Clonal relapse dynamics in acute myeloid leukemia following allogeneic hematopoietic cell transplantation

ABSTRACT

Patients with acute myeloid leukemia (AML) who experience relapse following allogeneic hematopoietic cell transplantation (alloHCT) face unfavorable outcomes regardless of the chosen relapse treatment. Early detection of relapse at the molecular level by measurable residual disease (MRD) assessment enables timely intervention, which may prevent hematological recurrence of the disease. It remains unclear whether molecular MRD assessment can detect MRD before impending relapse and, if so, how long in advance. This study elucidates the molecular architecture and kinetics preceding AML relapse by using error-corrected next-generation sequencing (NGS) in 74 patients with AML relapsing after alloHCT, evaluating 140 samples from peripheral blood collected 0.6 to 14 months before relapse. At least 1 MRD marker became detectable in 10%, 38%, and 64% of patients at 6, 3, and 1 month before relapse, respectively. By translating these proportions into monitoring intervals, 38% of relapses would have been detected through MRD monitoring every 3 months, whereas 64% of relapses would have been detected with monthly intervals. The relapse kinetics after alloHCT are influenced by the functional class of mutations and their stability during molecular progression. Notably, mutations in epigenetic modifier genes exhibited a higher prevalence of MRD positivity and greater stability before relapse, whereas mutations in signaling genes demonstrated a shorter lead time to relapse. Both DTA (DNMT3A, TET2, and ASXL1) and non-DTA mutations displayed similar relapse kinetics during the follow-up period after alloHCT. Our study sets a framework for MRD monitoring after alloHCT by NGS, supporting monthly monitoring from peripheral blood using all variants that are known from diagnosis.

UK Stakeholder Perspectives on Surrogate Endpoints in Cancer, and the Potential for UK Real-World Datasets to Validate Their Use in Decision-Making

Duration of overall survival in patients with cancer has lengthened due to earlier detection and improved treatments. However, these improvements have created challenges in assessing the impact of newer treatments, particularly those used early in the treatment pathway. As overall survival remains most decision-makers' preferred primary endpoint, therapeutic innovations may take a long time to be introduced into clinical practice. Moreover, it is difficult to extrapolate findings to heterogeneous populations and address the concerns of patients wishing to evaluate everyday quality and extension of life. There is growing interest in the use of surrogate or interim endpoints to demonstrate robust treatment effects sooner than is possible with measurement of overall survival. It is hoped that they could speed up patients' access to new drugs, combinations, and sequences, and inform treatment decision-making. However, while surrogate endpoints have been used by regulators for drug approvals, this has occurred on a case-by-case basis. Evidence standards are yet to be clearly defined for acceptability in health technology appraisals or to shape clinical practice. This article considers the relevance of the use of surrogate endpoints in cancer in the UK context, and explores whether collection and analysis of real-world UK data and evidence might contribute to validation.

Targeting Molecular Measurable Residual Disease and Low-Blast Relapse in AML With Venetoclax and Low-Dose Cytarabine: A Prospective Phase II Study (VALDAC)

PURPOSE

A prospective phase II study examined the safety and efficacy of venetoclax combined with low-dose cytarabine (LDAC) in AML at first measurable residual disease (MRD) or oligoblastic relapse.

METHODS

Patients with either MRD (≥1 log10 rise) or oligoblastic relapse (blasts 5%-15%) received venetoclax 600 mg once daily D1-28 plus LDAC once daily D1-10 in 28-day cycles. The primary objective was MRD response in the MRD relapse cohort or complete remission (CR/CRh/CRi) in the oligoblastic relapse cohort.

RESULTS

Forty-eight adults with either MRD (n = 26) or oligoblastic (n = 22) relapse were enrolled. Median age was 67 years (range, 18-80) and 94% had received previous intensive chemotherapy. Patients received a median of four cycles of therapy; 17% completed ≥12 cycles. Patients with oligoblastic relapse had more grade ≥3 anemia (32% v 4%; P = .02) and infections (36% v 8%; P = .03), whereas grade 4 neutropenia (32 v 23%) or thrombocytopenia (27 v 15%) were comparable with the MRD relapse cohort. Markers of molecular MRD relapse included mutant NPM1 (77%), CBFB::MYH11 (4%), RUNX1::RUNX1T1 (4%), or KMT2A::MLLT3 (4%). Three patients with a log10 rise in IDH1/2 (12%) were included. By cycle 2 in the MRD relapse cohort, a log10 reduction in MRD was observed in 69%; 46% achieved MRD negative remission. In the oligoblastic relapse cohort, 73% achieved CR/CRh/CRi. Overall, 21 (44%) underwent hematopoietic cell transplantation. Median overall survival (OS) was not reached in either cohort. Estimated 2-year OS rate was 67% (95% CI, 50 to 89) in the MRD and 53% (95% CI, 34 to 84) in the oligoblastic relapse cohorts.

CONCLUSION

For AML in first remission and either MRD or oligoblastic relapse, venetoclax plus LDAC is well tolerated and highly effective.

Diagnosis and management of acute promyelocytic leukemia: Brazilian consensus guidelines 2024 on behalf of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy

Improvements in clinical assessment have occurred since the last published recommendations on the diagnosis and treatment of acute promyelocytic leukemia in 2013. Here, a committee of specialists of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy presents a comprehensive review on the current knowledge, focusing on the advances in diagnosis, risk assessment, and frontline and salvage therapy. The concept of urgent diagnosis is explored as well as the management of critical situations such as coagulopathy and differentiation syndrome. Recent adjustments in risk stratification based on white blood cell counts only are presented together with the incorporation of chemo-free regimens for non-high-risk patients. Special conditions such as acute promyelocytic leukemia in children, the elderly and pregnant women are discussed. Finally, acute promyelocytic leukemia is presented as a highly curable disease because of the real possibility of targeted therapy towards differentiation, and, paradoxically, as a serious and urgent condition that deserves prompt recognition and management to avoid early mortality.

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.

FLT3 inhibitors as MRD-guided salvage treatment for molecular failure in FLT3 mutated AML

Patients with FLT3-mutated AML have a high relapse rate and suboptimal outcomes. Many have co-mutations suitable for measurable residual disease (MRD) monitoring by RT-qPCR and those destined to relapse can be identified by high or rising levels of MRD, called molecular failure.  This provides a window for pre-emptive intervention, but there is little evidence to guide treatment. The use of FLT3 inhibitors (FLT3i) appears attractive but their use has not yet been evaluated.  We identified 56 patients treated with FLT3i at molecular failure.  The FLT3 mutation was an ITD in 52, TKD in 7 and both in 3. Over half of patients had previously received midostaurin. Molecular failure occurred at a median 9.2 months from diagnosis and was treated with gilteritinib (n = 38), quizartinib (n = 7) or sorafenib (n = 11). 60% achieved a molecular response, with 45% reaching MRD negativity. Haematological toxicity was low, and 22 patients were bridged directly to allogeneic transplant with another 6 to donor lymphocyte infusion. 2-year overall survival was 80% (95%CI 69-93) and molecular event-free survival 56% (95%CI 44-72). High-sensitivity next-generation sequencing for FLT3-ITD at molecular failure identified patients more likely to benefit. FLT3i monotherapy for molecular failure is a promising strategy which merits evaluation in prospective studies.

