How I treat measurable (minimal) residual disease in acute leukemia after allogeneic hematopoietic cell transplantation

Consensus on the monitoring, treatment, and prevention of leukaemia relapse after allogeneic haematopoietic stem cell transplantation in China: 2024 update

The consensus in 2018 from The Chinese Society of Haematology (CSH) on the monitoring, treatment, and prevention of leukaemia relapse after allogeneic haematopoietic stem cell transplantation (HSCT) facilitated the standardization of clinical practices in China and progressive integration with the world. To integrate recent developments and further improve the consensus, a panel of experts from the CSH recently updated the following consensus: (1) integrate risk-adapted, measurable residual disease (MRD)-guided strategy on modified donor lymphocyte infusion (DLI) and interferon-α into total therapy, which was pioneered and refined by Chinese researchers; (2) provide additional evidence of the superiority of haploidentical HSCT (the dominant donor source in China) to matched HSCT for high-risk populations, especially for pre-HSCT MRD-positive patients; (3) support the rapid progress of techniques for MRD detection, such as next-generation sequencing (NGS) and leukaemia stem cell-based MRD detection; and (4) address the role of new targeted options in transplant settings. In conclusion, the establishment of a "total therapy" strategy represents a great step forward. We hope that the consensus updated by Chinese scholars will include the latest cutting-edge developments and inspire progress in post-HSCT relapse management.

Azacitidine combined with interferon-α for pre-emptive treatment of AML/MDS after allogeneic peripheral blood stem cell transplantation: A prospective phase II study

This prospective clinical study aimed to evaluate the efficacy and safety of the pre-emptive treatment modality of azacitidine in combination with interferon-α (IFN-α) in AML/MDS patients post-transplantation. Forty-seven patients aged 17-62 were enrolled with 14 patients having completed the planned 12 cycles. Following initiation, 72.3% responded positively after the first cycle, peaking at 77.2% by the fifth cycle. Notably, 24 patients maintained sustained responses throughout a median follow-up of 1050 days (range, 866-1234). Overall survival, leukaemia-free survival and event-free survival probabilities at 3 years were 69.5%, 60.4% and 35.7% respectively. Cumulative incidences of relapse and non-relapse mortality were 36.5% and 4.3% respectively. Multivariate analysis identified that receiving pre-emptive treatment for fewer than six cycles and the absence of chronic graft-versus-host disease after intervention was significantly associated with poorer clinical outcomes. The combination of azacitidine with IFN-α was well-tolerated with no observed severe myelotoxicity, and the majority of adverse events were reversible and manageable. In conclusion, the use of azacitidine in conjunction with IFN-α as pre-emptive therapy is a safe and effective treatment to prevent disease progression in AML/MDS patients with MRD positivity post-allo-HSCT.

Engineering the best transplant outcome for high-risk acute myeloid leukemia: the donor, the graft and beyond

Allogeneic hemopoietic cell transplantation remains the goal of therapy for high-risk acute myeloid leukemia (AML). However, treatment failure in the form of leukemia relapse or severe graft-versus-host disease remains a critical area of unmet need. Recently, significant progress has been made in the cell therapy-based interventions both before and after transplant. In this review, the Stem Cell Engineering Committee of the International Society for Cell and Gene Therapy summarizes the literature regarding the identification of high risk in AML, treatment approaches before transplant, optimal transplant platforms and measures that may be taken after transplant to ideally prevent, or, if need be, treat AML relapse. Although some strategies remain in the early phases of clinical investigation, they are built on progress in pre-clinical research and cellular engineering techniques that are already improving outcomes for children and adults with high-risk malignancies.

Haploidentical hematopoietic cell transplantation with or without an unrelated cord blood unit for adult acute myeloid leukemia: a multicenter, randomized, open-label, phase 3 trial

