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Measurable residual disease (MRD) is associated with relapse and survival in acute myeloid leukemia (AML). We aimed to quantify the impact of MRD on outcomes across clinical contexts, including its association with hematologic response and MRD assay sensitivity. We performed systematic literature review and meta-analysis of 48 studies that reported the association between MRD and overall survival (OS) or disease-free survival (DFS) in AML and provided information on the MRD threshold used and the hematologic response of the study population. Among studies limited to patients in complete remission (CR), the estimated 5-year OS for the MRD-negative and MRD-positive groups was 67% (95% Bayesian credible interval [CrI], 53-77%) and 31% (95% CrI, 18-44%), respectively. Achievement of an MRD-negative response was associated with superior DFS and OS, regardless of MRD threshold or analytic sensitivity. Among patients in CR, the benefit of MRD negativity was highest in studies using an MRD cutoff less than 0.1%. The beneficial impact of MRD negativity was observed across MRD assays and timing of MRD assessment. In patients with AML in morphological remission, achievement of MRD negativity is associated with superior DFS and OS, irrespective of hematologic response or the MRD threshold used.

Liposomal daunorubicin and cytarabine (CPX-351) improves overall survival (OS) compared to 7+3 chemotherapy in older patients with secondary acute myeloid leukaemia (AML); to date there have been no randomized studies in younger patients. The high-risk cohort of the UK NCRI AML19 trial (ISRCTN78449203) compared CPX-351 with FLAG-Ida in younger adults with newly-diagnosed adverse cytogenetic AML or high-risk myelodysplastic syndromes (MDS). 189 patients were randomized (median age 56y). By clinical criteria 49% had de novo AML, 20% secondary AML and 30% high risk MDS. MDS-related cytogenetics were present in 73% of patients, with complex karyotype in 49%. TP53 was the most commonly mutated gene, in 43%. Myelodysplasia-related gene mutations were present in 75 patients (44%). The overall response rate (CR + CRi) after course two was 64% and 76% for CPX-351 and FLAG-Ida (OR:0.54, 95%CI 0.28-1.04, p=0.06). There was no difference in OS (13.3 months vs 11.4 months, HR:0.78, 95%CI 0.55-1.12, p=0.17) or event-free survival (HR:0.90, 95%CI 0.64-1.27, p=0.55) in multivariable analyses. However, relapse-free survival was significantly longer with CPX-351 (median 22.1 vs 8.35 months, HR:0.58, 95% CI 0.36-0.95, p=0.03). There was no difference between the treatment arms in patients with clinically defined secondary AML (HR:1.1, 95%CI 0.52-2.30) or those with MDS-related cytogenetic abnormalities (HR:0.94, 95%CI 0.63-1.40), however an exploratory sub-group of patients with MDS-related gene mutations had significantly longer OS with CPX-351 (median 38.4 vs 16.3 months, HR:0.42, 95%CI 0.21-0.84, heterogeneity p=0.05). In conclusion, OS in younger patients with adverse risk AML/MDS was not significantly different between CPX-351 and FLAG-Ida.

Allogeneic stem-cell transplantation allows the delivery of curative graft-versus-leukemia (GVL) in patients with acute myeloid leukemia/myelodysplasia (AML/MDS). Surveillance of T-cell chimerism, measurable residual disease (MRD) and blast HLA-DR expression may inform whether GVL effectiveness is reduced. We report the prognostic impact of these biomarkers in patients allografted for AML/MDS. 187 patients from FIGARO, a randomized trial of reduced-intensity conditioning regimens in AML/MDS, were alive and relapse-free, at the first MRD timepoint and provided bone marrow for flow cytometric MRD monitoring and blood samples for T-cell chimerism analysis, requested to month+12. 29 (15.5%) patients had at least one MRD-positive result post-transplant. MRD-positivity was associated with reduced overall survival (OS) (HR:2.18, p=0.0028) as a time-varying Cox variable and remained significant irrespective of pre-transplant MRD status in multivariate analyses (p

Reduced intensity conditioning (RIC) transplantation is increasingly offered to older patients with acute myeloblastic leukemia. We have previously shown that a RIC allograft, particularly from a sibling donor, is beneficial in intermediate-risk patients aged 35-65 years. We here present analyses from the NCRI AML16 trial extending this experience to older patients aged 60-70 inclusive lacking favorable-risk cytogenetics. Nine hundred thirty-two patients were studied, with RIC transplant in first remission given to 144 (sibling n=52, matched unrelated donor n=92) with a median follow-up for survival from complete remission of 60 months. Comparisons of outcomes of patients transplanted versus those not were carried out using Mantel-Byar analysis. Among the 144 allografted patients, 93 had intermediate-risk cytogenetics, 18 had adverse risk and cytogenetic risk group was unknown for 33. In transplanted patients survival was 37% at 5 years, and while the survival for recipients of grafts from siblings (44%) was better than that for recipients of grafts from matched unrelated donors (34%), this difference was not statistically significant (P=0.2). When comparing RIC versus chemotherapy, survival of patients treated with the former was significantly improved (37% versus 20%, hazard ratio = 0.67 [0.53-0.84]; P

PURPOSE The optimum number of treatment courses for younger patients with acute myeloid leukemia (AML) is uncertain. The United Kingdom National Cancer Research Institute AML17 trial randomly assigned patients who were not high risk to a total of three versus four courses. PATIENTS AND METHODS Patients received two induction courses based on daunorubicin and cytarabine (Ara-C), usually with gemtuzumab ozogamicin. Following remission, 1,017 patients were randomly assigned to a third course, MACE (amsacrine, Ara-C, and etoposide), plus a fourth course of MidAc (mitoxantrone and Ara-C) and following an amendment to one or two courses of high-dose Ara-C. Primary end points were cumulative incidence of relapse (CIR), relapse-free survival (RFS), and overall survival (OS). Outcomes were correlated with patient characteristics, mutations, cytogenetics, induction treatments, and measurable residual disease (MRD) postinduction. RESULTS In logrank analyses, CIR and RFS at 5 years were improved in recipients of four courses (50% v 58%: hazard ratio [HR] 0.81 [0.69-0.97], P = .02 and 43% v 36%: HR 0.83 [0.71-0.98], P = .03, respectively). While OS was not significantly better (63% v 57%: HR 0.84 [0.69-1.03], P = .09), the noninferiority of three courses to four courses was not established. The impact on relapse was only significant when the fourth course was Ara-C. In exploratory analyses, although MRD impacted survival, a fourth course had no effect in either MRD-positive or MRD-negative patients. A fourth course was beneficial in patients who lacked a mutation of FLT3 or NPM1, had < 3 mutations in other genes, or had a presenting WBC of < 10 × 109 L−1. CONCLUSION Although a fourth course of high-dose Ara-C reduced CIR and improved RFS, it did not result in a significant OS benefit. Subsets including those with favorable cytogenetics, those lacking a mutation of FLT3 or NPM1, or those with < 3 other mutations may derive survival benefit.

PURPOSE Reduced-intensity conditioning (RIC) regimens have extended the curative potential of allogeneic stem-cell transplantation to older adults with high-risk acute myeloid leukemia (AML) and myelodysplasia (MDS) but are associated with a high risk of disease relapse. Strategies to reduce recurrence are urgently required. Registry data have demonstrated improved outcomes using a sequential transplant regimen, fludarabine/amsacrine/cytarabine-busulphan (FLAMSA-Bu), but the impact of this intensified conditioning regimen has not been studied in randomized trials. PATIENTS AND METHODS Two hundred forty-four patients (median age, 59 years) with high-risk AML (n = 164) or MDS (n = 80) were randomly assigned 1:1 to a fludarabine-based RIC regimen or FLAMSA-Bu. Pretransplant measurable residual disease (MRD) was monitored by flow cytometry (MFC-MRD) and correlated with outcome. RESULTS There was no difference in 2-year overall survival (hazard ratio 1.05 [85% CI, 0.80 to 1.38] P = .81) or cumulative incidence of relapse (CIR) (hazard ratio 0.94 [95%CI, 0.60 to 1.46] P = .81) between the control and FLAMSA-Bu arms. Detectable pretransplant MFC-MRD was associated with an increased CIR (2-year CIR 41.0% v 20.0%, P = .01) in the overall trial cohort with a comparable prognostic impact when measured by an unsupervised analysis approach. There was no evidence of interaction between MRD status and conditioning regimen intensity for relapse or survival. Acquisition of full donor T-cell chimerism at 3 months abrogated the adverse impact of pretransplant MRD on CIR and overall survival. CONCLUSION The intensified RIC conditioning regimen, FLAMSA-Bu, did not improve outcomes in adults transplanted for high-risk AML or MDS regardless of pretransplant MRD status. Our data instead support the exploration of interventions with the ability to accelerate acquisition of full donor T-cell chimerism as a tractable strategy to improve outcomes in patients allografted for AML.

In this issue of Blood, Murdock et al(1) apply extensive diagnostic molecular profiling and measurable residual disease (MRD) detection of persistent mutations in a real-world cohort of older adults with acute myeloid leukemia (AML) to extract the most useful predictors of relapse-free survival (RFS) after allogeneic transplantation in first remission. Their results indicate that molecular persistence in remission is frequent in older adults and does not retain prognostic value for posttransplant outcomes after adjusting for specific baseline molecular and clinical variables.

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.

