Allogeneic stem-cell transplantation in patients with NPM1-mutated acute myeloid leukemia: results from a prospective donor versus no-donor analysis of patients after upfront HLA typing within the SAL-AML 2003 trial

Postinduction molecular MRD identifies patients with NPM1 AML who benefit from allogeneic transplant in first remission

ABSTRACT

Selection of patients with NPM1-mutated acute myeloid leukemia (AML) for allogeneic transplant in first complete remission (CR1-allo) remains controversial because of a lack of robust data. Consequently, some centers consider baseline FLT3-internal tandem duplication (ITD) an indication for transplant, and others rely on measurable residual disease (MRD) status. Using prospective data from the United Kingdom National Cancer Research Institute AML17 and AML19 studies, we examined the impact of CR1-allo according to peripheral blood NPM1 MRD status measured by quantitative reverse transcription polymerase chain reaction after 2 courses of induction chemotherapy. Of 737 patients achieving remission, MRD was positive in 19%. CR1-allo was performed in 46% of MRD+ and 17% of MRD- patients. We observed significant heterogeneity of overall survival (OS) benefit from CR1-allo according to MRD status, with substantial OS advantage for MRD+ patients (3-year OS with CR1-allo vs without: 61% vs 24%; hazard ratio [HR], 0.39; 95% confidence interval [CI], 0.24-0.64; P < .001) but no benefit for MRD- patients (3-year OS with CR1-allo vs without: 79% vs 82%; HR, 0.82; 95% CI, 0.50-1.33; P = .4). Restricting analysis to patients with coexisting FLT3-ITD, again CR1-allo only improved OS for MRD+ patients (3-year OS, 45% vs 18%; compared with 83% vs 76% if MRD-); no interaction with FLT3 allelic ratio was observed. Postinduction molecular MRD reliably identifies those patients who benefit from allogeneic transplant in first remission. The AML17 and AML19 trials were registered at www.isrctn.com as #ISRCTN55675535 and #ISRCTN78449203, respectively.

What Influences the Decision to Proceed to Transplant for Patients With AML in First Remission?

Although allogeneic hematopoietic cell transplantation (allo-HCT) remains the backbone of curative treatment for the majority of fit adults diagnosed with AML, there is indeed a subset of patients for whom long-term remission may be achieved without transplantation. Remarkable changes in our knowledge of AML biology in recent years has transformed the landscape of diagnosis, management, and treatment of AML. Specifically, markedly increased understanding of molecular characteristics of AML, the expanded application of minimal/measurable residual diseases testing, and an increased armamentarium of leukemia-directed therapeutic agents have created a new paradigm for the medical care of patients with AML. An attempt is herein made to decipher the decision to proceed to transplant for patients with AML in first complete remission on the basis of the current best available evidence. The focus is on factors affecting the biology and treatment of AML itself, rather than on variables related to allo-HCT, an area characterized by significant advancements that have reduced overall therapy-related complications. This review seeks to focus on areas of particular complexity, while simultaneously providing clarity on how our current knowledge and treatment strategies may, or may not, influence the decision to pursue allo-HCT in patients with AML.

Allogeneic hematopoietic stem cell transplantation and pre-transplant strategies in patients with NPM1-mutated acute myeloid leukemia: a single center experience

Patients with acute myeloid leukemia (AML) and nucleophosmin 1 gene mutations (NPM1mut) show a favorable prognosis with chemotherapy (CT) in the absence of negative prognostic genetic abnormalities. Between 2008 and 2021 64 patients with NPM1mutAML received alloHSCT because of additional adverse prognostic factors (1st line), inadequate response to or relapse during or after CT (2nd line). To expand the evidence in alloTX in NPM1mut AML, clinical and molecular data were retrospectively analyzed with respect to pre-transplant strategies and outcome. Patients with minimal residual disease negative (MRD-) CR at transplant had better 2-y-PFS and 2-y-OS (77% and 88%) than patients with minimal residual disease positive (MRD+) CR (41% and 71%) or patients with active disease (AD) at transplant (20% and 52%). The 2nd line patients with relapse after completing CT responded well to high dose cytarabine based salvage chemotherapy (salvage CT) in contrast to patients relapsing while still on CT (90% vs 20%, P = 0.0170). 2-y-PFS and 2-y-OS was 86% in patients who achieved a 2nd MRD- CR pre alloHSCT. Outcome in NPM1mutAML depends on disease burden at alloHSCT. Time and type of relapse in relation to CT are predictive for response to salvage CT.

HLA Class I Genotype Is Associated with Relapse Risk after Allogeneic Stem Cell Transplantation for NPM1-Mutated Acute Myeloid Leukemia

Mutation-bearing peptide ligands from mutated nucleophosmin-1 (NPM1) protein have been empirically found to be presented by HLA class I in acute myeloid leukemia (AML). We hypothesized that HLA genotype may impact allogeneic hematopoietic stem cell transplantation (allo-HCT) outcomes in NPM1-mutated AML owing to differences in antigen presentation. We evaluated the effect of the variable of predicted strong binding to mutated NPM1 peptides using HLA class I genotypes from matched donor-recipient pairs on transplant recipients' overall survival (OS) and disease-free survival (DFS) as part of the primary objectives and cumulative incidence of relapse and nonrelapse mortality (NRM) as part of secondary objectives. Baseline and outcome data reported to the Center for International Blood and Marrow Transplant Research from a study cohort of adult patients (n = 1020) with NPM1-mutated de novo AML in first (71%) or second (29%) complete remission undergoing 8/8 matched related (18%) or matched unrelated (82%) allo-HCT were analyzed retrospectively. Class I alleles from donor-recipient pairs were analyzed for predicted strong HLA binding to mutated NPM1 using netMHCpan 4.0. A total of 429 (42%) donor-recipient pairs were classified as having predicted strong-binding HLA alleles (SBHAs) to mutated NPM1. In multivariable analyses adjusting for clinical covariates, the presence of predicted SBHAs was associated with a lower risk of relapse (hazard ratio [HR], .72; 95% confidence interval [CI], .55 to .94; P = .015). OS (HR, .81; 95% CI, .67 to .98; P = .028) and DFS (HR, .84; 95% CI, .69 to 1.01; P = .070) showed a suggestion of better outcomes if predicted SBHAs were present but did not meet the prespecified P value of <.025. NRM did not differ (HR, 1.04; P = .740). These hypothesis-generating data support further exploration of HLA genotype-neoantigen interactions in the allo-HCT context.

Impact of extramedullary disease in AML patients undergoing sequential RIC for HLA-matched transplantation: occurrence, risk factors, relapse patterns, and outcome

We sought to evaluate the role of extramedullary disease (EMD) in sequential RIC retrospectively analyzing data of 144 high-risk AML patients undergoing HLA-matched transplantation. Median long-term follow-up was 11.6 years. Eighteen percent of patients (n = 26/144) presented with extramedullary AML (EM AML) or a history of EMD at time of transplantation. Overall relapse rate was 25% (n = 36/144) with 15% (n = 21/144) of all patients developing isolated BM relapse and 10% (n = 15/144) developing EM AML relapse with or without concomitant BM relapse (EM ± BM). Manifestation of EM relapse after transplantation occurred frequently at multiple sites and presented mostly as solid tumor mass. Only 3/15 patients with EM ± BM relapse showed a prior EMD manifestation. EMD prior to allogeneic transplantation had no impact on post-transplant OS when compared to non-EMD (median post-transplant OS 3.8 years versus 4.8 years; ns). Risk factors (p =  < 0.1) for EM ± BM relapse included younger age and a higher number of prior intensive chemotherapies, whereas the presence of chronic GVHD was a protective factor. Median post-transplant OS (15.5 months vs. 15.5 months), RFS (9.6 months vs 7.3 months), and post-relapse OS (6.7 months vs. 6.3 months) were not significantly different between patients with isolated BM vs. EM ± BM relapse. Taken together, occurrence of EMD prior to as well as of EM ± BM AML relapse after transplantation was moderate, presenting mostly as solid tumor mass after transplantation. However, diagnosis of those does not seem to influence outcomes after sequential RIC. A higher number of chemotherapy cycles prior to transplantation was identified as recent risk factor for EM ± BM relapse.

