Association of Measurable Residual Disease With Survival Outcomes in Patients With Acute Myeloid Leukemia: A Systematic Review and Meta-analysis

Cell-free transcription amplification-based split-type electrochemical sensor using enzyme-linked magnetic microbeads for minimal residual leukemia detection

Constrained by detecting techniques, patients with acute promyelocytic leukemia (APL) are often confronted with minimal residual disease (MRD) and a high risk of relapse. Thus, a pragmatic and robust method for MRD monitoring is urgently needed. Herein, a novel split-type electrochemical sensor (E-sensor) was developed by integrating nucleic acid sequence-based amplification (NASBA) with enzyme-linked magnetic microbeads (MMBs) for ultra-sensitive detection of the PML/RARα transcript. In this system, NASBA facilitated efficient amplification under isothermal conditions, generating a large amount of RNA amplicons, which mediated the quick binding between horseradish peroxidase (HRP) and MMBs. The separately HRP-linked MMBs were subsequently transferred onto the surface of magnetic glass carbon electrode, producing a remarkably strong electrochemical signal in the presence of the HRP substrate. The proposed split-type E-sensor could detect the PML/RARα transcript with a high sensitivity (a limit detection of 100 aM), a high specificity (single base discrimination) as well as a high stability (a relative standard deviation of 8.3 % for 10 fM target RNA and 6.0 % for 100 fM target RNA). Finally, it could achieve both direct detection of serum cell-free RNA and specific intracellular RNA detection. Owing to its isothermal characteristics, robustness, and suitability for point-of-care testing, this method offers a powerful tool for the early diagnosis of APL and the monitoring of MRD, which holds a great significance for facilitating treatment response assessment and making treatment decisions.

Breaking the Bone Marrow Barrier: Peripheral Blood as a Gateway to Measurable Residual Disease Detection in Acute Myelogenous Leukemia

Acute myeloid leukemia (AML) is a genetically heterogeneous disease with high rates of relapse after initial treatment. Identifying measurable residual disease (MRD) following initial therapy is essential to assess response, predict patient outcomes, and identify those in need of additional intervention. Currently, MRD analysis relies on invasive, serial bone marrow (BM) biopsies, which complicate sample availability and processing time and negatively impact patient experience. Additionally, finding a positive result can generate more questions than answers, causing anxiety for both the patient and the provider. Peripheral blood (PB) evaluation has shown promise in detecting MRD and is now recommended by the European Leukemia Net for AML for certain genetic abnormalities. PB-based sampling allows for more frequent testing intervals and better temporal resolution of malignant expansion while sparing patients additional invasive procedures. In this review, we will discuss the current state of PB testing for MRD evaluation with a focus on next-generation sequencing methodologies that are capable of MRD detection across AML subtypes.

Advantages of a genomic DNA-based next-generation sequencing assay for detection of mutant NPM1 measurable residual disease in AML

ABSTRACT

Mutations in the nucleophosmin-1 (NPM1) gene are among the most common molecular aberrations in acute myeloid leukemia (AML). Various studies have established mutant NPM1 (mNPM1) as a faithful molecular measurable residual disease (MRD) marker with prognostic significance. Assessment of prognostic mNPM1 is included in the European LeukemiaNet recommendations on MRD detection in AML. Because of recent advancements of promising drugs targeting mNPM1 AML, monitoring of mNPM1 MRD has gained interest, and is generally done by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). However, these RT-qPCR assays use complementary DNA (cDNA) as input, are based on gene expression levels of mNPM1, and are generally limited to specific mNPM1 gene variants. The main advantages of next-generation sequencing (NGS) using genomic DNA as input are stability, independence of gene expression levels, and the ability to detect any NPM1 variant in a single assay. Here, we comprehensively investigated the applicability of NGS on DNA to detect mNPM1 MRD in a cohort of 119 (cDNA) and 310 (DNA) patients with mNPM1 AML in complete remission after 2 cycles of induction chemotherapy. We demonstrate high correlations in levels and prognostic value between RT-qPCR/cDNA and NGS/DNA approaches, postulating NGS/DNA as an attractive alternative to RT-qPCR. We report that the 2% mNPM1/ABL1 threshold by RT-qPCR/cDNA corresponds to an NGS/DNA variant allele frequency of 0.01%. The NGS/DNA threshold of >0.01% after 2 cycles of induction chemotherapy identifies significantly more patients with AML with an increased relapse risk than current RT-qPCR/cDNA assays. The prognostic significance of mNPM1 MRD appears greatest in patients with AML with FLT3-internal tandem duplications.

Measurable residual disease monitoring in AML: Prospects for therapeutic decision-making and new drug development

Measurable residual disease (MRD) is strongly associated with risk of relapse and long-term survival outcomes in patients with acute myeloid leukemia (AML). Apart from its clear prognostic impact, MRD information is also increasingly used to guide therapeutic decision-making, including selection of appropriate patients for stem cell transplant, use of post-transplant maintenance, and candidacy for non-transplant maintenance therapies or MRD-directed clinical trials. While much progress has been made in accurately assessing MRD and understanding its clinical importance, many questions remain about how to optimize MRD testing and guide treatment decisions for individual patients. In this review, we discuss the common methods to assess MRD in AML and the prognostic impact of MRD across common clinical scenarios. We also review emerging and investigational strategies to target MRD and discuss some of the important unanswered questions and challenges in the field.

Impact of high-sensitivity flow cytometry on peri-transplant minimal residual disease kinetics in acute leukemia

Minimal residual disease (MRD) detected before hematopoietic cell transplantation (HCT) is associated with adverse outcomes in patients with high-risk acute leukemia. However, the ideal time points for post-transplant MRD assessment and the clinical significance of low levels of residual disease in this context are unclear. We conducted a prospective real-world analysis of high-sensitivity flow cytometry MRD performed before and after transplant (at days 30, 60 and 100) in 77 acute leukemia patients. The aim was to evaluate the kinetics of disease elimination and correlate it with transplant outcomes. Pre-transplant MRD was negative in 42 (MRD-) and positive in 35 patients (MRD+). Post-transplant MRD assessment was feasible at day 30 (n = 30, 38.9%), day 60 (n = 27, 35.0%) and day 100 (n = 60, 77.9%). Relapses occurred in 8 patients in the MRD + group (22.9%) and three in the MRD-negative group (7.1%), p = 0.02. Pre-transplant MRD correlated with a decrease in overall survival (OS; 87.9% MRD- vs. 54.0% MRD+) and event-free survival (EFS; 85.3% MRD- vs. 51.1% MRD+), p = 0.001. Cumulative incidence of relapse (CIR) was 17.5% in MRD + vs. 2.6% in MRD- (p = 0.049). Non-relapse mortality (NRM) was 31.4% in MRD + vs. 12.1% in MRD- (p = 0.019). One-year OS was higher in patients with negative MRD at d100 (92.4%, 95% CI: 0.81-0.971) than positive d100 MRD (53.3%, 95% CI: 0.177-0.796), p < 0.0001. Disease status and d100 MRD were associated with OS, EFS and CIR. Differences in NRM between leukemia types (ALL: 18.9% MRD- vs. 50% MRD+, and AML 0% MRD- vs. 21.7% MRD+, p = 0.0158) were also observed. In conclusion, pre-transplant MRD assessed by highly sensitive flow cytometry accurately identified patients with adverse prognoses. Persistent MRD after HCT could predict relapse with high specificity and clinical sensitivity. These results highlight the importance of incorporating peri-transplant MRD kinetics into the routine treatment of acute leukemia, particularly in low/middle-income countries.