Coinfusion of unrelated cord blood (UCB) units in haploidentical hematopoietic cell transplantation (haplo-HCT) (haplo-cord HCT) for hematopoietic malignancies showed promising results in previous reports, but the efficiency of haplo-cord HCT in acute myeloid leukemia (AML) still lacks sufficient evidence. This multicenter, randomized, phase 3 trial (ClinicalTrials.gov NCT03719534) aimed to assess the efficacy and safety of haplo-cord HCT in AML patients. A total of 268 eligible patients aged 18-60 years, diagnosed with measurable residual disease in AML (excluding acute promyelocytic leukemia), with available haploidentical donors and suitable for allotransplantation, were randomly allocated (1:1) to receive haplo-cord HCT (n = 134) or haplo-HCT (n = 134). The 3-year overall survival (OS) was the primary endpoint in this study. Overall median follow-up was 36.50 months (IQR 24.75-46.50). The 3-year OS of Haplo-cord HCT group was better than haplo-HCT group (80.5%, 95% confidence interval [CI]: 73.7-87.9 vs. 67.8% 95% CI 60.0-76.5, p = 0.013). Favorable progression-free survival (70.3%, 95% CI 62.6-78.8 vs. 57.6%, 95% CI 49.6-67.0, p = 0.012) and cumulative incidence of relapse (12.1%, 95% CI 12.0-12.2 vs. 30.3%, 95% CI 30.1-30.4, p = 0.024) were observed in haplo-cord HCT group. Grade 3-4 adverse events (AEs) within two years posttransplantation in the two groups were similar. Haplo-cord HCT patients exhibited a faster cumulative incidence of neutrophil recovery (p = 0.026) and increased T-cell reconstitution in the early period posttransplantation. Haplo-cord HCT can improve OS in AML patients without excessive AEs, which may exert additional benefits for recipients of haplo-HCT.

Flares of acute graft-versus-host disease: a Mount Sinai Acute GVHD International Consortium analysis

ABSTRACT

The absence of a standardized definition for graft-versus-host disease (GVHD) flares and data on its clinical course are significant concerns. We retrospectively evaluated 968 patients across 23 Mount Sinai Acute GVHD International Consortium (MAGIC) transplant centers who achieved complete response (CR) or very good partial response (VGPR) within 4 weeks of treatment. The cumulative incidence of flares within 6 months was 22%, and flares were associated with a higher risk of nonrelapse mortality (NRM; adjusted hazard ratio [aHR], 4.84; 95% confidence interval [CI], 3.19-7.36; P < .001). Flares were more severe (grades 3/4, 41% vs 16%; P < .001) and had more frequent lower gastrointestinal (LGI) involvement (55% vs 32%; P < .001) than the initial GVHD. At CR/VGPR, elevated MAGIC biomarkers predicted the future occurrence of a flare, along with its severity and LGI involvement. In multivariate analyses, higher Ann Arbor (AA) biomarker scores at CR/VGPR were significant risk factors for flares (AA2 vs AA1: aHR, 1.81 [95% CI, 1.32-2.48; P = .001]; AA3 vs AA1: aHR, 3.14 [95% CI, 1.98-4.98; P < .001]), as were early response to initial treatment (aHR, 1.84; 95% CI, 1.21-2.80; P = .004) and HLA-mismatched unrelated donor (aHR, 1.74; 95% CI, 1.00-3.02; P = .049). MAGIC biomarkers also stratified the risk of NRM both at CR/VGPR and at the time of flare. We conclude that GVHD flares are common and carry a significant mortality risk. The occurrence of future flares can be predicted by serum biomarkers that may serve to guide adjustment and discontinuation of immunosuppression.

The effect of center experience on allogeneic hematopoietic cell transplantation outcomes in acute myeloid leukemia

This study aimed to address the prognostic impact of center experience based on the data of 7821 adults with acute myeloid leukemia who underwent allogeneic hematopoietic cell transplantation (HCT) from 2010 to 2019 in Japan, where medical care was provided within a uniform healthcare system. Center experience was defined based on the number of allogeneic HCTs performed for any indication during the study period, by which centers were divided into low-, intermediate-, and high-volume centers. After adjusting for known confounding factors, the risk of overall mortality was lowest for the high-volume centers and highest for the low-volume centers, with the difference between the center categories attributed primarily to the risk of relapse. Patients transplanted at high-volume centers had higher risks of acute and chronic graft-versus-host diseases but without an increased risk of non-relapse mortality (NRM). These findings reveal the presence of a center effect in allogeneic HCT conducted during the past decade in Japan, highlighting the difference in relapse based on center experience. The weaker effect on NRM compared with that on relapse suggests that the transplantation care quality is becoming equalized across the country.