Nucleophosmin 1: from its pathogenic role to a tantalizing therapeutic target in acute myeloid leukemia

Nucleophosmin 1 (NPM1, also known as B23) is a multifunctional protein involved in a variety of cellular processes, including ribosomal maturation, centrosome replication, maintenance of genomic stability, cell cycle control, and apoptosis. NPM1 is the most commonly mutated gene in adult acute myeloid leukemia (AML) and is present in approximately 40% of all AML cases. The underlying mechanisms of mutant NPM1 (NPM1^mut) in leukemogenesis remain unclear. This review summarizes the structure and physiological function of NPM1, mechanisms underlying the pathogenesis of NPM1-mutated AML, and the potential role of NPM1 as a therapeutic target. It is reported that dysfunctional NPM1 might cause AML pathogenesis via its role as a protein chaperone, inhibiting differentiation of leukemia stem cells and regulation of non-coding RNAs. Besides conventional chemotherapies, NPM1 is a promising therapeutic target against AML that warrants further investigation. NPM1-based therapeutic strategies include inducing nucleolar relocalisation of NPM1 mutants, interfering with NPM1 oligomerization, and NPM1 as an immune response target.

Dynamic assessment of measurable residual disease in favorable-risk acute myeloid leukemia in first remission, treatment, and outcomes

We aimed to investigate outcomes of different post-remission treatment (PRT) choices based on dynamic measurable residual disease (MRD) by multiparameter flow cytometry in favorable-risk AML (FR-AML). Four hundred and three younger patients with FR-AML in first complete remission (CR1) were enrolled in this registry-based cohort study, including 173 who received chemotherapy (CMT), 92 autologous stem cell transplantation (auto-SCT), and 138 allogeneic SCT (allo-SCT). The primary endpoint was the 5-year overall survival (OS). Subgroup analyses were performed based on dynamic MRD after the 1st, 2nd, and 3rd courses of chemotherapy. In subgroups of patients with negative MRD after 1 or 2 course of chemotherapy, comparable OS was observed among the CMT, auto-SCT, and allo-SCT groups (p = 0.340; p = 0.627, respectively). But CMT and auto-SCT had better graft-versus-host-disease-free, relapse-free survival (GRFS) than allo-SCT in both subgroups. For patients with negative MRD after three courses of chemotherapy, allo-SCT had better disease-free-survival than CMT (p = 0.009). However, OS was comparable among the three groups (p = 0.656). For patients with persistently positive MRD after 3 courses of chemotherapy or recurrent MRD, allo-SCT had better OS than CMT and auto-SCT (p = 0.011; p = 0.029, respectively). Dynamic MRD might improve therapy stratification and optimize PRT selection for FR-AML in CR1.

Genome-wide association study identifies susceptibility loci for acute myeloid leukemia

Acute myeloid leukemia (AML) is a hematological malignancy with an undefined heritable risk. Here we perform a meta-analysis of three genome-wide association studies, with replication in a fourth study, incorporating a total of 4018 AML cases and 10488 controls. We identify a genome-wide significant risk locus for AML at 11q13.2 (rs4930561; P = 2.15 × 10-8; KMT5B). We also identify a genome-wide significant risk locus for the cytogenetically normal AML sub-group (N = 1287) at 6p21.32 (rs3916765; P = 1.51 × 10-10; HLA). Our results inform on AML etiology and identify putative functional genes operating in histone methylation (KMT5B) and immune function (HLA).

Neoantigen-Specific T-Cell Immune Responses: The Paradigm of NPM1-Mutated Acute Myeloid Leukemia

The C-terminal aminoacidic sequence from NPM1-mutated protein, absent in normal human tissues, may serve as a leukemia-specific antigen and can be considered an ideal target for NPM1-mutated acute myeloid leukemia (AML) immunotherapy. Different in silico instruments and in vitro/ex vivo immunological platforms have identified the most immunogenic epitopes from NPM1-mutated protein. Spontaneous development of endogenous NPM1-mutated-specific cytotoxic T cells has been observed in patients, potentially contributing to remission maintenance and prolonged survival. Genetically engineered T cells, namely CAR-T or TCR-transduced T cells, directed against NPM1-mutated peptides bound to HLA could prospectively represent a promising therapeutic approach. Although either adoptive or vaccine-based immunotherapies are unlikely to be highly effective in patients with full-blown leukemia, these strategies, potentially in combination with immune-checkpoint inhibitors, could be promising in maintaining remission or preemptively eradicating persistent measurable residual disease, mainly in patients ineligible for allogeneic hematopoietic stem cell transplant (HSCT). Alternatively, neoantigen-specific donor lymphocyte infusion derived from healthy donors and targeting NPM1-mutated protein to selectively elicit graft-versus-leukemia effect may represent an attractive option in subjects experiencing post-HSCT relapse. Future studies are warranted to further investigate dynamics of NPM1-mutated-specific immunity and explore whether novel individualized immunotherapies may have potential clinical utility in NPM1-mutated AML patients.

NPM1-mutated acute myeloid leukemia: from bench to bedside

The nucleophosmin (NPM1) gene encodes for a multifunctional protein with prominent nucleolar localization that shuttles between nucleus and cytoplasm. NPM1 mutations represent the most common genetic lesion in adult acute myeloid leukemia (AML; about one third of cases), and they act deterministically to cause the aberrant cytoplasmic delocalization of NPM1 mutants. Because of its unique features, NPM1-mutated AML is recognized as a distinct entity in the 2017 World Health Organization (WHO) classification of hematopoietic neoplasms. Here, we focus on recently identified functions of wild-type NPM1 in the nucleolus and address new biological and clinical issues related to NPM1-mutated AML. The relevance of the cooperation between NPM1 and other mutations in driving AML with different outcomes is presented. We also discuss the importance of eradicating NPM1-mutated clones to achieve AML cure and the impact of preleukemic clonal hematopoiesis persistence in predisposing to second AML. The contribution of HOX genes' expression to the development of NPM1-mutated AML is also highlighted. Clinically, yet unsolved diagnostic issues in the 2017 WHO classification of myeloid neoplasms and the importance of NPM1 mutations in defining the framework of European LeukemiaNet genetic-based risk stratification are discussed. Finally, we address the value and limits of NPM1-based measurable residual disease assessment for treatment guidance and present the results of promising preclinical studies with XPO1 and menin-MLL inhibitors.

The evolving concept of indications for allogeneic hematopoietic cell transplantation during first complete remission of acute myeloid leukemia

The long-standing debate of whether patients with acute myeloid leukemia (AML) should proceed to allogeneic hematopoietic cell transplantation (HCT) during first complete remission (CR1) remains unsettled. Although allogeneic HCT during CR1 used to be recommended for those with intermediate or poor cytogenetics if they had a matched sibling donor, the concept of indications for allogeneic HCT during CR1 has been evolving by virtue of advances in understanding of the molecular pathogenesis of AML and innovations in transplantation practice attained over the last few decades. The incorporation of molecular profiles of leukemia has been shown to contribute to further refinements of risk classification that had previously relied mostly on cytogenetics, while the progress in transplantation procedures has made it possible to perform transplantations more safely even for patients without a matched sibling donor. These significant changes have underpinned the need to reappraise indications for allogeneic HCT during CR1 of AML. Improvements in clinical applications of genetic and measurable residual disease information as well as in transplantation technology are expected to further refine indications for allogeneic HCT during CR1, and thus promote an individualized approach for the treatment of AML.

The effect of the detection of minimal residual disease for the prognosis and the choice of post-remission therapy of intermediate-risk acute myeloid leukemia without FLT3-ITD, NPM1 and biallelic CEBPA mutations

BACKGROUND

Intermediate-risk acute myeloid leukemia (IR-AML) without FLT3-ITD, NPM1 and biallelic CEBPA mutations (here referred to as NPM1^mut-negCEBPA^dm-negFLT3-ITD^neg AML) is a clinically heterogeneous disease. The optimal post-remission therapy (PRT) is unclear for patients with NPM1^mut-negCEBPA^dm-negFLT3-ITD^neg AML who achieved first complete response (CR1). This study aims to explore clinical and molecular factors that can help determine the prognosis of those patients and their choice of PRT.