Leukaemic stem cells (LSC) have been experimentally defined as the leukaemia-propagating population and are thought to be the cellular reservoir of relapse in acute myeloid leukaemia (AML). Therefore, LSC measurements are warranted to facilitate accurate risk stratification. Previously, we published the composition of a one-tube flow cytometric assay, characterised by the presence of 13 important membrane markers for LSC detection. Here we present the validation experiments of the assay in several large AML research centres, both in Europe and the United States. Variability within instruments and sample processing showed high correlations between different instruments (Rpearson > 0·91, P high (>0·03% LSC) from LSClow (

MRD technologies increase our ability to measure response in acute myeloid leukemia (AML) beyond the limitations of morphology. When applied in clinical trials, molecular and immunophenotypic MRD assays have improved prognostic precision, providing a strong rationale for their use to guide treatment, as well as to measure its effectiveness. Initiatives such as those from the European Leukemia Network now provide a collaborative knowledge-based framework for selection and implementation of MRD assays most appropriate for defined genetic subgroups. For patients with mutated-NPM1 AML, quantitative polymerase chain reaction (qPCR) monitoring of mutated-NPM1 transcripts postinduction and sequentially after treatment has emerged as a highly sensitive and specific tool to predict relapse and potential benefit from allogeneic transplant. Flow cytometric MRD after induction is prognostic across genetic risk groups and can identify those patients in the wild-type NPM1 intermediate AML subgroup with a very high risk for relapse. In parallel with these data, advances in genetic profiling have extended understanding of the etiology and the complex dynamic clonal nature of AML, as well as created the opportunity for MRD monitoring using next-generation sequencing (NGS). NGS AML MRD detection can stratify outcomes and has potential utility in the peri-allogeneic transplant setting. However, there remain challenges inherent in the NGS approach of multiplex quantification of mutations to track AML MRD. Although further development of this methodology, together with orthogonal testing, will clarify its relevance for routine clinical use, particularly for patients lacking a qPCR genetic target, established validated MRD assays can already provide information to direct clinical practice.

PURPOSE: Patients with acute myeloid leukemia (AML) in remission remain at risk for relapse even after allogeneic hematopoietic cell transplantation (alloHCT). AML measurable residual disease (MRD) status before alloHCT has been shown to be prognostic. Whether modulation of the intensity of the alloHCT conditioning regimen in patients with AML who test positive for MRD can prevent relapse and improve survival is unknown. METHODS: Ultra-deep, error-corrected sequencing for 13 commonly mutated genes in AML was performed on preconditioning blood from patients treated in a phase III clinical trial that randomly assigned adult patients with myeloid malignancy in morphologic complete remission to myeloablative conditioning (MAC) or reduced-intensity conditioning (RIC). RESULTS: No mutations were detected in 32% of MAC and 37% of RIC recipients; these groups had similar survival (3-year overall survival [OS], 56% v 63%; P = .96). In patients with a detectable mutation (next-generation sequencing [NGS] positive), relapse (3-year cumulative incidence, 19% v 67%; P < .001) and survival (3-year OS, 61% v 43%; P = .02) was significantly different between the MAC and RIC arms, respectively. In multivariable analysis for NGS-positive patients, adjusting for disease risk and donor group, RIC was significantly associated with increased relapse (hazard ratio [HR], 6.38; 95% CI, 3.37 to 12.10; P < .001), decreased relapse-free survival (HR, 2.94; 95% CI, 1.84 to 4.69; P < .001), and decreased OS (HR, 1.97; 95% CI, 1.17 to 3.30; P = .01) compared with MAC. Models of AML MRD also showed benefit for MAC over RIC for those who tested positive. CONCLUSION: This study provides evidence that MAC rather than RIC in patients with AML with genomic evidence of MRD before alloHCT can result in improved survival.

Introduction Measurements of residual leukemia strongly correlate with survival, as well as relapse, in patients with acute myeloid leukemia (AML) and, therefore, when used appropriately with other prognostic variables, provide an opportunity to improve their treatment. However, the deployment and interpretation of measurable residual disease (MRD) tests in AML can be challenging, reflecting heterogeneity not only in the disease but also in the assays. Of the various technologies in use, multi-parameter flow cytometry (MFC) is arguably the most accessible and can be used to detect MRD by identification of abnormal leukemic immunophenotypes at a single-cell level in over 90% of patients, with a sensitivity of 10–3 to 10–4. MFC was the MRD methodology applied in 6,115 of the 11,151 patients in remission, as analyzed by the recently published meta-analysis of AML MRD studies.1 Since the first study in 2001,2 MFC-MRD has been extensively clinically validated, with its independent prognostic value most established after standard frontline chemotherapy and prior to allogeneic stem cell transplant. MFC-MRD has also been incorporated into trials of randomized treatment comparisons and MRD-directed therapy. Furthermore, guidelines for its use have been available since 2018,3 with an update forthcoming.

Measurable residual disease (MRD) is an important biomarker in acute myeloid leukemia (AML) that is used for prognostic, predictive, monitoring, and efficacy-response assessments. The European LeukemiaNet (ELN) MRD Working Party evaluated standardization and harmonization of MRD in an ongoing manner and has updated the 2018 ELN MRD recommendations based on significant developments in the field. New and revised recommendations were established during in-person and online meetings, and a 2-stage Delphi poll was conducted to optimize consensus. All recommendations are graded by levels of evidence and agreement. Major changes include technical specifications for next-generation sequencing-based MRD testing and integrative assessments of MRD irrespective of technology. Other topics include use of MRD as a prognostic and surrogate end point for drug testing; selection of the technique, material, and appropriate time points for MRD assessment; and clinical implications of MRD assessment. In addition to technical recommendations for flow- and molecular-MRD analysis, we provide MRD thresholds and define MRD response, and detail how MRD results should be reported and combined if several techniques are used. MRD assessment in AML is complex and clinically relevant, and standardized approaches to application, interpretation, technical conduct, and reporting are of critical importance.

Importance Measurable residual disease (MRD) refers to neoplastic cells that cannot be detected by standard cytomorphologic analysis. In patients with acute myeloid leukemia (AML), determining the association of MRD with survival may improve prognostication and inform selection of efficient clinical trial end points. Objective To examine the association between MRD status and disease-free survival (DFS) and overall survival (OS) in patients with AML using scientific literature. Data Sources Clinical studies on AML published between January 1, 2000, and October 1, 2018, were identified via searches of PubMed, Embase, and MEDLINE. Study Selection Literature search and study screening were performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Studies that assessed DFS or OS by MRD status in patients with AML were included. Reviews, non–English-language articles, and studies reporting only outcomes after hematopoietic cell transplantation or those with insufficient description of MRD information were excluded. Data Extraction and Synthesis Study sample size, median patient age, median follow-up time, MRD detection method, MRD assessment time points, AML subtype, specimen source, and survival outcomes were extracted. Meta-analyses were performed separately for DFS and OS using bayesian hierarchical modeling. Main Outcomes and Measures Meta-analyses of survival probabilities and hazard ratios (HRs) were conducted for OS and DFS according to MRD status. Results Eighty-one publications reporting on 11 151 patients were included. The average HR for achieving MRD negativity was 0.36 (95% bayesian credible interval [CrI], 0.33-0.39) for OS and 0.37 (95% CrI, 0.34-0.40) for DFS. The estimated 5-year DFS was 64% for patients without MRD and 25% for those with MRD, and the estimated OS was 68% for patients without MRD and 34% for those with MRD. The association of MRD negativity with DFS and OS was significant for all subgroups, with the exception of MRD assessed by cytogenetics or fluorescent in situ hybridization. Conclusions and Relevance The findings of this meta-analysis suggest that achievement of MRD negativity is associated with superior DFS and OS in patients with AML. The value of MRD negativity appears to be consistent across age groups, AML subtypes, time of MRD assessment, specimen source, and MRD detection methods. These results support MRD status as an end point that may allow for accelerated evaluation of novel therapies in AML.

Relapse remains the most common cause of treatment failure for patients with acute myeloid leukemia (AML) who undergo allogeneic stem cell transplantation (alloSCT), and carries a grave prognosis. Multiple studies have identified the presence of measurable residual disease (MRD) assessed by flow cytometry before alloSCT as a strong predictor of relapse, but it is not clear how these findings apply to patients who test positive in molecular MRD assays, which have far greater sensitivity. We analyzed pretransplant blood and bone marrow samples by reverse-transcription polymerase chain reaction in 107 patients with NPM1-mutant AML enrolled in the UK National Cancer Research Institute AML17 study. After a median follow-up of 4.9 years, patients with negative, low (

Measurable residual disease (MRD; previously termed minimal residual disease) is an independent, postdiagnosis, prognostic indicator in acute myeloid leukemia (AML) that is important for risk stratification and treatment planning, in conjunction with other well-established clinical, cytogenetic, and molecular data assessed at diagnosis. MRD can be evaluated using a variety of multiparameter flow cytometry and molecular protocols, but, to date, these approaches have not been qualitatively or quantitatively standardized, making their use in clinical practice challenging. The objective of this work was to identify key clinical and scientific issues in the measurement and application of MRD in AML, to achieve consensus on these issues, and to provide guidelines for the current and future use of MRD in clinical practice. The work was accomplished over 2 years, during 4 meetings by a specially designated MRD Working Party of the European LeukemiaNet. The group included 24 faculty with expertise in AML hematopathology, molecular diagnostics, clinical trials, and clinical medicine, from 19 institutions in Europe and the United States.