Minimal residual disease detection by next-generation sequencing of different immunoglobulin gene rearrangements in pediatric B-ALL

While the prognostic role of immunoglobulin heavy chain locus (IGH) rearrangement in minimal residual disease (MRD) in pediatric B-acute lymphoblastic leukemia (B-ALL) has been reported, the contribution of light chain loci (IGK/IGL) remains elusive. This study is to evaluate the prognosis of IGH and IGK/IGL rearrangement-based MRD detected by next-generation sequencing in B-ALL at the end of induction (EOI) and end of consolidation (EOC). IGK/IGL rearrangements identify 5.5% of patients without trackable IGH clones. Concordance rates for IGH and IGK/IGL are 79.9% (cutoff 0.01%) at EOI and 81.0% (cutoff 0.0001%) at EOC, respectively. Patients with NGS-MRD < 0.01% at EOI or <0.0001% at EOC present excellent outcome, with 3-year event-free survival rates higher than 95%. IGH-MRD is prognostic at EOI/EOC, while IGK-MRD at EOI/EOC and IGL-MRD at EOI are not. At EOI, NGS identifies 26.2% of higher risk patients whose MRD < 0.01% by flow cytometry. However, analyzing IGK/IGL along with IGH fails to identify additional higher risk patients both at EOI and at EOC. In conclusion, IGH is crucial for MRD monitoring while IGK and IGL have relatively limited value.

Single-Cell Next-Generation Sequencing to Monitor Hematopoietic Stem-Cell Transplantation: Current Applications and Future Perspectives

Acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) are genetically complex and diverse diseases. Such complexity makes challenging the monitoring of response to treatment. Measurable residual disease (MRD) assessment is a powerful tool for monitoring response and guiding therapeutic interventions. This is accomplished through targeted next-generation sequencing (NGS), as well as polymerase chain reaction and multiparameter flow cytometry, to detect genomic aberrations at a previously challenging leukemic cell concentration. A major shortcoming of NGS techniques is the inability to discriminate nonleukemic clonal hematopoiesis. In addition, risk assessment and prognostication become more complicated after hematopoietic stem-cell transplantation (HSCT) due to genotypic drift. To address this, newer sequencing techniques have been developed, leading to more prospective and randomized clinical trials aiming to demonstrate the prognostic utility of single-cell next-generation sequencing in predicting patient outcomes following HSCT. This review discusses the use of single-cell DNA genomics in MRD assessment for AML/MDS, with an emphasis on the HSCT time period, including the challenges with current technologies. We also touch on the potential benefits of single-cell RNA sequencing and analysis of accessible chromatin, which generate high-dimensional data at the cellular resolution for investigational purposes, but not currently used in the clinical setting.

Targeting Measurable Residual Disease (MRD) in Acute Myeloid Leukemia (AML): Moving beyond Prognostication

Measurable residual disease (MRD) assessment in acute myeloid leukemia (AML) has an established role in disease prognostication, particularly in guiding decisions for hematopoietic cell transplantation in first remission. Serial MRD assessment is now routinely recommended in the evaluation of treatment response and monitoring in AML by the European LeukemiaNet. The key question remains, however, if MRD in AML is clinically actionable or "does MRD merely portend fate"? With a series of new drug approvals since 2017, we now have more targeted and less toxic therapeutic options for the potential application of MRD-directed therapy. Recent approval of NPM1 MRD as a regulatory endpoint is also foreseen to drastically transform the clinical trial landscape such as biomarker-driven adaptive design. In this article, we will review (1) the emerging molecular MRD markers (such as non-DTA mutations, IDH1/2, and FLT3-ITD); (2) the impact of novel therapeutics on MRD endpoints; and (3) how MRD might be used as a predictive biomarker to guide therapy in AML beyond its prognostic role, which is the focus of two large collaborative trials: AMLM26 INTERCEPT (ACTRN12621000439842) and MyeloMATCH (NCT05564390).

Applying molecular measurable residual disease testing in acute myeloid leukaemia

Molecular testing in acute myeloid leukaemia (AML) has continued to dramatically advance in recent years, facilitating the ability to detect residual disease at exponentially lower levels. With the advent of the recently updated ELN consensus recommendations, there is increasing complexity to ordering and interpreting measurable residual disease (MRD) assays in AML. We outline the technology itself in conjunction with the relevant testing timepoints, clinically significant thresholds and potential prognostic and therapeutic significance of MRD testing for the major molecular targets in AML. This practical overview should assist haematologists in incorporating molecular MRD assays routinely into their personalised AML clinical management.