METHODS

We retrospectively analyzed 28 patients with NPM1^mut-negCEBPA^dm-negFLT3-ITD^neg AML who received induction chemotherapy and achieved CR1. For PRT, 17 patients received post-remission chemotherapy (PR-CT) and 11 patients received allogeneic hematopoietic stem cell transplantation (allo-HSCT).

RESULTS

For patients with NPM1^mut-negCEBPA^dm-negFLT3-ITD^neg AML, multivariate analysis indicated that allo-HSCT and negative minimal residual disease (MRD^neg) before PRT were favorable prognostic factors of overall survival (OS) (allo-HSCT, P = 0.002; MRD^neg, P = 0.018); whereas relapse was an adverse prognostic factor of OS (P = 0.003). Log-rank analysis showed that allo-HSCT significantly improved their OS and RFS compared with PR-CT (OS, P < 0.001; RFS, P = 001). Otherwise, allo-HSCT improved the OS and RFS of patients with NPM1^mut-negCEBPA^dm-negFLT3-ITD^neg AML, whether they obtained MRD^pos or MRD^neg before PRT (OS: MRD^neg, P = 0.036; MRD^pos, P = 0.012; RFS: MRD^neg, P = 0.047; MRD^pos, P = 0.030).

CONCLUSION

For patients with NPM1^mut-negCEBPA^dm-negFLT3-ITD^neg AML, MRD^neg before PRT and allo-HSCT were favorable prognostic factors of OS. Whether they obtain MRD^neg or not, allo-HSCT is the preferred PRT.

How I diagnose and treat NPM1-mutated AML

Mutations of the nucleophosmin (NPM1) gene, encoding for a nucleolar multifunctional protein, occur in approximately one-third of adult acute myeloid leukemia (AML). NPM1-mutated AML exhibits unique molecular, pathological, and clinical features, which led to its recognition as distinct entity in the 2017 World Health Organization (WHO) classification of myeloid neoplasms. Although WHO criteria for the diagnosis of NPM1-mutated AML are well established, its distinction from other AML entities may be difficult. Moreover, the percentage of blasts required to diagnose NPM1-mutated AML remains controversial. According to the European LeukemiaNet (ELN), determining the mutational status of NPM1 (together with FLT3) is mandatory for accurate relapse-risk assessment. NPM1 mutations are ideal targets for measurable residual disease (MRD) monitoring, since they are AML specific, frequent, very stable at relapse, and do not drive clonal hematopoiesis of undetermined significance. MRD monitoring by quantitative polymerase chain reaction of NPM1-mutant transcripts, possibly combined with ELN genetic-based risk stratification, can guide therapeutic decisions after remission. Furthermore, immunohistochemistry can be very useful in selected situations, such as diagnosis of NPM1-mutated myeloid sarcoma. Herein, we present 4 illustrative cases of NPM1-mutated AML that address important issues surrounding the biology, diagnosis, and therapy of this common form of leukemia.

miR-10a as a therapeutic target and predictive biomarker for MDM2 inhibition in acute myeloid leukemia

Pharmacological inhibition of MDM2/4, which activates the critical tumor suppressor p53, has been gaining increasing interest as a strategy for the treatment of acute myeloid leukemia (AML). While clinical trials of MDM2 inhibitors have shown promise, responses have been confined to largely molecularly undefined patients, indicating that new biomarkers and optimized treatment strategies are needed. We previously reported that the microRNA miR-10a is strongly overexpressed in some AML, and demonstrate here that it modulates several key members of the p53/Rb network, including p53 regulator MDM4, Rb regulator RB1CC1, p21 regulator TFAP2C, and p53 itself. The expression of both miR-10a and its downstream targets were strongly predictive of MDM2 inhibitor sensitivity in cell lines, primary AML specimens, and correlated to response in patients treated with both MDM2 inhibitors and cytarabine. Furthermore, miR-10a inhibition induced synergy between MDM2 inhibitor Nutlin-3a and cytarabine in both in vitro and in vivo AML models. Mechanistically this synergism primarily occurs via the p53-mediated activation of cytotoxic apoptosis at the expense of cytoprotective autophagy. Together these findings demonstrate that miR-10a may be useful as both a biomarker to identify patients most likely to respond to cytarabine+MDM2 inhibition and also a druggable target to increase their efficacy.

Hematopoietic Cell Transplantation in the Treatment of Newly Diagnosed Adult Acute Myeloid Leukemia: An Evidence-Based Review from the American Society of Transplantation and Cellular Therapy

The role of hematopoietic cell transplantation (HCT) in the management of newly diagnosed adult acute myeloid leukemia (AML) is reviewed and critically evaluated in this evidence-based review. An AML expert panel, consisting of both transplant and nontransplant experts, was invited to develop clinically relevant frequently asked questions covering disease- and HCT-related topics. A systematic literature review was conducted to generate core recommendations that were graded based on the quality and strength of underlying evidence based on the standardized criteria established by the American Society of Transplantation and Cellular Therapy Steering Committee for evidence-based reviews. Allogeneic HCT offers a survival benefit in patients with intermediate- and high-risk AML and is currently a part of standard clinical care. We recommend the preferential use of myeloablative conditioning in eligible patients. A haploidentical related donor marrow graft is preferred over a cord blood unit in the absence of a fully HLA-matched donor. The evolving role of allogeneic HCT in the context of measurable residual disease monitoring and recent therapeutic advances in AML with regards to maintenance therapy after HCT are also discussed.

Diagnostic and therapeutic pitfalls in NPM1-mutated AML: notes from the field

Mutations of Nucleophosmin (NPM1) are the most common genetic abnormalities in adult acute myeloid leukaemia (AML), accounting for about 30% of cases. NPM1-mutated AML has been recognized as distinct entity in the 2017 World Health Organization (WHO) classification of lympho-haematopoietic neoplasms. WHO criteria allow recognition of this leukaemia entity and its distinction from AML with myelodysplasia-related changes, AML with BCR-ABL1 rearrangement and AML with RUNX1 mutations. Nevertheless, controversial issues include the percentage of blasts required for the diagnosis of NPM1-mutated AML and whether cases of NPM1-mutated myelodysplasia and chronic myelomonocytic leukaemia do exist. Evaluation of NPM1 and FLT3 status represents a major pillar of the European LeukemiaNet (ELN) genetic-based risk stratification model. Moreover, NPM1 mutations are particularly suitable for assessing measurable residual disease (MRD) since they are frequent, stable at relapse and do not drive clonal haematopoiesis. Ideally, combining monitoring of MRD with the ELN prognostication model can help to guide therapeutic decisions. Here, we provide examples of instructive cases of NPM1-mutated AML, in order to provide criteria for the appropriate diagnosis and therapy of this frequent leukaemia entity.

NPM1 Biology in Myeloid Neoplasia

PURPOSE OF REVIEW

Nucleophosmin (NPM1) mutations are encountered in myeloid neoplasia and are present in ~ 30% of de novo acute myeloid leukemia cases. This review summarizes features of mutant NPM1-related disease, with a particular emphasis on recent discoveries relevant to disease monitoring, prognostication, and therapeutic intervention.

RECENT FINDINGS

Recent studies have shown that HOX/MEIS gene overexpression is central to the survival of NPM1-mutated cells. Two distinct classes of small molecule drugs, BH3 mimetics and menin-MLL interaction inhibitors, have demonstrated exquisite leukemic cell toxicity in preclinical AML models associated with HOX/MEIS overexpression, and the former of these has shown efficacy in older treatment-naïve NPM1-mutated AML patients. The results of ongoing clinical trials further investigating these compounds will be of particular importance and may alter the clinical management of patients with NPM1-mutated myeloid neoplasms. Significant scientific advancements over the last decade, including improved sequencing and disease monitoring techniques, have fostered a much deeper understanding of mutant NPM1 disease biology, prognostication, and opportunities for therapeutic intervention. These discoveries have led to the development of clinical assays that permit the detection and monitoring of mutant NPM1 and have paved the way for future investigation of targeted therapeutics using emerging cutting-edge techniques.