Error-corrected ultradeep next-generation sequencing for detection of clonal haematopoiesis and haematological neoplasms - sensitivity, specificity and accuracy

Clonal haematopoiesis of indeterminate potential (CHIP) is an aging-associated phenomenon that has recently been correlated with a broad spectrum of human diseases, including haematological malignancy, cytopenia, coronary heart disease, stroke, and overall mortality. CHIP is defined as a somatic variant in blood cells with an allele frequency (VAF) ≥ 0.02, however recent reports show smaller clones are associated with poorer clinical outcome. Error-corrected ultradeep next-generation sequencing (NGS) assays detecting variants < 0.02 VAF also have clinical value for monitoring measurable residual disease (MRD) for myeloid neoplasms. However, limited data are available on optimal parameters, limits of detection, and accuracy of ultra-sensitive detection. We investigated parameters to improve accuracy of Illumina sequencing-by-synthesis method, including read depth, input DNA quantity, and molecular barcoding-based data filtering, while adhering to clinical accreditation criteria. Validation data were generated from reference standards and reference samples from a clinically accredited pathology laboratory. Analytical range measurements included linearity and bias, and precision included repeatability, reproducibility and detection rate. The lower limit of detection was ≥ 0.004 (0.4%) at depth > 3,000 × . Trueness measured using reference standards demonstrated a sensitivity, specificity, positive and negative predictive values, and accuracy of 100%, including FLT3-ITD, and 100% concordance was achieved with reference samples for reported variants and absence of variants. Sequencing blood samples from 383 community-dwelling adults (mean depth 3758×) revealed 2,190 somatic variants/sample, > 99.9% were < 0.02 VAF. Our data including cost-benefit analysis enables pathology and research laboratories to make informed decisions for detection of CHIP (VAF ≥ 0.02), sub-CHIP (VAF 0.01-0.02) and MRD (VAF ≥ 0.004).

Long-term real-world evidence of CPX-351 of high-risk patients with AML identified high rate of negative MRD and prolonged OS

ABSTRACT

CPX-351 has been approved for patients with therapy-related acute myeloid leukemia (t-AML) or AML with myelodysplasia-related changes (MRC-AML). No extensive data are available on measurable residual disease (MRD) and long-term clinical outcome using CPX-351 in AML in real life. We retrospectively collected data from 168 patients in 36 centers in France and Italy who had received 1 or 2 cycles of induction with CPX-351. All patients were aged >18 years and had newly diagnosed, untreated t-AML or MRC-AML. With a median follow-up of 3 years, the median overall survival (OS) was 13.3 months. The median OS was 20.4 months vs 12.9 months for patients with MRD below or above 10-3, respectively (P = .006). In a multivariate analysis, only MRD >10-3 was associated with a poorer OS (hazard ratio, 2.6; 95% confidence interval, 1.2-5.5; P = .013). We also observed a trend toward a better median OS in patients who underwent hematopoietic stem cell transplantation with MRD <10-3 (not reached vs 26.0 months; P = .06). Achievement of MRD negativity contributed to the improvement of OS in the overall population and, maybe, in patients receiving transplant. These data provide the rationale for the 2 ongoing studies evaluating CPX-351 vs 7+3 in non-MRC-AML and non-t-AML using MRD as the primary end point for ALFA-2101 phase 2 clinical trial and event-free survival for AMLSG 30-18 phase 3 clinical trial.

Impact of measurable residual disease clearance kinetics in patients with AML undergoing intensive chemotherapy

ABSTRACT

The prognostic impact of measurable residual disease (MRD) in acute myeloid leukemia (AML) is unequivocal; however, the optimal time point for achieving undetectable MRD is unclear. We retrospectively studied patients with newly diagnosed (ND) AML who achieved remission with frontline intensive chemotherapy and had MRD assessed by flow cytometry after induction (time point 1 [TP1]) and after cycles 2 or 3 (TP2). Cases were grouped into MRD negative (Neg)/Neg, positive (Pos)/Neg, or Pos/Pos at TP1 and TP2, respectively. Of 1980 patients with ND AML, 277 met the inclusion criteria and were included in this analysis. The median relapse-free survival (RFS) was 73 months, 22 months, and 5 months for the MRD Neg/Neg, Pos/Neg, and Pos/Pos groups, respectively (P < .01). There was a significant difference between the Neg/Neg and Pos/Neg groups (P = .05), suggesting benefit to early MRD negativity. The median overall survival (OS) was 81 months, 40 months, and 9 months, respectively (P < .01), but the difference between Neg/Neg and Pos/Neg was not statistically significant (P = .19). Landmark analysis demonstrated the benefit of stem cell transplant (SCT), particularly in Neg/Neg intermediate-risk AML (median RFS, not reached vs 15 months; P < .01). On multivariable analysis, MRD Pos/Neg was independently associated with a worse RFS than Neg/Neg (hazard ratio, 1.73; 95% confidence interval, 1.09-2.75; P = .02) but not for OS (P = .15). In conclusion, undetectable flow MRD after induction is associated with better RFS than undetectable MRD achieved later during consolidation. SCT benefited patients with intermediate-risk AML, regardless of MRD kinetics.

Proteomic Comparison of Acute Myeloid Leukemia Cells and Normal CD34+ Bone Marrow Cells: Studies of Leukemia Cell Differentiation and Regulation of Iron Metabolism/Ferroptosis

Acute myeloid leukemia (AML) is an aggressive bone marrow malignancy that can be cured only by intensive chemotherapy possibly combined with allogeneic stem cell transplantation. We compared the pretreatment proteomic profiles of AML cells derived from 50 patients at the time of first diagnosis with normal CD34+ bone marrow cells. A comparison based on all AML and CD34+ normal cell populations identified 121 differentially abundant proteins that showed at least 2-fold differences, and these proteins included several markers of neutrophil differentiation (e.g., TLR2, the integrins ITGM and ITGX, and downstream mediators including RHO GTPase, S100A8, S100A9, S100A22). However, the expression of these 121 proteins varied between patients, and a subset of 28 patients was characterized by increased long-term AML-free survival, signs of myeloid AML cell differentiation, and favorable genetic abnormalities. These two main patient subsets (28 with differentiation versus 22 with fewer signs of differentiation) also differed with regard to the phosphorylation of 16 differentially abundant proteins. Furthermore, we also classified our patients based on their expression of 16 proteins involved in the regulation of iron metabolism/ferroptosis and showing differential expression when comparing AML cells and normal CD34+ cells. Among the 22 patients with less favorable prognosis, we could then identify a genetically heterogeneous subset characterized by adverse prognosis (i.e., death from primary resistance/relapse) and an iron metabolism/ferroptosis protein profile showing similarities with normal CD34+ cells. We conclude that proteomic profiles differ between AML and normal CD34+ cells; especially, proteomic differences reflecting differentiation and regulation of iron metabolism/ferroptosis are associated with risk of relapse after intensive conventional therapy.

Significance of Measurable Residual Disease in Patients Undergoing Allogeneic Hematopoietic Cell Transplantation for Acute Myeloid Leukemia

Allogeneic hematopoietic cell transplantation (HCT) remains an important curative-intent treatment for many patients with acute myeloid leukemia (AML), but AML recurrence after allografting is common. Many factors associated with relapse after allogeneic HCT have been identified over the years. Central among these is measurable ("minimal") residual disease (MRD) as detected by multiparameter flow cytometry, quantitative polymerase chain reaction, and/or next-generation sequencing. Demonstration of a strong, independent prognostic role of pre- and early post-HCT MRD has raised hopes MRD could also serve as a predictive biomarker to inform treatment decision-making, with emerging data indicating the potential value to guide candidacy assessment for allografting as a post-remission treatment strategy, the selection of conditioning intensity, use of small molecule inhibitors as post-HCT maintenance therapy, and preemptive infusion of donor lymphocytes. Monitoring for leukemia recurrence after HCT and surrogacy for treatment response are other considerations for the clinical use of MRD data. In this review, we will outline the current landscape of MRD as a biomarker for patients with AML undergoing HCT and discuss areas of uncertainty and ongoing research.

Maintenance therapy with the FMS-like tyrosine kinase 3 inhibitor gilteritinib in patients with FMS-like tyrosine kinase 3-internal tandem duplication acute myeloid leukemia: A phase 2 study

BACKGROUND

The GOSSAMER phase 2 study assessed the FMS-like tyrosine kinase 3 (FLT3) inhibitor gilteritinib as maintenance therapy in patients with FLT3-internal tandem duplication (FLT3-ITD) acute myeloid leukemia (AML) in first complete remission without previous hematopoietic stem cell transplantation (HSCT).

METHODS

Patients had to be within 2 months of their last consolidation cycle and have completed the recommended number of cycles per local practice. FLT3 inhibitors were allowed only during induction and/or consolidation. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS), event-free survival, and measurable residual disease (MRD).