A venetoclax and azacitidine bridge-to-transplant strategy for NPM1-mutated acute myeloid leukaemia in molecular failure

NPM1-mutated acute myeloid leukaemia (NPM1mut AML) represents a mostly favourable/intermediate risk disease that benefits from allogeneic haematopoietic stem cell transplantation (HSCT) in case of measurable residual disease (MRD) relapse or persistence after induction chemotherapy. Although the negative prognostic role of pre-HSCT MRD is established, no recommendations are available for the management of peri-transplant molecular failure (MF). Based on the efficacy data of venetoclax (VEN)-based treatment in NPM1mut AML older patients, we retrospectively analysed the off-label combination of VEN plus azacitidine (AZA) as bridge-to-transplant strategy in 11 NPM1mut MRD-positive fit AML patients. Patients were in MRD-positive complete remission (CRMRDpos ) at the time of treatment: nine in molecular relapse and two in molecular persistence. After a median number of two cycles (range 1-4) of VEN-AZA, 9/11 (81.8%) achieved CRMRD -negative (CRMRDneg ). All 11 patients proceeded to HSCT. With a median follow-up from treatment start of 26 months, and a median post-HSCT follow-up of 19 months, 10/11 patients are alive (1 died from non-relapse mortality), and 9/10 patients are in MRDneg status. This patient series highlights the efficacy and safety of VEN-AZA to prevent overt relapse, achieve deep responses and preserve patient fitness before HSCT, in patients with NPM1mut AML in MF.

Assessment of acute myeloid leukemia molecular measurable residual disease testing in an interlaboratory study

The European LeukaemiaNet (ELN) measurable residual disease (MRD) working group has published consensus guidelines to standardize molecular genetic MRD testing of the t(8;21)(q22;q22.1) RUNX1::RUNX1T1, inv(16)(p13.1q22) CBFB::MYH11, t(15;17)(q24.1;q21.2) PML::RARA, and NPM1 type A markers. A study featuring 29 international laboratories was performed to assess interlaboratory variation in testing and the subsequent interpretation of results, both crucial to patient safety. Most participants in this study were able to detect, accurately quantify, and correctly interpret MRD testing results, with a level of proficiency expected from a clinical trial or standard-of-care setting. However, a few testing and interpretive errors were identified that, in a patient setting, would have led to misclassification of patient outcomes and inappropriate treatment pathways being followed. Of note, a high proportion of participants reported false-positive results in the NPM1 marker-negative sample. False-positive results may have clinical consequences, committing patients to unneeded additional chemotherapy and/or transplant with the attendant risk of morbidity and mortality, which therefore highlights the need for ongoing external quality assessment/proficiency testing in this area. Most errors identified in the study were related to the interpretation of results. It was noted that the ELN guidance lacks clarity for certain clinical scenarios and highlights the requirement for urgent revision of the guidelines to elucidate these issues and related educational efforts around the revisions to ensure effective dissemination.

Minimal residual disease status improved the response evaluation in patients with Waldenström's macroglobulinemia

Introduction

Minimal residual disease (MRD) has been recognized as an important prognostic factor of survival in patients with hematological malignancies. However, the prognostic value of MRD in Waldenström macroglobulinemia (WM) remains unexplored.

Methods

We analyzed 108 newly diagnosed WM patients receiving systematic therapy and assessed for MRD by multiparameter flow cytometry (MFC) using bone marrow samples.

Results

Of the total patients, 34 (31.5%) achieved undetectable MRD (uMRD). A hemoglobin level of >115 g/L (P=0.03), a serum albumin level of >35 g/L (P=0.01), a β2-MG level of ≤3 mg/L (P=0.03), and a low-risk International Prognostic Scoring System for WM (IPSSWM) stage (P<0.01) were associated with a higher rate of uMRD. Improvements in monoclonal immunoglobulin (P<0.01) and hemoglobin (P=0.03) levels were more evident in uMRD patients compared with that in MRD-positive patients. The 3-year progression-free survival (PFS) was better in uMRD patients compared with that in MRD-positive patients (96.2% vs. 52.8%; P=0.0012). Landmark analysis also showed that uMRD patients had better PFS compared with MRD-positive patients after 6 and 12 months. Patients who achieved partial response (PR) and uMRD had a 3-year PFS of 100%, which was significantly higher than that of patients with MRD-positive PR (62.6%, P=0.029). Multivariate analysis showed that MRD positivity was an independent factor of PFS (HR: 2.55, P=0.03). Moreover, the combination of the 6th International Workshop on WM assessment (IWWM-6 Criteria) and MRD assessment had a higher 3-year AUC compared with the IWWM-6 criteria alone (0.71 vs. 0.67).

Discussion

MRD status assessed by MFC is an independent prognostic factor for PFS in patients with WM, and its determination could improve the precision of response evaluation, especially in patients who achieved PR.

Loss of IRF8 inhibits the growth of acute myeloid leukemia cells

The transcription factor interferon regulatory factor 8 (IRF8), as a member of the IRF family, is essential for myeloid cell differentiation. However, the precise role of IRF8 in the pathogenesis of acute myeloid leukemia (AML) remains unknown. By using multivariate analysis, we discovered that high IRF8 expression was an independent poor predictor of overall survival (OS) in AML patients from our clinical follow-up study. The proliferation of three AML cell lines was significantly inhibited by shRNA-mediated knockdown of IRF8, owing to cell cycle S-phase arrest. Furthermore, we demonstrated that knocking down IRF8 could suppress the expression of CyclinA and CyclinB1, resulting in a shift in cell cycle distribution. Loss of IRF8 in AML cells decreased the expression of STAT3 and phosphor-STAT3 (pSTAT3), which are key factors in JAK/STAT signal pathway and are important for AML progression. Using a xenograft mouse model, we discovered the antiproliferative effect of losing IRF8 in vivo. In conclusion, this study found that IRF8 may play a prognostic factor and therapeutic target in AML.

Integrated analysis of next generation sequencing minimal residual disease (MRD) and PET scan in transplant eligible myeloma patients

Minimal residual disease (MRD) assays allow response assessment in patients with multiple myeloma (MM), and negativity is associated with improved survival outcomes. The role of highly sensitive next generation sequencing (NGS) MRD in combination with functional imaging remains to be validated. We performed a retrospective analysis on MM patients who underwent frontline autologous stem cell transplant (ASCT). Patients were evaluated at day 100 post-ASCT with NGS-MRD and positron emission tomography (PET-CT). Patients with ≥ 2 MRD measurements were included in a secondary analysis for sequential measurements. 186 patients were included. At day 100, 45 (24.2%) patients achieved MRD negativity at a sensitivity threshold of 10-6. MRD negativity was the most predictive factor for longer time to next treatment (TTNT). Negativity rates did not differ according to MM subtype, R-ISS Stage nor cytogenetic risk. PET-CT and MRD had poor agreement, with high rates of PET-CT negativity in MRD-positive patients. Patients with sustained MRD negativity had longer TTNT, regardless of baseline risk characteristics. Our results show that the ability to measure deeper and sustainable responses distinguishes patients with better outcomes. Achieving MRD negativity was the strongest prognostic marker and could help guide therapy-related decisions and serve as a response marker for clinical trials.