Post-Hematopoietic Cell Transplantation Relapsed Acute Lymphoblastic Leukemia: Current Challenges and Future Directions

Allogeneic hematopoietic cell transplantation (allo-HCT) represents an important and potentially curative treatment option for adult patients with acute lymphoblastic leukemia. Relapse continues to remain the most important factor influencing overall survival post allo-HCT. We discuss early identification, clinical manifestations, and management of relapsed disease. Routine evaluation of measurable residual disease (MRD) and change in donor chimerism play a crucial role in early detection. Pivotal clinical trials have led to FDA approval of multiple novel agents like blinatumomab and inotuzumab. Combining targeted therapy with cellular immunotherapy serves as the backbone for prolonging overall survival in these patients. Donor lymphocyte infusions have traditionally been used in relapsed disease with suboptimal outcomes. This review provides insight into use of cellular therapy in MRD positivity and decreasing donor chimerism. It also discusses various modalities of combining cellular therapy with novel agents and discussing the impact of chimeric antigen receptor T-cell therapy in the setting of post allo-HCT relapse both as consolidative therapy and as a bridge to second transplant.

How I treat high-risk acute myeloid leukemia using preemptive adoptive cellular immunotherapy

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a potentially curative treatment for patients with high-risk acute leukemias, but unfortunately disease recurrence remains the major cause of death in these patients. Infusion of donor lymphocytes (DLI) has the potential to restore graft-versus-leukemia immunologic surveillance; however, efficacy varies across different hematologic entities. Although relapsed chronic myeloid leukemia, transplanted in chronic phase, has proven remarkably susceptible to DLI, response rates are more modest for relapsed acute myeloid leukemia and acute lymphoblastic leukemia. To prevent impending relapse, a number of groups have explored administering DLI preemptively on detection of measurable residual disease (MRD) or mixed chimerism. Evidence for the effectiveness of this strategy, although encouraging, comes from only a few, mostly single-center retrospective, nonrandomized studies. This article seeks to (1) discuss the available evidence supporting this approach while highlighting some of the inherent challenges of MRD-triggered treatment decisions post-transplant, (2) portray other forms of postremission cellular therapies, including the role of next-generation target-specific immunotherapies, and (3) provide a practical framework to support clinicians in their decision-making process when considering preemptive cellular therapy for this difficult-to-treat patient population.

Achieving MRD negativity in AML: how important is this and how do we get there?

Multiple studies have demonstrated that patients with acute myeloid leukemia (AML) who have measurable residual disease (MRD) detected during or after treatment have higher relapse rates and worse survival than similar patients testing negative. Updated response criteria for AML reflect the understanding that achievement of complete remission (CR) with no detectable MRD using high-sensitivity tests represents a superior response over conventional cytomorphological CR alone. Potential use cases for AML MRD testing are diverse and include patient selection for clinical trials and therapeutic assignment, early relapse detection and intervention during sequential monitoring, and drug development, including deep quantification for antileukemia efficacy and as a surrogate endpoint for overall survival in regulatory approvals. Testing for AML MRD has not, however, been harmonized, and many technical and clinical questions remain. The implications of MRD test results for specific therapeutic combinations, molecular subsets, test types, treatment time points, sample types, and patient characteristics remain incompletely defined. No perfect AML MRD test or testing strategy currently exists, and the evidence basis for clinical recommendations in this rare disease is sparse but growing. It is unproven whether conversion of an MRD test result from positive to negative by additional therapeutic intervention improves relapse risk and survival. Several national- and international-level consortia have recently been initiated to advance the generation and collection of evidence to support the use of AML MRD testing in clinical practice, drug development, and regulatory approvals.