RESULTS

In total, 98 patients were randomized (gilteritinib, n = 63; placebo, n = 35). RFS was not significantly different between the arms (hazard ratio, 0.74; 95% confidence interval, 0.41-1.34; p = .16). RFS rates for the gilteritinib and placebo arms were 68.5% and 55.3% at 1 year, 51.8% and 44.9% at 2 years, and 41.2% and 40.8% at 3 years, respectively. OS was not significantly different between the arms but may have been affected by subsequent AML therapies after discontinuation. In patients who received subsequent therapy (gilteritinib, 46.8%; placebo, 60.0%), a higher percentage of placebo-treated (57.1%) versus gilteritinib-treated patients (27.6%) underwent HSCT. At the end of treatment, 96.4% of gilteritinib-treated and 85.7% of placebo-treated patients had undetectable MRD. Relapsed placebo-treated (86.7%) versus gilteritinib-treated patients (34.8%) had a greater FLT3 mutational burden. No new significant safety concerns were noted.

CONCLUSIONS

The primary end point was not achieved; however, an observed trend toward potential benefit was noted in patients with FLT3-ITD AML who had not undergone prior HSCT.

Acute Myeloid Leukemia: 2025 Update on Diagnosis, Risk-Stratification, and Management

DISEASE OVERVIEW

Acute myeloid leukemia (AML) is a bone marrow stem cell cancer that is often fatal despite available treatments. Diagnosis, risk assessment, monitoring, and therapeutic management of AML have changed dramatically in the last decade due to increased pathophysiologic understanding, improved assessment technology, and the addition of at least 12 approved therapies.

DIAGNOSIS

The diagnosis is based on the presence of immature leukemia cells in the blood, and/or bone marrow or less often in extra-medullary tissues. New biological insights have been integrated into recent classification systems.

RISK ASSESSMENT

The European Leukemia Network has published risk classification algorithms for both intensively and non-intensively treated patients based on cytogenetic and on molecular findings. Prognostic factors may differ based on the therapeutic approach.

MONITORING

Our increasing ability to quantify lower levels of measurable residual disease (MRD) potentially allows better response assessment, as well as dynamic monitoring of disease status. The incorporation of MRD findings into therapeutic decision-making is rapidly evolving.

RISK ADAPTED THERAPY

The availability of 12 newly approved agents has been welcomed; however, optimal strategies incorporating newer agents into therapeutic algorithms are debated. The overarching approach integrates patient and caregiver goals of care, comorbidities, and disease characteristics.

Measurable residual disease as predictor of post-day +100 relapses after allografting in adult AML

ABSTRACT

Measurable residual disease (MRD) by multiparametric flow cytometry (MFC) before allogeneic hematopoietic cell transplantation (HCT) identifies patients at high risk of acute myeloid leukemia (AML) relapse, often occurring early after allografting. To examine the role of MFC MRD testing to predict later relapses, we examined 935 adults with AML or myelodysplastic neoplasm/AML transplanted in first or second morphologic remission who underwent bone marrow restaging studies between day 70 and 100 after HCT and were alive and without relapse by day +100. Of 935 adults, 136 (15%) had MRD before HCT, whereas only 11 (1%) had MRD at day +70 to +100. In day +100 landmark analyses, pre-HCT and day +70 to +100 MFC MRD were both associated with relapse (both P < .001), relapse-free survival (RFS; both P < .001) overall survival (OS; both P < .001), and, for post-HCT MRD, nonrelapse mortality (P = .001) after multivariable adjustment. Importantly, although 126/136 patients (92%) with MRD before HCT tested negative for MRD at day +70 to +100, their outcomes were inferior to those without MRD before HCT and at day +70 to +100, with 3-year relapse risk of 40% vs 15% (P < .001), 3-year RFS of 50% vs 72% (P < .001), and 3-year OS of 56% vs 76% (P < .001), whereas 3-year nonrelapse mortality estimates were similar (P = .53). Thus, despite high MRD conversion rates, outcomes MRD positive/MRD negative (MRDneg) patients are inferior to those of MRDneg/MRDneg patients, suggesting all patients with pre-HCT MRD should be considered for preemptive therapies after allografting.

Flow cytometry evaluation of acute myeloid leukemia minimal residual disease based on an understanding of the normal maturation patterns in the blast compartments

OBJECTIVE

Detection of minimal/measurable disease (MRD) in acute myeloid leukemia (AML) is critical for both clinical decision-making and prognostication, yet remains a challenge. Flow cytometry is a well-established method for MRD detection. Flow cytometric (FC) evaluation of MRD must consider a complex maturational pattern of normal hematopoietic development to separate normal from abnormal progenitors. Here, we offer an example of an interpretive approach based on a thorough understanding of stage- and lineage-specific hematopoietic maturation.

METHODS

We provide a comprehensive overview of blast maturation from early precursors (hematopoietic stem cells) to committed late-stage unilineage progenitors and commonly observed stage-specific abnormalities based on cases we have encountered in practice. We emphasize the importance of stage-specific comparisons for accurate MRD detection by flow cytometry.

RESULTS

The AML blasts almost invariably show abnormal phenotypes, and the phenotypes may evolve upon therapy. The detected phenotypes are necessarily confined to the target antigens included in the panel. It is therefore critical to evaluate a range of antigens to establish a specific stage/state of lineage commitment and detect potential common abnormalities. Moreover, enough cells must be acquired to allow for the detection of MRD at desired levels. Significant technical and analytical validation is critical.

CONCLUSIONS

Flow cytometry offers a powerful single-cell-based platform for MRD detection in AML, and the results have been proven critical for disease management. Leukemia-associated phenotype-informed difference from the normal approach presented in this review presents an analytical framework for sensitive and accurate MRD detection.

Measurable residual mutated IDH2 before allogeneic transplant for acute myeloid leukemia

Routine genetic profiling of acute myeloid leukemia (AML) at initial diagnosis has allowed subgroup specific prognostication, drug development, and clinical management strategies. The optimal approach for treatment response assessment for AML subgroups has not yet however been determined. A nationwide cohort of 257 adult patients in first remission (CR1) from AML associated with an IDH2 mutation (IDH2m) undergoing allogeneic transplant during the period 2013-2019 in the United States had rates of relapse and survival three years after transplantation of 24% and 71%, respectively. Pre-transplant clinical flow cytometry assessment was not useful in stratifying patients based on risk of post-transplant relapse or death. DNA-sequencing was performed on CR1 blood collected within 100 days before transplant. Persistent detection of IDH2m was common (51%) and associated with increased relapse and death compared to testing negative. Co-mutation at initial diagnosis with mutated NPM1 and/or FLT3-ITD was common in this cohort (41%) and use of these validated MRD markers provided superior stratification compared to IDH2m testing. Patients testing negative for IDH2m prior to transplant had low relapse-related death, regardless of conditioning intensity. Post-transplant relapse rates for those with persistently detectable IDH2m in pre-transplant remission were lower after the FDA approval of enasidenib in August 2017.

Measurable residual disease testing and allogeneic hematopoietic cell transplantation for AML: adapting Pre-MEASURE to clinical practice

Measurable residual disease (MRD) testing in patients with acute myelogenous leukemia (AML) represents a heterogenous assessment process designed to quantify leukemia-specific biomarkers that are not ascertainable by routine pathologic evaluation. The most common tools used to assess MRD are multiparameter flow cytometry (MPFC), and polymerase chain reaction (PCR) based tools, including quantitative or digital droplet PCR (qPCR, ddPCR), or next-generation sequencing (NGS) technologies. Collectively, MRD assessments have become an important clinical tool in the management of patients with AML. Despite progress, significant questions remain with respect to the appropriate timing, frequency, and methodology of MRD assessment, and whether or how to adapt therapy based on MRD results. Recent data from the Pre-MEASURE study, a retrospective cohort analysis of error corrected NGS based MRD assessment prior to allogeneic hematopoietic cell transplantation (alloHCT) in patients with AML, provides additional key information with respect to the emerging role of NGS-based technology in MRD assessment. In the context of this review, we evaluate the Pre-MEASURE study as well as other recent, high-quality assessments of MRD in AML. Our focus is to provide a practical assessment of the use of emerging MRD technologies in patients with AML with an emphasis on the role of peri-transplant MRD for the practicing clinician.