Multiparametric in situ imaging of NPM1-mutated acute myeloid leukemia reveals prognostically-relevant features of the marrow microenvironment

Ancillary testing during the initial workup of acute myeloid leukemia (AML) is largely performed using aspirated materials. We utilized multiplex immunofluorescence (MIF) imaging with digital image analysis to perform an in situ analysis of the microenvironment in NPM1-mutated AML using diagnostic bone marrow biopsy tissues (N = 17) and correlated these findings with diagnostic next-generation sequencing (NGS, N = 17), flow cytometry (FC, N = 14), and first remission (CR1) NPM1-specific molecular MRD (n = 16) data. The total CD3-positive T-cell percentages correlated positively between FC and MIF (r = 0.53, p = 0.05), but were significantly lower by MIF (1.62% vs. 3.4%, p = 0.009). The percentage of mutant NPM1-positive (NPM1c+) cells ranged from 9.7 to 90.8% (median 45.4%) and did not correlate with the NPM1 mutant allele fraction by NGS (p > 0.05). The percentage of CD34+/NPM1c+ cells ranged from 0 to 1.8% (median 0.07%). The percentage of NPM1c+ cells correlated inversely (34% vs. 62%, p = 0.03), while the percentages of CD3-/NPM1c- cells (64% vs. 35%, p = 0.03), and specifically CD3-/CD4-/NPM1c- cells (26% vs. 13%, p = 0.04), correlated positively with subsequent MRD. Discordances between MIF and FC/NGS data suggest that aspirate materials are likely an imperfect reflection of the core biopsy tissue. Furthermore, increased numbers of NPM1 wild-type cells within the microenvironment at diagnosis correlate with the subsequent presence of MRD.

Risk stratification using FLT3 and NPM1 in acute myeloid leukemia patients autografted in first complete remission

FLT3-ITD and NPM1 mutation refine prognostic stratification in acute myeloid leukemia (AML) with intermediate-risk cytogenetics. However, data on their role in patients undergoing autologous stem cell transplantation (Auto-SCT) as post-remission therapy (PRT) are limited. We therefore sought to retrospectively evaluate the role of FLT3-ITD and NPM1 in a cohort of AML patients (n = 405) with intermediate-risk cytogenetics, autografted in first complete remission (CR1). Patients were transplanted between 2000 and 2014 and reported to the European Society for Blood and Marrow Transplantation (EBMT) registry. Leukemia-free survival (LFS) was the primary outcome. Median follow-up was 5.5 years. FLT3-ITD^neg/NPM1^WT was the leading molecular subtype (50%), followed by FLT3-ITD^neg/NPM1^mut (30%). In the univariate analysis, molecular subtype was associated with LFS, overall survival (OS), and relapse incidence (RI) (p < 0.001); 5-year LFS: FLT3-ITD^neg/NPM1^mut 62%, FLT3-ITD^pos/NPM1^mut 38%, FLT3-ITD^neg/NPM1^WT 32%, and FLT3-ITD^pos/NPM1^WT 21%. At 5 years, OS and RI in the FLT3-ITD^neg/NPM1^mut subtype were 74% and 35%, respectively. The corresponding OS and RI in other subtypes were below 48% and over 57%. In a Cox multivariable model, molecular subtype was the strongest predictor of LFS, OS, and relapse. In conclusion, AML patients with intermediate-risk cytogenetics and FLT3-ITD^neg/NPM1^mut experience favorable outcomes when autografted in CR1, suggesting that Auto-SCT is a valid PRT option.

Chromosomal Abnormalities and Prognosis in NPM1-Mutated Acute Myeloid Leukemia: A Pooled Analysis of Individual Patient Data From Nine International Cohorts

PURPOSE

Nucleophosmin 1 (NPM1) mutations are associated with a favorable prognosis in acute myeloid leukemia (AML) when an internal tandem duplication (ITD) in the fms-related tyrosine kinase 3 gene (FLT3) is absent (FLT3-ITD^neg) or present with a low allelic ratio (FLT3-ITD^low). The 2017 European LeukemiaNet guidelines assume this is true regardless of accompanying cytogenetic abnormalities. We investigated the validity of this assumption.

METHODS

We analyzed associations between karyotype and outcome in intensively treated patients with NPM1^mut/FLT3-ITD^neg/low AML who were prospectively enrolled in registry databases from nine international study groups or treatment centers.

RESULTS

Among 2,426 patients with NPM1^mut/FLT3-ITD^neg/low AML, 2,000 (82.4%) had a normal and 426 (17.6%) had an abnormal karyotype, including 329 patients (13.6%) with intermediate and 83 patients (3.4%) with adverse-risk chromosomal abnormalities. In patients with NPM1^mut/FLT3-ITD^neg/low AML, adverse cytogenetics were associated with lower complete remission rates (87.7%, 86.0%, and 66.3% for normal, aberrant intermediate, and adverse karyotype, respectively; P < .001), inferior 5-year overall (52.4%, 44.8%, 19.5%, respectively; P < .001) and event-free survival (40.6%, 36.0%, 18.1%, respectively; P < .001), and a higher 5-year cumulative incidence of relapse (43.6%, 44.2%, 51.9%, respectively; P = .0012). These associations remained in multivariable mixed-effects regression analyses adjusted for known clinicopathologic risk factors (P < .001 for all end points). In patients with adverse-risk chromosomal aberrations, we found no significant influence of the NPM1 mutational status on outcome.

CONCLUSION

Karyotype abnormalities are significantly associated with outcome in NPM1^mut/FLT3-ITD^neg/low AML. When adverse-risk cytogenetics are present, patients with NPM1^mut share the same unfavorable prognosis as patients with NPM1 wild type and should be classified and treated accordingly. Thus, cytogenetic risk predominates over molecular risk in NPM1^mut/FLT3-ITD^neg/low AML.

Molecular Detection of Minimal Residual Disease before Allogeneic Stem Cell Transplantation Predicts a High Incidence of Early Relapse in Adult Patients with NPM1 Positive Acute Myeloid Leukemia

We analyzed the impact of alloHSCT in a single center cohort of 89 newly diagnosed NPM1^mut AML patients, consecutively treated according to the Northern Italy Leukemia Group protocol 02/06 [NCT00495287]. After two consolidation cycles, the detection of measurable residual disease (MRD) by RQ-PCR was strongly associated with an inferior three-year overall survival (OS, 45% versus 84%, p = 0.001) and disease-free survival (DFS, 44% versus 76%, p = 0.006). In MRD-negative patients, post-remissional consolidation with alloHSCT did not provide a significant additional benefit over a conventional chemotherapy in terms of overall survival [OS, 89% (95% CI 71–100%) versus 81% (95% CI 64–100%), p = 0.59] and disease-free survival [DFS, 80% (95% CI 59–100%) versus 75% (95% CI 56–99%), p = 0.87]. On the contrary, in patients with persistent MRD positivity, the three-year OS and DFS were improved in patients receiving an alloHSCT compared to those allocated to conventional chemotherapy (OS, 52% versus 31%, p = 0.45 and DFS, 50% versus 17%, p = 0.31, respectively). However, in this group of patients, the benefit of alloHSCT was still hampered by a high incidence of leukemia relapse during the first year after transplantation (43%, 95% CI 25–60%). Consolidative alloHSCT improves outcomes compared to standard chemotherapy in patients with persistent NPM1^mut MRD positivity, but in these high-risk patients, the significant incidence of leukemia relapse must be tackled by post-transplant preemptive treatments.

