More Than 2% of Circulating Tumor Plasma Cells Defines Plasma Cell Leukemia-Like Multiple Myeloma

Circulating plasma cells as a predictive biomarker in Multiple myeloma: an updated systematic review and meta-analysis

BACKGROUND

Circulating plasma cells (CPCs) are defined by the presence of peripheral blood clonal plasma cells, which would contribute to the progression and dissemination of multiple myeloma (MM). An increasing number of studies have demonstrated the predictive potential of CPCs in the past few years. Therefore, there is a growing need for an updated meta-analysis to identify the specific relationship between CPCs and the prognosis of MM based on the current research status.

METHODS

The PubMed, Embase, and Cochrane Library databases were screened to determine eligible studies from inception to November 5, 2023. Publications that reported the prognostic value of CPCs in MM patients were included. Hazard ratios (HRs) with 95% confidence intervals (CIs) of overall survival (OS) and progression-free survival (PFS) were extracted to pool the results. Subgroup analyses were performed based on region, sample size, cut-off value, detection time, initial treatment, and data type. The association between CPCs level and clinicopathological characteristics, including the International Staging System (ISS), Revised-ISS (R-ISS), and cytogenetic abnormalities were also evaluated. Statistical analyses were conducted using STATA 17.0 software.

RESULTS

Twenty-two studies with a total of 5637 myeloma patients were enrolled in the current meta-analysis. The results indicated that myeloma patients with elevated CPCs were expected to have a poor OS (HR = 2.19, 95% CI: 1.81-2.66, p < 0.001) and PFS (HR = 2.45, 95% CI: 1.93-3.12, p < 0.001). Subgroup analyses did not alter the prognostic role of CPCs, regardless of region, sample size, cut-off value, detection time, initial treatment, or data type. Moreover, the increased CPCs were significantly related to advanced tumour stage (ISS III vs. ISS I-II: pooled OR = 2.89, 95% CI: 2.41-3.46, p < 0.001; R-ISS III vs. R-ISS I-II: pooled OR = 3.65, 95% CI: 2.43-5.50, p < 0.001) and high-risk cytogenetics (high-risk vs. standard-risk: OR = 2.22, 95% CI: 1.60-3.08, p < 0.001).

CONCLUSION

Our meta-analysis confirmed that the increased number of CPCs had a negative impact on the PFS and OS of MM patients. Therefore, CPCs could be a promising prognostic biomarker that helps with risk stratification and disease monitoring.

An automated workflow based on data independent acquisition for practical and high-throughput personalized assay development and minimal residual disease monitoring in multiple myeloma patients

OBJECTIVES

Minimal residual disease (MRD) status in multiple myeloma (MM) is an important prognostic biomarker. Personalized blood-based targeted mass spectrometry detecting M-proteins (MS-MRD) was shown to provide a sensitive and minimally invasive alternative to MRD-assessment in bone marrow. However, MS-MRD still comprises of manual steps that hamper upscaling of MS-MRD testing. Here, we introduce a proof-of-concept for a novel workflow using data independent acquisition-parallel accumulation and serial fragmentation (dia-PASEF) and automated data processing.

METHODS

Using automated data processing of dia-PASEF measurements, we developed a workflow that identified unique targets from MM patient sera and personalized protein sequence databases. We generated patient-specific libraries linked to dia-PASEF methods and subsequently quantitated and reported M-protein concentrations in MM patient follow-up samples. Assay performance of parallel reaction monitoring (prm)-PASEF and dia-PASEF workflows were compared and we tested mixing patient intake sera for multiplexed target selection.

RESULTS

No significant differences were observed in lowest detectable concentration, linearity, and slope coefficient when comparing prm-PASEF and dia-PASEF measurements of serial dilutions of patient sera. To improve assay development times, we tested multiplexing patient intake sera for target selection which resulted in the selection of identical clonotypic peptides for both simplex and multiplex dia-PASEF. Furthermore, assay development times improved up to 25× when measuring multiplexed samples for peptide selection compared to simplex.

CONCLUSIONS

Dia-PASEF technology combined with automated data processing and multiplexed target selection facilitated the development of a faster MS-MRD workflow which benefits upscaling and is an important step towards the clinical implementation of MS-MRD.