Long-Term Results of Allogeneic Stem Cell Transplantation in Adult Ph- Negative High-Risk Acute Lymphoblastic Leukemia

Allogeneic hematopoietic stem cell transplantation (HCT) is standard treatment for adult high-risk (HR) acute lymphoblastic leukemia (ALL) and contributed to the overall improved outcome. We report a consecutive cohort of prospectively defined HR patients treated on German Multicenter Acute Lymphoblastic Leukemia trials 06/99-07/03 with similar induction/consolidation therapy and HCT in first remission. A total of 542 patients (15-55 years) with BCR-ABL-negative ALL were analyzed. Sixty-seven percent received HCT from matched unrelated donors (MUD) and 32% from matched sibling donors (MSD). The incidence of non-relapse mortality (NRM) was 20% at 5 years. NRM occurred after median 6.6 months; the leading cause (46%) was infection. NRM after MUD decreased from 39% in trial 06/99 to 16% in trial 07/03 (P < .00001). Patient age was the strongest predictor of NRM. The 5-year relapse incidence was 23% using MSD and 25% using MUD. Minimal residual disease (MRD) was the strongest predictor of relapse (45% for molecular failure versus 6% for molecular CR; P < .0001). The median follow-up was 67 months, and the 5-year survival rate was 58%. Age, subtype/high risk feature, MRD status, trial and acute GvHD were significant prognostic factors. We provide a large reference analysis with long follow-up confirming a similar outcome of MSD and MUD HCT and improved NRM for MUD HCT over years. MRD has a strong impact on relapse risk, whereas age was the strongest predictor of NRM. New adapted conditioning strategies should be considered for older patients combined with the goal to reduce the MRD level before stem cell transplantation.

Clinical Impact of Measurable Residual Disease in Acute Myeloid Leukemia

Simple Summary

Advances in immunophenotyping and molecular techniques have allowed for the development of more sensitive diagnostic tests in acute leukemia. These techniques can identify low levels of leukemic cells (quantified as 10⁻⁴ to 10⁻⁶ ratio to white blood cells) in patient samples. The presence of such low levels of leukemic cells, termed “measurable/minimal residual disease” (MRD), has been shown to be a marker of disease burden and patient outcomes. In acute lymphoblastic leukemia, new agents are highly effective at eliminating MRD for patients whose leukemia progressed despite first line therapies. By comparison, the role of MRD in acute myeloid leukemia is less clear. This commentary reviews select data and remaining questions about the clinical application of MRD to the treatment of patients with acute myeloid leukemia.

Abstract

Measurable residual disease (MRD) has emerged as a primary marker of risk severity and prognosis in acute myeloid leukemia (AML). There is, however, ongoing debate about MRD-based surveillance and treatment. A literature review was performed using the PubMed database with the keywords MRD or residual disease in recently published journals. Identified articles describe the prognostic value of pre-transplant MRD and suggest optimal timing and techniques to quantify MRD. Several studies address the implications of MRD on treatment selection and hematopoietic stem cell transplant, including patient candidacy, conditioning regimen, and transplant type. More prospective, randomized studies are needed to guide the application of MRD in the treatment of AML, particularly in transplant.

MRD in ALL: Optimization and Innovations

PURPOSE OF REVIEW

Measurable residual disease (MRD) is an important monitoring parameter that can help predict survival outcomes in acute lymphoblastic leukemia (ALL). Identifying patients with MRD has the potential to decrease the risk of relapse with the initiation of early salvage therapy and to help guide decision making regarding allogeneic hematopoietic cell transplantation. In this review, we discuss MRD in ALL, focusing on advantages and limitations between MRD testing techniques and how to monitor MRD in specific patient populations.

RECENT FINDINGS

MRD has traditionally been measured through bone marrow samples, but more data for evaluation of MRD via peripheral blood is emerging. Current and developmental testing strategies for MRD include multiparametric flow cytometry (MFC), next-generation sequencing (NGS), quantitative polymerase chain reaction (qPCR), and ClonoSeq. Novel therapies are incorporating MRD as an outcome measure to demonstrate efficacy, including blinatumomab, inotuzumab ozogamicin, and chimeric antigen receptor T (CAR-T) cell therapy. Understanding how to incorporate MRD testing into the management of ALL could improve patient outcomes and predict efficacy of new therapy options.