Minimal residual disease detection by mutation-specific droplet digital PCR for leukemia/lymphoma

Minimal residual disease (MRD) is usually defined as the small number of cancer cells that remain in the body after treatment. The clinical significance of MRD kinetics is well recognized in treatment of hematologic malignancies, particularly acute lymphoblastic leukemia (ALL). Real time quantitative PCR targeting immunoglobulin (Ig) or T-cell receptor (TCR) rearrangement (PCR-MRD), as well as multiparametric flow cytometric analysis targeting antigen expression, are widely used in MRD detection. In this study, we devised an alternative method to detect MRD using droplet digital PCR (ddPCR), targeting somatic single nucleotide variants (SNVs). This ddPCR-based method (ddPCR-MRD) had sensitivity up to 1E-4. We assessed ddPCR-MRD at 26 time points from eight T-ALL patients, and compared it to the results of PCR-MRD. Almost all results were concordant between the two methods, but ddPCR-MRD detected micro-residual disease that was missed by PCR-MRD in one patient. We also measured MRD in stored ovarian tissue of four pediatric cancer patients, and detected 1E-2 of submicroscopic infiltration. Considering the universality of ddPCR-MRD, the methods can be used as a complement for not only ALL, but also other malignant diseases regardless of tumor-specific Ig/TCR or surface antigen patterns.

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).

The menin inhibitor revumenib in KMT2A-rearranged or NPM1-mutant leukaemia

Targeting critical epigenetic regulators reverses aberrant transcription in cancer, thereby restoring normal tissue function1-3. The interaction of menin with lysine methyltransferase 2A (KMT2A), an epigenetic regulator, is a dependence in acute leukaemia caused by either rearrangement of KMT2A or mutation of the nucleophosmin 1 gene (NPM1)4-6. KMT2A rearrangements occur in up to 10% of acute leukaemias and have an adverse prognosis, whereas NPM1 mutations occur in up to 30%, forming the most common genetic alteration in acute myeloid leukaemia7,8. Here, we describe the results of the first-in-human phase 1 clinical trial investigating revumenib (SNDX-5613), a potent and selective oral inhibitor of the menin-KMT2A interaction, in patients with relapsed or refractory acute leukaemia (ClinicalTrials.gov, NCT04065399). We show that therapy with revumenib was associated with a low frequency of grade 3 or higher treatment-related adverse events and a 30% rate of complete remission or complete remission with partial haematologic recovery (CR/CRh) in the efficacy analysis population. Asymptomatic prolongation of the QT interval on electrocardiography was identified as the only dose-limiting toxicity. Remissions occurred in leukaemias refractory to multiple previous lines of therapy. We demonstrate clearance of residual disease using sensitive clinical assays and identify hallmarks of differentiation into normal haematopoietic cells, including differentiation syndrome. These data establish menin inhibition as a therapeutic strategy for susceptible acute leukaemia subtypes.

The menin inhibitor revumenib in KMT2A-rearranged or NPM1-mutant leukaemia

Targeting critical epigenetic regulators reverses aberrant transcription in cancer, thereby restoring normal tissue function^1-3. The interaction of menin with lysine methyltransferase 2A (KMT2A), an epigenetic regulator, is a dependence in acute leukaemia caused by either rearrangement of KMT2A or mutation of the nucleophosmin 1 gene (NPM1)^4-6. KMT2A rearrangements occur in up to 10% of acute leukaemias and have an adverse prognosis, whereas NPM1 mutations occur in up to 30%, forming the most common genetic alteration in acute myeloid leukaemia^7,8. Here, we describe the results of the first-in-human phase 1 clinical trial investigating revumenib (SNDX-5613), a potent and selective oral inhibitor of the menin-KMT2A interaction, in patients with relapsed or refractory acute leukaemia (ClinicalTrials.gov, NCT04065399). We show that therapy with revumenib was associated with a low frequency of grade 3 or higher treatment-related adverse events and a 30% rate of complete remission or complete remission with partial haematologic recovery (CR/CRh) in the efficacy analysis population. Asymptomatic prolongation of the QT interval on electrocardiography was identified as the only dose-limiting toxicity. Remissions occurred in leukaemias refractory to multiple previous lines of therapy. We demonstrate clearance of residual disease using sensitive clinical assays and identify hallmarks of differentiation into normal haematopoietic cells, including differentiation syndrome. These data establish menin inhibition as a therapeutic strategy for susceptible acute leukaemia subtypes.

Current and Emerging Techniques for Diagnosis and MRD Detection in AML: A Comprehensive Narrative Review

Acute myeloid leukemia (AML) comprises a group of hematologic neoplasms characterized by abnormal differentiation and proliferation of myeloid progenitor cells. AML is associated with poor outcome due to the lack of efficient therapies and early diagnostic tools. The current gold standard diagnostic tools are based on bone marrow biopsy. These biopsies, apart from being very invasive, painful, and costly, have low sensitivity. Despite the progress uncovering the molecular pathogenesis of AML, the development of novel detection strategies is still poorly explored. This is particularly important for patients that check the criteria for complete remission after treatment, since they can relapse through the persistence of some leukemic stem cells. This condition, recently named as measurable residual disease (MRD), has severe consequences for disease progression. Hence, an early and accurate diagnosis of MRD would allow an appropriate therapy to be tailored, improving a patient's prognosis. Many novel techniques with high potential in disease prevention and early detection are being explored. Among them, microfluidics has flourished in recent years due to its ability at processing complex samples as well as its demonstrated capacity to isolate rare cells from biological fluids. In parallel, surface-enhanced Raman scattering (SERS) spectroscopy has shown outstanding sensitivity and capability for multiplex quantitative detection of disease biomarkers. Together, these technologies can allow early and cost-effective disease detection as well as contribute to monitoring the efficiency of treatments. In this review, we aim to provide a comprehensive overview of AML disease, the conventional techniques currently used for its diagnosis, classification (recently updated in September 2022), and treatment selection, and we also aim to present how novel technologies can be applied to improve the detection and monitoring of MRD.

Measurable Residual Disease and Clonal Evolution in Acute Myeloid Leukemia from Diagnosis to Post-Transplant Follow-Up: The Role of Next-Generation Sequencing

It has now been ascertained that acute myeloid leukemias-as in most type of cancers-are mixtures of various subclones, evolving by acquiring additional somatic mutations over the course of the disease. The complexity of leukemia clone architecture and the phenotypic and/or genotypic drifts that can occur during treatment explain why more than 50% of patients-in hematological remission-could relapse. Moreover, the complexity and heterogeneity of clone architecture represent a hindrance for monitoring measurable residual disease, as not all minimal residual disease monitoring methods are able to detect genetic mutations arising during treatment. Unlike with chemotherapy, which imparts a relatively short duration of selective pressure on acute myeloid leukemia clonal architecture, the immunological effect related to allogeneic hematopoietic stem cell transplant is prolonged over time and must be overcome for relapse to occur. This means that not all molecular abnormalities detected after transplant always imply inevitable relapse. Therefore, transplant represents a critical setting where a measurable residual disease-based strategy, performed during post-transplant follow-up by highly sensitive methods such as next-generation sequencing, could optimize and improve treatment outcome. The purpose of our review is to provide an overview of the role of next-generation sequencing in monitoring both measurable residual disease and clonal evolution in acute myeloid leukemia patients during the entire course of the disease, with special focus on the transplant phase.

