The clinical significance of stringent complete response in multiple myeloma is surpassed by minimal residual disease measurements

Measurable Residual Disease and Decision-Making in Multiple Myeloma

Measurable (minimal) residual disease (MRD) has already proven to be one of the most important prognostic factors in multiple myeloma (MM). Each improvement in the depth of MRD testing has led to superior discrimination of outcomes, and sustained MRD negativity seems to be paramount to durable responses. Peripheral blood assays to assess for MRD are still under investigation but hold promise as complementary tools to bone marrow MRD assays such as next-generation sequencing and flow cytometry. Herein, the authors explore the evidence and potential benefits and drawbacks of MRD-adapted clinical decision-making in MM.

Progression free survival of myeloma patients who become IFE-negative correlates with the detection of residual monoclonal free light chain (FLC) by mass spectrometry

Deeper responses are associated with improved survival in patients being treated for myeloma. However, the sensitivity of the current blood-based assays is limited. Historical studies suggested that normalisation of the serum free light chain (FLC) ratio in patients who were negative by immunofixation electrophoresis (IFE) was associated with improved outcomes. However, recently this has been called into question. Mass spectrometry (MS)-based FLC assessments may offer a superior methodology for the detection of monoclonal FLC due to greater sensitivity. To test this hypothesis, all available samples from patients who were IFE negative after treatment with carfilzomib and lenalidomide-based induction and autologous stem cell transplantation (ASCT) in the Myeloma XI trial underwent FLC-MS testing. FLC-MS response assessments from post-induction, day+100 post-ASCT and six months post-maintenance randomisation were compared to serum FLC assay results. Almost 40% of patients had discordant results and 28.7% of patients with a normal FLC ratio had residual monoclonal FLC detectable by FLC-MS. FLC-MS positivity was associated with reduced progression-free survival (PFS) but an abnormal FLC ratio was not. This study demonstrates that FLC-MS provides a superior methodology for the detection of residual monoclonal FLC with FLC-MS positivity identifying IFE-negative patients who are at higher risk of early progression.

Performance Characteristics and Limitations of the Available Assays for the Detection and Quantitation of Monoclonal Free Light Chains and New Emerging Methodologies

Light chain measurements form an essential component of the testing strategy for the detection and monitoring of patients with suspected and/or proven plasma cell disorders. Urine-based electrophoretic assays remain at the centre of the international guidelines for response assessment but the supplementary role of serum-free light chain (FLC) assays in response assessment and the detection of disease progression due to their increased sensitivity has been increasingly recognised since their introduction in 2001. Serum FLC assays have also been shown to be prognostic across the spectrum of plasma cell disorders and are now incorporated into risk stratification scores for patients with monoclonal gammopathy of undetermined significance (MGUS), smouldering multiple myeloma, and light chain amyloidosis (AL amyloidosis), as well as being incorporated into the criteria for defining symptomatic multiple myeloma. There are now multiple different commercially available serum FLC assays available with differing performance characteristics, which are discussed in this review, along with the implications of these for patient monitoring. Finally, newer methodologies for the identification and characterisation of monoclonal FLC, including modifications to electrophoretic techniques, mass spectrometry-based assays and Amylite, are also described along with the relevant published data available regarding the performance of each assay.

M-protein detection by mass spectrometry for minimal residual disease in multiple myeloma

Multiple myeloma (MM) is characterized by excessive production of monoclonal immunoglobulins (M proteins). Routine screening methods for M proteins to assess prognosis are unable to detect low levels of M proteins produced by residual tumor cells, ie, minimal residual disease (MRD). Assessment of MRD can be conducted by examining residual tumor cells in bone marrow or circulating M proteins. Advances in mass spectrometry have enabled reliable and highly sensitive detection of low abundance serum biomarkers making it a viable and significantly less invasive approach. Mass spectrometry can achieve dynamic monitoring of MRD and identify therapeutic monoclonal antibodies as well as oligoclonal proteins. In this review we summarize mass spectrometry methods in M protein detection and their applications of MRD detection in MM.