High NPM1 mutant allele burden at diagnosis correlates with minimal residual disease at first remission in de novo acute myeloid leukemia

Acute myeloid leukemia (AML) with mutated NPM1 is a newly recognized separate entity in the revised 2016 WHO classification, and is associated with a favorable prognosis. While previous studies have evaluated NPM1 in a binary fashion, we recently demonstrated a significant independent negative prognostic effect of high NPM1 mutant allele burden (VAF) at diagnosis in a cohort of de novo AML patients. Although the importance of minimal residual disease (MRD) monitoring in NPM1-mutated AML has been well characterized, the potential relationship between diagnostic allele burden and MRD is unknown. We retrospectively evaluated for MRD at first remission (CR1). We used either next-generation sequencing (NGS) [n = 71], and/or immunohistochemistry (IHC) for mutant NPM1 (NPM1c) [n = 60], in a subset of patients from our recently examined cohort. We identified a statistically significant positive correlation between the VAF at diagnosis, and at CR1 (Spearman r = 0.4, P = .006), and enrichment for MRD in high diagnostic VAF patients (P = .05), as previously defined. IHC-positivity also correlated significantly with a higher median diagnostic NPM1 VAF (0.42 vs 0.39, P = .02), and with the VAF at CR1 (Spearman r = 0.7, P = .003). In multivariable analyses, both high diagnostic VAF (P = .003) and MRD (P = .02) were independent predictors of shorter event-free survival (EFS). Our findings suggest a relationship between the NPM1 mutant allele burden at diagnosis, and the presence of MRD at first remission. Our findings support IHC as a potentially useful adjunctive tool for disease monitoring.

Precision medicine and novel molecular target therapies in acute myeloid leukemia: the background of hematologic malignancies (HM)-SCREEN-Japan 01

The development of allogeneic hematopoietic-stem-cell transplantation has improved the prognosis of younger acute myeloid leukemia (AML) patients. However, the outcome of older AML patients remains poor. The majority of AML patients are elderly. For elderly AML patients unfit for intensive chemotherapy, less toxic single agent that targets a specific gene mutation or combination therapy with a single agent is needed. The role of chromosomal abnormalities and genetic mutations in leukemia has become more apparent, and detailed prognostic stratification based on the type of genetic mutation has been established. Next-generation sequencing (NGS) has been used for gene analysis of AML. In the future, the evaluation of biologically homogeneous population on the basis of chromosomal abnormalities and gene mutations will lead to a paradigm shift that will help in the development of optimized therapy. As rapid diagnosis of gene mutations is required by the clinical physicians to decide on induction therapy, it is important to have a swift turnaround time for comprehensive DNA sequencing to provide actionable data to clinical physicians. It is required to conduct a feasibility study to evaluate the turnaround time from sending the specimens to receiving the results while maintaining the quality of the specimens contributing to gene analysis. To detect infrequent gene mutations, investigators need to perform multicenter studies and/or cooperative-group trials with a certain sample size to examine the frequency of the gene mutations in elderly AML patients, enabling sufficient statistical power for meaningful comparisons.

Superior outcome of patients with favorable-risk acute myeloid leukemia using consolidation with autologous stem cell transplantation

Autologous stem cell transplantation (ASCT), intensifying anti-leukemic effects without significant treatment-related mortality (TRM), is particularly appealing in AML with favorable genetic/molecular profile. This study retrospectively evaluated the outcomes of post-remission treatment in consecutive favorable-risk AML patients. Sixty-six patients were included: 32 had mutated NPM1/wild-type FLT-ITD, 16 had t(8:21) and 18 - inv(16). Forty patients received chemotherapy alone, 26 underwent ASCT upfront. In time-dependent analysis, the ASCT group demonstrated higher relapse-free (RFS) (p = .001) and overall survivals (OS) (p = .0007). The 1-year RFS and OS were 44.2% vs 88% and 71% vs 96% for chemotherapy and ASCT, respectively. The corresponding TRM was 4/40 (10.0%) and 0/26 (0%), with relapse rates of 70.0% and 19.2% (p = .0002). In multivariate analysis, ASCT was associated with superior OS and RFS. In conclusion, ASCT offers significantly superior RFS and OS in favorable-risk AML in first complete remission. These data support the recent resurgence of interest in ASCT for AML.

Hematopoietic stem cell transplantation for adult patients with isolated NPM1 mutated acute myeloid leukemia in first remission

Acute myeloid leukemia (AML) in first remission (CR1) with isolated NPM1 mutation (iNPM1m) is considered a good prognosis genotype, although up to one-third relapse. To evaluate the best transplant strategy, we retrospectively compared autologous stem cell transplantation (auto-SCT), related (MSD), and fully matched unrelated (MUD) allogeneic stem cell transplantation (allo-SCT). We identified 256 adult patients including 125 auto-SCT, 72 MSD, and 59 MUD. The 2-year leukemia-free survival (LFS) was 62% in auto-SCT, 69% in MUD, and 81% in MSD (P = .02 for MSD vs others). The 2-year overall survival (OS) was not different among auto-SCT, MUD, and MSD, reaching 83% (P = .88). The 2-year non-relapse mortality (NRM) was 2.5% in auto-SCT and 7.5% in allo-SCT (P = .04). The 2-year cumulative incidence of relapse (RI) was higher after auto-SCT (30%) than after MUD (22%) and MSD (12%, P = .01). In multivariate analysis, MSD versus auto-SCT but not MUD versus auto-SCT was associated with lower RI (P < .01 and P = .13, respectively) and better LFS (P = .01 and P = .31, respectively). Age correlated with higher NRM (P < .01). Allo-SCT using MSD appears as a reasonable transplant option for young patients with iNPM1m AML in CR1. Auto-SCT was followed by worse RI and LFS, but similar OS to both allo-SCT modalities.

Minimal/Measurable Residual Disease Monitoring in NPM1-Mutated Acute Myeloid Leukemia: A Clinical Viewpoint and Perspectives

Acute myeloid leukemia (AML) with NPM1 gene mutations is currently recognized as a distinct entity, due to its unique biological and clinical features. We summarize here the results of published studies investigating the clinical application of minimal/measurable residual disease (MRD) in patients with NPM1-mutated AML, receiving either intensive chemotherapy or hematopoietic stem cell transplantation. Several clinical trials have so far demonstrated a significant independent prognostic impact of molecular MRD monitoring in NPM1-mutated AML and, accordingly, the Consensus Document from the European Leukemia Net MRD Working Party has recently recommended that NPM1-mutated AML patients have MRD assessment at informative clinical timepoints during treatment and follow-up. However, several controversies remain, mainly with regard to the most clinically significant timepoints and the MRD thresholds to be considered, but also with respect to the optimal source to be analyzed, namely bone marrow or peripheral blood samples, and the correlation of MRD with other known prognostic indicators. Moreover, we discuss potential advantages, as well as drawbacks, of newer molecular technologies such as digital droplet PCR and next-generation sequencing in comparison to conventional RQ-PCR to quantify NPM1-mutated MRD. In conclusion, further prospective clinical trials are warranted to standardize MRD monitoring strategies and to optimize MRD-guided therapeutic interventions in NPM1-mutated AML patients.

New approaches in allogenic transplantation in AML

Acute myeloid leukemia (AML) is a heterogeneous disorder with high morbidity and mortality. Allogeneic stem cell transplantation (allo-SCT) is an effective, and sometimes the only, curative postremission therapy for AML patients. Based on genetic risk classification, the published data have suggested that allo-SCT be recommended for high- and most intermediate-risk AML but not for low-risk AML in first complete remission (CR1). Recently, the role of allo-SCT in low-risk AML in CR1 is being established with the development of a risk-directed, minimal residual disease-based strategy. Though human leukocyte antigen-matched sibling transplantation remains the preferred therapeutic option for AML, modern approaches and developments pre-, peri- and post-transplant have facilitated other transplant modalities, especially haploidentical SCT, as promising valid alternative choices. In this paper, we review recent advances in allo-SCT for AML, weigh the benefits of allo-SCT for high-, intermediate-, and even low-risk AML in CR1, discuss the best choice of allo-SCT donor for the treatment of AML, and summarize new approaches for refractory and relapsed AML pre- or post-allo-SCT.

Effects of all-trans retinoic acid (ATRA) in addition to chemotherapy for adults with acute myeloid leukaemia (AML) (non-acute promyelocytic leukaemia (non-APL))

BACKGROUND

Acute myeloid leukaemia (AML) is the most common acute leukaemia affecting adults. Most patients diagnosed with AML are at advanced age and present with co-morbidities, so that intensive therapy such as stem cell transplantation (SCT) is impossible to provide or is accompanied by high risks for serious adverse events and treatment-related mortality. Especially for these patients, it is necessary to find out whether all-trans retinoic acid (ATRA), an intermediate of vitamin A inducing terminal differentiation of leukaemic cell lines, added to chemotherapy confers increased benefit or harm when compared with the same chemotherapy alone.