The significance of mixed chimaerism and cell lineage chimaerism monitoring in paediatric patients post haematopoietic stem cell transplant

Haematopoietic stem cell transplants (HSCTs) are carried out across the world to treat haematological and immunological diseases which would otherwise prove fatal. Certain diseases are predominantly encountered in paediatric patients, such severe primary immunodeficiencies (PID) and diseases of inborn errors of metabolism (IEM). Chimaerism testing for these disorders has different considerations compared to adult diseases. This review focuses on the importance of cell-lineage-specific chimaerism testing and examines the appropriate cell populations to be assessed in individual paediatric patient groups. By analysing disease-associated subpopulations, abnormalities are identified significantly earlier than in whole samples and targeted clinical decisions can be made. Chimaerism methods have evolved over time and lead to an ever-increasing level of sensitivity and biomarker arrays to distinguish between recipient and donor cells. Short tandem repeat (STR) is still the gold standard for routine chimaerism assessment, and hypersensitive methods such as quantitative and digital polymerase chain reaction (PCR) are leading the forefront of microchimaerism testing. The rise of molecular methods operating with minute DNA amounts has been hugely beneficial to chimaerism testing of paediatric samples. As HSCTs are becoming increasingly personalised and risk-adjusted towards a child's individual needs, chimaerism testing needs to adapt alongside these medical advances ensuring the best possible care.

Case Report: Preemptive Treatment With Low-Dose PD-1 Blockade and Azacitidine for Molecular Relapsed Acute Myeloid Leukemia With RUNX1-RUNX1T1 After Allogeneic Hematopoietic Stem Cell Transplantation

Acute myeloid leukemia (AML) patients who develop hematological relapse (HR) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) generally have dismal clinical outcomes. Measurable residual disease (MRD)-directed preemptive interventions are effective approaches to prevent disease progression and improve prognosis for molecular relapsed patients with warning signs of impending HR. In this situation, boosting the graft-vs-leukemia (GVL) effect with immune checkpoint inhibitors (ICIs) might be a promising prevention strategy, despite the potential for causing severe graft-vs-host disease (GVHD). In the present study, we reported for the first time an AML patient with RUNX1-RUNX1T1 who underwent preemptive treatment with the combined application of tislelizumab (an anti-PD-1 antibody) and azacitidine to avoid HR following allo-HSCT. On day +81, molecular relapse with MRD depicted by RUNX1-RUN1T1-positivity as well as mixed donor chimerism occurred in the patient. On day +95, with no signs of GVHD and an excellent eastern cooperative oncology group performance status (ECOG PS), the patient thus was administered with 100 mg of tislelizumab on day 1 and 100 mg of azacitidine on days 1-7. After the combination therapy, complete remission was successfully achieved with significant improvement in hematologic response, and the MRD marker RUNX1-RUNX1T1 turned negative, along with a complete donor chimerism in bone marrow. Meanwhile, the patient experienced moderate GVHD and immune-related adverse events (irAEs), successively involving the lung, liver, lower digestive tract and urinary system, which were well controlled by immunosuppressive therapies. As far as we know, this case is the first one to report the use of tislelizumab in combination with azacitidine to prevent post-transplant relapse in AML. In summary, the application of ICIs in MRD positive patients might be an attractive strategy for immune modulation in the future to reduce the incidence of HR in the post-transplant setting, but safer clinical application schedules need to be explored.

Prophylactic or Preemptive Low-Dose Azacitidine and Donor Lymphocyte Infusion to Prevent Disease Relapse following Allogeneic Transplantation in Patients with High-Risk Acute Myelogenous Leukemia or Myelodysplastic Syndrome

Because of the persistently high rates of relapse of patients with high-risk acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS) following allogeneic hematopoietic stem cell transplantation (allo-HSCT), post-transplantation maintenance therapy has been proposed. We previously initiated a Phase II trial in which epigenetic therapy was combined with immunotherapy in an attempt to reduce disease relapse. In that study, low-dose azacitidine (AZA) and escalating doses of donor lymphocyte infusion (DLI) were given as post-allo-HSCT maintenance treatment. In the present study, we retrospectively analyze a larger cohort of patients receiving post-transplantation maintenance therapy and provide updates on some patients of the earlier study. The objectives of the present study were to analyze the cumulative incidence of relapse (CIR), overall survival (OS), and progression-free survival (PFS) and the incidence of acute and chronic graft-versus-host disease (GVHD) of patients with high-risk AML or MDS receiving post-transplantation maintenance treatment with AZA with or without DLI. We retrospectively analyzed 77 patients (54 with AML, 23 with MDS) considered at high risk based on either their genomic or clinical status at transplantation. Following allogeneic transplantation, they received at least 1 cycle of prophylactic or preemptive low-dose AZA with or without escalating doses of DLI to prevent disease relapse. Almost one-half of the patients (47%) were able to receive the full 12 cycles of scheduled AZA, and a majority (79%) received at least 1 DLI. With a median follow-up of 24 months, 19 patients (25%; 16 with AML, 3 with MDS) relapsed, at a median of 9.8 months (range, 4 to 58.6 months), giving a 22% CIR at 24 months. OS and PFS at 24 months were 70.8% and 68.3%, respectively. The cumulative incidences of grade II-IV acute GVHD and chronic GVHD were 27.4% and 45%, respectively. Only a minority of patients (11%) required delayed administration of AZA. These findings confirm that AZA-DLI maintenance is both tolerable and effective in reducing the risk of post-transplantation relapse.