TO THE EDITOR: Addition of the CD33-targeted immunoconjugate gemtuzumab ozogamicin (GO; Pfizer) has been shown to improve the response to standard-induction chemotherapy and results in better long-term survival in adult patients with acute myeloid leukemia (AML).[1][1] The greatest impact was

Background Early data suggest that patients undergoing salvage chemotherapy for relapsed or refractory (R/R) acute myeloid leukaemia (AML) have poor outcomes if infected with SARS-CoV-2, and nosocomial transmission has been a major problem worldwide. Gilteritinib is effective in R/R FLT3 mutated AML, is significantly less immunosuppressive and does not require hospital admission, however at the start of the pandemic this was not yet approved for routine use in all countries. In the United Kingdom, the National Health Service (NHS) made gilteritinib available as an emergency measure from late April 2020 to patients aged >16y with R/R FLT3 mutated AML, with the aim of reducing both mortality and healthcare resource use. We report a health-system-wide real world data collection for toxicity and patient outcomes across 27 NHS Hospitals. Methods Each patient was registered on a central NHS database, with clinicians certifying that their patient met the above criteria. Anonymised data were retrospectively collected by treating physicians. Gilteritinib dose, duration and toxicity information was requested for the first 4 cycles of therapy. Response definitions were as per European Leukaemia Network (ELN) guidelines. A total of 81 patients have been registered on the scheme, with outcomes reported here for those with follow-up information at a data cut on 1st August 2021. Results Fifty patients were included with a median age of 59y (range 19 - 77) and 50% male. The majority (83%) had an ECOG performance status of 0-1. AML was secondary to a previous haematological disorder in 12%, therapy-related in 4% and de novo in the remaining 84%. The disease was refractory to the last therapy in 38%. Most patients had previously received 1 (65%) or 2 (33%) lines of therapy, including intensive chemotherapy in a majority (86%). A FLT3 inhibitor had previously been administered to 45% and 35% were post allogeneic transplant. The FLT3 mutation was an internal tandem duplication (ITD) in 80% and tyrosine kinase domain (TKD) mutation in 22%. NPM1 mutations were detected in 34%. Next-generation sequencing results were available for 94% of patients, with mutations in IDH1 or IDH2 in 12.5%, ASXL1 in 2%, RUNX1 in 21% and no TP53 mutations. Patients spent a median 3.5 days in hospital in cycle 1, 0 days in cycles 2 and 3 and 1 day in cycle 4. In cycles 1, 2, 3 and 4, the median number of days of grade 4 neutropenia was 18, 7, 7.5, and 6.5 respectively, and the grade 4 thrombocytopenia was 2, 7, 0.5 and 0.5. The composite complete remission (CR) / CR with incomplete haematological recovery (CRi) rate was 27%. MRD data is being collected. The best response was morphological leukaemia free state (MLFS) in 4%, partial remission (PR) in 25% and refractory disease in 38%. The rate of combined CR/CRi did not differ in those with previous exposure to FLT3 inhibitors (23% vs 32%, p=0.6) or with past allogeneic transplant (29% vs 27%, p=0.3). There were no CR/CRi in patients with adverse cytogenetic risk. Median follow-up was 10.5 months (95%CI 7.3 - 12.3) with median overall survival (OS) 6.7 months (95%CI 4.5 - not reached). Mortality at day 30 was 0% and day 60 was 14%. 12-month overall survival was 38%. Patients who achieved a CR/CRi had a 12-month OS of 83%, and for PR this was 35%. Survival did not differ in those with previous FLT3 inhibitor exposure (HR 1.0, p>0.9) or allogeneic transplant (HR 0.63, p=0.3). Seven patients (14%) so far have been bridged with gilteritinib to allogeneic transplant. Conclusion Our data demonstrate that gilteritinib is well tolerated and clinically active in adults with relapsed FLT3 mutated AML. Importantly, during the COVID-19 pandemic, its availability has permitted the great majority of treatment to be delivered as an outpatient with significant resource saving at a time of critically constrained inpatient resources. Patients who achieve CR/CRi have good short-term outcomes and are able to proceed to a potentially curative allogeneic stem cell transplant. Figure 1 Figure 1. Disclosures Belsham: Celgene: Other: meeting attendance; Abbvie: Other: meeting attendance. Byrne: Incyte: Honoraria. Khan: Abbvie: Honoraria; Astellas: Honoraria; Takeda: Honoraria; Jazz: Honoraria; Gilead: Honoraria; Novartis: Honoraria. Khwaja: Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Latif: Kite: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Speakers Bureau; Takeda UK: Speakers Bureau. Loke: Amgen: Honoraria; Daichi Sankyo: Other: Travel Support; Janssen: Honoraria; Novartis: Other: Travel Support; Pfizer: Honoraria. Munisamy: Jazz Pharmaceuticals: Speakers Bureau; Roche: Speakers Bureau. Murthy: Abbvie: Other: support to attend educational conferences.. Smith: Daiichi Sankyo: Speakers Bureau; Pfizer: Speakers Bureau; ARIAD: Honoraria. Craddock: Novartis Pharmaceuticals: Other: Advisory Board ; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding. Dillon: Amgen: Other: Research support (paid to institution); Astellas: Consultancy, Other: Educational Events , Speakers Bureau; Menarini: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Session chair (paid to institution), Speakers Bureau; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: educational events; Jazz: Other: Education events; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research Support, Educational Events.

Background Based on early evidence of a high rate of coronavirus mortality in patients with acute myeloid leukaemia (AML) undergoing intensive chemotherapy (IC), the national health service (NHS) in the United Kingdom temporarily made venetoclax available as an alternative therapy, with the aim of reducing both mortality and healthcare resource use. From late April 2020, venetoclax was available to patients aged >16y with NPM1 mutation without FLT3 internal tandem duplication (ITD), patients aged >50y with NPM1, IDH1 or IDH2 mutations (regardless of FLT3 status) and patients aged >60y without favourable-risk cytogenetics. Venetoclax could be given with either azacitidine or low-dose cytarabine (LDAC), with the latter recommended mainly for patients with NPM1 mutation. We report a health-system-wide real world data collection for toxicity and patient outcomes across 65 NHS Hospitals. Methods Each patient was registered on a central NHS database. Clinicians certified that their patient met the above criteria, had not received previous AML treatment, and was fit for induction chemotherapy. Anonymised data were retrospectively collected by treating physicians. Venetoclax dose, duration and toxicity information was requested for the first 4 cycles of therapy. Response definitions were as per European Leukaemia Network (ELN) guidelines. A total of 870 patients have been registered on the scheme, with outcomes reported here for those with follow-up information at a data cut on 1st August 2021. Results There were 301 patients, median age 72y (range 34 - 90) with 62% male. The majority (81%) had an ECOG performance status of 0-1. AML was secondary to a previous haematological disorder in 33%, therapy-related in 10% and de novo in the remaining 57%. MRC cytogenetic risk was intermediate in 70% and adverse in 27%. NPM1 mutations were detected in 28% and FLT3-ITD in 12%. Next-generation sequencing results were available in 86% of patients, which detected mutations in IDH1 or IDH2 in 28%, ASXL1 in 20%, RUNX1 in 17% and TP53 in 12%. The ELN risk was favourable for 23%, intermediate for 30% and adverse for 44%. A majority received venetoclax in combination with azacitidine (85%), with the remaining 15% receiving LDAC. The LDAC cohort was enriched for de novo AML (76% vs 54%) and NPM1-mutated disease (56% vs 23%). Most patients (81%) followed the recommended initial schedule of venetoclax 100mg daily for 28 days in combination with posaconazole or voriconazole. Patients spent a median 14 days in hospital in cycle 1, then a median of 0 days for cycles 2-4. In cycles 1, 2, 3 and 4, the median number of days for recovery of neutrophils to >0.5x10 9/L was 33, 25, 24 and 14 respectively, and the median number of days to recovery of platelets to >50x10 9/L was 22, 3, 0 (no drop below 50) and 0. The composite complete remission (CR) / CR with incomplete haematological recovery (CRi) rate was 70%. MRD data is being collected. The best response was morphological leukaemia free state (MLFS) in 2%, partial remission in 7% and refractory disease in 11%. CR/CRi was higher in de novo (78%) compared to secondary AML (57%, p=0.02); NPM1 mutated (78% vs 67%, p=0.02) and IDH1/IDH2 mutated disease (85% vs 62%, p=0.02). ELN favourable risk patients had the highest CR/CRi rate (85%, intermediate 71%, adverse 60%, p=0.01). Median follow-up was 8.2 months (95%CI 7.8 - 9.0) with median overall survival (OS) 12.8 months (95%CI 10.9 - not reached). Mortality at day 30 was 5.7% and day 60 was 8.4%. 12-month overall survival was 51%, increasing to 71% in those who achieved CR/CRi. Survival was poorer in secondary (HR 1.9, p Conclusion This large real-world study demonstrates CR/CRi and survival rates comparable to those reported in prospective clinical trials. Importantly, during the COVID-19 pandemic, the adoption of venetoclax regimens permitted the great majority of treatment to be delivered as an outpatient with significant resource saving at a time of critically constrained inpatient resources. The data support prospective comparisons of venetoclax-based regimens to IC in fit adults with AML particularly in older patients with de novo AML, NPM1-mutated and IDH-mutated disease. Figure 1 Figure 1. Disclosures Belsham: Celgene: Other: meeting attendance; Abbvie: Other: meeting attendance. Khan: Abbvie: Honoraria; Astellas: Honoraria; Takeda: Honoraria; Jazz: Honoraria; Gilead: Honoraria; Novartis: Honoraria. Khwaja: Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Latif: Kite: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Speakers Bureau; Takeda UK: Speakers Bureau. Loke: Pfizer: Honoraria; Amgen: Honoraria; Janssen: Honoraria; Novartis: Other: Travel; Daichi Sankyo: Other: Travel. Murthy: Abbvie: Other: support to attend educational conferences.. Smith: ARIAD: Honoraria; Pfizer: Speakers Bureau; Daiichi Sankyo: Speakers Bureau. Whitmill: Daiichi-sankyo: Other: travel fees; EHA in stockholm: Other: conference support. Craddock: Novartis Pharmaceuticals: Other: Advisory Board ; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding. Dillon: Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Jazz: Other: Education events; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: educational events; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Session chair (paid to institution), Speakers Bureau; Menarini: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Other: Educational Events , Speakers Bureau; Amgen: Other: Research support (paid to institution); Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research Support, Educational Events.