The mythological chimera and new era of relapse prediction post-transplant

Allogeneic hemopoietic stem cell transplantation is the treatment of choice for high-risk or relapsed acute leukemia. However, unfortunately, relapse post-transplant continues to be the most common cause of treatment failure with 20-80% of patients relapsing based on disease risk and status at transplant. Advances in molecular profiling of different hematological malignancies have enabled us to monitor low level disease before and after transplant and develop a more personalized approach to the management of these disease including early detection post-transplant. While, in general, detectable disease by morphology remains the gold standard to diagnosing relapse, multiple approaches have allowed detection of cancer cells earlier, using peripheral blood-based methods with sensitivities as high as 1:10⁶, together called minimal/measurable residual disease (MRD) detection. However, a in significant number of patients with acute leukemia where no such molecular markers exist it remains challenging to detect early relapse. In such patients who receive transplantation, chimerism monitoring remains the only option. An increase in mixed chimerism in post allogeneic HCT patients has been correlated with relapse in multiple studies. However, chimerism monitoring, while commonly accepted as a tool for assessing engraftment, has not been routinely used for relapse detection, at least in part because of the lack of standardized, high sensitivity, reliable methods for chimerism detection. In this paper, we review the various methods employed for MRD and chimerism detection post-transplant and discuss future trends in MRD and chimerism monitoring from the viewpoint of the practicing transplant physician.

Fusion transcript analysis reveals slower response kinetics than multiparameter flow cytometry in childhood acute myeloid leukaemia

INTRODUCTION

Analysis of measurable residual disease (MRD) is increasingly being implemented in the clinical care of children and adults with acute myeloid leukaemia (AML). However, MRD methodologies differ and discordances in results lead to difficulties in interpretation and clinical decision-making. The aim of this study was to compare results from reverse transcription quantitative polymerase chain reaction (RT-qPCR) and multiparameter flow cytometry (MFC) in childhood AML and describe the kinetics of residual leukaemic burden during induction treatment.

METHODS

In 15 children who were treated in the NOPHO-AML 2004 trial and had fusion transcripts quantified by RT-qPCR, we compared MFC with RT-qPCR for analysis of MRD during (day 15) and after induction therapy. Eight children had RUNX1::RUNX1T1, one CBFB::MYH11 and six KMT2A::MLLT3.

RESULTS

When ≥0.1% was used as cut-off for positivity, 10 of 22 samples were discordant. The majority (9/10) were MRD positive with RT-qPCR but MRD negative with MFC, and several such cases showed the presence of mature myeloid cells. Fusion transcript expression was verified in mature cells as well as in CD34 expressing cells sorted from diagnostic samples.

CONCLUSIONS

Measurement with RT-qPCR suggests slower response kinetics than indicated from MFC, presumably due to the presence of mature cells expressing fusion transcript. The prognostic impact of early measurements with RT-qPCR remains to be determined.

Circulating lnc-LOC as a novel noninvasive biomarker in the treatment surveillance of acute promyelocytic leukaemia

BACKGROUND

Acute promyelocytic leukaemia (APL) is a unique subtype of acute myeloid leukaemia (AML) characterized by haematopoietic failure caused by the accumulation of abnormal promyelocytic cells in bone marrow (BM). However, indispensable BM biopsy frequently afflicts patients in leukaemia surveillance, which increases the burden on patients and reduces compliance. This study aimed to explore whether the novel circulating long noncoding RNA LOC100506453 (lnc-LOC) could be a target in diagnosis, assess the treatment response and supervise the minimal residual disease (MRD) of APL, thereby blazing a trail in noninvasive lncRNA biomarkers of APL.

METHODS

Our study comprised 100 patients (40 with APL and 60 with non-APL AML) and 60 healthy donors. BM and peripheral blood (PB) sample collection was accomplished from APL patients at diagnosis and postinduction. Quantitative real-time PCR (qRT-PCR) was conducted to evaluate lnc-LOC expression. A receiver operating characteristic (ROC) analysis was implemented to analyse the value of lnc-LOC in the diagnosis of APL and treatment monitoring. For statistical analysis, the Mann-Whitney U test, a t test, and Spearman's rank correlation test were utilized.

RESULTS

Our results showed that BM lnc-LOC expression was significantly different between APL and healthy donors and non-APL AML. lnc-LOC was drastically downregulated in APL patients' BM after undergoing induction therapy. Lnc-LOC was upregulated in APL cell lines and downregulated after all-trans retinoic acid (ATRA)-induced myeloid differentiation, preliminarily verifying that lnc-LOC has the potential to be considered a treatment monitoring biomarker. PB lnc-LOC was positively correlated with BM lnc-LOC in APL patients, non-APL AML patients and healthy donors and decreased sharply after complete remission (CR). However, upregulated lnc-LOC was manifested in relapsed-refractory patients. A positive correlation was revealed between PB lnc-LOC and PML-RARα transcript levels in BM samples. Furthermore, we observed a positive correlation between PB lnc-LOC and BM lnc-LOC expression in APL patients, suggesting that lnc-LOC can be utilized as a noninvasive biomarker for MRD surveillance.

CONCLUSIONS

Our study demonstrated that PB lnc-LOC might serve as a novel noninvasive biomarker in the treatment surveillance of APL, and it innovated the investigation and application of newly found lncRNAs in APL noninvasive biomarkers used in diagnosis and detection.

The cure of leukemia through the optimist's prism

Progress is occurring at a dizzying rate across all leukemias. Since the authors' review of the topic in Cancer in 2018, numerous discoveries have been made that have improved the therapy and outcomes of several leukemia subsets. Hairy cell leukemia is potentially curable with a single course of cladribine followed by rituximab (10-year survival, ≥90%). Acute promyelocytic leukemia is curable at a rate of 80% to 90% with a nonchemotherapy regimen of all-trans retinoic acid and arsenic trioxide. The cure rate for core-binding factor acute myeloid leukemia (AML) is ≥75% with fludarabine, high-dose cytarabine, and gemtuzumab ozogamicin. Survival for patients with chronic myeloid leukemia is close to that for an age-matched normal population with BCR-ABL1 tyrosine kinase inhibitors (TKIs). Chronic lymphocytic leukemia, a previously incurable disease, may now be potentially curable with a finite duration of therapy with Bruton tyrosine kinase inhibitors and venetoclax. The estimated 5-year survival rate for patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL) exceeds 70% with intensive chemotherapy and ponatinib, a third-generation BCR-ABL1 TKI, and more recent nonchemotherapy regimens using dasatinib or ponatinib with blinatumomab are producing outstanding results. Survival in both younger and older patients with ALL has improved with the addition of antibodies targeting CD20, CD19 (blinatumomab), and CD22 (inotuzumab) to chemotherapy. Several recent drug discoveries (venetoclax, FLT3 and IDH inhibitors, and oral hypomethylating agents) are also improving outcomes for younger and older patients with AML and for those with higher risk myelodysplastic syndrome.

History of Acute Promyelocytic Leukemia

In this article, we discuss the history of acute promyelocytic leukemia (APL) from the pre-therapeutic era, which began after its recognition by Hillestad in 1947 as a nosological entity, to the present day. It is a paradigmatic history that has transformed the “most malignant leukemia form” into the most curable one. The identification of a balanced reciprocal translocation between chromosomes 15 and 17, resulting in fusion between the promyelocytic leukemia gene and the retinoic acid receptor alpha, has been crucial in understanding the mechanisms of leukemogenesis, and responsible for the peculiar response to targeted therapy with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). We review the milestones that marked successive therapeutic advances, beginning with the introduction of the first successful chemotherapy in the early 1970s, followed by a subsequent incorporation of ATRA and ATO in the late 1980s and early 1990s which have revolutionized the treatment of this disease. Over the past two decades, treatment optimization has relied on the combination of ATRA, ATO, and chemotherapy according to risk-adapted approaches, which together with improvements in supportive therapy have paved the way for cure for most patients with APL.