Low circulating tumor cell levels correlate with favorable outcomes and distinct biological features in multiple myeloma

There is growing interest in multiple myeloma (MM) circulating tumor cells (CTCs), but their rareness in peripheral blood (PB) and inconsistency in cutoffs question their clinical utility. Herein, we applied next-generation flow cytometry in 550 bone marrow (BM) and matched PB samples to define an optimal CTC cutoff for both transplant-eligible and transplant-ineligible newly diagnosed MM (NDMM) patients. Deep phenotyping was performed to investigate unique microenvironmental features associated with CTC dissemination. CTCs were detected in 90% of patients (median 0.01%; range: 0.0002%-12.6%) and increased levels associated with adverse features. Correlations were observed between high CTC percentages and a diffused MRI pattern, a distinct BM composition characterized by altered B-cell differentiation together with an expansion of effector cells and tumor-associated macrophages, as well as a greater phenotypic dissimilarity between BM and PB clonal cells. Progression-free survival (PFS) and overall survival (OS) gradually worsened with each logarithmic increment of CTCs. Conversely, NDMM patients without CTCs showed unprecedented outcomes, with 5-year PFS and OS rates of 83% and 97%, respectively. A cutoff of 0.02% CTCs was independent of the ISS, LDH, and cytogenetics in a multivariate analysis of risk factors for PFS. The 0.02% CTC cutoff synergized with the MGUS-like phenotype and the R-ISS for improving the risk stratification systems. MRD negativity was less frequent if CTCs were ≥0.02% at diagnosis, but whenever achieved, the poor prognosis of these patients was abrogated. This study shows the clinical utility of CTC assessment in MM and provides evidence toward a consensus cutoff for risk stratification.

Beyond the marrow: insights from comprehensive next-generation sequencing of extramedullary multiple myeloma tumors

Extramedullary multiple myeloma (EMM) is an aggressive form of multiple myeloma (MM). This study represents the most comprehensive next-generation sequencing analysis of EMM tumors (N = 14) to date, uncovering key molecular features and describing the tumor microenvironment. We observed the co-occurrence of 1q21 gain/amplification and MAPK pathway mutations in 79% of EMM samples, suggesting that these are crucial mutational events in EMM development. We also demonstrated that patients with mutated KRAS and 1q21 gain/amplification at the time of diagnosis have a significantly higher risk of EMM development (HR = 2.4, p = 0.011) using data from a large CoMMpass dataset. We identified downregulation of CXCR4 and enhanced cell proliferation, along with reduced expression of therapeutic targets (CD38, SLAMF7, GPRC5D, FCRH5), potentially explaining diminished efficacy of immunotherapy. Conversely, we identified significantly upregulated EZH2 and CD70 as potential future therapeutic options. For the first time, we report on the tumor microenvironment of EMM, revealing CD8+ T cells and NK cells as predominant immune effector cells using single-cell sequencing. Finally, this is the first longitudinal study in EMM revealing the molecular changes from the time of diagnosis to EMM relapse.

Navigating High-Risk and Ultrahigh-Risk Multiple Myeloma: Challenges and Emerging Strategies

Despite significant improvement in the outcomes of patients with newly diagnosed multiple myeloma (NDMM) with novel therapies, there is still an underserved high-risk (HR) population that experiences early disease progression and death. With the median survival crossing 10 years, we defined ultrahigh-risk (uHR)MM as MM leading to death within 24-36 months of diagnosis and HRMM as MM leading to death within 36-60 months. Several features have emerged as markers of uHRMM: the co-occurrence of two or more high-risk cytogenetic abnormalities, extramedullary disease, plasma cell leukemia and a high-risk gene expression profiling signature. The heterogeneous risk definition across trials, the few trials available designed for HR patients, and the small HR subgroups in all-comers trials make it difficult to generate recommendations with high levels of evidence. Nevertheless, regardless of treatment administered, several studies consistently showed that achieving and maintaining measurable residual disease negativity is now considered the main factor able to mitigate the adverse prognosis related to baseline features. For fit patients with HR transplant-eligible (TE) NDMM, quadruplet induction/consolidation treatment with anti-CD38 monoclonal antibodies, immunomodulatory agents, proteasome inhibitors and dexamethasone, and autologous stem-cell transplant and maintenance with, if available, at least a doublet combination could be considered the option of choice. For non-TE NDMM, considering the recent data generated and carefully reviewing those upcoming, quadruplet treatment consisting of anti-CD38 monoclonal antibodies, immunomodulatory agents, proteasome inhibitors, and dexamethasone should also be considered. Future trials integrating BCMA-directed novel generation immunotherapies hold great potential for further advancing the treatment landscape in all NDMM patients with HR disease.