Allogeneic stem-cell transplantation is an important curative strategy in acute myeloid leukaemia (AML) consequent upon the development of a graft-versus-leukaemia (GVL) effect. Disease relapse is the major cause of transplant failure and novel therapeutic strategies are required in patients with measurable residual disease (MRD) post-transplant. Recognizing that full donor T cell chimerism serves as a biomarker of GVL and that mixed donor T cell chimerism reflects the presence of bi-directional tolerance, we report the first prospective correlation of the impact of post-transplant T cell chimerism and MRD in patients allografted for AML/MDS. Methods: 186 patients from FIGARO, a prospective randomized trial of reduced intensity conditioning regimens in AML/MDS, were alive and relapse free, at the first MRD timepoint and provided post-transplant bone marrow samples for flow cytometric MRD monitoring (day+42, month+3/+6/+9/+12) and peripheral blood samples for T cell chimerism analysis (3-monthly during the first year). Results were not available to clinicians. Flow cytometric MRD incorporating an unsupervised immunophenotypic analysis approach was used on 778 sequential samples. The prognostic significance of post-transplant MRD from each sampling timepoint was assessed by landmark analysis. Results: 29 (15.6%) patients were MRD+ at one or more timepoints in the first year after transplant. The presence of post-transplant MRD was associated with reduced OS (HR:2.19, p=0.0026) and RFS (HR:5.36, p Next, we examined the impact of T-cell chimerism, and post-transplant MRD on outcomes. In patients with mixed-donor T-cell chimerism (MDTC) at month+3 or +6, the presence of post-transplant MRD (preceding or at time of first MDTC) was associated with decreased OS (p=0.001) and RFS. Specifically, 2yr RFS in MRD+ patients was 23.1% (95%CI:5.6-47.5), compared to 63.6% (95%CI:44.9-77.5) in patients who were MRD negative (p=0.004) (Figure). In contrast, in 48 patients with full donor T-cell chimerism (FDTC) at months 3 and 6, only 5 patients were MRD+ post-transplant and their outcomes were equivalent to patients who were MRD negative (FDTC/MRD negative 2yr RFS: 80.9% (95% CI:65.3-90.0)). Downregulation of HLA class II molecules on AML blasts after transplant may result in immune evasion from GVL: we examined whether this had an additional impact on outcome in post-transplant MRD+ patients. Both RFS and OS were significantly lower in MRD+ patients when MRD+ blasts had down-regulated HLA-DR expression. In MRD+ patients, 2yr OS was 20.0% (95%CI:3.1-47.5) in those with HLA-DR down-regulation, versus 57.9% (95%CI 33.2-76.3) in those without (p=0.001). Conclusion We demonstrate that dynamic assessment of post-transplant MRD is an important predictor of outcome in patients allografted for AML/MDS, with additional prognostic value to pre-transplant MRD assessment. Post-transplant MRD and T-cell chimerism results are most informative when combined, underlining the importance of a GVL effect in AML/MDS. This suggests post-transplant strategies which result in FDTC may improve outcomes in patients allografted for AML/MDS. Our data also supports the clinical relevance of monitoring for leukemic immune escape as HLA-DR down-regulation identifies a post-transplant MRD positive subgroup at risk of almost inevitable relapse. Figure 1 Figure 1. Disclosures Loke: Novartis: Other: Travel; Janssen: Honoraria; Amgen: Honoraria; Pfizer: Honoraria; Daichi Sankyo: Other: Travel. Protheroe: Jazz Pharmaceuticals: Honoraria; Astellas: Honoraria; Kite Gilead: Honoraria. Dillon: Amgen: Other: Research support (paid to institution); Astellas: Consultancy, Other: Educational Events , Speakers Bureau; Jazz: Other: Education events; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: educational events; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Session chair (paid to institution), Speakers Bureau; Menarini: Membership on an entity's Board of Directors or advisory committees; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research Support, Educational Events. Craddock: Novartis Pharmaceuticals: Other: Advisory Board ; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background: The poor-risk cytogenetic subgroup of acute myeloid leukaemia (AML) includes various chromosomal aberrations and represents a heterogeneous population of patients with a dismal 10-year overall survival. While the success of genetic landscaping studies is encouraging, it is debatable whether genomics, or indeed any single-omics platform alone, is sufficient to capture the biology of a disease that continues to evade our existing treatments so effectively. Instead, we need to develop a much better understanding of the complexity of this subgroup of AMLs: the relationship and interdependencies across biochemical pathways, how these may differ between patients and their impact on the leukemia and normal stem cell compartments. To launch this process, we have completed a multi-omics profiling programme to shed new light on the genetic and biochemical features of poor-risk AML (https://poor-risk-aml.bham.ac.uk/). Aims: Application of multi-omics and integrative approaches to decipher the complexities of cytogenetically poor-risk AML Methods: Sample inclusion criteria were based on cytogenetics and availability of sufficient diagnostic bone marrow or peripheral blood material for analysis. The 50 primary AMLs included 17 cases with complex karyotype, 13 -7/del(7), 11 KMT2A rearrangements (with the exception of t(9;11)), 4 t(6;9), 3 -5/de(5), 1 del(17) and 1 inv(3). Profiles consisted of a combination of genomics (whole genome sequencing (WGS, 60X for tumour and 30X for germ-line controls), targeted sequencing of 54 myeloid loci, and total RNA-seq (100 million reads per bulk sample), mass spectrometry proteomics and phosphoproteomics (with >6,000 proteins and > 25,000 phosphorylation sites detected and quantified), mass cytometry (CyTOF, 39 markers), drug screening (ranging from 200-500 approved or investigational compounds) and the selective generation of patient-derived xenograft (PDX) models. Results: Near complete datasets have been compiled on all 50 primary AMLs, with the exception of WGS analysis where profiling was restricted to cases where corresponding germline DNA was available. Integration of WGS and RNA-seq data identified 122 genes having notable allele-specific expression (ASE) in ≥ 5 samples supported by ≥ 3 SNPs and these included the transcription factor GATA2 and the DNA topoisomerase TOP1MT. Use of RNA fusion capture tools resolved novel inter- and intra- chromosomal gene rearrangements that were confirmed by WGS. The four t(6;9)(p23;q34)/DEK-NUP214 cases, with a mean age of diagnosis of 43.5 years and all harboring FLT3-ITD mutations, arose from the most immature hematopoietic compartment (CD34+CD117+ enrichment) and demonstrated a unique transcriptomic signature, which included upregulation of FOXO3 and GRP56. Collectively, t(6;9) primary samples also showed a selective drug sensitivity to XPO1 (selinexor and eltanexor) and JAK inhibitors (ruxolitinib, tofacitinib and momelotinib) compared to other cytogenetic risk groups. On the other hand, a comparison of in vitro drug sensitivity data with genomic data of our entire cohort of patients demonstrated that TP53 wt AMLs (n=37) were more sensitive to all four MDM2 inhibitors (AMG-232, idasanutlin, SAR405838 and NVP-CGM097) compared to TP53 mutated cases (n=13). Comparisons of transcriptomics with the in vitro sensitivity to drugs included in early/late phase AML clinical trials, identified signatures of response associated with MDM2 and Aurora B kinase (AZD1152-HQPA) inhibitors. Phosphoproteomics analysis and machine learning modeling separated KMT2A rearranged leukemias into 2 discrete groups (group A: MLLT4, MLLT10 and TET1; group B with MLLT6, ELL and SEP9 fusion partners). Functionally, group A presented with elevated HOXA10 protein expression and enhanced in vitro response to genotoxic drugs and cell cycle inhibitors when compared to group B leukemia. Conclusions: Our study demonstrates the feasibility of simultaneously generating omics data from several different platforms and highlights that a combination of genetic and proteomic profiles may help to inform the choice of therapies based on the underlying biology of a patient's AML. Disclosures Wennerberg: Novartis: Research Funding; Pfizer: Honoraria. Heckman:Celgene: Research Funding; Novartis: Research Funding; Oncopeptides: Research Funding; Orion Pharma: Research Funding; Innovative Mediicines Initiative project Harmony: Research Funding.