Rationale and design of the 2 by 2 factorial design GnG-trial: a randomized phase-III study to compare two schedules of gemtuzumab ozogamicin as adjunct to intensive induction therapy and to compare double-blinded intensive postremission therapy with or without glasdegib in older patients with newly diagnosed AML

BACKGROUND

Overall survival remains poor in older patients with acute myeloid leukemia (AML) with less than 10% being alive after 5 years. In recent studies, a significant improvement in event-free, relapse-free and overall survival was shown by adding gemtuzumab ozogamicin (GO), a humanized antibody-drug conjugate directed against CD33, to intensive induction therapy once or in a sequential dosing schedule. Glasdegib, the small-molecule inhibitor of smoothened (SMO), also showed improved overall survival in patients not eligible for intensive chemotherapy when combined with low-dose cytarabine compared to low-dose cytarabine alone. These findings warrant further investigations in the phase III GnG trial.

METHODS/DESIGN

This is a randomized phase III trial with measurable residual disease (MRD) after induction therapy and event-free survival (EFS) as primary endpoints. The two research questions are addressed in a 2 by 2 factorial design. Patients age 60 years and older are upfront randomized 1:1 in one of the two induction arms: GO administered to intensive induction therapy on days 1,4, and 7 versus GO administered once on day 1 (GO-147 versus GO-1), and double-blinded 1:1 in one of the subsequent treatment arms glasdegib vs. placebo as adjunct to consolidation therapy and as single-agent maintenance therapy for six months. Chemotherapy backbone for induction therapy consists of standard 7 + 3 schedule with cytarabine 200 mg/m² continuously days 1 to 7, daunorubicin 60 mg/m² days 1, 2, and 3 and high-dose cytarabine (1 g/m², bi-daily, days 1, 2, and 3) for consolidation therapy. Addressing two primary endpoints, MRD-negativity after induction therapy and event-free survival (EFS), 252 evaluable patients are needed to reject each of the two null hypotheses at a two-sided significance level of 2.5% with a power of at least 85%.

ETHICS AND DISSEMINATION

Ethical approval and approvals from the local and federal competent authorities were granted. Trial results will be reported via peer-reviewed journals and presented at conferences and scientific meetings.

TRIAL STATUS

Protocol version: 1st version 20.10.2020, no amendments yet. Study initiation on February 16, 2021. First patient was recruited on April 1st.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04093505 ; EudraCT 2019-003913-32. Registered on October 30, 2018.

Value of measurable residual disease monitoring in patients with acute promyelocytic leukemia in the era of frontline 'chemotherapy-free' therapy

Acute promyelocytic leukemia (APL) is characterized by the chromosomal translocation t(15;17) and the resulting gene PML-RARA, used for measurable residual disease (MRD) monitoring. Despite highly effective therapy for APL, MRD monitoring practices are not fully established. We aimed to assess the value of MRD monitoring by RT-qPCR in patients with APL treated with ATRA and arsenic trioxide +/- GO. We reviewed 223 patients with APL treated with this regimen. RT-qPCR for PML-RARA was measured every 3 months, and at 12, 18, and 24 months after therapy. Seven patients relapsed. Time to relapse was 7.9-12.4 months in 6 patients, and one patient relapsed after 79.5 months. These data show that MRD monitoring may be important for the detection of relapse in patients treated with this regimen within one year after completing therapy, however, since late molecular relapse is rare, our data suggest a low value of MRD monitoring beyond that first year.

Acute promyelocytic leukemia derived extracellular vesicles conserve PML-RARα transcript from storage-inflicted degradation: a stable diagnosis tool in APL patients

The early death, which is more common in acute promyelocytic leukemia (APL) patients rather than other types of acute myelocytic leukemia (AML) highlights the importance of appropriate diagnostic method for early detection of this disease. The low sensitivity of the conventional methods, low tumor burden in some patients, and the need for bone marrow sampling are some of the diagnostic challenges on the way of proper detection of APL. Given these, we aimed to compare the efficacy of extracellular vesicles (EVs), as a diagnostic tool, with the existing methods. RT-PCR, qPCR, and flow cytometry were applied on EVs and their corresponding associated cellular component collected from 18 APL new cases, 23 patients with minimal residual disease (MRD), and NB4 cell line. RT-PCR results were positive in both cellular and vesicular components of all new cases, NB4 cells, and EVs in contrary to MRD cases. Normalized copy numbers (NCN) of PML-RARα were 5100 and 3950 for cell and EVs, respectively (p < 0.05). There was a significant difference in the NCN of PML-RARα between cells and EVs in BM samples. Investigating the effect of storage at room temperature revealed that PML-RARα level was retained near to the baseline level in EVs, but there was a significant reduction in its copy number in the cellular component during 7 days. Taken together, given to the acceptable stability, EVs could be introduced as a non-invasive liquid biopsy that alongside existing methods could remarkably change the paradigm of APL diagnostic approaches.

PML-RARA transcript levels at the end of induction therapy are associated with prognosis in non-high-risk acute promyelocytic leukaemia with all-trans retinoic acid plus arsenic in front-line therapy: long-term follow-up of a single-centre cohort study

Despite the high cure probability for acute promyelocytic leukaemia (APL), a minority of patients will relapse and the risk factors for relapse are unclear. We retrospectively analysed 212 patients who were diagnosed with non-high-risk APL and received all-trans retinoic acid (ATRA) plus arsenic as front-line therapy at Peking University Institute of Hematology from February 2014 to December 2018. A total of 176 patients (83%) received oral arsenic (realgar-indigo naturalis formula) plus ATRA, 36 patients (17%) received arsenic trioxide plus ATRA and 203 patients were evaluable for relapse. After a median (range) follow-up of 53·6 (24·3-85·4) months, two patients had molecular relapse and eight had haematological relapse. A promyelocytic leukaemia/retinoic acid receptor alpha (PML-RARA) transcript level of ≥6·5% at the end of induction therapy was associated with relapse (P = 0·031). The 5-year cumulative incidence of relapse, event-free survival and overall survival were 5·5%, 92·3% and 96·3% respectively. In conclusion, the present long-term follow-up study further confirmed the high cure probability of ATRA plus oral arsenic as front-line therapy for non-high-risk APL and showed that the PML-RARA transcript level at the end of induction therapy was associated with relapse.

Pre-transplant minimal residual disease assessment and transplant-related factors predict the outcome of acute myeloid leukemia patients undergoing allogeneic stem cell transplantation

We studied pretransplant minimal residual disease (MRD) in 224 patients (median age 44 years; range 17-65) with acute myeloid leukemia (AML) undergoing allogeneic stem cell transplant (HSCT) in complete remission. MRD was evaluated on marrow samples using multicolor flow cytometry and assessment of WT1 gene expression. Both methods showed a strong prognostic value and their combination allowed the identification of three groups of patients with different risk of relapse. In multivariate analysis, combined MRD was the only predictor of cumulative incidence of relapse, regardless of donor type, conditioning regimen, first or second CR at HSCT, HSCT year, and ELN risk group. Multivariate regression model showed that only negative combined MRD status (P < .001) and myeloablative conditioning (P = .004) were independently associated with better OS. Among MRD-positive patients, a reduced incidence of relapse was observed in patients receiving haplo transplant (P < .05) and in patients who showed grade II-IV aGVHD (P < .03). In patients with negative combined MRD, the intensity of conditioning regimen did not affect the overall favorable outcome. We suggest that pretransplant MRD evaluation combined with transplant-related factors can identify AML patients at higher risk for relapse and might help in defining the overall transplant strategy.