Imaging flow cytometric detection of del(17p) in bone marrow and circulating plasma cells in multiple myeloma

BACKGROUND

Detection of del(17p) in myeloma is generally performed by fluorescence in situ hybridization (FISH) on a slide with analysis of up to 200 nuclei. The small cell sample analyzed makes this a low precision test. We report the utility of an automated FISH method, called "immuno-flowFISH", to detect plasma cells with adverse prognostic risk del(17p) in bone marrow and blood samples of patients with myeloma.

METHODS

Bone marrow (n = 31) and blood (n = 19) samples from 35 patients with myeloma were analyzed using immuno-flowFISH. Plasma cells were identified by CD38/CD138-immunophenotypic gating and assessed for the 17p locus and centromere of chromosome 17. Cells were acquired on an AMNIS ImageStreamX MkII imaging flow cytometer using INSPIRE software.

RESULTS

Chromosome 17 abnormalities were identified in CD38/CD138-positive cells in bone marrow (6/31) and blood (4/19) samples when the percent plasma cell burden ranged from 0.03% to 100% of cells. Abnormalities could be identified in 14.5%-100% of plasma cells.

CONCLUSIONS

The "immuno-flowFISH" imaging flow cytometric method could detect del(17p) in plasma cells in both bone marrow and blood samples of myeloma patients. This method was also able to detect gains and losses of chromosome 17, which are also of prognostic significance. The lowest levels of 0.009% (bone marrow) and 0.001% (blood) for chromosome 17 abnormalities was below the detection limit of current FISH method. This method offers potential as a new means of identifying these prognostically important chromosomal defects, even when only rare cells are present and for serial disease monitoring.

Bone marrow stromal cells induce chromatin remodeling in multiple myeloma cells leading to transcriptional changes

The natural history of multiple myeloma is characterized by its localization to the bone marrow and its interaction with bone marrow stromal cells. The bone marrow stromal cells provide growth and survival signals, thereby promoting the development of drug resistance. Here, we show that the interaction between bone marrow stromal cells and myeloma cells (using human cell lines) induces chromatin remodeling of cis-regulatory elements and is associated with changes in the expression of genes involved in the cell migration and cytokine signaling. The expression of genes involved in these stromal interactions are observed in extramedullary disease in patients with myeloma and provides the rationale for survival of myeloma cells outside of the bone marrow microenvironment. Expression of these stromal interaction genes is also observed in a subset of patients with newly diagnosed myeloma and are akin to the transcriptional program of extramedullary disease. The presence of such adverse stromal interactions in newly diagnosed myeloma is associated with accelerated disease dissemination, predicts the early development of therapeutic resistance, and is of independent prognostic significance. These stromal cell induced transcriptomic and epigenomic changes both predict long-term outcomes and identify therapeutic targets in the tumor microenvironment for the development of novel therapeutic approaches.

Prognostic Implications of Circulating Plasma Cell Percentage in Multiple Myeloma and Primary Plasma Cell Leukemia Defined by New Criteria

INTRODUCTION

The definition of primary plasma cell leukemia (pPCL) has been revised from ≥20% to ≥5% circulating plasma cells (CPC). However, the precise prognosis associated with CPC remains controversial. This study aimed to investigate prognostic biomarkers for myeloma patients based on CPC presence.

METHODS

A comprehensive analysis was conducted on 309 consecutive patients diagnosed with either multiple myeloma or pPCL, utilizing peripheral blood smears stained with Wright-Giemsa.