OBJECTIVES

This review aims to determine benefits and harms of ATRA in addition to chemotherapy compared to chemotherapy alone for adults with AML (not those with acute promyelocytic leukaemia (non-APL)).

SEARCH METHODS

We searched the Central Register of Controlled Trials (CENTRAL), MEDLINE, study registries and relevant conference proceedings up to July 2018 for randomised controlled trials (RCTs). We also contacted experts for unpublished data.

SELECTION CRITERIA

We included RCTs comparing chemotherapy alone with chemotherapy plus ATRA in patients with all stages of AML. We excluded trials if less than 80% of participants were adults or participants with AML, and if no subgroup data were available. Patients with myelodysplastic syndrome (MDS) were included, if they had a refractory anaemia and more than 20% of blasts.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the quality of trials. We contacted study authors to obtain missing information. We used hazard ratios (HR) for overall survival (OS) and disease-free survival (DFS; instead of the pre-planned event-free survival, as this outcome was not reported), and we calculated risk ratios (RR) for the other outcomes quality of life, on-study mortality and adverse events. We presented all measures with 95% confidence intervals (CIs). We assessed the certainty of evidence using GRADE methods.

MAIN RESULTS

Our search resulted in 2192 potentially relevant references, of which we included eight trials with 28 publications assessing 3998 patients. Overall, we judged the potential risk of bias of the eight included trials as moderate. Two of eight trials were published as abstracts only. All the included trials used different chemotherapy schedules and one trial only evaluated the effect of the hypomethylating agent decitabine, a drug know to affect epigenetics, in combination with ATRA.The addition of ATRA to chemotherapy resulted in probably little or no difference in OS compared to chemotherapy only (2985 participants; HR 0.94 (95% confidence interval (CI) 0.87 to 1.02); moderate-certainty evidence). Based on a mortality rate at 24 months of 70% with chemotherapy alone, the mortality rate with chemotherapy plus ATRA was 68% (95% CI 65% to 71%).For DFS, complete response rate (CRR) and on-study mortality there was probably little or no difference between treatment groups (DFS: 1258 participants, HR 0.99, 95% CI 0.87 to 1.12; CRR: 3081 participants, RR 1.02, 95% CI 0.96 to 1.09; on-study mortality: 2839 participants, RR 1.02, 95% CI 0.81 to 1.30, all moderate-certainty evidence).Three trials with 1428 participants reported the adverse events 'infection' and 'cardiac toxicity': There was probably no, or little difference in terms of infection rate between participants receiving ATRA or not (RR 1.05, 95% CI 0.96 to 1.15; moderate-certainty evidence). We are uncertain whether ATRA decreases cardiac toxicity (RR 0.46, 95% CI 0.24 to 0.90; P = 0.02, very low certainty-evidence, however, cardiac toxicity was low).Rates and severity of diarrhoea and nausea/vomiting were assessed in two trials with 337 patients and we are uncertain whether there is a difference between treatment arms (diarrhoea: RR 2.19, 95% CI 1.07 to 4.47; nausea/vomiting: RR 1.46, 95% CI 0.75 to 2.85; both very low-certainty evidence).Quality of life was not reported by any of the included trials.

AUTHORS' CONCLUSIONS

We found no evidence for a difference between participants receiving ATRA in addition to chemotherapy or chemotherapy only for the outcome OS. Regarding DFS, CRR and on-study mortality, there is probably no evidence for a difference between treatment groups. Currently, it seems the risk of adverse events are comparable to chemotherapy only.As quality of life has not been evaluated in any of the included trials, further research is needed to clarify the effect of ATRA on quality of life.

Profiling of aberrant DNA methylation in acute myeloid leukemia reveals subclasses of CG-rich regions with epigenetic or genetic association

Malignant transformation is frequently associated with disease-specific epigenetic alterations, but the underlying mechanisms and pathophysiological consequences remain poorly understood. Here, we used global comparative DNA methylation profiling at CG-rich regions of 27 acute myeloid leukemia (AML) samples to select a subset of aberrantly methylated CG-rich regions (~400 regions, ~15,000 CpGs) for quantitative DNA methylation profiling in a large cohort of AML patients (n = 196) using MALDI-TOF analysis of bisulfite-treated DNA. Meta-analysis separated a subgroup of CG-rich regions showing highly correlated DNA methylation changes that were marked by histone H3 lysine 27 trimethylation in normal hematopoietic progenitor cells. While the group of non-polycomb group (PcG) target regions displayed methylation patterns that correlated well with molecular and cytogenetic markers, PcG target regions displayed a much weaker association with genetic features. However, the degree of methylation gain across the latter panel showed significant correlation with active DNMT3A levels and with overall survival. Our study suggests that both epigenetic as well as genetic aberrations underlay AML-related changes in DNA methylation at CG-rich regions and that the former may provide a marker to improve classification and prognostication of adult AML patients.

[Prognostic significance of early assessment of minimal residual disease in acute myeloid leukemia with mutated NPM1 patients]

目的

探讨NPM1突变阳性急性髓系白血病（AML）患者化疗后早期微小残留病（MRD）水平与预后的关系。

方法

回顾性分析137例初治成人伴NPM1基因主要突变（A、B、D突变）AML患者的治疗结果，以及化疗后早期时间点MRD（NPM1突变转录本）水平对预后的影响。

结果

在137例患者中，男67例（48.9%），中位年龄49（16~67）岁，染色体正常核型107例（78.1%），FLT3-ITD突变阳性57例（41.6%），初诊时NPM1基因突变转录本中位水平84.1%（4.1%~509.9%）。在134例可评估的患者中，115例（85.8%）最终获完全缓解（CR）。多因素分析显示，WBC<100×10⁹/L（OR=0.3，95% CI 0.1~0.9，P=0.027）和初始诱导治疗为“IA10”方案（OR=0.3，95% CI 0.1~0.8，P=0.015）是获得CR的有利因素。在108例可评估的CR患者中，存活患者中位随访24（2~91）个月，3年无病生存（DFS）和总生存（OS）率分别为48.0%和63.9%。多因素分析显示，FLT3-ITD突变阳性（HR=3.2，95% CI 1.6~6.7，P=0.002）、巩固治疗2个疗程后MRD高水平（NPM1突变转录本水平较治疗前下降<3个对数级，HR=23.2，95% CI 7.0~76.6，P<0.001）、未接受异基因造血干细胞移植（allo-HSCT）（HR=2.6，95% CI 1.0~6.6，P=0.045）是影响患者DFS的不利因素；MRD在首次获得CR时高水平（NPM1突变转录本水平下降<2个对数级，HR=2.5，95% CI 1.0~6.1，P=0.040）和巩固治疗2个疗程后高水平（HR=4.5，95% CI 2.0~10.3，P<0.001）是影响患者OS的不利因素。进一步分析78例接受化疗（或自体移植）的CR患者，3年DFS和OS率分别为39.7%和59.1%，FLT3-ITD突变阳性和巩固治疗2个疗程后MRD高水平是独立影响患者DFS（HR=3.5，95% CI 1.6~7.6，P=0.002和HR=8.9，95% CI 3.8~20.7，P<0.001）和OS（HR=2.7，95% CI 1.1~6.9，P=0.036和HR=3.1，95% CI 1.2~8.0，P=0.021）的共同不利因素，此外，首次获得CR时MRD高水平（HR=3.1，95% CI 1.2~8.0，P=0.022）也是影响患者OS的不利因素。

结论

在NPM1突变阳性AML患者中，伴有FLT3-ITD突变和化疗后早期MRD高水平预示不良预后。

High NPM1-mutant allele burden at diagnosis predicts unfavorable outcomes in de novo AML

Acute myeloid leukemia (AML) with mutated NPM1 is a newly recognized separate entity in the revised 2016 World Health Organization classification and is associated with a favorable prognosis. Although previous studies have evaluated NPM1 in a binary fashion, little is known about the significance of its mutant allele burden at diagnosis, nor has the effect of comutations (other than FLT3) been extensively evaluated. We retrospectively used targeted sequencing data from 109 patients with de novo AML with mutated NPM1 to evaluate the potential significance of NPM1 variant allele frequency (VAF), comutations, and clinical parameters with regard to patient outcomes. We observed that high NPM1 VAF (uppermost quartile) correlated with shortened overall survival (median, 12.1 months vs not reached; P < .0001) as well as event-free survival (median, 7.5 vs 65.44 months; P < .0001) compared with the other NPM1-mutated cases. In both univariate and multivariable analyses, high NPM1 VAF had a particularly adverse prognostic effect in the subset of patients treated with stem-cell transplantation in first remission (P = .0004) and in patients with mutated DNMT3A (P < .0001). Our findings indicate that the prognostic effect of NPM1 mutation in de novo AML may be influenced by the relative abundance of the mutated allele.