Highlighting the Prognostic Importance of Measurable Residual Disease Among Acute Myeloid Leukemia Risk Factors

Objective:

The optimal timing of measurable residual disease (MRD) evaluation in acute myeloid leukemia (AML) patients has not been well defined yet. We aimed to investigate the impact of MRD in pre- and post-allogeneic hematopoietic stem cell transplantation (AHSCT) periods on prognostic parameters.

Materials and Methods:

Seventy-seven AML patients who underwent AHSCT in complete morphological remission were included. MRD analyses were performed by 10-color MFC and 10^-4 was defined as positive. Relapse risk and survival outcomes were assessed based on pre- and post-AHSCT MRD positivity.

Results:

The median age of the patients was 46 (range: 18-71) years, and 41 (53.2%) were male while 36 (46.8%) were female. The median follow-up after AHSCT was 12.2 months (range: 0.2-73.0). The 2-year overall survival (OS) in the entire cohort was 37.0%, with a significant difference between patients who were MRD-negative and MRD-positive before AHSCT, estimated as 63.0% versus 16.0%, respectively (p=0.005). MRD positivity at +28 days after AHSCT was also associated with significantly inferior 2-year OS when compared to MRD negativity (p=0.03). The risk of relapse at 1 year was 2.4 times higher (95% confidence interval: 1.1-5.6; p=0.04) in the pre-AHSCT MRD-positive group when compared to the MRD-negative group regardless of other transplant-related factors, including pre-AHSCT disease status (i.e., complete remission 1 and 2). Event-free survival (EFS) was significantly shorter in patients who were pre-AHSCT MRD-positive (p=0.016). Post-AHSCT MRD positivity was also related to an increased relapse risk. OS and EFS were significantly inferior among MRD-positive patients at +28 days after AHSCT (p=0.03 and p=0.019).

Conclusion:

Our results indicate the importance of MRD before and after AHSCT independently of other factors.

Posttransplantation MRD monitoring in patients with AML by next-generation sequencing using DTA and non-DTA mutations

Next-generation sequencing (NGS)-based measurable residual disease (MRD) monitoring in patients with acute myeloid leukemia (AML) is widely applicable and prognostic prior to allogeneic hematopoietic cell transplantation (alloHCT). We evaluated the prognostic role of clonal hematopoiesis-associated DNMT3A, TET2, and ASXL1 (DTA) and non-DTA mutations for MRD monitoring post-alloHCT to refine MRD marker selection. Of 154 patients with AML, 138 (90%) had at least one mutation at diagnosis, which were retrospectively monitored by amplicon-based error-corrected NGS on day 90 and/or day 180 post-alloHCT. MRD was detected in 34 patients on day 90 and/or day 180 (25%). The rate of MRD positivity was similar when DTA and non-DTA mutations were considered separately (17.6% vs 19.8%). DTA mutations had no prognostic impact on cumulative incidence of relapse, relapse-free survival, or overall survival in our study and were removed from further analysis. In the remaining 131 patients with at least 1 non-DTA mutation, clinical and transplantation-associated characteristics were similarly distributed between MRD-positive and MRD-negative patients. In multivariate analysis, MRD positivity was an independent adverse predictor of cumulative incidence of relapse, relapse-free survival, and overall survival but not of nonrelapse mortality. The prognostic effect was independent of different cutoffs (above limit of detection, 0.1% and 1% variant allele frequency). MRD log-reduction between diagnosis and post-alloHCT assessment had no prognostic value. MRD status post-alloHCT had the strongest impact in patients who were MRD positive prior to alloHCT. In conclusion, non-DTA mutations are prognostic NGS-MRD markers post-alloHCT, whereas the prognostic role of DTA mutations in the posttransplant setting remains open.