RESULTS

Patients were grouped by CPC percentage: 0% (221, 71.5%), 1-4% (49, 15.9%), 5-19% (16, 5.2%), ≥20% (23, 7.4%). CPC >5% correlated with unfavorable characteristics, including anemia, renal dysfunction, and advanced International Staging System. Common cytogenetic abnormalities such as 1q21 amplification, 17p deletion, and Myc rearrangement were prevalent among CPC-positive patients. Median progression-free survival (PFS) and overall survival (OS) were shorter in patients with CPC ≥5% (29.47 vs. 10.03 months; 64.10 vs. 12.30 months). Additionally, PFS and OS were shorter in CPC-positive patients without autologous hematopoietic stem cell transplantation (ASCT) and those with response < partial remission to the first-line regimen. Furthermore, an association emerged between soft tissue-related extramedullary disease and inferior PFS, while Myc rearrangement correlated with abbreviated OS.

CONCLUSION

Biological characteristics displayed greater aggressiveness in patients with positive CPC, leading to significantly shorter PFS and OS. The presence of CPC, ASCT, and overall response rate were independent prognostic factors. While no new threshold for pPCL with CPCs is proposed, Myc rearrangements and CPC positivity could serve as ultra-high-risk factors for multiple myeloma.

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

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

Circulating tumor plasma cells and peripheral blood measurable residual disease assessment in multiple myeloma patients not planned for upfront transplant

Circulating tumor plasma cells (CTPCs) provide a noninvasive alternative for measuring tumor burden in newly diagnosed multiple myeloma (NDMM). Moreover, measurable residual disease (MRD) assessment in peripheral blood (PBMRD) can provide an ideal alternative to bone marrow MRD, which is limited by its painful nature and technical challenges. However, the clinical significance of PBMRD in NDMM still remains uncertain. Additionally, data on CTPC in NDMM patients not treated with transplant are scarce. We prospectively studied CTPC and PBMRD in 141 NDMM patients using highly sensitive multicolor flow cytometry (HS-MFC). PBMRD was monitored at the end of three cycles (PBMRD1) and six cycles (PBMRD2) of chemotherapy in patients with detectable baseline CTPC. Patients received bortezomib-based triplet therapy and were not planned for an upfront transplant. Among baseline risk factors, CTPC ≥ 0.01% was independently associated with poor progression-free survival (PFS) (hazard ratio [HR] = 2.77; p = 0.0047) and overall survival (OS) (HR = 2.9; p = 0.023) on multivariate analysis. In patients with detectable baseline CTPC, undetectable PBMRD at both subsequent time points was associated with longer PFS (HR = 0.46; p = 0.0037), whereas detectable PBMRD at any time point was associated with short OS (HR = 3.25; p = 0.004). Undetectable combined PBMRD (PBMRD1 and PBMRD2) outperformed the serum-immunofixation-based response. On multivariate analysis, detectable PBMRD at any time point was independently associated with poor PFS (HR = 2.0; p = 0.025) and OS (HR = 3.97; p = 0.013). Thus, our findings showed that CTPC and PBMRD assessment using HS-MFC provides a robust, noninvasive biomarker for NDMM patients not planned for an upfront transplant. Sequential PBMRD monitoring has great potential to improve the impact of the existing risk stratification and response assessment models.

Multiparametric Flow Cytometry in the Evaluation of Plasma Cell Proliferative Disorders: Current Paradigms for Clinical Practice

Diagnosis of plasma cell proliferative disorders (PCPDs) is primarily based on the demonstration of monoclonal protein (M-Protein) in blood and/ or urine which often precedes clinical manifestations of the disease. The basic pathophysiology behind the M-protein presence is the proliferation of clonal plasma cells (PCs) in bone marrow or extramedullary sites and is assessed using cytomorphology and immunophenotyping. The role of multiparametric flow cytometry (MFC) for PC identification is technically the most valuable tool in this context as it characterizes as well as quantifies the clonal PCs based on differential expression of various immunophenotypic (IPT) markers. From a diagnostic perspective, MFC is critical in the definite identification of the clonal PCs and delineates benign and borderline entities at one end of the spectrum (MGUS, SMM) with lower clonal PC% and, malignant diseases at the other end (MM and PCL) with higher clonal PC fraction. The role of MFC in assessment of measurable residual disease (MRD) and monitoring of progression in MM and various PCPDs has been validated in multiple clinical studies and is probably one of the most promising tools for predicting treatment outcomes. Furthermore, MFC also plays a crucial role in disease prognostication based on specific IPT profiles. An additional role of MFC in the current clinical scenario is the evaluation of tumor microenvironment based on immune cell repertoire, which is reflecting encouraging results across. Thus, in the current review we concisely describe the role of MFC as a reliable and essential modality in PCPDs, from diagnosis to prediction of treatment outcome and disease monitoring.