Background: The persistence of measurable residual disease (MRD) has been shown to correlate with higher rates of relapse and worse survival in several leukemias. Individual studies have similarly suggested that the detection of MRD is associated with inferior outcomes in patients with acute myeloid leukemia (AML) undergoing frontline therapy; however, the optimal use of MRD information to risk stratify patients and inform clinical decision-making has been limited in part by the heterogeneity of these reports. To better understand the relationship between MRD and clinical outcomes in AML, we performed a literature-based meta-analysis of published AML studies reporting the association of MRD with survival outcomes. Methods: We conducted independent searches of PubMed, MEDLINE, and Embase for papers published between January 1, 2000 and October 1, 2018 that included the keywords "AML," "acute myeloid leukemia," or "acute myelogenous leukemia," in combination with the keywords "MRD," "minimal residual disease," or "measurable residual disease." Reviews, non-English articles, and studies only reporting outcomes after hematopoietic stem cell transplantation or those with insufficient description of MRD information were excluded. Study sample size, patient age, median follow-up time, MRD detection method, MRD assessment time point(s), AML subtype, specimen source, and survival outcomes were extracted. Meta-analyses of survival probabilities and hazard ratios (HRs) were performed separately for disease-free survival (DFS) and overall survival (OS) using Bayesian hierarchical modeling. Results: Eighty-one publications reporting on 11,151 patients were included in the meta-analysis (17 studies for OS, 20 studies for DFS, and 44 for both). Both OS and DFS were better for those who achieved MRD negativity (Figure 1). At 5 years, the estimated OS was 68% (95% Bayesian credible interval [CrI], 63%-73%) for the MRD negative group versus 34% (95% CrI, 28%-40%) for the MRD positive group. Similarly, the estimated DFS at 5 years for the MRD negative and MRD positive groups were 64% (95% CrI, 59%-70%) and 25% (95% CrI, 20%-32%), respectively. The relative benefit of achieving MRD negativity was comparable for both OS and DFS (average HR, 0.36; 95% CrI, 0.33-0.39 for OS; average HR, 0.37; 95% CrI, 0.34-0.40 for DFS). Achievement of MRD negativity was associated with superior DFS and OS irrespective of age group (adult or pediatric), MRD assessment time point (induction, during consolidation or after consolidation), AML subgroup (core-binding factor [CBF] or non-CBF), or specimen source (bone marrow or peripheral blood) (Figure 2). While most of the MRD detection methods were able to identify a difference in DFS and OS between groups with MRD negativity versus MRD positivity, the MRD effect using cytogenetics/FISH was not significant (average HR, 0.77; 95% CrI, 0.39-1.56 for OS and average HR, 0.65; 95% CrI, 0.34-1.23 for DFS), possibly due to only 2 studies being included in this subgroup analysis. The effect of MRD on survival was more profound in studies reporting outcomes of CBF AML compared to non-CBF AML, with a posterior probability of 0.999 for OS and 0.997 for DFS. Interestingly, across AML subtypes, peripheral blood assessment of MRD better distinguished MRD-positive and MRD-negative groups as compared to bone marrow assessment of MRD, with a posterior probability of 0.918 for OS and 0.999 for DFS. Multivariate analysis was performed to control for possible confounding factors that might influence the subgroup analyses. Overall, multivariate results were consistent with the univariate results. All subgroups showed DFS and OS benefit to achievement of MRD negativity, with the exception of MRD detection by cytogenetics/FISH. Conclusions: In this large-cohort meta-analysis, achievement of MRD negativity was strongly associated with superior DFS and OS in patients with AML, an association that was observed across ages, disease subtypes, time of assessment, specimen source, and most MRD detection methods. Given the robustness of the association of MRD with long-term outcomes across studies, MRD status may serve as a valuable clinical endpoint that may allow for accelerated evaluation of novel therapies in AML. Disclosures Short: Astellas: Research Funding; Takeda Oncology: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy; Amgen: Honoraria. Berry:Berry Consultants LLC.: Other: Co-owner. Walter:StemLine: Research Funding; Selvita: Research Funding; Seattle Genetics: Research Funding; Race Oncology: Consultancy; BioLineRx: Consultancy, Research Funding; Astellas: Consultancy; Arog: Research Funding; Argenx: Consultancy; Aptevo: Consultancy, Research Funding; Amphivena: Current equity holder in publicly-traded company; Amgen: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Jazz: Consultancy, Research Funding; ImmunoGen: Research Funding; Genentech: Consultancy; Daiichi: Consultancy; Celgene: Consultancy, Research Funding; Boston Biomedical: Consultancy; BiVictriX: Consultancy; Pfizer: Consultancy, Research Funding; New Link Genetics: Consultancy; Macrogenics: Research Funding; Kite: Consultancy. Kantarjian:Immunogen: Research Funding; Daiichi-Sankyo: Honoraria, Research Funding; BioAscend: Honoraria; Delta Fly: Honoraria; Abbvie: Honoraria, Research Funding; Ascentage: Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Janssen: Honoraria; Oxford Biomedical: Honoraria; Adaptive biotechnologies: Honoraria; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Research Funding; Aptitute Health: Honoraria; BMS: Research Funding; Jazz: Research Funding. Ravandi:Orsenix: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Macrogenics: Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Research Funding.

Fms-like tyrosine kinase 3 (Flt3) is expressed on progenitor cells and acute myeloid leukemia (AML) blasts. Fms-like tyrosine kinase 3 ligand (Flt3L) is detectable during homeostasis and increases in hypoplasia due to genetic defects or treatment with cytoreductive agents. Conversely, Flt31 AML is associated with depletion of Flt3L to undetectable levels. After induction chemotherapy, Flt3L is restored in patients entering complete remission (CR) but remains depressed in those with refractory disease. Weekly sampling reveals marked differences in the kinetics of Flt3L response during the first 6 weeks of treatment, proportionate to the clearance of blasts and cellularity of the bone marrow. In the UK NCRI AML17 trial, Flt3L was measured at day 26 in a subgroup of 140 patients with Flt3 mutation randomized to the tyrosine kinase inhibitor lestaurtinib or placebo. In these patients, attainment of CR was associated with higher Flt3L at day 26 (Mann-Whitney U P, .0001). Day 26 Flt3L was also associated with survival; Flt3L #291 pg/mL was associated with inferior event-free survival (EFS), and Flt3L .1185 pg/mL was associated with higher overall survival (OS; P 5 .0119). The separation of EFS and OS curves increased when minimal residual disease (MRD) status was combined with Flt3L measurement, and Flt3L retained a near-significant association with survival after adjusting for MRD in a proportional hazards model. Serial measurement of Flt3L in patients who had received a hematopoietic stem cell transplant for AML illustrates the potential value of monitoring Flt3L to identify relapse. Measurement of Flt3L is a noninvasive test with the potential to inform clinical decisions in patients with AML.

Aims In AML, several risk factors obtained at first diagnosis (FD) have been reported to be associated with shorter RFS and OS. The primary prognostic relevance of multicolour flow cytometry (MFC) has been a matter of debate for years. During follow-up (FU), the prognostic relevance of MRD as detected by MFC is less controversial and MFC is recommended in particular (but not exclusive) for those patients (pts) with no reliable genetic marker. We thought to evaluate the prognostic value at FD of a recently established antigen panel and a corresponding analysis strategy, which had been originally developed for MRD-detection. Methods Based on an 8-colour antibody panel (CD45, CD34, CD117, HLA-DR, CD13, CD33, CD7, CD56), we have developed a hierarchical gating strategy with mainly fixed gates. That allows to detect MRD with a high level of standardization and inter-observer reliability (Röhnert M., et al. 25th EHA 2020). Four distinct categories of aberrations (deficiency of CD13 or CD33, cross-lineage expression of CD7 or CD56) detectable on at least 10% of the myeloid blast population were used to define aberrant phenotypes termed leukemia associated immunophenotypes (LAIP) at FD. These categories were also chosen to define MRD during FU. MRDpos by LAIP was defined as the (re-)occurrence of an aberrant category already detectable at FD, while MRDpos by DfN (different from normal) was defined by the de-novo detection of an aberrant category at FU. The prognostic value of the aberrant phenotypes at FD was examined in a cohort of 528 pts. In 122 pts, we further analysed MRD (LAIP/DfN) after completion of intensive induction chemotherapy (IT). Consolidation therapy consisted of allogeneic hematopoietic stem cell transplantation (n=77) or chemotherapy (n=45). The bone marrow samples were measured centrally and analysed independently by three different investigators. Results The probability to achieve a complete remission (CR) varied between the different aberrant phenotypes (LAIP) at FD. Compared to pts without aberrant phenotype (CR rate=68%, n/N=100/148), pts with CD56only (the sole aberrant category was a cross-lineage expression of CD56=only) had a significantly lower CR rate (46%, n/N=15/33, p=0.019). The other exclusive aberrant categories did not significantly influence CR rates compared to pts without LAIP: CD13only (75%, n/N=53/71, p=0.286), CD33only (64%, n/N=59/97, p=0.28) and CD7only (62%, n/N=31/50, p=0.472). In pts with possibly co-occurring aberrant categories (compound aberrant phenotype=comp), the CR rate was significantly higher in CD13comp compared to all other patients (75% vs. 64%, 107/143 vs. 246/385, p=0.018). The other compound aberrancies did not significantly influence CR rates: CD33comp (63% vs. 68%, 90/143 vs. 263/385, p=0.244), CD7comp (66% vs. 67%, 72/109 vs. 281/419, p=0.842) and CD56comp (68% vs. 66%, 84/123 vs. 269/405, p=0.699). Regarding overall survival (OS), just CD56only retained its statistical significance (HR 2.5, CI 1.4-4.7, p=0.004). CD13comp was associated with favourable outcome but without reaching statistical significance (HR 0.7, CI 0.4-1.0, p=0.059). In the cohort of pts with MRD assessment at the end of IT, 67% were classified as responders (CR n=62, CRi n=19) and 33% as non-responders (PR n=14, refractory n=26) by cytomorphology. By MFC, 71% of these pts were classified as MRDpos (n=51/36 responders/non-responders) and 29% as MRDneg (n=30/4). MRDpos was defined by LAIP only (23%), DfN only (44%) or concordantly by LAIP+DfN (33%). OS of MRDneg pts was significantly longer compared to MRDpos patients (HR 4.3, CI 1.0-18.1, p=0.033). Conclusions Using our analysis approach originally developed for MRD monitoring, MFC could provide additional information for initial risk stratification. The presence of an isolated cross-lineage expression of CD56 (CD56only) was associated with a lower CR rate and significant shorter OS. In contrast, CD13comp (CD13 deficiency ± other aberrant categories) was associated with a higher CR rate and prolonged OS. Furthermore, MRDpos as defined by the combined LAIP/DfN strategy provided significant prognostic information. The presented results are currently refined and validated using genetically defined subcategories. The approach has to be confirmed in an independent cohort of pts. Disclosures Rollig: Amgen, Astellas, BMS, Daiichi Sankyo, Janssen, Roche: Consultancy; Abbvie, Novartis, Pfizer: Consultancy, Research Funding. Buecklein:Pfizer: Consultancy; Novartis: Research Funding; Celgene: Research Funding; Amgen: Consultancy; Gilead: Consultancy, Research Funding. Subklewe:Novartis: Consultancy, Research Funding; Janssen: Consultancy; Roche AG: Consultancy, Research Funding; AMGEN: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Morphosys: Research Funding; Seattle Genetics: Research Funding; Pfizer: Consultancy, Honoraria; Gilead Sciences: Consultancy, Honoraria, Research Funding. Krause:Pfizer: Honoraria; MSD: Honoraria; Takeda: Honoraria; Gilead: Other: Travel Support; Celgene: Other: Travel Support; Siemens: Research Funding. Schlenk:Roche: Research Funding; AstraZeneca: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; PharmaMar: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accomodations, Expenses, Research Funding, Speakers Bureau; Novartis: Speakers Bureau.