Evaluation of arsenic species in leukocytes and granulocytes of acute promyelocytic leukemia patients treated with arsenic trioxide

Concentrations of arsenic metabolites were important to clarify the sensitivity and resistance of APL (acute promyelocytic leukemia) patients to arsenic trioxide (As₂O₃). Our purpose was to evaluate levels and distributions of arsenic species in leukocytes and granulocytes of APL patients. Inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured by high performance liquid chromatography coupled inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Leukocytes were collected from 21 patients treated with As₂O₃ during induction, consolidation, and drug-withdrawal period. The upregulation of granulocytes in induction period was closely related to the differentiation of promyelocytes. Therefore, granulocytes were collected during induction period from 4 APL patients and purified by flow cytometry sorting using a panel of monoclonal antibodies specific for CD45, CD3, CD14, and CD19. The developed HPLC-ICP-MS method was precise and accurate with the limit of quantification of 0.5 ng/mL. During induction, consolidation, and drug-withdrawal period, the general trend of arsenic species was iAs > MMA > DMA (P < 0.05) in leukocytes. iAs was predominant arsenic species with median concentration of 10.84 (6.03-14.62) ng/mL. MMA was major methylated metabolite with median concentration of 0.94 (0.60-2.50) ng/mL. Moreover, arsenicals were detected in leukocytes during drug-withdrawal. In granulocytes, iAs was found during induction period with median concentration of 1.08 ng/mL, while MMA and DMA were not detected. These results showed that iAs was the primary arsenic species in leukocytes and granulocytes from APL patients treated with As₂O₃. This study suggested that iAs might play a dominant therapeutic role during the whole treatment process of APL.

Minimal residual disease monitoring in acute myeloid leukemia with non-A/B/D-NPM1 mutations by digital polymerase chain reaction: feasibility and clinical use

Not available.

Clinical implications of sequential MRD monitoring by NGS at 2 time points after chemotherapy in patients with AML

Next-generation sequencing (NGS) has been applied to measurable/minimal residual disease (MRD) monitoring after induction chemotherapy in patients with acute myeloid leukemia (AML), but the optimal time point for the test remains unclear. In this study, we aimed to investigate the clinical significance of NGS MRD at 2 different time points. We performed targeted NGS of 54 genes in bone marrow cells serially obtained at diagnosis, first complete remission (first time point), and after the first consolidation chemotherapy (second time point) from 335 de novo AML patients. Excluding DNMT3A, TET2, and ASXL1 mutations, which are commonly present in individuals with clonal hematopoiesis of indeterminate potential, MRD could be detected in 46.4% of patients at the first time point (MRD1st), and 28.9% at the second time point (MRD2nd). The patients with detectable NGS MRD at either time point had a significantly higher cumulative incidence of relapse and shorter relapse-free survival and overall survival. In multivariate analysis, MRD1st and MRD2nd were both independent poor prognostic factors. However, the patients with positive MRD1st but negative MRD2nd had a similar good prognosis as those with negative MRD at both time points. The incorporation of multiparameter flow cytometry and NGS MRD revealed that the presence of NGS MRD predicted poorer prognosis among the patients without detectable MRD by multiparameter flow cytometry at the second time point but not the first time point. In conclusion, the presence of NGS MRD, especially after the first consolidation therapy, can help predict the clinical outcome of AML patients.

Acute Myeloid Leukemia: Historical Perspective and Progress in Research and Therapy Over 5 Decades

With the Food and Drug Administration approval of 9 agents for different acute myeloid leukemia (AML) indications, the prognosis and management of AML is evolving rapidly. Herein, we review the important milestones in the history of AML research and therapy, discuss insights regarding prognostic assessment and prediction of treatment outcome, detail practical supportive care measures, and summarize the current treatment landscape and areas of evolving research.

Measurable Residual Disease Detected by Multiparameter Flow Cytometry and Sequencing Improves Prediction of Relapse and Survival in Acute Myeloid Leukemia

The clinically ideal time point and optimal approach for the assessment of measurable residual disease (MRD) in patients with acute myeloid leukemia (AML) are still inconclusive. We investigated the clinical value of multiparameter flow cytometry-based MRD (MFC MRD) after induction (n = 492) and two cycles of consolidation (n = 421). The latter time point was proved as a superior indicator with independent prognostic significance for both relapse-free survival (RFS, HR = 3.635, 95% CI: 2.433-5.431, P <0.001) and overall survival (OS: HR = 3.511, 95% CI: 2.191-5.626, P <0.001). Furthermore, several representative molecular MRD markers were compared with the MFC MRD. Both approaches can establish prognostic value in patients with NPM1 mutations, and FLT3, C-KIT, or N-RAS mutations involved in kinase-related signaling pathways, while the combination of both techniques further refined the risk stratification. The detection of RUNX1-RUNX1T1 fusion transcripts achieved a considerable net reclassification improvement in predicting the prognosis. Conversely, for patients with biallelic CEBPA or DNMT3A mutations, only the MFC method was recommended due to the poor prognostic discriminability in tracking mutant transcripts. In conclusion, this study demonstrated that the MFC MRD after two consolidation cycles independently predicted clinical outcomes, and the integration of MFC and molecular MRD should depend on different types of AML-related genetic lesions.

Integration of Genomic and Transcriptomic Markers Improves the Prognosis Prediction of Acute Promyelocytic Leukemia

PURPOSE

The current stratification system for acute promyelocytic leukemia (APL) is based on the white blood cell (WBC) and the platelet counts (i.e., Sanz score) over the past two decades. However, the borderlines among different risk groups are sometimes ambiguous, and for some patients, early death and relapse remained challenges. Besides, with the evolving of the treatment strategy from all-trans-retinoic acid (ATRA) and chemotherapy to ATRA-arsenic trioxide-based synergistic targeted therapy, the precise risk stratification with molecular markers is needed.

EXPERIMENTAL DESIGN

This study performed a systematic analysis of APL genomics and transcriptomics to identify genetic abnormalities in 348 patients mainly from the APL2012 trial (NCT01987297) to illustrate the potential molecular background of Sanz score and further optimize it. The least absolute shrinkage and selection operator algorithm was used to analyze the gene expression in 323 cases to establish a scoring system (i.e., APL9 score).

RESULTS

Through combining NRAS mutations, APL9 score, and WBC, 321 cases can be stratified into two groups with significantly different outcomes. The estimated 5-year overall (P = 0.00031), event-free (P < 0.0001), and disease-free (P = 0.001) survival rates in the revised standard-risk group (95.6%, 93.8%, and 98.1%, respectively) were significantly better than those in the revised high-risk group (82.9%, 77.4%, and 88.4%, respectively), which could be validated using The Cancer Genome Atlas dataset.

CONCLUSIONS

We have proposed a two-category system for improving prognosis in patients with APL. Molecular markers identified in this study may also provide genomic insights into the disease mechanism for improved therapy.

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.