Prognostic value of circulating plasma cells detected by flow cytometry in newly diagnosed multiple myeloma patients: a systematic review and meta-analysis

OBJECTIVES

Multiple myeloma (MM) is a malignant plasma cell disorder. The most widely accepted staging system for MM is the revised International Staging System based on cytogenetic and clinical biomarkers. The circulating clonal plasma cells (CPCs) were reported to have potential prognostic impact on MM. Among various diagnostic approaches, multiparametric flow cytometry (FCM) offers heightened sensitivity, minimal invasiveness and reproducibility. We conducted a meta-analysis to evaluate the prognostic value of quantifying CPCs via FCM in newly diagnosed symptomatic MM (NDMM) patients.

DESIGN

Systematic review and meta-analysis.

DATA SOURCE

PubMed, Web of Science, Embase and references of included studies.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

We included observational studies that evaluated the prognostic value of CPCs detected by FCM in NDMM.

DATA EXTRACTION AND SYNTHESIS

Data were screened and extracted independently by two investigators. The pooled results originated from random effects models. The primary endpoint was overall survival (OS). The secondary endpoint was progression-free survival (PFS). To evaluate the prognostic value of CPCs in NDMM, HRs and their 95% CI for both OS and PFS were derived using COX multivariable models. These values were then used to compute the pooled estimated effect.

RESULTS

Our meta-analysis encompassed a total of 2704 NDMM patients from 11 studies up to 27 August 2022. The pooled HR for OS and PFS in CPC-positive (CPCs+) group and CPC-negative group were 1.95 (95% CI 1.24 to 3.07) and 2.07 (95% CI 1.79 to 2.39), respectively. The autologous stem cell transplantation (ASCT) failed to eliminate the adverse impact on OS and PFS. The heterogeneity may stem from the use of novel agents or traditional chemotherapy as initial treatment.

CONCLUSION

This meta-analysis indicates CPCs+ had an adverse impact on the prognosis of NDMM patients in the total population, and the adverse impact could not be eliminated by ASCT.

PROSPERO REGISTRATION NUMBER

CRD42021272381.

Analysis of baseline circulating tumor cells integrated with PET/CT findings in transplant-ineligible multiple myeloma

ABSTRACT

We aimed to improve prognostic predictors in patients with transplant-ineligible multiple myeloma (TIE-MM) by combining baseline circulating clonal tumor cells (CTCs) and positron emission tomography/computed tomography (PET/CT) findings. The factors associated with prognosis were retrospectively investigated in 126 patients with TIE-MM who underwent CTC quantification by multiparameter flow cytometry and PET/CT at the initial presentation. The total lesion glycolysis (TLG) level was calculated using the Metavol software. The median percentage of CTC was 0.06% (range, 0%-4.82%), and 54 patients (42.9%) demonstrated high CTC levels. High CTC levels were associated with significantly poorer progression-free survival (PFS, 2-year 43.4% vs 68.1%; P < .001) and overall survival (OS, 5-year 39.0% vs 68.3%; P < .001). Similarly, high TLG levels significantly worsened the PFS (2-year, 41.2% vs 67.6%; P = .038) and OS (5-year, 37.7% vs 63.1%; P = .019). The multivariate analyses showed that Revised International Staging System (R-ISS) III, high CTC and TLG levels, and complete response were significant prognostic factors for PFS and OS. A novel predictive model was constructed using CTCs, TLG, and R-ISS III. The patients were stratified into 3 groups according to the number of risk factors, revealing an extremely high-risk group with a 2-year PFS of 0% and a 5-year OS of 20%. Patients without any high-risk features had better prognosis, with a 2-year PFS of 78.6% and a 5-year OS of 79.5%. The combination of CTCs and volumetric assessment of PET/CT at diagnosis augments the existing stratification systems and may pave the way for a risk-adapted treatment approach.