Terms of Use.\udJournal of Clinical Oncology\udLog In\udassignment_turned_inSubmit\udmail_outlineE-Alerts\udadd_shopping_cartSubscribe\ud\udOpenAthens/Shibboleth »\udAdvanced Search\ud\ud Newest Articles\ud Issues\ud Special Content\ud Authors\ud Subscribers\ud About\ud ASCO Publications\ud Career Center\ud COVID-19\ud\ud\ud\ud\ud\ud\ud\ud\ud\ud\ud\ud\ud\ud Journal of Clinical Oncology > List of Issues > Volume 36, Issue 15 > \ud\udORIGINAL REPORTS Hematologic Malignancy\udArticle Tools\udOPTIONS & TOOLS\udExport Citation \udTrack Citation \udAdd To Favorites \udPurchase\ud\ud Rights & Permissions \ud\udArticle has an altmetric score of 27\udCOMPANION ARTICLES\ud\ud Minimal Residual Disease Testing After Induction Chemotherapy for Acute Myeloid Leukemia: Moving Beyond Prognostication?. April 06, 2018\ud\udARTICLE CITATION\ud\udDOI: 10.1200/JCO.2017.76.3425 Journal of Clinical Oncology - published online before print March 30, 2018\ud\udPMID: 29601212\udMeasurable Residual Disease at Induction Redefines Partial Response in Acute Myeloid Leukemia and Stratifies Outcomes in Patients at Standard Risk Without NPM1 Mutations\udSylvie D. Freeman, Robert K. Hills, Paul Virgo, Naeem Khan, Steve Couzens, Richard Dillon, ...\udShow More\ud\udS.D.F. and R.K. H. contributed equally to this work.\ud\ud Abstract\ud Full Text\ud PDF\ud Figures and Tables\ud Supplements\ud\udPurpose\ud\udWe investigated the effect on outcome of measurable or minimal residual disease (MRD) status after each induction course to evaluate the extent of its predictive value for acute myeloid leukemia (AML) risk groups, including NPM1 wild-type (wt) standard risk, when incorporated with other induction response criteria.\udMethods\ud\udAs part of the NCRI AML17 trial, 2,450 younger adult patients with AML or high-risk myelodysplastic syndrome had prospective multiparameter flow cytometric MRD (MFC-MRD) assessment. After course 1 (C1), responses were categorized as resistant disease (RD), partial remission (PR), and complete remission (CR) or complete remission with absolute neutrophil count < 1,000/µL or thrombocytopenia < 100,000/μL (CRi) by clinicians, with CR/CRi subdivided by MFC-MRD assay into MRD+ and MRD−. Patients without high-risk factors, including Flt3 internal tandem duplication wt/−NPM1-wt subgroup, received a second daunorubicin/cytosine arabinoside induction; course 2 (C2) was intensified for patients with high-risk factors.\udResults\ud\udSurvival outcomes from PR and MRD+ responses after C1 were similar, particularly for good- to standard-risk subgroups (5-year overall survival [OS], 27% RD v 46% PR v 51% MRD+ v 70% MRD−; P < .001). Adjusted analyses confirmed significant OS differences between C1 RD versus PR/MRD+ but not PR versus MRD+. CRi after C1 reduced OS in MRD+ (19% CRi v 45% CR; P = .001) patients, with a smaller effect after C2. The prognostic effect of C2 MFC-MRD status (relapse: hazard ratio [HR], 1.88 [95% CI, 1.50 to 2.36], P < .001; survival: HR, 1.77 [95% CI, 1.41 to 2.22], P < .001) remained significant when adjusting for C1 response. MRD positivity appeared less discriminatory in poor-risk patients by stratified analyses. For the NPM1-wt standard-risk subgroup, C2 MRD+ was significantly associated with poorer outcomes (OS, 33% v 63% MRD−, P = .003; relapse incidence, 89% when MRD+ ≥ 0.1%); transplant benefit was more apparent in patients with MRD+ (HR, 0.72; 95% CI, 0.31 to 1.69) than those with MRD− (HR, 1.68 [95% CI, 0.75 to 3.85]; P = .16 for interaction).\udConclusion\ud\udMFC-MRD can improve outcome stratification by extending the definition of partial response after first induction and may help predict NPM1-wt standard-risk patients with poor outcome who benefit from transplant in the first CR.

It is postulated that disease relapse in patients with acute myeloid leukemia (AML) is consequent upon chemoresistance within leukemic stem/progenitor cell (LSC) populations from which bulk blasts arise1. In adults with high risk AML, allogeneic hematopoietic cell transplantation (HCT) has become a central component of the treatment algorithm to overcome this chemoresistance as it delivers maximal anti-leukemic activity through both dose intensification and by the genesis of a potent graft-versus-leukemia (GVL) effect2-4. However relapse still occurs in a significant proportion of allografted patients and now represents the major cause of treatment failure particularly with reduced intensity conditioning (RIC) regimens5. Whilst minimal residual disease (MRD) from the bulk leukemic population is known to be prognostic, more accurate predictors of relapse risk might be developed from detection of putative LSC populations pre- or post-transplant. However, to date an association between LSC and transplant outcome remains uncertain.

INTRODUCTION: Allogeneic stem cell transplantation (allo-SCT) is an important curative strategy in adults with high risk acute myeloid leukemia (AML) and myelodysplasia (MDS). Disease relapse represents the major cause of treatment failure and whilst retrospective analyses have identified that pre-transplant measurable residual disease (MRD) is an important predictor of transplant outcome this has never been examined prospectively. The advent of reduced intensity conditioning (RIC) regimens has substantially increased the number of older adults eligible for allo-SCT but the optimal RIC regimen in high risk AML remains unknown. Registry data have demonstrated improved outcomes using a sequential transplant regimen utilizing cytosine arabinoside (araC)/amsacrine (AMSA) cytoreduction followed by a fludarabine (Flu)/busulfan (Bu) based RIC regimen (FLAMSA-Bu). However, although the FLAMSA-Bu regimen is now widely used in adults with high risk AML and MDS its benefit has not been evaluated in a randomized trial. We report the results of a randomized trial evaluating the FLAMSA-Bu regimen compared with standard RIC regimens which also represents the first prospective evaluation of the impact of pre-transplant MRD levels on transplant outcome. PATIENTS AND METHODS: 244 patients (median age 59 yrs) with high risk AML (n=164) or high risk myelodysplasia (n=80) were randomized 1:1 to a control arm determined by investigator's choice of either Flu/B2/ATG (Flu, Bu 3.2 mg/kg x 2 days, ATG 2.5 mg/kg x 2 days); Flu/Mel/Alemtuzumab (A) (Flu, Mel 140 mg/m2, A 50 mg) or Flu/Bu2/A (Flu, Bu 3.2 mg/kg x 2 days, A 50 mg) versus an experimental arm of FLAMSA-Bu (Flu, araC 2g/m2 x 4 days, AMSA 100mg/m2 x 4 days, Bu -total dose 11.2 mg/kg). Patients over the age of 60 received an adjusted FLAMSA-Bu regimen utilising a reduced dose of araC (1mg/m2 x 4 days) and a total Bu dose of 6.4 mg/kg. Patients were transplanted using either an HLA identical sibling (n=49) or matched (10/10 or 9/10) unrelated donor (n=195). All patients received cyclosporine GVHD prophylaxis. 155 patients with AML were in CR1 or CR2 at the time of transplant and 9 had primary refractory disease. MRD was monitored by flow cytometry (applying different-from-normal analysis when no diagnostic/relapse leukemic aberrant immunophenotype was available). Pre-transplant MRD levels were measured up to four weeks prior to transplantation in 201 patients (MRD positive = 80 (40%), MRD negative = 94 (47%), inadequate sample = 27 (13%)). MRD results were not reported to clinicians. The primary outcome was overall survival. RESULTS: Baseline characteristics including CR1/CR2 status, adverse cytogenetics and MRD levels were similar between regimens. Median follow up was 35 months. Transplant outcomes were comparable between patients allografted in the control and FLAMSA-Bu arms. 2 yr overall survival (OS) and cumulative incidence of relapse (CIR) were 61% and 30% respectively in the control arm vs 62% and 26% for the FLAMSA-Bu arm. Transplant related mortality at 100 days was 3.0% in patients allografted using the control regimen vs 14% in patients allografted using the FLAMSA-Bu regimen and 17% vs 21% at 1 year. In the study cohort pre-transplant MRD positivity was associated with both an increased CIR compared to patients testing MRD negative (2 yr CIR 42% vs 19%, p=0.009) and decreased OS (2 yr OS 52% vs 71%, p=0.048). The FLAMSA-Bu regimen failed to improve OS or reduce CIR in either MRD positive or MRD negative patients. CONCLUSIONS: This trial, the largest randomized trial of RIC regimens in AML to date, did not detect any benefit of intensification of the conditioning regimen in adults with high risk AML or MDS. Specifically, the FLAMSA-Bu regimen was not associated with improved transplant outcome in patients who were MRD positive pre-transplant. These data include the first demonstration in a prospective analysis that the presence of pre-transplant MRD measured in real time is associated with reduced OS consequent upon an increased risk of disease relapse. Further randomized studies of novel conditioning regimens in adult AML, crucially with integrated MRD studies, are now required but these results support exploration of alternative strategies, such as pre or post-transplant pharmacological intervention, as the most promising strategy to reduce the risk of disease relapse post allograft. Disclosures Russell: Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy, Honoraria, Speakers Bureau. Freeman:Jazz Pharmaceuticals: Speakers Bureau. OffLabel Disclosure: We report data using the combination of fludarabine, busulphan, amsacrine and cytosine arabinsoide as a conditioning regimen in patients allografted for high risk acute myeloid leukemia