Understanding the Constraints and Optimization of Serum Immunofixation Electrophoresis and Serum Free Light Chains for Detecting Monoclonal Proteins: A Single-Center Experience

Introduction  Serum immunofixation electrophoresis (SIFE) and serum free light chain (SFLC) assay are imperative investigations in diagnosis and follow-up of multiple myeloma (MM). SFLC assays are reported to have higher sensitivity than SIFE. However, discrepancies have been reported between them. The current study was aimed at assessing concordance and discordance between SIFE and SFLC results in MM. Methods  A total of 450 observations of both SIFE and SFLC were obtained from treatment-naive and follow-up MM patients. Results  One hundred and twenty-nine (28.7%) values were observed as discordant, that is, positive SIFE with normal SFLC ratio or negative SIFE with abnormal SFLC ratio ( p -value < 0.00001). Proportion of discordance was higher in SIFE positive-SFLC normal cases than SIFE negative-SFLC abnormal cases. Discordance was more frequent in follow-up cases. Conclusion  Negative SFLC alone may not be reliable for MM follow-up. Algorithm may be based on SFLC measurements on each follow-up till attainment of normal SFLC ratio. Once SFLC normalizes, follow-up may be done with SIFE. If SIFE is positive, further follow-up with SIFE may be initiated.

Liquid biopsy-based monitoring of residual disease in multiple myeloma by analysis of the rearranged immunoglobulin genes-A feasibility study

The need for sensitive monitoring of minimal/measurable residual disease (MRD) in multiple myeloma emerged as novel therapies led to deeper responses. Moreover, the potential benefits of blood-based analyses, the so-called liquid biopsy is prompting more and more studies to assess its feasibility. Considering these recent demands, we aimed to optimize a highly sensitive molecular system based on the rearranged immunoglobulin (Ig) genes to monitor MRD from peripheral blood. We analyzed a small group of myeloma patients with the high-risk t(4;14) translocation, using next-generation sequencing of Ig genes and droplet digital PCR of patient-specific Ig heavy chain (IgH) sequences. Moreover, well established monitoring methods such as multiparametric flow cytometry and RT-qPCR of the fusion transcript IgH::MMSET (IgH and multiple myeloma SET domain-containing protein) were utilized to evaluate the feasibility of these novel molecular tools. Serum measurements of M-protein and free light chains together with the clinical assessment by the treating physician served as routine clinical data. We found significant correlation between our molecular data and clinical parameters, using Spearman correlations. While the comparisons of the Ig-based methods and the other monitoring methods (flow cytometry, qPCR) were not statistically evaluable, we found common trends in their target detection. Regarding longitudinal disease monitoring, the applied methods yielded complementary information thus increasing the reliability of MRD evaluation. We also detected indications of early relapse before clinical signs, although this implication needs further verification in a larger patient cohort.

Efficacy and safety of pomalidomide, bortezomib, and dexamethasone combination chemotherapy for newly diagnosed multiple myeloma: POMACE Phase II Study

Bortezomib, lenalidomide, and dexamethasone induction chemotherapy (VRd), followed by autologous stem cell transplantation (ASCT), are the standard of care for patients with newly diagnosed multiple myeloma (NDMM). Pomalidomide is currently approved for relapsed-refractory multiple myeloma. This single-arm, open-label, phase 2 study was the prospective evaluation of the efficacy and safety of bortezomib, pomalidomide, and dexamethasone (VPd) induction for NDMM. We used Fleming's two-stage design for sample size calculation. We included transplant-eligible and ineligible patients aged 18-75 years in the study. The patients received four cycles of VPd induction followed by response assessment. Thirty-four patients were included in the study, of which 31 completed all four cycles of induction. The median age was 52 years (32-72). Thirty (91%) patients had multiple myeloma, and three had multiple plasmacytomas with less than 10% bone marrow involvement. Nine (27%) had ISS-I, 9 (27%) had ISS-II, and 15 (46%) had ISS-III myeloma. Three patients had high-risk cytogenetic abnormalities. After four cycles of VPd induction, ten patients (32%) achieved stringent CR, nine had CR (29%), eight (26%) had VGPR, and 4 (13%) had PR. Fifteen (48%) had a complete metabolic response (CMR) on PET-CT. Two patients developed SAEs. Anemia was the most common hematological toxicity. Peripheral neuropathy and constipation were the most common non-hematological toxicities. Patients with ≥VGPR had significantly better 12-month PFS than those with PR. Patients with ≥VGPR and CMR on PET-CT had significantly better 12-month OS. Our study showed VPd induction is safe and efficacious in NDMM. Further Phase 3 studies are necessary to establish the superiority and survival benefits.