Measurable residual mutated IDH1 before allogeneic transplant for acute myeloid leukemia

Measurable residual disease (MRD) in adults with acute myeloid leukemia (AML) in complete remission is an important prognostic marker, but detection methodology requires optimization. Persistence of mutated NPM1 or FLT3-ITD in the blood of adult patients with AML in first complete remission (CR1) prior to allogeneic hematopoietic cell transplant (alloHCT) associates with increased relapse and death after transplant. The prognostic implications of persistence of other common AML-associated mutations, such as IDH1, at this treatment landmark however remain incompletely defined. We performed testing for residual IDH1 variants (IDH1m) in pre-transplant CR1 blood of 148 adult patients undergoing alloHCT for IDH1-mutated AML at a CIBMTR reporting site between 2013 and 2019. No statistically significant post-transplant differences were observed between those testing IDH1m positive (n = 53, 36%) and negative pre-transplant (overall survival (OS): p = 0.4; relapse: p = 0.5). For patients with IDH1 mutated AML co-mutated with NPM1 and/or FLT3-ITD, only detection of persistent mutated NPM1 and/or FLT3-ITD was associated with significantly higher rates of relapse (p = 0.01). These data, from the largest study to date, do not support the detection of IDH1 mutation in CR1 blood prior to alloHCT as evidence of AML MRD for increased post-transplant relapse risk.

Cellular heterogeneity and cytokine signatures in acute myeloid leukemia: A novel prognostic model

Acute Myeloid Leukemia (AML) is a complex hematological malignancy distinguished by its heterogeneity in genetic aberrations, cellular composition, and clinical outcomes. This diversity complicates the development of effective, universally applicable therapeutic strategies and highlights the necessity for personalized approaches to treatment. In our study, we utilized high-resolution single-cell RNA sequencing from publicly available datasets to dissect the complex cellular landscape of AML. This approach uncovered a diverse array of cellular subpopulations within the bone marrow samples of AML patients. Through meticulous analysis, we identified 156 differentially expressed cytokine-related genes that underscore the nuanced interplay between AML cells and their microenvironment. Leveraging this comprehensive dataset, we constructed a prognostic risk score model based on seven pivotal cytokine-related genes: CCL23, IL2RA, IL3RA, IL6R, INHBA, TNFSF15, and TNFSF18. The mRNA levels of 7 genes in the risk score model have significant different. This model was rigorously validated across several independent AML patient cohorts, showcasing its robust prognostic capability to stratify patients into distinct risk categories. Patients classified under the high-risk category exhibited significantly poorer survival outcomes compared to their low-risk counterparts, underscoring the model's clinical relevance. Additionally, our in-depth investigation into the immune landscape revealed marked differences in immune cell infiltration and cytokine signaling between the identified risk groups, shedding light on potential immune-mediated mechanisms driving disease progression and treatment resistance. This comprehensive analysis not only advances our understanding of the cellular and molecular underpinnings of AML but also introduces a novel, clinically applicable risk score model. This tool holds significant promise for enhancing the precision of prognostic assessments in AML, thereby paving the way for more tailored and effective therapeutic interventions. Our findings represent a pivotal step toward the realization of personalized medicine in the management of AML, offering new avenues for research and treatment optimization in this challenging disease landscape.

Diverse real-life outcomes after intensive risk-adapted therapy for 1034 AML patients from the CETLAM Group

Given the heterogeneity of acute myeloid leukemia patients, it is necessary to identify patients considered fit for intensive therapy but who will perform poorly, and in whom alternative approaches deserve investigation. We analyzed 1034 fit adults ≤70 years intensively treated between 2012 and 2022 in the CETLAM group. Young adults ( ≤ 60 years) presented higher remission rates and improved survival than older adults above that age (CR 79% vs. 73%; p = 0.03 and 4-yr OS 53% vs. 33%; p < 0.001). Remission and survival outcomes varied among different genetic subsets. An especially adverse genetic group included complex, monosomal karyotype, TP53 alterations (deleted/mutated), and MECOMr. Transplant feasibility in this very adverse risk group was low, and OS and EFS at 4 years were 14% and 12%, in contrast to 70% and 57% in the favorable group and 38% and 32% in all other patients. We integrated clinical and genetic data into the Intensive Chemotherapy Score for AML (ICSA) with 6-risk categories with significantly different remission rates and OS, validated in another cohort of 581 AML patients from a previous CETLAM protocol. In summary, we identified groups of fit patients that benefit differently from an intensive approach which may be helpful in future treatment decisions.

Prognostic Value of Dynamic Measurable Residual Disease Monitoring by Multiflowcytometry in Elderly Patients With Nonintensively Treated Acute Myeloid Leukemia

PURPOSE

The clinical prognostic value of monitoring minimal residual disease (MRD) in acute myeloid leukemia (AML) patients undergoing nonintensive treatment remains insufficiently established. The aim of this work was to examine MRD status at various time points, highlighting the potential for pre-emptive therapy to improve patient outcomes.

METHODS

Inpatient data from 2017 to 2024 were used in this retrospective study. Bone marrow samples were analyzed for MRD using multiparametric flow cytometry at the end of cycles 1, 2, 4, and 7, before the next therapy course. Kaplan-Meier method and Cox regression were used to assess factors affecting overall survival (OS) and disease-free survival (DFS), and logistic regression evaluated the interaction between MRD and baseline features.

RESULTS

A total of 108 patients were enrolled for MRD evaluation. MRD1, MRD2, MRD4, and MRD7 was significantly associated with both OS and DFS. Early MRD negativity leads to longer survival time, and the later MRD turns negative, the higher the risk of relapse, and ELN 2017 high risk and myeloid gene mutation are adverse factors affecting time to MRD negative status.

CONCLUSION

Dynamic MRD monitoring has predictive value for nonintensive treatment in AML patients. Proper use of MRD and baseline features allows treatment adjustments based on an accurate estimation of relapse risk.

The role of the primitive marker CD133 in CD34-negative acute myeloid leukemia for the detection of leukemia stem cells

The most important reason for dismal outcomes in acute myeloid leukemia (AML) is the development of relapse. Leukemia stem cells (LSCs) are hypothesized to initiate relapse, and high CD34+CD38- LSC load is associated with poor prognosis. In 10% of AML patients, CD34 is not or is low expressed on the leukemic cells (<1%), and CD34+CD38- LSCs are absent. These patients are classified as CD34-negative. We aimed to determine whether the primitive marker CD133 can detect LSCs in CD34-negative AML. We retrospectively quantified 148 CD34-negative patients for proportions of CD34-CD133+ and CD133+CD38- cell fractions in the diagnostic samples of CD34-negative patients in the HOVON102 and HOVON132 trials. No prognostic difference was found between patients with high or low proportions of CD34-CD133+, which is found to be aberrantly expressed in AML. A high level of CD133+CD38- cells was not associated with poor overall survival, and expression in AML was similar to normal bone marrow. To conclude, CD133 is useful as an additional primitive marker for the detection of leukemic blast cells in CD34-negative AML. However, CD133+CD38 alone is not suitable for the detection of LSCs at diagnosis.

Pre-emptive therapeutic decisions based on measurable residual disease status in acute myeloid leukemia: ready for prime time?

The use of measurable residual disease (MRD) as a biomarker for prognostication, risk stratification, and therapeutic decision-making in acute myeloid leukemia (AML) is gaining prominence. MRD monitoring for NPM1-mutated and core-binding factor AML using PCR techniques is well-established for assessing disease after intensive chemotherapy. AML with persistent FLT3-ITD MRD post-intensive chemotherapy and pre-allogeneic hematopoietic cell transplantation (pre-allo-HCT) is associated with an increased risk of relapse and lower survival. Pre-allo-HCT MRD is an independent risk factor for post-allo-HCT outcomes, including relapse and death. Therefore, preemptive interventions on the natural history of MRD positivity are an active area of research beyond its initial prognostic function. Targeting MRD in AML with innovative treatment strategies can improve patient outcomes.