Measurable residual disease as a biomarker in acute myeloid leukemia: theoretical and practical considerations

Several methodologies that rely on the detection of immunophenotypic or molecular abnormalities of the neoplastic cells are now available to quantify measurable ("minimal") residual disease (MRD) in acute myeloid leukemia (AML). Although the perfect MRD test does not (yet) exist, the strong association between MRD and adverse patient outcomes has provided the impetus to use measures of MRD as biomarker in the routine care of AML patients and during clinical trials. MRD test results may inform the selection of postremission therapy in some patients but evidence supporting the use of MRD as predictive biomarker is still limited. Several retrospective studies have shown that conversion from undetectable to detectable MRD or increasing MRD over time is associated with overt disease recurrence, and MRD testing may therefore be valuable as a monitoring biomarker for early detection of relapse. Interpreting serial MRD data is complex, with open questions regarding the optimal timing and frequency of testing, as well as the identification of test-specific thresholds to define relapse. Importantly, it is unknown whether intervening at the time of MRD detection, rather than at overt disease recurrence, improves outcomes. Finally, using MRD as a surrogate efficacy-response biomarker to accelerate drug development/approval has already been accepted by regulatory authorities in other diseases and is of great interest as a potential strategy in AML. While the prognostic value of MRD in AML is well established, data from prospective clinical trials confirming that treatment effects on MRD directly relate to clinical outcomes are needed to further establish the role of MRD as a surrogate endpoint in AML.

Acute myeloid leukemia: Treatment and research outlook for 2021 and the MD Anderson approach

The unraveling of the pathophysiology of acute myeloid leukemia (AML) has resulted in rapid translation of the information into clinical practice. After more than 40 years of slow progress in AML research, the US Food and Drug Administration has approved nine agents for different AML treatment indications since 2017. In this review, we detail the progress that has been made in the research and treatment of AML, citing key publications related to AML research and therapy in the English literature since 2000. The notable subsets of AML include acute promyelocytic leukemia (APL), core-binding factor AML (CBF-AML), AML in younger patients fit for intensive chemotherapy, and AML in older/unfit patients (usually at the age cutoff of 60-70 years). We also consider within each subset whether the AML is primary or secondary (therapy-related, evolving from untreated or treated myelodysplastic syndrome or myeloproliferative neoplasm). In APL, therapy with all-trans retinoic acid and arsenic trioxide results in estimated 10-year survival rates of ≥80%. Treatment of CBF-AML with fludarabine, high-dose cytarabine, and gemtuzumab ozogamicin (GO) results in estimated 10-year survival rates of ≥75%. In younger/fit patients, the "3+7" regimen (3 days of daunorubicin + 7 days of cytarabine) produces less favorable results (estimated 5-year survival rates of 35%; worse in real-world experience); regimens that incorporate high-dose cytarabine, adenosine nucleoside analogs, and GO are producing better results. Adding venetoclax, FLT3, and IDH inhibitors into these regimens has resulted in encouraging preliminary data. In older/unfit patients, low-intensity therapy with hypomethylating agents (HMAs) and venetoclax is now the new standard of care. Better low-intensity regimens incorporating cladribine, low-dose cytarabine, and other targeted therapies (FLT3 and IDH inhibitors) are emerging. Maintenance therapy now has a definite role in the treatment of AML, and oral HMAs with potential treatment benefits are also available. In conclusion, AML therapy is evolving rapidly and treatment results are improving in all AML subsets as novel agents and strategies are incorporated into traditional AML chemotherapy. LAY SUMMARY: Ongoing research in acute myeloid leukemia (AML) is progressing rapidly. Since 2017, the US Food and Drug Administration has approved 10 drugs for different AML indications. This review updates the research and treatment pathways for AML.

Acute myeloid leukemia: current progress and future directions

Progress in the understanding of the biology and therapy of acute myeloid leukemia (AML) is occurring rapidly. Since 2017, nine agents have been approved for various indications in AML. These included several targeted therapies like venetoclax, FLT3 inhibitors, IDH inhibitors, and others. The management of AML is complicated, highlighting the need for expertise in order to deliver optimal therapy and achieve optimal outcomes. The multiple subentities in AML require very different therapies. In this review, we summarize the important pathophysiologies driving AML, review current therapies in standard practice, and address present and future research directions.

Patients with triple-negative, JAK2V617F- and CALR-mutated essential thrombocythemia share a unique gene expression signature

Approximately 10% to 15% of patients with essential thrombocythemia (ET) lack the common driver mutations, so-called "triple-negative" (TN) disease. We undertook a systematic approach to investigate for somatic mutations and delineate gene expression signatures in 46 TN patients and compared the results to those with known driver mutations and healthy volunteers. Deep, error-corrected, next-generation sequencing of peripheral blood mononuclear cells using the HaloPlexHS platform and whole-exome sequencing was performed. Using this platform, 10 (22%) of 46 patients had detectable mutations (MPL, n = 6; JAK2V617F, n = 4) with 3 of 10 cases harboring germline MPL mutations. RNA-sequencing and DNA methylation analysis were also performed by using peripheral blood mononuclear cells. Pathway analysis comparing healthy volunteers and ET patients (regardless of mutational status) identified significant enrichment for genes in the tumor necrosis factor, NFκB, and MAPK pathways and upregulation of platelet proliferative drivers such as ITGA2B and ITGB3. Correlation with DNA methylation showed a consistent pattern of hypomethylation at upregulated gene promoters. Interrogation of these promoter regions highlighted enrichment of transcriptional regulators, which were significantly upregulated in patients with ET regardless of mutation status, including CEBPβ and NFκB. For "true" TN ET, patterns of gene expression and DNA methylation were similar to those in ET patients with known driver mutations. These observations suggest that the resultant ET phenotype may, at least in part and regardless of mutation type, be driven by transcriptional misregulation and may propagate downstream via the MAPK, tumor necrosis factor, and NFκB pathways with resultant JAK-STAT activation. These findings identify potential novel mechanisms of disease initiation that require further evaluation.

UK Experience of an Alternative ATO Dosing Regimen in APL

The introduction of all-trans retinoic acid (ATRA), and more recently of arsenic trioxide (ATO) in the treatment of Acute Promyelocytic Leukaemia (APL), has been instrumental in achieving the high cure rates recently reported. For the majority of patients, it is now possible to successfully treat this disease “chemo-free” without the use of cytotoxic chemotherapy as reflected in current clinical guidelines. The Sanz risk score developed by the GIMEMA and PETHEMA groups categorizes patients into three risk groups—low, intermediate, and high and correlates with relapse-free survival (RFS). Low- and intermediate-risk APL are now often considered together as ‘standard-risk’ defined by a white blood cell count (WBC) of less than 10 x 10⁹/L. High-risk APL has a WBC greater than 10 x 10⁹/L. In the UK our approach for patients with standard risk APL is to treat with ATRA and ATO without the use of cytotoxic chemotherapy. This approach is based on results from two large randomized clinical trials. The GIMEMA APL0406 trial showed an overall survival advantage compared to anthracycline-based chemotherapy plus ATRA. The UK NCRI AML17 trial which used an attenuated dose of ATO demonstrated a significant reduction in relapse and improved relapse-free survival. In the UK, the National Institute for Clinical Excellence approved both ATO plus ATRA regimens for re-imbursement for standard risk Acute Promyelocytic Leukaemia (APL). We use the AML17 schedule in standard-risk patients upfront and also in patients with relapsed Acute Promyelocytic Leukaemia (APL) previously treated with chemotherapy or in those with molecular persistence. The treatment of high-risk Acute Promyelocytic Leukaemia (APL) remains an area of contention as ATO is not approved for this indication. These patients have a greater risk of complications during remission induction with ATO including differentiation syndrome. The optimal approach is to incorporate chemotherapy early into the treatment schedule with either Gemtuzumab Ozogamicin (GO) as in the high-risk arm of the NCRI AML17 trial and MD Anderson Cancer Centre studies or Idarubicin as in the Australian APML4 study.