Reproducibility of low-level residual myeloma immunoglobulin detection using ultra-deep sequencing

Multiple myeloma, a mature B-cell neoplasm, is the second most common hematologic malignancy. Despite advancements in treatment, the disease remains incurable, with more than 100,000 annual deaths worldwide. As recommended by the International Myeloma Working Group, measurable residual disease (MRD) should be addressed at a 10^-5 sensitivity level or beyond for practical purposes. Next-generation sequencing (NGS) has provided new opportunities with deep sequencing of clonal rearrangements of the immunoglobulin heavy chain (IGH) locus in B-cell malignancies. Although the ability to resolve one cancerous cell in a million other B cells is becoming attractive as a prognostic indicator in sustained patients who are MRD-negative, reaching consistent sensitivity levels is challenging because of sample stochasticity and the substantial amount of deoxyribonucleic acid (DNA) required for library preparation. Thus, in the presented study, we implemented ultra-deep sequencing of rearranged IGH to investigate the reproducibility and consistency aimed at the 10^-5 sensitivity level. In this controlled setup, our data provided stable MRD detection of 1.2 clonal cells per 100,000 analyzed cells and longitudinal reproducibility. We also demonstrated a low false-negative rate using 4-5 replicates and 700-800 ng DNA per sequencing replicate. In conclusion, adding an internal control to the replicates enabled clonal cell normalization for MRD evaluation as a stable reference. These findings may guide MRD-level reporting and comparisons between laboratories.

Role of serum-free light chain assay for defining response and progression in immunoglobulin secretory multiple myeloma

The International Myeloma Working Group (IMWG) guidelines recommend using electrophoresis and immunofixation to define response and progressive disease (PD) in immunoglobulin (Ig) secretory multiple myeloma (Ig-MM), whereas the role of serum-free light chain (sFLC) is controversial. We retrospectively analyzed the value of adding sFLC assays in the definition of response and PD according to IMWG criteria in 339 Ig-MM patients treated with a first-line novel agent-based therapy (median follow-up 54 months). sFLC PD was defined according to conventional criteria plus increased sFLC levels, or sFLC escape (sFLCe); progression/sFLCe-free survival (ePFS) was the time from the start of treatment to the date of first PD or sFLCe, or death; overall survival after PD/sFLCe (OS after Pe) was the time from first PD or sFLCe to the date of death. 148 (44%) patients achieved a complete response and 198 (60%) a normal sFLC ratio (sFLCR). sFLCR normalization was an independent prognostic factor for extended PFS (HR = 0.46, p = 0.001) and OS (HR = 0.47, p = 0.006) by multivariable analysis. 175 (52%) patients experienced PD according to the IMWG criteria, whereas 180 (53%) experienced PD or sFLCe. Overall, a sFLCe was observed in 31 (9%) patients. Median PFS and ePFS were both equal to 36 (95% CI = 32-42, and 32-40, respectively) months. sFLC PD adversely affected the OS after Pe compared to PD with increasing monoclonal Ig only (HR = 0.52, p = 0.012). Our results support the inclusion of the sFLC assay for defining response and PD in Ig-MM.

Prognostic significance of CD56 antigen in newly diagnosed multiple myeloma: A real-world retrospective study

The prognostic value of plasma cell CD56 expression of patients with multiple myeloma (MM) has been reported in many studies, but the results are controversial. This study aimed to examine the prognostic significance of CD56 in MM patients. Eighty seven patients with newly diagnosed MM were enrolled in this study, and their clinical characteristics, immunophenotypes, and cytogenetics were retrospectively analyzed to explore the prognostic significance of CD56 expression. Multiparameter flow cytometry was used to detect MM in bone marrow samples from all patients. Patients were divided into 2 groups based on whether they expressed CD56: CD56 + group and CD56 - group. After 4 cycles of chemotherapy, the overall response rate of the CD56 - patients was lower than that of the CD56 + patients (60.0% vs 81.1%, P = .036). Survival analysis showed that the median progression-free survival (PFS) was 10 months for the CD56 - group and 27 months for the CD56 + group (P = .007). The median overall survival (OS) of patients for the CD56 - group was 25 months versus not reached in the CD56 + group (P = .010). In addition, among the high-risk patients detected by fluorescence in situ hybridization (FISH), the median PFS was 4 months for the CD56 - group and 16 months for the CD56 + group (P = .012). The median OS of the CD56 + group and CD56 - group was 36 months and 15 months, respectively, with statistically significant differences (P = .017). Our study confirmed that CD56 - patients with MM had a worse prognosis than that of CD56 + patients with MM. Among the patients with ≥ 2 high-risk cytogenetics, the existence of the CD56 negativity can further identify MM patients with poor PFS and OS.