Acute myeloid leukemia management and research in 2025

The first 5 decades of research in acute myeloid leukemia (AML) were dominated by the cytarabine plus anthracyclines backbone, with advances in strategies including allogeneic hematopoietic stem cell transplantation, high-dose cytarabine, supportive care measures, and targeted therapies for the subset of patients with acute promyelocytic leukemia. Since 2017, a turning point in AML research, 12 agents have received regulatory approval for AML in the United States: venetoclax (BCL2 inhibitor); gemtuzumab ozogamicin (CD33 antibody-drug conjugate); midostaurin, gilteritinib, and quizartinib (fms-like tyrosine kinase 3 inhibitors); ivosidenib, olutasidenib, and enasidenib (isocitrate dehydrogenase 1 and 2 inhibitors); oral azacitidine (a partially absorbable formulation); CPX351 (liposomal encapsulation of cytarabine:daunorubicin at a molar ratio of 5:1); glasdegib (hedgehog inhibitor); and recently revumenib (menin inhibitor; approved November 2024). Oral decitabine-cedazuridine, which is approved as a bioequivalent alternative to parenteral hypomethylating agents in myelodysplastic syndrome, can be used for the same purpose in AML. Menin inhibitors, CD123 antibody-drug conjugates, and other antibodies targeting CD123, CD33, and other surface markers are showing promising results. Herein, the authors review the frontline and later line therapies in AML and discuss important research directions.

Clinical perspectives on post-induction maintenance therapy in patients with acute myeloid leukaemia in remission who are ineligible for allogeneic haematopoietic stem cell transplantation

For patients with acute myeloid leukaemia (AML) who achieve complete remission (CR) after induction therapy, subsequent allogeneic haematopoietic stem cell transplantation (allo-HSCT) reduces the risk of relapse. However, not all patients are eligible, warranting effective alternative maintenance strategies. Oral azacitidine is the only non-targeted therapy approved by both the United States (US) Food and Drug Administration and the European Medicines Agency for the maintenance or continued treatment of allo-HSCT-ineligible patients with AML achieving CR or CR with incomplete haematological recovery following induction chemotherapy. Midostaurin and histamine dihydrochloride are approved in Europe as maintenance therapy for AML in remission, and quizartinib is approved in the United States and Europe for the treatment and maintenance of patients with newly diagnosed FLT3-ITD AML. Barriers to maintenance treatment include limited clinical trial data informing appropriate patient and treatment selection, patient preference, financial burden and paucity of real-world data. This article discusses current maintenance treatment guidelines for patients with AML in remission but not proceeding to allo-HSCT and reviews clinical trial data for agents approved for use in remission. Ongoing studies of interest and considerations for future efforts are also discussed.

Risk stratification in the clinical application of minimal residual disease assessment in acute myeloid leukemia

BACKGROUND

In acute myeloid leukemia (AML), further investigation is warranted to integrate measurable residual disease (MRD) with genetic characteristics for formulating a dynamic prognostic system for predicting response and selecting appropriate postremission therapeutic strategies.

METHODS

The authors incorporated MRD with genetic risk classification and assessed its impact on transplantation decision making within different risk cohorts, comprising 769 patients with newly diagnosed AML across three clinical trials. Only patients who achieved complete remission (CR) within two courses of chemotherapy were selected.

RESULTS

In the favorable-risk and intermediate-risk groups, patients who underwent transplantation according to the protocol experienced significant 3-year overall survival (OS) benefits compared with those who did not (favorable-risk group: hazard ratio [HR], 0.38; 95% confidence interval [CI], 0.20-0.73l p = .004; intermediate-risk group: HR, 0.53; 95% CI, 0.33-0.85; p = .008). In the intermediate-risk group, early detection of MRD positivity, even after the initial course of chemotherapy, was associated with a significantly elevated cumulative incidence of relapse (47.2% vs. 36.0%; p = .009) and a notable extension of OS with allogeneic hematopoietic stem cell transplantation (HR, 0.47; 95% CI, 0.28-0.79; p = .004). Conversely, patients who achieved MRD negativity at either of the two time points had comparable OS in the favorable-risk and intermediate-risk groups, regardless of whether they underwent transplant or not. In the adverse-risk group, allogeneic hematopoietic stem cell transplantation led to improvements in OS irrespective of MRD status (HR, 0.51; 95% CI, 0.38-0.69; p < .001).

CONCLUSIONS

Early clearance of MRD demonstrated significant prognostic value, particularly for patients in the favorable-risk and intermediate-risk groups. Positive MRD status after two courses of intensive chemotherapy were associated with a higher relapse rate and inferior OS, necessitating allogeneic hematopoietic stem cell transplantation.

High-Sensitivity Flow Cytometry for the Reliable Detection of Measurable Residual Disease in Hematological Malignancies in Clinical Laboratories

BACKGROUND

Monitoring of measurable residual disease (MRD) requires highly sensitive flow cytometry protocols to provide an accurate prediction of shorter progression-free survival. High assay sensitivity generally requires rapid processing to avoid cell loss from small bone marrow sample volumes, but this requirement conflicts with the need in most clinical cytometry laboratories for long processing and acquisition times, especially when multiple MRD studies coincide on the same day.

METHODS

The proposed protocol was applied to 226 human bone marrow and 45 peripheral blood samples submitted for the study of MRD or the detection of rare cells. Samples were processed within 24 h of extraction and acquired with an eight-color flow cytometer.

RESULTS

The FACSLyse-Bulk protocol allows for the labelling of millions of cells in under 90 min in small sample volumes without affecting the FSC/SSC pattern or antigen expression, and it also allows antigens to be fixed to the membrane, thus avoiding the capping phenomenon.

CONCLUSIONS

The proposed protocol would allow clinical flow cytometry laboratories to perform MRD studies in house and easily achieve a limit of detection and limit of quantification <0.001%, thus avoiding the need to outsource analysis to specialized cytometry laboratories.

Computational assessment of measurable residual disease in acute myeloid leukemia using mixture models

BACKGROUND

The proportion of residual leukemic blasts after chemotherapy assessed by multiparameter flow cytometry, is an important prognostic factor for the risk of relapse and overall survival in acute myeloid leukemia (AML). This measurable residual disease (MRD) is used in clinical trials to stratify patients for more or less intensive consolidation therapy. However, an objective and reproducible analysis method to assess MRD status from flow cytometry data is lacking, yet is highly anticipated for broader implementation of MRD testing.

METHODS

We propose a computational pipeline based on Gaussian mixture modeling that allows a fully automated assessment of MRD status while remaining completely interpretable for clinical diagnostic experts. Our pipeline requires limited training data, which makes it easily transferable to other medical centers and cytometry platforms.

RESULTS

We identify all healthy and leukemic immature myeloid cells in with high concordance (Spearman's Rho = 0.974) and classification performance (median F-score = 0.861) compared to manual analysis. Using control samples (n = 18), we calculate a computational MRD percentage with high concordance to expert gating (Spearman's rho = 0.823) and predict MRD status in a cohort of 35 AML follow-up measurements with high accuracy (97%).

CONCLUSIONS

We demonstrate that our pipeline provides a powerful tool for fast (~3 s) and objective automated MRD assessment in AML.

Mutations and MRD: clinical implications of clonal ontogeny

Measurable residual disease (MRD) is a strong but imprecise predictor of relapse in acute myeloid leukemia. Many patients fall into the outlier categories of MRD positivity without relapse or MRD negativity with relapse. Why? We will discuss these states in the context of "clonal ontogeny" examining how mutations, clonal structure, and Darwinian rules impact response, resistance, and relapse.

Detection methods and prognosis implications of measurable residual disease in acute myeloid leukemia

Measurable residual disease (MRD) in acute myeloid leukemia (AML) refers to the quantity of residual leukemic cells in a patient after treatment.According to the latest agreements, MRD in AML offering essential prognostic insights. However, there is ongoing debate regarding MRD-based monitoring and treatment strategies. There are multiple platforms for detecting MRD, each varying in sensitivity and suitability for different patients. MRD not only predicts treatment outcomes but also serves as an indicator of treatment effectiveness and a prognostic biomarker. In AML, most retrospective studies indicate that patients who are MRD-positive or show increasing MRD levels at specific time points during remission have significantly higher risks of relapse and mortality compared to MRD-negative patients. Although achieving MRD-negative status can improve patient prognosis, the possibility of relapse remains. Despite the correlation between MRD and clinical outcomes, MRD assessment methods are not yet standardized, leading to discrepancies in results across different techniques. To provide reliable MRD results, it is essential to optimize and standardize MRD detection methods. Methods for assessing MRD include multiparameter flow cytometry (MFC) and molecular assays, chosen based on disease characteristics. This review focuses on currently available MRD detection methods and discusses how the prognostic value of MRD test results informs personalized treatment strategies for AML patients.