How we use molecular minimal residual disease (MRD) testing in acute myeloid leukaemia (AML)

In recent years there have been major advances in the use of molecular diagnostic and monitoring techniques for patients with acute myeloid leukaemia (AML). Coupled with the simultaneous explosion of new therapeutic agents, this has sown the seeds for significant improvements to treatment algorithms. Here we show, using a selection of real-life examples, how molecular monitoring can be used to refine clinical decision-making and to personalise treatment in patients with AML with nucleophosmin (NPM1) mutations, core binding factor translocations and other fusion genes. For each case we review the established evidence base and provide practical recommendations where evidence is lacking or conflicting. Finally, we review important technical considerations that clinicians should be aware of in order to safely exploit these technologies as they undergo widespread implementation.

Relapse of acute myeloid leukemia after allogeneic hematopoietic cell transplantation: clinical features and outcomes

Posttransplant relapse represents the greatest obstacle to the success of allogeneic hematopoietic cell transplantation (HCT) for patients with acute myeloid leukemia (AML). This study investigated clinical features and outcomes of posttransplant relapse of AML based on data for 1265 patients with AML suffering relapse after allogeneic HCT conducted during complete remission (CR). Relapse occurred at a median of 6.1 months. The incidence rate of relapse peaked at 29.0 per 100 patient-years during the first 3-6 months period post transplant, after which the rate declined over time, and after 3 years remained consistently at less than 1 per 100 patient-years. The probability of overall survival (OS) after posttransplant relapse was 19% at 2 years, with 68% of deaths being attributed to leukemia. The interval from transplantation to relapse was identified as the strongest indicator for OS. Donor lymphocyte infusion (DLI) and second allogeneic HCT (HCT2) were administered to 152 (12%) and 481 (38%) patients, respectively. Landmark analyses showed some signs of survival benefit when these procedures were performed during CR, but no benefit was gained when performed during non-CR. Our findings clarify clinical features of posttransplant relapse of AML, and indicate the urgent need for developing effective bridging to cellular therapies.

Pharmacologic Therapies to Prevent Relapse of Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is the main cause of mortality in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Adverse cytogenetic or molecular risk factors, as well as refractory disease or persistent measurable residual disease (MRD) at the time of transplantation are associated with an increased risk of recurrence. Salvage therapy for AML relapse after allo-HSCT is often limited to chemotherapy, donor lymphocyte infusions and/or second transplants and is rarely successful. Effective post-transplant preventive intervention in high risk AML may be crucial. The most frequent and promising approach is the use of post-transplant maintenance with hypomethylating agents or with FLT3 tyrosine kinase inhibitors when the target is present. Moreover, IDH1/IDH2 inhibitors and BCL-2 inhibitors in combination with other strategies are promising approaches in the maintenance setting. Here we summarize the current knowledge about the preemptive and prophylactic use of pharmacologic agents after allo-HSCT to prevent relapse of AML.

Comparison of salvage chemotherapy regimens and prognostic significance of minimal residual disease in relapsed/refractory acute myeloid leukemia

We compared the outcomes of salvage chemotherapy in 146 patients with relapsed (57.5%) or refractory (42.5%) AML who received CLAG-M (51%), MEC (39%) or CLAG (10%). Minimal residual disease (MRD) was assessed by flow cytometry. Bivariate, Kaplan-Meier, and Cox regression analyses were conducted. Complete remission (CR) rate of 46% (CLAG-M 54% versus MEC/CLAG 40%, p = .045) was observed with MRD-negative CR of 33% (CLAG-M 39% versus MEC/CLAG 22%, p = .042). Median overall survival (OS) was 9.7 months; the longest OS occurred with CLAG-M (13.3, 95%CI 2.4-24.3) versus MEC (6.9, 95%CI 2.9-10.9) or CLAG (6.2, 95%CI 2.4-12.6) (p = .025). When adjusted for age, gender, relapsed/refractory AML, poor risk AML, MRD, chemotherapy and transplant, CLAG-M (HR 0.63, 95% CI 0.40-0.98, p = .042), MRD-negativity (HR 0.15, 95% CI 0.07-0.30, p < .001) and transplant (HR 0.22, 95% CI 0.13-0.39, p < .001) were associated with higher OS. Our findings confirm that CLAG-M is a reasonable salvage regimen for RR-AML followed by transplant.