Clinical Utility of Next-Generation Flow-Based Minimal Residual Disease Assessment in Patients with Multiple Myeloma

Background

Minimal residual disease (MRD) is an important prognostic factor for evaluating a deeper treatment response in patients with multiple myeloma (MM). We evaluated the clinical utility of next-generation flow (NGF)-based MRD assessment in a heterogeneous MM patient population.

Methods

Patients with suspected morphological remission after or during MM treatment were prospectively enrolled. In total, 108 bone marrow samples from 90 patients were analyzed using NGF-based MRD assessment according to the EuroFlow protocol, and progression-free survival (PFS) was evaluated according to the International Myeloma Working Group response status, cytogenetic risk, and MRD status.

Results

The overall MRD-positive rate was 31.5% (34/108 samples), and MRD-positive patients showed a lower PFS than MRD-negative patients (P=0.005). MRD-positive patients showed inferior PFS than MRD-negative in patients with stringent complete remission (sCR)/complete remission (P=0.014) and high-risk cytogenetic abnormalities (P=0.016). MRD was assessed twice in 18 patients with a median interval of 12 months. Sustained MRD negativity was only observed in patients with sustained sCR, and their PFS was superior to that of patients who were not MRD-negative (P=0.035).

Conclusions

Clinical application of NGF-based MRD assessment can provide valuable information for predicting disease progression in patients with MM in remission, including those with high-risk cytogenetic abnormalities.

Minimal residual disease detection by next-generation sequencing in multiple myeloma: Promise and challenges for response-adapted therapy

Assessment of minimal residual disease (MRD) is becoming a standard diagnostic tool for curable hematological malignancies such as chronic and acute myeloid leukemia. Multiple myeloma (MM) remains an incurable disease, as a major portion of patients even in complete response eventually relapse, suggesting that residual disease remains. Over the past decade, the treatment landscape of MM has radically changed with the introduction of new effective drugs and the availability of immunotherapy, including targeted antibodies and adoptive cell therapy. Therefore, conventional serological and morphological techniques have become suboptimal for the evaluation of depth of response. Recently, the International Myeloma Working Group (IMWG) introduced the definition of MRD negativity as the absence of clonal Plasma cells (PC) with a minimum sensitivity of <10⁻⁵ either by next-generation sequencing (NGS) using the LymphoSIGHT platform (Sequenta/Adaptative) or by next-generation flow cytometry (NGF) using EuroFlow approaches as the reference methods. While the definition of the LymphoSIGHT platform (Sequenta/Adaptive) as the standard method derives from its large use and validation in clinical studies on the prognostic value of NGS-based MRD, other commercially available options exist. Recently, the LymphoTrack assay has been evaluated in MM, demonstrating a sensitivity level of 10⁻⁵, hence qualifying as an alternative effective tool for MRD monitoring in MM. Here, we will review state-of-the-art methods for MRD assessment by NGS. We will summarize how MRD testing supports clinical trials as a useful tool in dynamic risk-adapted therapy. Finally, we will also discuss future promise and challenges of NGS-based MRD determination for clinical decision-making. In addition, we will present our real-life single-center experience with the commercially available NGS strategy LymphoTrack-MiSeq. Even with the limitation of a limited number of patients, our results confirm the LymphoTrack-MiSeq platform as a cost-effective, readily available, and standardized workflow with a sensitivity of 10⁻⁵. Our real-life data also confirm that achieving MRD negativity is an important prognostic factor in MM.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

The potential role of mass spectrometry for the identification and monitoring of patients with plasma cell disorders: Where are we now and which questions remain unanswered?

