibited by BCR-ABL positive ALL to induction of energy and ER-stress

BCR-ABL positive (+) acute lymphoblastic leukemia (ALL) accounts for ∼30% of cases of ALL. We recently demonstrated that 2-deoxy-d-glucose (2-DG), a dual energy (glycolysis inhibition) and ER-stress (N-linked-glycosylation inhibition) inducer, leads to cell death in ALL via ER-stress/UPR-mediated apoptosis. Among ALL subtypes, BCR-ABL+ ALL cells exhibited the highest sensitivity to 2-DG suggesting BCR-ABL expression may be linked to this increased vulnerability. To confirm the role of BCR-ABL, we constructed a NALM6/BCR-ABL stable cell line and found significant increase in 2-DG-induced apoptosis compared to control. We found that Mcl-1 was downregulated by agents inducing ER-stress and Mcl-1 levels correlated with ALL sensitivity. In addition, we showed that Mcl-1 expression is positively regulated by the MEK/ERK pathway, dependent on BCR-ABL, and further downregulated by combining ER-stressors with TKIs. We determined that energy/ER stressors led to translational repression of Mcl-1 via the AMPK/mTOR and UPR/PERK/eIF2α pathways. Taken together, our data indicate that BCR-ABL+ ALL exhibits heightened sensitivity to induction of energy and ER-stress through inhibition of the MEK/ERK pathway, and translational repression of Mcl-1 expression via AMPK/mTOR and UPR/PERK/eIF2α pathways. This study supports further consideration of strategies combining energy/ER-stress inducers with BCR-ABL TKIs for future clinical translation in BCR-ABL+ ALL patients.