Allogeneic hematopoietic cell transplantation in intermediate risk acute myeloid leukemia negative for FLT3-ITD, NPM1- or biallelic CEBPA mutations

Background

The value of allogeneic hematopoietic cell transplantation (alloHCT) as postremission treatment is not well defined for patients with intermediate-risk acute myeloid leukemia (AML) without FLT3-ITD, biallelic CEBPA-, or NPM1 mutations (here referred to as NPM1mut-neg/CEBPAdm-neg/FLT3-ITDneg AML) in first complete remission (CR1).

Patients and methods

We addressed this question using data from two prospective randomized controlled trials on intensive induction- and risk-stratified postremission therapy. The NPM1mut-neg/CEBPAdm-neg/FLT3-ITDneg AML subgroup comprised 497 patients, aged 18-60 years.

Results

In donor versus no-donor analyses, patients with a matched related donor had a longer relapse-free survival (HR 0.5; 95% CI 0.3-0.9, P = 0.02) and a trend toward better overall survival (HR 0.6, 95% CI 0.3-1.1, P = 0.08) compared with patients who received postremission chemotherapy. Notably, only 58% of patients in the donor group were transplanted in CR1. We therefore complemented the donor versus no-donor analysis with multivariable Cox regression analyses, where alloHCT was tested as a time-dependent covariate: overall survival (HR 0.58, 95% CI 0.37-0.9, P = 0.02) and relapse-free survival (HR 0.51, 95% CI 0.34-0.76; P = 0.001) for patients who received alloHCT compared with chemotherapy in CR1 were significantly longer.

Conclusion

Outside clinical trials, alloHCT should be the preferred postremission treatment of patients with intermediate risk NPM1mut-neg/CEBPAdm-neg/FLT3-ITDneg AML in CR1.

Cinicaltrials.gov identifier

NCT00180115, NCT00180102.

Targeting Leukemia Stem Cells in the Bone Marrow Niche

Abstract: The bone marrow (BM) niche encompasses multiple cells of mesenchymal and hematopoietic origin and represents a unique microenvironment that is poised to maintain hematopoietic stem cells. In addition to its role as a primary lymphoid organ through the support of lymphoid development, the BM hosts various mature lymphoid cell types, including naïve T cells, memory T cells and plasma cells, as well as mature myeloid elements such as monocyte/macrophages and neutrophils, all of which are crucially important to control leukemia initiation and progression. The BM niche provides an attractive milieu for tumor cell colonization given its ability to provide signals which accelerate tumor cell proliferation and facilitate tumor cell survival. Cancer stem cells (CSCs) share phenotypic and functional features with normal counterparts from the tissue of origin of the tumor and can self-renew, differentiate and initiate tumor formation. CSCs possess a distinct immunological profile compared with the bulk population of tumor cells and have evolved complex strategies to suppress immune responses through multiple mechanisms, including the release of soluble factors and the over-expression of molecules implicated in cancer immune evasion. This chapter discusses the latest advancements in understanding of the immunological BM niche and highlights current and future immunotherapeutic strategies to target leukemia CSCs and overcome therapeutic resistance in the clinic.

The who, how and why: Allogeneic transplant for acute myeloid leukemia in patients older than 60years

Acute myelogenous leukemia (AML) is primarily a disease of the elderly, and as such, our approach to treatment needs to be tailored to address an aging population. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only potentially curative treatment for intermediate and high risk AML, and until recently, its use had been limited to a younger population and dependent on availability of a donor. Advances in conditioning regimens, supportive care, and the use of alternative donor sources have greatly expanded access to this therapy. In this review, we summarize the challenges and unique biological aspects of treatment with allogeneic stem cell transplantation in this group of patients older than 60years. We also highlight areas of ongoing research including measurement of residual disease prior to and following transplant, post-remission maintenance therapy, and natural killer cell immunotherapy. Finally, we propose future directions for AML treatment in an elderly and aging population.

[A retrospective analysis of prognosis in favorable-risk acute myeloid leukemia patients with different consolidation regimens]

Objective: To explore the impact on prognosis in favorable-risk acute myeloid leukemia (AML) patients with different consolidation regimens after first complete remission (CR(1)). Methods: A total of 107 cases of non-refractory adult AML from January 2010 to June 2015 in single center were enrolled in the study. HD-Ara-C group (38 cases) as the control group, we explore the prognosis in three consolidation regimens, including micro-transplantation (16 cases) , autologous transplantation (auto-PBSCT, 14 cases) , allogeneic transplantation (allo-HSCT, 39 cases). Results: Of 107 patients (59 males and 48 females) , with a median age of 33 (16-59) years old and a median follow-up of 36.5 (5.3-79.1) months, the overall relapse rate was 20.6% (22/107) , and overall mortality rate was 18.7% (20/107). The 5 years cumulative relapse rate (CIR) of HD-Ara-C, micro-transplantation, auto-PBSCT and allo-HSCT group were 39.7%, 6.2%, 14.3% and 5.6%, respectively (P<0.001). The CIR of the observed group was lower than the HD-Ara-C group. The 5 years progression-free survival (PFS) rate of HD-Ara-C, micro-transplantation, auto-PBSCT and allo-HSCT group were 44.7%, 93.8%, 85.7% and 78.1%, respectively (P=0.011). The PFS of observed groups were similar, but superior to that in HD-Ara-C group. The 5-year overall survival (OS) in four groups was 54.9%, 100%, 92.9% and 77.4%, respectively (P>0.05). Multiple factors analysis showed that compared to HD-Ara-C regimen, allo-HSCT could improve PFS (HR=0.376, P=0.031) , but not OS (P>0.05) ; micro-transplantation and auto-PBSCT could not improve the PFS or OS (P>0.05). Conclusion: As compared with HD-Ara-C regimen, allo-HSCT could obviously decrease CIR, improve PFS, but treatment-related mortality is high. These results show that auto-PBSCT and micro-transplantation have similar outcomes, compared to HD-Ara-C regimen, so both can be used as a option of consolidation treatment for favorable-risk AML.

A Two-Phase Expansion Protocol Combining Interleukin (IL)-15 and IL-21 Improves Natural Killer Cell Proliferation and Cytotoxicity against Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue malignancy in children. Despite intensive research in recent decades the prognosis for patients with metastatic or relapsed diseases has hardly improved. New therapeutic concepts in anti-tumor therapy aim to modulate the patient’s immune system to increase its aggressiveness or targeted effects toward tumor cells. Besides surgery, radiotherapy and chemotherapy, immune activation by direct application of cytokines, antibodies or adoptive cell therapy are promising approaches. In the last years, adoptive transfer of natural killer (NK) cells came into the focus of translational medicine, because of their high cytotoxic potential against transformed malignant cells. A main challenge of NK cell therapy is that it requires a high amount of functional NK cells. Therefore, ex vivo NK cell expansion protocols are currently being developed. Many culturing strategies are based on the addition of feeder or accessory cells, which need to be removed prior to the clinical application of the final NK cell product. In this study, we addressed feeder cell-free expansion methods using common γ-chain cytokines, especially IL-15 and IL-21. Our results demonstrated high potential of IL-15 for NK cell expansion, while IL-21 triggered NK cell maturation and functionality. Hence, we established a two-phase expansion protocol with IL-15 to induce an early NK cell expansion, followed by short exposure to IL-21 that boosted the cytotoxic activity of NK cells against RMS cells. Further functional analyses revealed enhanced degranulation and secretion of pro-inflammatory cytokines such as interferon-γ and tumor necrosis factor-α. In a proof of concept in vivo study, we also observed a therapeutic effect of adoptively transferred IL-15 expanded and IL-21 boosted NK cells in combination with image guided high precision radiation therapy using a luciferase-transduced RMS xenograft model. In summary, this two-phased feeder cell-free ex vivo culturing protocol combined efficient expansion and high cytolytic functionality of NK cells for treatment of radiation-resistant RMS.