Early Detection and Diagnostic Approach Through Automated Hematological Analysis for Plasma Cell Leukemia

Plasma cell leukemia (PCL) is a clinically aggressive variant of multiple myeloma, characterized by a high burden of circulating plasma cells, necessitating swift and accurate diagnosis due to its poor prognosis. The conventional diagnostic criteria, including the recent recommendation by the International Myeloma Working Group (IMWG) of > 5% circulating plasma cells as positive, have evolved over time. In this context, we present a detailed case report that underscores the pivotal role of the ADVIA 2120 automated hematology counter in detecting plasma cells through cytogram analysis, along with the significance of routine peripheral blood smear analysis and the utility of a large unstained cells (LUCs) threshold of > 4.5% as an indicator for PCL. The case involves a 64-year-old patient with relapsed multiple myeloma and stable paraprotein levels who experienced sudden renal impairment. In this case report, we highlight how ADVIA analysis and cytochemistry assisted in the diagnosis, and further explore ADVIA's utility in this challenging leukemia.

Recommendations for the study of monoclonal gammopathies in the clinical laboratory. A consensus of the Spanish Society of Laboratory Medicine and the Spanish Society of Hematology and Hemotherapy. Part I: Update on laboratory tests for the study of monoclonal gammopathies

Monoclonal gammopathies (MG) are characterized by the proliferation of plasma cells that produce identical abnormal immunoglobulins (intact or some of their subunits). This abnormal immunoglobulin component is called monoclonal protein (M-protein), and is considered a biomarker of proliferative activity. The identification, characterization and measurement of M-protein is essential for the management of MG. We conducted a systematic review of the different tests and measurement methods used in the clinical laboratory for the study of M-protein in serum and urine, the biochemistry and hematology tests necessary for clinical evaluation, and studies in bone marrow, peripheral blood and other tissues. This review included literature published between 2009 and 2022. The paper discusses the main methodological characteristics and limitations, as well as the purpose and clinical value of the different tests used in the diagnosis, prognosis, monitoring and assessment of treatment response in MG. Included are methods for the study of M-protein, namely electrophoresis, measurement of immunoglobulin levels, serum free light chains, immunoglobulin heavy chain/light chain pairs, and mass spectrometry, and for the bone marrow examination, morphological analysis, cytogenetics, molecular techniques, and multiparameter flow cytometry.

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.

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

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

Variability of definition of high-risk multiple myeloma across phase III clinical trials

The definition of high-risk multiple myeloma (HRMM) is evolving. Use of a clear definition of HRMM in clinical trials was not previously studied. We explored the definition of HRMM in completed phase III clinical trials. There is extreme variability in the definition and cutoffs used to define HRMM, with a significant number of studies lacking a clear definition. Our study provides a quantification of the variability in defining HRMM and suggests a need to better define HRMM in future clinical trials to enable more consistent treatment recommendations.

Daratumumab with lenalidomide and dexamethasone in relapsed or refractory multiple myeloma patients - real world evidence analysis

We performed real world evidence (RWE) analysis of daratumumab, lenalidomide and dexamethasone (Dara-Rd) versus lenalidomide and dexamethasone (Rd) treatment in relapsed/refractory multiple myeloma patients (RRMM). In total, 240 RRMM patients were treated with Dara-Rd from 2016 to 2022 outside of clinical trials in all major Czech hematology centers. As a reference, 531 RRMM patients treated with Rd were evaluated. Patients' data were recorded in the Czech Registry of Monoclonal Gammopathies (RMG). Partial response (PR) or better response (ORR) was achieved in significantly more patients in Dara-Rd than in Rd group (91.2% vs. 69.9%; p < 0.001). The median progression free survival (PFS) was 26.9 months in the Dara-Rd and 12.8 months in the Rd group (p < 0.001). Median overall survival (OS) was not reached in the Dara-Rd compared to 27.2 months in the Rd group (p = 0.023). In patients with 1-3 previous treatment lines, there was significant PFS benefit of Dara-Rd compared to Rd (median PFS not reached vs. 13.2 months; p < 0.001). In patients with > 3 previous treatment lines, there was no significant PFS benefit of Dara-Rd treatment (7.8 months vs. 9.9 months; p = 0.874), similarly in patients refractory to PI + IMIDs (11.5 months vs. 9.2 months; p = 0.376). In RWE conditions, the median PFS in RRMM patients treated with Dara-Rd is shorter when compared to clinical trials. In heavily pretreated RRMM patients, efficacy of Dara-Rd treatment is limited; best possible outcomes of Dara-Rd are achieved in minimally pretreated patients.