Purpose Older patients with acute myeloid leukemia (AML) have a high relapse rate after standard chemotherapy. We investigated whether measuring chemotherapy sensitivity by multiparameter flow cytometric minimal residual disease (MFC-MRD) detection has prognostic value in patients older than age 60 years or is simply a surrogate for known age-related risk factors. Patient and Methods Eight hundred ninety-two unselected patients treated intensively in the United Kingdom National Cancer Research Institute AML16 Trial were assessed prospectively for MFC-MRD during treatment. Eight hundred thirty-three patients had leukemia-associated immunophenotypes (LAIPs) identified by pretreatment screening. Four hundred twenty-seven patients entered complete remission (CR) after one or two courses (designated C1 and C2, respectively) and were MFC-MRD assessable by LAIP detection in CR bone marrow for at least one of these time points. MRD positivity was defined as residual disease detectable by LAIP. Results MFC-MRD negativity, which was achieved in 51% of patients after C1 (n = 286) and 64% of patients after C2 (n = 279), conferred significantly better 3-year survival from CR (C1: 42% v 26% in MRD-positive patients, P < .001; C2: 38% v 18%, respectively; P < .001) and reduced relapse (C1: 71% v 83% in MRD-positive patients, P < .001; C2: 79% v 91%, respectively; P < .001), with higher risk of early relapse in MRD-positive patients (median time to relapse, 8.5 v 17.1 months, respectively). In multivariable analysis, MRD status at the post-C1 time point independently predicted survival, identifying a subgroup of intermediate-risk patients with particularly poor outcome. However, survival benefit from gemtuzumab ozogamicin was not associated with MFC-MRD chemotherapy sensitivity. Conclusion Early assessment of treatment response using flow cytometry provides powerful independent prognostic information in older adults with AML, lending support to the incorporation of MRD detection to refine risk stratification and inform clinical trial design in this challenging group of patients.

Quek and colleagues identify human leukemic stem cells (LSCs) present in CD34− AML. In-depth characterization of the functional and clonal aspects of CD34− LSCs indicates that most are similar to myeloid precursors., Our understanding of the perturbation of normal cellular differentiation hierarchies to create tumor-propagating stem cell populations is incomplete. In human acute myeloid leukemia (AML), current models suggest transformation creates leukemic stem cell (LSC) populations arrested at a progenitor-like stage expressing cell surface CD34. We show that in ∼25% of AML, with a distinct genetic mutation pattern where >98% of cells are CD34−, there are multiple, nonhierarchically arranged CD34+ and CD34− LSC populations. Within CD34− and CD34+ LSC–containing populations, LSC frequencies are similar; there are shared clonal structures and near-identical transcriptional signatures. CD34− LSCs have disordered global transcription profiles, but these profiles are enriched for transcriptional signatures of normal CD34− mature granulocyte–macrophage precursors, downstream of progenitors. But unlike mature precursors, LSCs express multiple normal stem cell transcriptional regulators previously implicated in LSC function. This suggests a new refined model of the relationship between LSCs and normal hemopoiesis in which the nature of genetic/epigenetic changes determines the disordered transcriptional program, resulting in LSC differentiation arrest at stages that are most like either progenitor or precursor stages of hemopoiesis.

Despite the molecular heterogeneity of standard-risk acute myeloid leukemia (AML), treatment decisions are based on a limited number of molecular genetic markers and morphology-based assessment of remission. Sensitive detection of a leukemia-specific marker (e.g., a mutation in the gene encoding nucleophosmin [NPM1]) could improve prognostication by identifying submicroscopic disease during remission.We used a reverse-transcriptase quantitative polymerase-chain-reaction assay to detect minimal residual disease in 2569 samples obtained from 346 patients with NPM1-mutated AML who had undergone intensive treatment in the National Cancer Research Institute AML17 trial. We used a custom 51-gene panel to perform targeted sequencing of 223 samples obtained at the time of diagnosis and 49 samples obtained at the time of relapse. Mutations associated with preleukemic clones were tracked by means of digital polymerase chain reaction.Molecular profiling highlighted the complexity of NPM1-mutated AML, with segregation of patients into more than 150 subgroups, thus precluding reliable outcome prediction. The determination of minimal-residual-disease status was more informative. Persistence of NPM1-mutated transcripts in blood was present in 15% of the patients after the second chemotherapy cycle and was associated with a greater risk of relapse after 3 years of follow-up than was an absence of such transcripts (82% vs. 30%; hazard ratio, 4.80; 95% confidence interval [CI], 2.95 to 7.80; P0.001) and a lower rate of survival (24% vs. 75%; hazard ratio for death, 4.38; 95% CI, 2.57 to 7.47; P0.001). The presence of minimal residual disease was the only independent prognostic factor for death in multivariate analysis (hazard ratio, 4.84; 95% CI, 2.57 to 9.15; P0.001). These results were validated in an independent cohort. On sequential monitoring of minimal residual disease, relapse was reliably predicted by a rising level of NPM1-mutated transcripts. Although mutations associated with preleukemic clones remained detectable during ongoing remission after chemotherapy, NPM1 mutations were detected in 69 of 70 patients at the time of relapse and provided a better marker of disease status.The presence of minimal residual disease, as determined by quantitation of NPM1-mutated transcripts, provided powerful prognostic information independent of other risk factors. (Funded by Bloodwise and the National Institute for Health Research; Current Controlled Trials number, ISRCTN55675535.).

Purpose There has been little survival improvement in older patients with acute myeloid leukemia (AML) in the last two decades. Improving induction treatment may improve the rate and quality of remission and consequently survival. In our previous trial, in younger patients, we showed improved survival for the majority of patients when adding gemtuzumab ozogamicin (GO) to induction chemotherapy. Patients and Methods Untreated patients with AML or high-risk myelodysplastic syndrome (median age, 67 years; range, 51 to 84 years) were randomly assigned to receive induction chemotherapy with either daunorubicin/ara-C or daunorubicin/clofarabine, with (n = 559) or without (n = 556) GO 3 mg/m2 on day 1 of course one of therapy. The primary end point was overall survival (OS). Results The overall response rate was 69% (complete remission [CR], 60%; CR with incomplete recovery [CRi], 9%), with no difference between GO (70%) and no GO (68%) arms. There was no difference in 30- or 60-day mortality and no major increase in toxicity with GO. With median follow-up of 30 months (range, 5.5 to 54.6 months), 3-year cumulative incidence of relapse was significantly lower with GO (68% v 76%; hazard ratio [HR], 0.78; 95% CI, 0.66 to 0.93; P = .007), and 3-year survival was significantly better (25% v 20%; HR, 0.87; 95% CI, 0.76 to 1.00; P = .05). The benefit was apparent across subgroups. There was no interaction with other treatment interventions. A meta-analysis of 2,228 patients in two United Kingdom National Cancer Research Institute trials showed significant improvements in relapse (HR, 0.82; 95% CI, 0.72 to 0.93; P = .002) and OS (HR, 0.88; 95% CI, 0.79 to 0.98; P = .02). Conclusion Adding GO (3 mg/m2) to induction chemotherapy reduces relapse risk and improves survival with little increase in toxicity.

The haematopoietic system is prone to age-related disorders ranging from deficits in functional blood cells to the development of neoplastic states. Such neoplasms often involve recurrent cytogenetic abnormalities, among which a deletion in the long arm of chromosome 20 (del20q) is common in myeloid malignancies. The del20q minimum deleted region contains nine genes, including MYBL2, which encodes a key protein involved in the maintenance of genome integrity. Here, we show that mice expressing half the normal levels of Mybl2 (Mybl2(+/Δ)) develop a variety of myeloid disorders upon ageing. These include myeloproliferative neoplasms, myelodysplasia (MDS) and myeloid leukaemia, mirroring the human conditions associated with del20q. Moreover, analysis of gene expression profiles from patients with MDS demonstrated reduced levels of MYBL2, regardless of del20q status and demonstrated a strong correlation between low levels of MYBL2 RNA and reduced expression of a subset of genes related to DNA replication and checkpoint control pathways. Paralleling the human data, we found that these pathways are also disturbed in our Mybl2(+/Δ) mice. This novel mouse model, therefore, represents a valuable tool for studying the initiation and progression of haematological malignancies during ageing, and may provide a platform for preclinical testing of therapeutic approaches.