Impact of FAB classification on predicting outcome in acute myeloid leukemia, not otherwise specified, patients undergoing allogeneic stem cell transplantation in CR1: An analysis of 1690 patients from the acute leukemia working party of EBMT

The French, American, and British (FAB) classification system for acute myeloid leukemia (AML) is extensively used and is incorporated into the AML, not otherwise specified (NOS) category in the 2016 WHO edition of myeloid neoplasm classification. While recent data proposes that FAB classification does not provide additional prognostic information for patients for whom NPM1 status is available, it is unknown whether FAB still retains a current prognostic role in predicting outcome of AML patients undergoing allogeneic stem cell transplantation. Using the European Society of Blood and Bone Marrow Transplantation registry we analyzed outcome of 1690 patients transplanted in CR1 to determine if FAB classification provides additional prognostic value. Multivariate analysis revealed that M6/M7 patients had decreased leukemia free survival (hazard ratio (HR) of 1.41, 95% confidence interval (CI), 1.01-1.99; P = .046) in addition to increased nonrelapse mortality (NRM) rates (HR, 1.79; 95% CI, 1.06-3.01; P = .028) compared with other FAB types. In the NPM1^wt AML, NOS cohort, FAB M6/M7 was also associated with increased NRM (HR, 2.17; 95% CI, 1.14-4.16; P = .019). Finally, in FLT3-ITD⁺ patients, multivariate analyses revealed that specific FAB types were tightly associated with adverse outcome. In conclusion, FAB classification may predict outcome following transplantation in AML, NOS patients.

Combination of cytogenetic classification and MRD status correlates with outcome of autologous versus allogeneic stem cell transplantation in adults with primary acute myeloid leukemia in first remission

Both autologous and allogeneic stem cell transplantation (auto- and allo-SCT) are treatment choice for adults with acute myeloid leukemia (AML) after complete remission (CR). However, the decision-making remains controversial in some situations. To figure out the treatment choice, we retrospectively investigated 172 consecutive patients with primary AML who received auto- (n=46) or allo-SCT (n=126) from a single transplant center. Auto- and allo-SCT group demonstrated comparable overall survival (OS) and disease-free survival (DFS) (P=0.616, P=0.559, respectively). Cytogenetic classification and minimal residual disease (MRD) after one course of consolidation were identified as independent risk factors for DFS (hazard ratio (HR), 1.800; 95% CI, 1.172-2.763; P=0.007; HR, 2.042; 95%CI, 1.003-4.154; P=0.049; respectively). We subsequently found that auto- and allo-SCT offered comparable DFS to patients with favorable or intermediate risk and were tested MRD^neg after one course of consolidation (P=0.270) otherwise auto-SCT were inferior due to increased risk of leukemia relapse. Our study indicated that the combination of cytogenetic classification and MRD monitoring correlated with outcome of auto- versus allo-SCT and might help the choice between the two types of SCT for adults with primary AML, which is of significance for patients with expected intermediate prognosis in the current scenario.

Marker chromosomes can arise from chromothripsis and predict adverse prognosis in acute myeloid leukemia

Metaphase karyotyping is an established diagnostic standard in acute myeloid leukemia (AML) for risk stratification. One of the cytogenetic findings in AML is structurally highly abnormal marker chromosomes. In this study, we have assessed frequency, cytogenetic characteristics, prognostic impact, and underlying biological origin of marker chromosomes. Given their inherent gross structural chromosomal damage, we speculated that they may arise from chromothripsis, a recently described phenomenon of chromosome fragmentation in a single catastrophic event. In 2 large consecutive prospective, randomized, multicenter, intensive chemotherapy trials (AML96, AML2003) from the Study Alliance Leukemia, marker chromosomes were detectable in 165/1026 (16.1%) of aberrant non-core-binding-factor (CBF) karyotype patients. Adverse-risk karyotypes displayed a higher frequency of marker chromosomes (26.5% in adverse-risk, 40.3% in complex aberrant, and 41.2% in abnormality(17p) karyotypes, P < .0001 each). Marker chromosomes were associated with a poorer prognosis compared with other non-CBF aberrant karyotypes and led to lower remission rates (complete remission + complete remission with incomplete recovery), inferior event-free survival as well as overall survival in both trials. In multivariate analysis, marker chromosomes independently predicted poor prognosis in the AML96 trial ≤60 years. As detected by array comparative genomic hybridization, about one-third of marker chromosomes (18/49) had arisen from chromothripsis, whereas this phenomenon was virtually undetectable in a control group of marker chromosome-negative complex aberrant karyotypes (1/34). The chromothripsis-positive cases were characterized by a particularly high degree of karyotype complexity, TP53 mutations, and dismal prognosis. In conclusion, marker chromosomes are indicative of chromothripsis and associated with poor prognosis per se and not merely by association with other adverse cytogenetic features.

Should autotransplantation in acute myeloid leukemia in first complete remission be revisited?

PURPOSE OF REVIEW

Despite numerous studies, the best postremission therapy in acute myeloid leukemia (AML) is a subject of intense controversy. Major prognostic factors for disease outcome are the genetic alterations of AML, patient's age, and performance status. AML is more common in older adults, with a median age of 72 years. However, in this age group the unfavorable cytogenetics dominates at a time when biologically it may be most difficult to administer optimal intensive therapy.

RECENT FINDINGS

Autologous stem cell transplantation (ASCT) enables the administration of high-dose therapy supported by stem cell infusion with a treatment-related toxicity not significantly higher than that associated with chemotherapy and significantly lower than in allogeneic stem cell transplantation. The dilemma of best postremission therapy has not been resolved because of the paucity of randomized controlled studies, especially in various cytogenetic risk and age groups. Instead, the use of genetic randomization by donor availability, analysis of outcome based on intention-to-treat, and mixed populations in the registry data produce variable results.

SUMMARY

ASCT has been associated with prolonged disease-free survival as compared to chemotherapy, especially in the favorable and intermediate risk groups. Advances in immunotherapy in AML may propel ASCT as a platform for various immunologic maneuvers.

Risk factors for relapse after allogeneic transplantation in acute myeloid leukemia

Acute myeloid leukemia is a clonal neoplasm derived from myeloid progenitor cells with a varying outcome. The initial goal of treatment is the achievement of complete remission, defined for over 40 years by morphology. However, without additional post-remission treatment the majority of patients relapse. In many cases of acute myeloid leukemia, allogeneic stem cell transplantation offers the best prospects of cure. In 2013, 5608 stem cell transplantations in acute myeloid leukemia were performed in Europe (5228 allogeneic and 380 autologous stem cell transplantations). Most stem cell transplantations are performed in first complete remission. However, despite a considerable reduction in the chance of relapse, in most studies, overall survival benefit of allogeneic stem cell transplantation is modest due to substantial non-relapse mortality. Here we discuss the many factors related to the risk of relapse after allogeneic stem cell transplantation.

'Acute myeloid leukemia: a comprehensive review and 2016 update'

Acute myeloid leukemia (AML) is the most common acute leukemia in adults, with an incidence of over 20 000 cases per year in the United States alone. Large chromosomal translocations as well as mutations in the genes involved in hematopoietic proliferation and differentiation result in the accumulation of poorly differentiated myeloid cells. AML is a highly heterogeneous disease; although cases can be stratified into favorable, intermediate and adverse-risk groups based on their cytogenetic profile, prognosis within these categories varies widely. The identification of recurrent genetic mutations, such as FLT3-ITD, NMP1 and CEBPA, has helped refine individual prognosis and guide management. Despite advances in supportive care, the backbone of therapy remains a combination of cytarabine- and anthracycline-based regimens with allogeneic stem cell transplantation for eligible candidates. Elderly patients are often unable to tolerate such regimens, and carry a particularly poor prognosis. Here, we review the major recent advances in the treatment of AML.