Increased Th17 and Treg levels in peripheral blood positively correlate with minimal residual disease in acute myeloid leukaemia

PURPOSE

Immune dysregulation plays a key role in acute myeloid leukemia (AML). We aimed to explore the correlation between T helper cell 17 (Th17) and the regulatory cells (Tregs) in the peripheral blood of patients with newly diagnosed (ND) AML and bone marrow blast cells, as well as minimal residual disease (MRD) before and after treatment.

METHODS

Changes in Th17 and Treg cells in the peripheral blood of 32 patients with ND AML were observed before and after induction chemotherapy with cytarabine for seven days and anthracycline for three days. The levels of inflammatory cytokines were measured using an enzyme-linked immunosorbent assay. Correlation analysis between bone marrow blast cells and Th17 and Treg cell frequencies was performed using the Pearson's correlation test. Frequencies of Th17 and Treg cells and MRD were assessed using flow cytometry.

RESULTS

IL-6, IL-10, IL-17A, and GM-CSF levels gradually increased in patients with ND AML and CR and NR patients. The percentages of Th17 and Treg cells positively correlated with those of blast cells. In addition, the frequencies of Th17 and Treg cells in MRD-positive patients were higher than those in MRD-negative patients at the initial induction and after three months of chemotherapy. The frequencies of Tregs and Th17 cells positively correlated with MRD onset.

CONCLUSION

Increased Th17 and Treg cell levels were positively correlated with onset of AML, poor remission, and MRD.

Ven the dose matters: Venetoclax dosing in the frontline treatment of AML

Older/unfit adults with AML have worse outcomes and fewer treatment options than their younger/fit counterparts. In vitro studies have found a synergistic effect of hypomethylating agents (HMA) with venetoclax (VEN) on AML cells and since the phase 3 VIALE-A trial demonstrated a survival benefit, HMA + VEN has become the standard of care in the frontline setting for older/unfit adults with AML. Unfortunately, the standard 28-day cycle of VEN is associated with a high degree of myelosuppression leading to treatment delays and dose modifications. Many small retrospective studies have successfully shown comparable outcomes to VIALE-A with reduced dose/duration of VEN. Furthermore, low dose metronomic dosing of HMA + VEN has shown clinical benefit while minimizing myelotoxicity. Future trials are vital to understand the appropriate dose of VEN in combination with HMA, to evaluate HMA + VEN compared to intensive therapy for younger/fit patients, and to explore its utility in the relapsed/refractory setting.

Measurable residual disease assessment prior to allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia and myelodysplastic syndromes: a 20-year monocentric study

Patients with acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) who undergo allogeneic hematopoietic stem-cell transplantation (alloHSCT) can have divergent survival outcomes while all in morphological complete remission (CR). Techniques of measurable residual disease (MRD) have allowed us to refine their prognosis in two categories: MRD-positive and MRD-negative patients. We conducted a monocentric retrospective study (01/2000-12/2020) to assess the prognosis of pretransplant MRD status measured by multiparametric flow cytometry (MFC) and molecular biology assessed by PCR. 192 patients were included. The median follow-up period was 77 months. Among patients undergoing alloHSCT in CR, overall survival (median-OS: 130.6 vs. 16.0 months, P < 0.001), disease-free survival (median-DFS: 109.6 vs. 7.1 months, P < 0.001) and cumulative incidence of relapse (12-month CIR: 7.3% vs. 33.7%, P < 0.0001) were significantly different between MRD-negative and MRD-positive patients. Patients with discordant intermethod results had intermediate DFS. MRD-negative patients according to molecular PCR-based techniques, WT1 overexpression and MFC had longer median-DFS, compared to MRD-positive patients (P = 0.001, P < 0.001, P < 0.001, respectively). Looking into subgroups, MRD-positive patients among the ELN2017 adverse-category (P < 0.0001), myeloablative and reduced-intensity conditioning regimens (P < 0.0001, P = 0.005), < 60-year patients (P < 0.001) and AML patients (P < 0.001) were associated with lower DFS. This difference was not found in ≥ 60-year patients (P = 0.27) and MDS patients (P = 0.70). MRD-positive patients within the favorable/intermediate ELN2017 category trended toward lower DFS (P = 0.05). We confirmed that MRD status prior to alloHSCT is a strong prognostic factor for OS, DFS and CIR. Combining MFC and molecular-PCR techniques to assess MRD seems primordial as inter-method discordance can be consequential.

SOHO State of the Art Updates and Next Questions: Pre-emptive Therapy at Molecular Measurable Residual Disease Failure in Acute Myeloid Leukemia

Molecular measurable residual disease (MRD, eg, by real-time quantitative polymerase chain reaction, RT-qPCR), is an integral part of response assessment in acute myeloid leukemia (AML) with established prognostic and evolving therapeutic significance. MRD failure can occur through several pathways (namely MRD persistence at the end of treatment at a high level, MRD progression from a low level or MRD re-emergence during follow up; the latter two constitute MRD relapse as defined by the European Leukemia Net) and is clinically actionable, with survival benefit reported in AML subgroups. Selection of pre-emptive therapy at MRD failure relies upon an integrated clinico-molecular assessment and is subset-specific. In acute promyelocytic leukemia, arsenic trioxide-based regimen for MRD failure following frontline treatment with all-trans-retinoic acid plus chemotherapy represents standard of care, while hypomethylating agents (eg, azacitidine), salvage chemotherapy (eg, FLAG-IDA) and venetoclax-based regimens are effective in NPM1-mutated AML. Specific inhibitors of FLT3 have emerging use in FLT3-mutated AML and are associated with minimal toxicity. Furthermore, immunotherapeutic approaches such as donor lymphocyte infusions and interferon-⍺ are efficacious options in the post-allogeneic-HSCT settings. Enrollment into clinical trials with genomic-guided assignment of pre-emptive therapy at MRD failure should be prioritized. Finally, with the emergence of novel agents (eg, menin inhibitors) and approaches (eg, adoptive cellular and immunological therapy), an exciting future lies ahead where a broad array of highly active pre-emptive therapeutic options will likely be clinically applicable to a wide range of AML subsets.

Single-cell immune landscape of measurable residual disease in acute myeloid leukemia

Measurable residual disease (MRD) is a powerful prognostic factor of relapse in acute myeloid leukemia (AML). We applied the single-cell RNA sequencing to bone marrow (BM) samples from patients with (n=20) and without (n=12) MRD after allogeneic hematopoietic stem cell transplantation. A comprehensive immune landscape with 184,231 cells was created. Compared with CD8+ T cells enriched in the MRD-negative group (MRD-_CD8), those enriched in the MRD-positive group (MRD+_CD8) showed lower expression levels of cytotoxicity-related genes. Three monocyte clusters (i.e., MRD+_M) and three B-cell clusters (i.e., MRD+_B) were enriched in the MRD-positive group. Conversion from an MRD-positive state to an MRD-negative state was accompanied by an increase in MRD-_CD8 clusters and vice versa. MRD-enriched cell clusters employed the macrophage migration inhibitory factor pathway to regulate MRD-_CD8 clusters. These findings revealed the characteristics of the immune cell landscape in MRD positivity, which will allow for a better understanding of the immune mechanisms for MRD conversion.