Mass spectrometry (MS) techniques provide a highly sensitive methodology for the assessment and monitoring of paraproteins compared to standard electrophoretic techniques. The International Myeloma Working Group (IMWG) recently approved the use of intact light chain matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in lieu of immunofixation in the clinical assessment of patients and the assessment of patients enrolled on clinical trials. The increased sensitivity of these assays may help to detect and monitor monoclonal proteins (MP) in many patients with previously non-measurable disease, will reduce complete response (CR) rates and increase detection of low-level MP. The ability to track the unique mass or amino acid sequence of the MP also eliminates interference from therapeutic monoclonal antibodies (tmAbs) in most patients with IgG kappa myeloma. The intact light chain assays also provide structural information about the monoclonal light chain, including the presence of N-linked glycosylation, which has been shown to be commoner on amyloidogenic light chains and may have prognostic significance in monoclonal gammopathy of undetermined significance (MGUS). In this review, we discuss these issues alongside differences in the analytical and practical aspects related to the different MS assays under development and the challenges for MS.

The changing landscape of relapsed and/or refractory multiple myeloma (MM): fundamentals and controversies

The increase in the number of therapeutic alternatives for both newly diagnosed and relapsed/refractory multiple myeloma (RRMM) patients has widened the clinical scenario, leading to a level of complexity that no algorithm has been able to cover up to date. At present, this complexity increases due to the wide variety of clinical situations found in MM patients before they reach the status of relapsed/refractory disease. These different backgrounds may include primary refractoriness, early relapse after completion of first-line therapy with latest-generation agents, or very late relapse after chemotherapy or autologous transplantation. It is also important to bear in mind that many patient profiles are not fully represented in the main randomized clinical trials (RCT), and this further complicates treatment decision-making. In RRMM patients, the choice of previously unused drugs and the number and duration of previous therapeutic regimens until progression has a greater impact on treatment efficacy than the adverse biological characteristics of MM itself. In addition to proteasome inhibitors, immunomodulatory drugs, anti-CD38 antibodies and corticosteroids, a new generation of drugs such as XPO inhibitors, BCL-2 inhibitors, new alkylators and, above all, immunotherapy based on conjugated anti-BCMA antibodies and CAR-T cells, have been developed to fight RRMM. This comprehensive review addresses the fundamentals and controversies regarding RRMM, and discusses the main aspects of management and treatment. The basis for the clinical management of RRMM (complexity of clinical scenarios, key factors to consider before choosing an appropriate treatment, or when to treat), the arsenal of new drugs with no cross resistance with previously administered standard first line regimens (main phase 3 clinical trials), the future outlook including the usefulness of abandoned resources, together with the controversies surrounding the clinical management of RRMM patients will be reviewed in detail.

Prediction of Early Treatment Response in Multiple Myeloma Using MY-RADS Total Burden Score, ADC, and Fat Fraction From Whole-Body MRI: Impact of Anemia on Predictive Performance

Background: The recently released Myeloma Response Assessment and Diagnosis System (MY-RADS) for multiple myeloma (MM) evaluation by whole-body MRI (WB-MRI) describes the total burden score. However, assessment is confounded by red bone marrow hyperplasia in anemia. Objective: To assess utility of the MY-RADS total burden score, ADC, and fat fraction (FF) from WB-MRI in predicting early treatment response in patients with newly diagnosed MM and to compare these measures' utility between patients with and without anemia. Methods: This retrospective study included 56 patients (mean age 57.4±9.6 years; 40 men, 16 women) with newly diagnosed MM who underwent baseline WB-MRI including DWI and mDixon sequences. Two radiologists recorded total burden score using MY-RADS and measured ADC and FF of diffuse and focal disease sites. Mean values across sites were derived. Interobserver agreement was evaluated; readers' mean assessments were used for further analyses. Presence of deep response after four cycles of induction chemotherapy was recorded. Patients were classified as anemic if having hemoglobin less than 100 g/L. Utility of WB-MRI parameters in predicting deep response was assessed. Results: A total of 24/56 patients showed deep response; a total of 25/56 patients had anemia. Interobserver agreement, expressed using intraclass correlation coefficients, ranged from 0.95 to 0.99. Among patients without anemia, those with deep response compared with those without deep response exhibited lower total burden score (9.0 vs 18.0), lower ADC (0.79x10-3mm²/s vs 1.08x10-3mm²/s), and higher FF (0.21 vs 0.10) (all p<.001). The combination of these three parameters (optimal cutoffs: <15 for total burden score, <0.84×10-3mm²/s for ADC, >0.16 for FF) achieved sensitivity of 93.8%, specificity of 93.3%, and accuracy of 93.5% for predicting deep response. In patients with anemia, none of the three parameters were significantly different between those with and without deep response (all p>.05), and the combination of parameters achieved sensitivity of 56.3%, specificity of 100.0%, and accuracy of 72.0%. Conclusion: Low total burden score, low ADC, and high FF from WB-MRI may predict deep response in MM, though only among those patients without anemia. Clinical Impact: WB-MRI findings may help guide determination of prognosis and initial treatment selection in MM.