BACKGROUND: The current World Health Organization classification of myelodysplastic syndromes is based morphological evaluation of bone marrow dysplasia. In clinical practice, the reproducibility of the recognition of dysplasia is usually poor especially in cases that lack specific markers such as ring sideroblasts and clonal cytogenetic abnormalities. DESIGN AND METHODS: We aimed to develop and validate a flow cytometric score for the diagnosis of myelodysplastic syndrome. Four reproducible parameters were analyzed: CD34(+) myeloblast-related and B-progenitor-related cluster size (defined by CD45 expression and side scatter characteristics CD34(+) marrow cells), myeloblast CD45 expression and granulocyte side scatter value. The study comprised a "learning cohort" (n=538) to define the score and a "validation cohort" (n=259) to confirm its diagnostic value. RESULTS: With respect to non-clonal cytopenias, patients with myelodysplastic syndrome had increased myeloblast-related cluster size, decreased B-progenitor-related cluster size, aberrant CD45 expression and reduced granulocyte side scatter (P

Introduction Relapse remains the most common cause of treatment failure for patients with acute myeloid leukaemia (AML) who undergo allogeneic stem cell transplantation (SCT) and carries a grave prognosis. Multiple studies have identified the presence of minimal residual disease (MRD) prior to SCT assessed by flow cytometry (FCM) as a strong predictor of relapse: however, little is known about the impact of molecular MRD pre-SCT. Molecular techniques can provide 100-1000 fold greater sensitivity than FCM in NPM1 mutated AML allowing identification of patients with very low level MRD prior to SCT. Peri-transplant management decisions for patients with positive molecular MRD are highly challenging due to the absence of robust outcome data. Methods Between 2009-14 the NCRI AML17 study enrolled 3215 adult non-APML patients aged 16-77 eligible for intensive chemotherapy. Central screening for NPM1 mutations was positive in 861/2949 (29%); 530 patients provided serial samples for MRD monitoring. Paired blood (PB) and bone marrow aspirates (BM) were requested after each chemotherapy cycle and then quarterly; additional samples were requested pre- and post-SCT. Samples were analysed by RT-qPCR using a suite of 27 mutation-specific reverse primers. Results were only fed back to clinicians after June 2012 when patients could be treated for confirmed re-emergent or persistent molecular positivity. Post-remission treatment was determined according to the validated NCRI risk score, with poor-risk patients recommended for SCT during first complete remission (CR1). Survival analysis was performed using the logrank test. Results In total 108/530 patients received SCT (CR1 57 (52%), after molecular relapse or progression (MR) 30 (28%), CR2 21 (19%)). Five-year survival post-SCT (5y-OS) was 65% in CR1, and 54% in MR/CR2 (p=0.3). After MR 26/30 patients received chemotherapy prior to SCT. Evaluable pre-SCT PB and BM samples taken within 60 days of SCT were available for 104 and 78 patients (both available n=74). Considering PB samples, 5y-OS was 73% (median OS (mOS) not reached (NR)) for MRD-ve patients (n=74) vs. 30% (mOS 8.1 m) for any PB positivity (n=30) (p Of the 47 patients who received additional chemotherapy for morphologic or molecular relapse or progression, 26 (55%) converted to MRD negativity accounting for 44% of 59 patients who were MRD negative pre-SCT. Ninety-three per cent of 59 pre SCT-MRD negative patients had been MRD negative in the PB after the second cycle of induction (a previously identified marker of favourable outcome). A threshold of 200 mutant NPM1 transcripts/105 ABL copies in the pre-SCT PB sample split patients into 3 groups with 2y-OS of 81% (negative, n=74), 54% (low, n=13) and 9% (high, n=17; p Thirty four patients were positive for FLT3-ITD at diagnosis (5y-OS 55%) and 74 were negative (5y-OS 62%; p=0.3). For patients without FLT3 ITD, negative, low and high levels of MRD in the pre-SCT PB sample were associated with 2y-OS of 79% (n=53), 88% (n=8) and 0% (n=9) (p We assigned 80 patients to high and low risk groups based on FLT3 ITD status and pre-SCT MRD level in PB and BM. High-risk patients (FLT3 ITD and any detectable level of MRD in the PB or BM, or FLT3 ITD negative with > 200 copies in the PB or > 1000 copies in the BM) had 3y-OS of 14% (n=27, mOS 6.5 months) compared with 80% for low-risk patients (n=53, p Conclusions Patients who test negative for NPM1 mutant transcripts immediately before SCT have a favourable outcome which is also observed in FLT3 ITD negative patients who are MRD positive at levels which do not exceed 200 copies in the PB or 1000 copies in the BM. FLT3 ITD mutated patients with any level of MRD prior to SCT, and FLT3 ITD negative patients with transcript levels above these thresholds, have a very high risk of relapse and may benefit from further chemotherapy or FLT3 inhibition prior to or after SCT; studies to investigate this are urgently needed. Disclosures Hills: Daiichi Sankyo: Consultancy, Honoraria. Cavenagh:Celgene: Honoraria, Research Funding, Speakers Bureau; Amgen: Honoraria, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; Takeda: Research Funding, Speakers Bureau; Novartis: Honoraria, Speakers Bureau. Russell:Daiichi Sankyo: Consultancy; Pfizer: Consultancy, Honoraria, Speakers Bureau; Jazz Pharma: Speakers Bureau.

Minimal (or measurable) residual (MRD) disease provides a biomarker of response quality for which there is robust validation in the context of modern intensive treatment for younger patients with Acute Myeloid Leukemia (AML). Nevertheless, it remains a relatively unexplored area in older patients with AML. The lack of progress in this field can be attributed to two main reasons. First, physicians have a general reluctance to submitting older adults to intensive chemotherapy due to their frailty and to the unfavourable biological disease profile predicting a poor outcome following conventional chemotherapy. Second, with the increasing use of low-intensity therapies (i.e., hypomethylating agents) differing from conventional drugs in mechanism of action and dynamics of response, there has been concomitant skepticism that these schedules can produce deep hematological responses. Furthermore, age dependent differences in disease biology also contribute to uncertainty on the prognostic/predictive impact in older adults of certain genetic abnormalities including those validated for MRD monitoring in younger patients. This review examines the evidence for the role of MRD as a prognosticator in older AML, together with the possible pitfalls of MRD evaluation in older age.

The past 40 years have witnessed major advances in defining the cytogenetic aberrations, mutational landscape, epigenetic profiles, and expression changes underlying hematological malignancies. Although it has become apparent that acute myeloid leukemia (AML) is highly heterogeneous at the molecular level, the standard framework for risk stratification guiding transplant practice in this disease remains largely based on pretreatment assessment of cytogenetics and a limited panel of molecular genetic markers, coupled with morphological assessment of bone marrow (BM) blast percentage after induction. However, application of more objective methodology such as multiparameter flow cytometry (MFC) has highlighted the limitations of morphology for reliable determination of remission status. Moreover, there is a growing body of evidence that detection of subclinical levels of leukemia (ie, minimal residual disease, MRD) using MFC or molecular-based approaches provides powerful independent prognostic information. Consequently, there is increasing interest in the use of MRD detection to provide early end points in clinical trials and to inform patient management. However, implementation of MRD assessment into clinical practice remains a major challenge, hampered by differences in the assays and preferred analytical methods employed between routine laboratories. Although this should be addressed through adoption of standardized assays with external quality control, it is clear that the molecular heterogeneity of AML coupled with increasing understanding of its clonal architecture dictates that a “one size fits all” approach to MRD detection in this disease is not feasible. However, with the range of platforms now available, there is considerable scope to realistically track treatment response in every patient.

Sialic acid-binding immunoglobulin-like lectin (Siglec)-5 or CD170 is a CD33-related receptor, containing cytoplasmic immune receptor-based tyrosine signalling motifs, that has previously been reported to be myeloid-specific like CD33 and thus may be useful in the characterization of both normal and malignant haemopoiesis. This study showed that Siglec-5 had a distinct expression pattern to CD33 both on normal myeloid cells and in acute myeloid leukaemia (AML). In normal bone marrow and cord blood, myeloid cells predominantly expressed Siglec-5 at the later stages of granulocytic differentiation. Siglec-5 was not expressed at significant levels by CD34+ progenitors either from bone marrow or mobilized peripheral blood. During in vitro myeloid differentiation of cord blood purified CD34+ cells, Siglec-5 was upregulated later than CD33. Siglec-5 expression remained absent or very low on cultured CD34+ cells, unlike CD33, which was present on almost all CD34+ cells by day 4. However, analysis of blasts from 23 patients with AML revealed aberrant expression of Siglec-5 with CD34 in 50% (seven of 14) of patients with CD34+ AML; 61% (14 of 23) of AML cases were positive for Siglec-5 with an increased frequency in the French-American-British subtypes M3-5 (80%) compared with M0-2 (25%). All 13 acute lymphoblastic leukaemic (ALL) samples tested, including a CD33+ ALL, were Siglec-5 negative. These results support the further evaluation of Siglec-5 antibodies in the diagnosis and monitoring of AML.