Immunophenotypic markers for the evaluation of minimal/measurable residual disease in acute megakaryoblastic leukemia

Acute megakaryoblastic leukemia is characterized by heterogeneous biology and clinical behavior. Immunophenotypic characteristics include the expression of megakaryocytic differentiation markers (e.g. CD41, CD42a, CD42b, CD61) associated with immaturity markers (CD34, CD117, HLA-DR) and myeloid markers (e.g. CD13, CD33) and even with lymphoid cross-lineage markers (e.g. CD7, CD56). Although the diagnostic immunophenotype has already been well described, given the rarity of the disease, its immunophenotypic heterogeneity and post-therapeutic instability, there is no consensus on the combination of monoclonal markers to detect minimal/measurable residual disease (MRD). Currently, MRD is an important tool for assessing treatment efficacy and prognostic risk. In this study, we evaluated the immunophenotypic profile of MRD in a retrospective cohort of patients diagnosed with acute megakaryoblastic leukemia, to identify which markers, positive or negative, were more stable after treatment and which could be useful for MRD evaluation. The expression profile of each marker was evaluated in sequential MRD samples. In conclusion, the markers evaluated in this study can be combined in an MRD immunophenotypic panel to investigate for megakaryoblastic leukemia. Although this study is retrospective and some data are missing, the information obtained may contribute to prospective studies to validate more specific strategies in the detection of MRD in acute megakaryoblastic leukemia.

Immunophenotypic features of early haematopoietic and leukaemia stem cells

Many tumours are organised in a hierarchical structure with at its apex a cell that can maintain, establish, and repopulate the tumour-the cancer stem cell. The haematopoietic stem cell (HSC) is the founder cell for all functional blood cells. Like HSCs, the leukaemia stem cells (LSC) are hypothesised to be the leukaemia-initiating cells, which have features of stemness such as self-renewal, quiescence, and resistance to cytotoxic drugs. Immunophenotypically, CD34+CD38- defines HSCs by adding lineage negativity and CD90+CD45RA-. At which stage of maturation the further differentiation is blocked, determines the type of leukaemia, and determines the immunophenotype of the LSC specific to the leukaemia type. No apparent LSC phenotype has been described in lymphoid leukaemia, and it is debated if a specific acute lymphocytic leukaemia-initiating cell is present, as all cells are capable of engraftment in a secondary mouse model. In chronic lymphocytic leukaemia, a B-cell clone is responsible for uncontrolled proliferation, not a specific LSC. In chronic and acute myeloid leukaemia, LSC is described as CD34+CD38- with the expression of a marker that is aberrantly expressed (LSC marker), such as CD45RA, CD123 or in the case of chronic myeloid leukaemia CD26. In acute myeloid leukaemia, the LSC load had prognostic relevance and might be a biomarker that can be used for monitoring and as an addition to measurable residual disease. However, challenges such as the CD34-negative immunophenotype need to be explored.

Current status and research directions in acute myeloid leukemia

The understanding of the molecular pathobiology of acute myeloid leukemia (AML) has spurred the identification of therapeutic targets and the development of corresponding novel targeted therapies. Since 2017, twelve agents have been approved for the treatment of AML subsets: the BCL2 inhibitor venetoclax; the CD33 antibody drug conjugate gemtuzumab ozogamicin; three FLT3 inhibitors (midostaurin, gilteritinib, quizartinib); three IDH inhibitors (ivosidenib and olutasidenib targeting IDH1 mutations; enasidenib targeting IDH2 mutations); two oral hypomethylating agents (oral poorly absorbable azacitidine; fully absorbable decitabine-cedazuridine [latter approved as an alternative to parenteral hypomethylating agents in myelodysplastic syndrome and chronic myelomonocytic leukemia but commonly used in AML]); and CPX-351 (encapsulated liposomal 5:1 molar ratio of cytarabine and daunorubicin), and glasdegib (hedgehog inhibitor). Other targeted therapies (menin inhibitors, CD123 antibody-drug conjugates) are showing promising results. To achieve optimal results in such a rare and heterogeneous entity as AML requires expertise, familiarity with this rare cancer, and the access to, and delivery of disparate therapies under rigorous supportive care conditions. In this review, we update the standard-of-care and investigational therapies and outline promising current and future research directions.

Identification of circulating tumor DNA as a biomarker for diagnosis and response to therapies in cancer patients

The sampling of circulating biomarkers provides an opportunity for non-invasive evaluation and monitoring of cancer activity. In modern day practice, this has typically been in the form of circulating tumor DNA (ctDNA) detected in plasma. The field of ctDNA has been a burgeoning technology, with prominent applications for blood-based cancer screening and in disease status assessment, especially after curative-intent surgery to evaluate for minimal residual disease (MRD). Clinical applications for the latter show an incredibly high sensitivity in certain cancer types with a need for additional studies to determine how much clinical decision-making should be adapted based on ctDNA results and which cancer types, stages, and treatments are best informed by ctDNA results. This chapter provides an overview of ctDNA detection as tool for cancer screening, detecting MRD, and/or molecularly characterizing a cancer, highlighting the rapidly amassing research as a prognostic biomarker and emerging data on ctDNA as a predictive biomarker.

Spontaneous-stimulated Raman co-localization dual-modal analysis approach for efficient identification of tumor cells

The study of highly heterogeneous tumor cells, especially acute myeloid leukemia (AML) cells, usually relies on invasive analytical methods such as morphology, immunology, cytogenetics, and molecular biology classification, which are complex and time-consuming to perform. Mortality is high if patients are not diagnosed in a timely manner, so rapid label-free analysis of gene expression and metabolites within single-cell substructures is extremely important for clinical diagnosis and treatment. As a label-free and non-destructive vibrational detection technique, spontaneous Raman scattering provides molecular information across the full spectrum of the cell but lacks rapid imaging localization capabilities. In contrast, stimulated Raman scattering (SRS) provides a high-speed, high-resolution imaging view that can offer real-time subcellular localization assistance for spontaneous Raman spectroscopic detection. In this paper, we combined multi-color SRS microscopy with spontaneous Raman to develop a co-localized Raman imaging and spectral detection system (CRIS) for high-speed chemical imaging and quantitative spectral analysis of subcellular structures. Combined with multivariate statistical analysis methods, CRIS efficiently differentiated AML from normal leukocytes with an accuracy of 98.1 % and revealed the differences in the composition of nuclei and cytoplasm of AML relative to normal leukocytes. Compared to conventional Raman spectroscopy blind sampling without imaging localization, CRIS increased the efficiency of single-cell detection by at least three times. In addition, using the same approach for further identification of AML subtypes M2 and M3, we demonstrated that intracytoplasmic differential expression of proteins is a marker for their rapid and accurate classifying. CRIS analysis methods are expected to pave the way for clinical translation of rapid tumor cell identification.

Molecular relapse after first-line intensive therapy in patients with CBF or NPM1-mutated acute myeloid leukemia - a FILO study

Patients with Core-Binding Factor (CBF) and NPM1-mutated acute myeloid leukemia (AML) can be monitored by quantitative PCR after having achieved first complete remission (CR) to detect morphologic relapse and drive preemptive therapy. How to best manage these patients is unknown. We retrospectively analyzed 303 patients with CBF and NPM1-mutated AML, aged 18-60 years, without allogeneic hematopoietic cell transplantation (HCT) in first CR, with molecular monitoring after first-line intensive therapy. Among these patients, 153 (51%) never relapsed, 95 (31%) had molecular relapse (53 received preemptive therapy and 42 progressed to morphologic relapse at salvage therapy), and 55 (18%) had upfront morphologic relapse. Patients who received preemptive therapy had higher OS than those who received salvage therapy after having progressed from molecular to morphologic relapse and those with upfront morphologic relapse (three-year OS: 78% vs. 51% vs. 51%, respectively, P = 0.01). Preemptive therapy included upfront allogeneic HCT (n = 19), intensive chemotherapy (n = 21), and non-intensive therapy (n = 13; three-year OS: 92% vs. 79% vs. 58%, respectively, P = 0.09). Although not definitive due to the non-randomized allocation of patients to different treatment strategies at relapse, our study suggests that molecular monitoring should be considered during follow-up to start preemptive therapy before overt morphologic relapse.