Minimal Residual Disease in Multiple Myeloma: Potential for Blood-Based Methods to Monitor Disease

In recent years, the life expectancy of Multiple Myeloma (MM) patients has substantially improved, but this cancer remains incurable with increasing incidence in the developed world. Most MM patients will eventually relapse due to residual drug-resistant cancerous cells that survive treatment, commonly referred to as minimal residual disease (MRD). Methods to improve MRD detection in MM patients are generating considerable interest as a means of monitoring patients' response to treatment. In clinical laboratories, these methods currently require bone marrow aspirates which are invasive and frequently miss detection of localised disease due to the spatial heterogeneity of disease infiltration. By simplifying serial sampling and allowing for the detection of extramedullary disease, a blood-based method could significantly impact treatment duration and intensity and minimise chemotherapy-induced toxicity. This review will describe the current blood-based techniques available to detect MRD in MM and compare their potential to evaluate patient prognosis and drive therapeutic decisions.

Prognostic value of minimal residual disease negativity in myeloma: combined analysis of POLLUX, CASTOR, ALCYONE, MAIA

We explored minimal residual disease (MRD) in relapsed/refractory multiple myeloma (RRMM) and transplant-ineligible newly diagnosed multiple myeloma (TIE NDMM) using data from four phase 3 studies (POLLUX, CASTOR, ALCYONE, and MAIA). Each study previously demonstrated that daratumumab-based therapies improved MRD-negativity rates and reduced the risk of disease progression or death by approximately half versus standards of care. We conducted a large-scale pooled analysis for associations between patients achieving complete response (CR) or better with MRD-negative status, and progression-free survival (PFS). MRD was assessed via next-generation sequencing (10‒5 threshold). Patient-level data were pooled from all four studies, and for patients with TIE NDMM plus patients with RRMM who received ≤2 prior lines of therapy (≤2PL). PFS was evaluated by response and MRD status. Median follow-up (months) was: POLLUX, 54.8; CASTOR, 50.2; ALCYONE, 40.1; and MAIA, 36.4. Patients who achieved ≥CR and MRD negativity had improved PFS versus those who failed to reach CR or were MRD positive (TIE NDMM and RRMM hazard ratio [HR] 0.20, P < .0001; TIE NDMM and RRMM ≤2PL HR 0.20, P < .0001). This benefit occurred irrespective of therapy or disease setting. A time-varying Cox proportional hazard model confirmed that ≥CR with MRD negativity was associated with improved PFS. Daratumumab-based treatment was associated with more patients reaching ≥CR and MRD negativity. These findings represent the first large-scale analysis with robust methodology to support ≥CR with MRD negativity as a prognostic factor for PFS in RRMM and TIE NDMM. These trials were registered at www.ClinicalTrials.gov: NCT02076009/NCT02136134/NCT02195479/NCT02252172.

Measurable residual disease in multiple myeloma and light chain amyloidosis: more than meets the eye

The emergence of highly effective multiple myeloma (MM) treatments may bring cure within reach and highlights the need for highly sensitive measurable residual disease (MRD) techniques to replace conventional response assessments. MRD is being incorporated as an endpoint in an increasing number of studies and had been repeatedly shown to be both a predictive marker of response to treatment and a prognostic marker for future relapse. However, those results should be cautiously interpreted due to non-uniform reporting and the need for longer follow up to assess for sustained MRD negativity. This review aims to critically analyze the key MRD aspects including the current evidence supporting the use of MRD in clinical practice and the pitfalls of the various methods used to assess MRD. The utility of MRD for light chain (AL) amyloidosis will also be discussed.