Acute myeloid leukaemia therapeutic innovation and clinical trials: past, present and future

Outcomes in acute myeloid leukaemia have improved steadily over the last six decades thanks to advances in disease classification, risk stratification and the advent of new drug and transplant therapies. Over this period the UK has made a major contribution to this international effort, both through its delivery of large prospective randomised trials with integrated genomic and measurable residual disease assessments and its pioneering role in the development of allogeneic stem cell transplantation as a potent anti-leukaemic therapy.

Advancing leukemia diagnostics: Role of Next Generation Sequencing (NGS) in acute myeloid leukemia

AML diagnostics, initially based solely on morphological evaluation, now relies on multiple disciplines to reach its full potential. Only by integrating the results of cytomorphology, cytochemistry, immunophenotyping, cytogenetics and molecular genetics it is possible to fulfil WHO classification and ELN prognostication systems. Especially molecular genetics has gained a lot of interest over the last decade, mainly through the introduction of next generation sequencing (NGS). NGS application ranges from the investigation of single genes and panels to even whole exomes, transcriptomes and genomes. In routine AML diagnostics panels are the preferred NGS methodology. Here, we will review the power and limitations of NGS in the context of diagnosis, prognosis and precision medicine. Due to high dimensionality, NGS data interpretation is challenging but it also offers a unique investigatory chance and the opportunity to apply data mining techniques such as artificial intelligence. We will also reflect on how the incorporation of the improved knowledge base into routine diagnostics can pave the way for better treatment and more cure in AML.

Clinical and molecular consequences of fusion genes in myeloid malignancies

Leukemias are heterogeneous diseases characterized by aberrant hematopoietic stem and progenitor cells (HSPCs). Oncogenic fusion genes and proteins, produced via gross chromosomal rearrangements, such as chromosomal translocation, insertion, and inversion, play important roles in hematologic malignancies. These oncoproteins alter fundamental cellular properties, such as self-renewal, differentiation, and proliferation, and confer leukemogenic potential to HSPCs. In addition to providing fundamental insights into the process of leukemic transformation, these fusion genes provide targets for treatment and monitoring of myeloid leukemias. Furthermore, new technologies such as next-generation sequencing have allowed additional insights into the nature of leukemic fusion genes. In this review, we discuss the history, biologic effect, and clinical impact of fusion genes in the field of myeloid leukemias.

No prognostic significance of normalized copy number of PML-RARA transcript at diagnosis in patients with acute promyelocytic leukemia

BACKGROUND

Acute promyelocytic leukemia is a peculiar disease with few studies that have investigated the prognostic significance of PML/RARA transcript level at diagnosis.

PATIENTS AND METHODS

This retrospective study included all cases diagnosed with acute promyelocytic leukemia over the period from June 2015 to March 2019. The normalized copy number (NCN) was tested by real-time polymerase chain reaction at diagnosis, and at the end of induction regimen.

RESULTS

Our study included 83 de novo APL patients, 53 (63.9%) were adults and 30 (36.1%) were children. The median (range) age of our patients was 28.0 (1.0-70.0) years. The pediatric group had a significantly higher prevalence in males (p = 0.02), higher incidence of disseminated intravascular coagulopathy (p = 0.014), and high-risk groups (p = 0.017). At diagnosis, the median NCN (%) of the entire group at 22.5 was set as the cut off value. There was no significant association between NCN at diagnosis and other prognostic variables except for bone marrow promyelocytes (p = 0.006). High-risk group APL patients as well as those presenting with hemorrhage had an inferior overall survival (OS) (p = 0.007; p < 0.001) respectively. PML-RARA NCN at diagnosis did not have an impact on the OS or increased risk of relapse of our patients (p = 0.434; p = 0.721).

CONCLUSION

the initial PML/RARA tumor burden is not a prognostic factor for APL. The initial TLC at 10x10⁹/L cut off is the most important predictive for OS. Early detection and close monitoring are required to decrease the high rate of early deaths in developing countries.

Measurable residual disease after the first consolidation predicts the outcomes of patients with acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy

We stratified patients with newly diagnosed acute promyelocytic leukemia (APL) according to a white blood cell (WBC) count of ≥ 3 × 10⁹/L (high risk) or < 3 × 10⁹/L (low risk) before administering risk-adapted chemotherapy in combination with all-trans retinoic acid (ATRA). In total, 27 low-risk and 23 high-risk patients were assigned to receive induction and three courses of consolidation with ATRA and anthracycline, followed by 2-year maintenance regimen. High-risk group additionally received cytarabine during 1st consolidation and another one-shot idarubicin treatment during 3rd consolidation. We prospectively monitored measurable residual disease (MRD) after induction and each consolidation. In the low-risk and high-risk groups, 5-year disease-free survival (DFS) rates were 86.5% and 81.2% (p = 0.862), and 5-year overall survival rates were 100% and 84.8% (p = 0.062), respectively. In the MRD-negative and MRD-positive groups, 5-year DFS rates were 91.7% and 78.4% (p = 0.402) and 84.7% and 60.0% (p = 0.102) after induction and 1st consolidation, respectively. Relapse rates were 8.3% and 13.3% (p = 0.570) and 9.0% and 40.0% (p = 0.076) after induction and 1st consolidation, respectively. Achieving MRD-negativity after 1st consolidation, rather than after induction, was a potential predictor of relapse and DFS in patients with APL treated with ATRA + chemotherapy.

Acute myeloid leukemia with NPM1 mutation and favorable European LeukemiaNet category: outcome after preemptive intervention based on measurable residual disease

In the European LeukemiaNet favourable risk category, allogeneic haematopoietic stem cell transplantation (alloSCT) is not indicated in first complete remission for patients with acute myeloid leukaemia (AML) with NPM1 mutations (ELNfav NPM1 AML), although a proportion of these patients will relapse. Given the prognostic importance of measurable residual disease (MRD), CETLAM-12 considered a pre-emptive intervention in patients with molecular failure (MF). We analyzed 110 ELNfav NPM1 AML patients achieving complete remission (CR) after induction chemotherapy. Two-year cumulative incidence of relapse (CIR), overall survival (OS) and leukaemia-free survival (LFS) were 17%, 81·5% and 82%, respectively. Forty-six patients required additional therapy for MF (n = 33) or haematological relapse (HemR; n = 13), resulting in a molecular LFS (molLFS) and a cumulative incidence of MF at two years of 61% and 38% respectively. Two-year OS for these 46 patients was 66%, with a different outcome between patients with MF (86%) and HemR (42%) (P = 0·002). Quantitative NPM1 detection at different timepoints was predictive of molLFS; an MRD ratio (NPM1mut/ABL1 × 100) cut-off of 0·05 after first consolidation identified two cohorts with a two-year molLFS of 77% and 40% for patients below and above 0·05, respectively. In conclusion, MRD-based pre-emptive intervention resulted in a favourable outcome for ELNfav NPM1 AML patients.