Second Allogeneic Hematopoietic Cell Transplantation for Relapsed Adult Acute Myeloid Leukemia: Outcomes and Prognostic Factors

Second allogeneic hematopoietic cell transplantation (HCT2) is potentially curative for adults with acute myeloid leukemia (AML) or myelodysplastic neoplasm (MDS)/AML experiencing relapse after a first allograft (HCT1), but prognostic factors for outcomes are poorly characterized. To provide a detailed analysis of HCT2 outcomes and associated prognostic factors in a large single-center cohort, with a focus on identifying predictors of relapse and nonrelapse mortality (NRM), we studied adults ≥18 years who underwent HCT2 at a single institution between April 2006 and June 2022 for relapsed AML (n = 73) or MDS/AML (n = 8). With a median follow-up among survivors of 74.0 (range: 10.4 to 187.3) months, there were 30 relapses and 57 deaths, of which 29 were NRM events, contributing to the estimates for relapse, overall survival (OS), relapse-free survival (RFS), and NRM. Three-year estimates for relapse, RFS, and OS were 37% (95% confidence interval: 27% to 48%), 32% (23% to 44%), and 35% (26% to 47%). The rate of NRM at 100 days and 18 months was 20% (12% to 29%) and 28% (19% to 39%). Outcomes differed markedly across patient subsets and were substantially worse for patients who underwent HCT2 with active disease (ie, morphologic evidence of bone marrow and/or extramedullary disease), for patients who relapsed ≤6 months after HCT1, and for patients with higher HCT-specific Comorbidity Index (HCT-CI) or treatment-related mortality (TRM) scores. After multivariable adjustment, active disease was associated with a higher risk of relapse (hazard ratio [HR] = 3.19, P = .006) and shorter RFS (HR = 2.41, P = .008) as well as OS (HR = 2.17, P = .027) compared to transplant in morphologic remission without multiparameter flow cytometric evidence of measurable residual disease. Similarly, a relapse-free interval ≤6 months after the first allograft was associated with higher risk of relapse (HR = 5.86, P < .001) and shorter RFS (HR = 2.86; P = .001) and OS (HR = 2.45, P = .003). Additionally, a high HCT-CI score was associated with increased NRM (HR = 4.30, P = .035), and shorter RFS (HR = 3.87, P = .003) and OS (HR = 3.74, P = .006). Likewise, higher TRM scores were associated with increased risk of relapse (HR = 2.27; P = .024) and NRM (HR = 2.01, P = .001), and inferior RFS (HR = 1.90 P = .001) and OS (HR = 1.88, P = .001). A significant subset of patients with AML or MDS/AML relapse after HCT1 are alive and leukemia-free 3 years after undergoing HCT2. Our study identifies active leukemia at the time of HCT2 and early relapse after HCT1 as major adverse prognostic factors, highlighting patient subsets in particular need of novel therapeutic approaches, and supports the use of the HCT-CI and TRM scores for outcome prognostication.

High-dose alemtuzumab and cyclosporine vs tacrolimus, methotrexate, and sirolimus for chronic graft-versus-host disease prevention

ABSTRACT

Chronic graft-versus-host disease (cGVHD) remains a significant problem for patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although in vivo lymphodepletion for cGVHD prophylaxis has been explored in the myeloablative setting, its effects after reduced-intensity conditioning (RIC) are not well described. Patients (N = 83) with hematologic malignancies underwent targeted lymphodepletion chemotherapy followed by a RIC allo-HSCT using peripheral blood stem cells from unrelated donors. Patients were randomized to 2 GVHD prophylaxis arms: alemtuzumab and cyclosporine (AC; n = 44) or tacrolimus, methotrexate, and sirolimus (TMS; n = 39), with the primary end point of cumulative incidence of severe cGVHD. The incidence of severe cGVHD was lower with AC vs TMS prophylaxis at 1- and 5-years (0% vs 10.3% and 4.5% vs 28.5%; overall, P = .0002), as well as any grade (P = .003) and moderate-severe (P < .0001) cGVHD. AC was associated with higher rates of grade 3 to 4 infections (P = .02) and relapse (52% vs 21%; P = .003) with no difference in 5-year GVHD-free-, relapse-free-, or overall survival. AC severely depleted naïve T-cell reconstitution, resulting in reduced T-cell receptor repertoire diversity, smaller populations of CD4Treg and CD8Tscm, but a higher ratio of Treg to naïve T-cells at 6 months. In summary, an alemtuzumab-based regimen successfully reduced the rate and severity of cGVHD after RIC allo-HSCT and resulted in a distinct immunomodulatory profile, which may have reduced cGVHD incidence and severity. However, increased infections and relapse resulted in a lack of survival benefit after long-term follow-up. This trial was registered at www.ClinicalTrials.gov as #NCT00520130.

Optimizing maintenance therapy in acute myeloid leukemia: where do we stand in the year 2024?

INTRODUCTION

Despite the prognosis of patients affected by acute myeloid leukemia (AML) improved in the last decade, most patients relapse. Maintenance therapy after a chemotherapy approach with or without allogeneic stem cell transplantation could be a way to control the undetectable residual burden of leukemic cells. Several studies are being carried out as maintenance therapy in AML. Some critical points need to be defined, how the physician can choose among the various drugs available.

AREAS COVERED

This review discusses the advances and controversies surrounding maintenance therapy for AML patients.

EXPERT OPINION

Patients withFLT3-positive AML should receive midostaurin or quizartinib in the first-linesetting. For a patient initially receiving midostaurin, consider switching to sorafenib in the post-transplant setting. Because of the improved safety profile and potency, many experts will lean toward using a second-generation FLT3 inhibitor such as quizartinib or gilteritinib. Finally, no data indicate whether maintenance therapy should be prolonged until progression or for a defined period.

What clinicians should know about surrogate end points in hematologic malignancies

ABSTRACT

Use of surrogates as primary end points is commonplace in hematology/oncology clinical trials. As opposed to prognostic markers, surrogates are end points that can be measured early and yet can still capture the full effect of treatment, because it would be captured by the true outcome (eg, overall survival). We discuss the level of evidence of the most commonly used end points in hematology and share recommendations on how to apply and evaluate surrogate end points in research and clinical practice. Based on the statistical literature, this clinician-friendly review intends to build a bridge between clinicians and surrogacy specialists.

Bulk lysis procedures alter target cell population counts

To achieve high-sensitivity cell measurements (<1 in 105 cells) by flow cytometry (FCM), the minimum number of acquired cells must be considered and conventional immunophenotyping protocols fall short of these numbers. The bulk lysis (BL) assay is a standardized erythrocyte lysing approach that allows the analysis of the millions of cells required for high-sensitivity measurable residual disease (MRD) detection. However, this approach has been associated with significant cell loss, along with potential over or underestimates of rare cells when using this method. The aim of this study was to evaluate bulk lysis protocols and compare them with minimal sample perturbation (MSP) protocols, which are reported to better preserve the native cellular state and avoid significant cell loss due to washing steps. To achieve this purpose, we first generated an MRD model by spiking fresh peripheral blood with K562 cells, stably expressing EGFP, at known percentages of EGFP positive cells to leukocytes. Samples were then prepared with BL and MSP protocols and analyzed using FCM. For all percentages of K562 cells established and evaluated, a significant decrease of this population was detected in BL samples compared with MSP samples, even at low K562 cell percentages. Significant decreases for non-necrotic cells were also observed in BL samples relative to MSP samples. In conclusion, the evaluation of the potential effects of BL protocols in obtaining the final count is of great interest, especially for over- or under-estimation of target cells, as in the case of measurable residual disease. Since conventional flow cytometry or minimal sample perturbation assays fall short in obtaining the minimum numbers required to reach high sensitivity measurements, significant efforts may be needed to improve bulk lysis solution reagents.

Turning the tide in aggressive lymphoma: liquid biopsy for risk-adapted treatment strategies

Diffuse large B cell lymphoma (DLBCL) exhibits significant biological and clinical heterogeneity that presents challenges for risk stratification and disease surveillance. Existing tools for risk stratification, including the international prognostic index (IPI), tissue molecular analyses, and imaging, have limited accuracy in predicting outcomes. The therapeutic landscape for aggressive lymphoma is rapidly evolving, and there is a pressing need to identify patients at risk of refractory or relapsed (R/R) disease in the context of personalized therapy. Liquid biopsy, a minimally invasive method for cancer signal detection, has been explored to address these challenges. We review advances in liquid biopsy strategies focusing on circulating nucleic acids in DLBCL patients and highlight their clinical potential. We also provide recommendations for biomarker-guided trials to support risk-adapted treatment modalities.