Improved outcome of pediatric patients with acute megakaryoblastic leukemia in the AML-BFM 04 trial

Outcomes and prognosis of haploidentical haematopoietic stem cell transplantation in children with FLT3-ITD mutated acute myeloid leukaemia

The presence of internal tandem duplication mutations in the FMS-like tyrosine kinase 3 receptor (FLT3-ITD) is a poor prognostic predictor in paediatric patients with acute myeloid leukaemia (AML). We evaluated the treatment outcomes and prognostic factors of 45 paediatric patients with FLT3-ITD AML who achieved complete remission before haploidentical haematopoietic stem cell transplantation (haplo-HSCT) at our institution from 2012 to 2021. Among the 45 patients, the overall survival (OS), event‑free survival (EFS), and cumulative incidence of relapse (CIR) rates were 74.9% ± 6.6%, 64.1% ± 7.2%, and 31.4% ± 7.1%, respectively, with 48.8 months of median follow-up. Univariate and multivariate analyses associated positive minimal residual disease (MRD) at pre-HSCT and non-remission (NR) after introduce 1 with inferior long-term survival. The 100-day cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was 35.6% ± 5.2%, and that of grade III-IV aGVHD was 15.6% ± 3.0% The overall 4-year cumulative incidence of chronic graft-versus-host disease after transplantation was 35.7% ± 9.8%, respectively. In conclusion, haplo-HSCT may be a feasible strategy for paediatric patients with FLT3-ITD AML, and pre-HSCT MRD status and NR after introduce 1 significantly affected the outcomes.

A retrospective analysis of gene fusions and treatment outcomes in pediatric acute megakaryoblastic leukemia without Down syndrome

Not available.

Clinical Analysis of Pediatric Acute Megakaryocytic Leukemia With CBFA2T3-GLIS2 Fusion Gene

CBFA2T3-GLIS2 is the most frequent chimeric oncogene identified to date in non-Down syndrome acute megakaryocytic leukemia (AMKL), which is associated with extremely poor clinical outcome. The presence of this fusion gene is associated with resistance to high-intensity chemotherapy, including hematopoietic stem cell transplantation (HSCT), and a high cumulative incidence of relapse frequency. The clinical features and clinical effects of China Children's Leukemia Group-acute myeloid leukemia (AML) 2015/2019 regimens and haploidentical HSCT (haplo-HSCT) for treatment of 6 children harboring the CBFA2T3-GLIS2 fusion gene between January 2019 and December 2021 were retrospectively analyzed. The 6 patients included 4 boys and 2 girls with a median disease-onset age of 19.5 months (range: 6-67 mo) who were diagnosed with AMKL. Flow cytometry demonstrated CD41a, CD42b, and CD56 expression and lack of HLA-DR expression in all 6 patients. All the children were negative for common leukemia fusion genes by reverse transcription polymerase chain reaction, but positive for the CBFA2T3-GLIS2 fusion gene by next-generation sequencing and RNA sequencing. All patients received chemotherapy according to China Children's Leukemia Group-AML 2015/2019 regimens, and 4 achieved complete remission. Four children underwent haplo-HSCT with posttransplant cyclophosphamide-based conditioning; 3 had minimal residual disease negative (minimal residual disease <0.1%) confirmed by flow cytometry at the end of the follow-up, with the remaining patient experiencing relapse at 12 months after transplantation. Transcriptome RNA sequencing is required for the detection of the CBFA2T3-GLIS2 fusion gene and for proper risk-based allocation of pediatric patients with AML in future clinical strategies. Haplo-HSCT with posttransplant cyclophosphamide-based conditioning may improve survival in children with AMKL harboring the fusion gene.

Rare Hematologic Malignancies and Pre-Leukemic Entities in Children and Adolescents Young Adults

There are a variety of rare hematologic malignancies and germline predispositions syndromes that occur in children and adolescent young adults (AYAs). These entities are important to recognize, as an accurate diagnosis is essential for risk assessment, prognostication, and treatment. This descriptive review summarizes rare hematologic malignancies, myelodysplastic neoplasms, and germline predispositions syndromes that occur in children and AYAs. We discuss the unique biology, characteristic genomic aberrations, rare presentations, diagnostic challenges, novel treatments, and outcomes associated with these rare entities.

Myeloid sarcoma with RBM15::MRTFA (MKL1) mimicking vascular neoplasm

Extramedullary involvement of acute myeloid leukemia (AML), aka myeloid sarcoma, is a rare phenomenon in acute megakaryoblastic leukemia with RBM15:: MRTFA(MKL1) fusion, which might mimic non-hematologic malignancies. A 7-month-old infant presented with leukocytosis, hepatosplenomegaly, multiple lymphadenopathies, and a solid mass in the right thigh. Initially, the patient was diagnosed with a malignant vascular tumor regarding the expression of vascular markers from the biopsy of the right thigh lesion that was performed after the inconclusive bone marrow biopsy. The second bone marrow biopsy, which was performed due to the partial response to sarcoma treatment, showed hypercellular bone marrow with CD34 and CD61-positive spindle cell infiltration and > 20% basophilic blasts with cytoplasmic blebs. RNA sequencing of soft tissue biopsy revealed the presence of RBM15::MRTFA(MKL1) fusion. Based on these findings, myeloid sarcoma/AML with RBM15::MRTFA(MKL1) fusion diagnosis was made. AML with RBM15::MRTFA(MKL1) fusion can initially present as extramedullary lesions and might cause misdiagnosis of non-hematologic malignancies.

Long-term follow-up of haploidentical haematopoietic stem cell transplantation in paediatric patients with high-risk acute myeloid leukaemia: Report from a single centre

Data from 200 children with high-risk acute myeloid leukaemia who underwent their first haploidentical haematopoietic stem cell transplantation (haplo-HSCT) between 2015 and 2021 at our institution were analysed. The 4-year overall survival (OS), event-free survival (EFS) and cumulative incidence of relapse (CIR) were 71.9%, 62.3% and 32.4% respectively. The 100-day cumulative incidences of grade II-IV and III-IV acute graft-versus-host disease (aGVHD) were 41.1% and 9.5% respectively. The 4-year cumulative incidence of chronic GVHD (cGVHD) was 56.1%, and that of moderate-to-severe cGVHD was 27.3%. Minimal residual disease (MRD)-positive (MRD+) status pre-HSCT was significantly associated with lower survival and a higher risk of relapse. The 4-year OS, EFS and CIR differed significantly between patients with MRD+ pre-HSCT (n = 97; 63.4%, 51.4% and 41.0% respectively) and those with MRD-negative (MRD-) pre-HSCT (n = 103; 80.5%, 73.3% and 23.8% respectively). Multivariate analysis also revealed that acute megakaryoblastic leukaemia without Down syndrome (non-DS-AMKL) was associated with extremely poor outcomes (hazard ratios and 95% CIs for OS, EFS and CIR: 3.110 (1.430-6.763), 3.145 (1.628-6.074) and 3.250 (1.529-6.910) respectively; p-values were 0.004, 0.001 and 0.002 respectively). Thus, haplo-HSCT can be a therapy option for these patients, and MRD status pre-HSCT significantly affects the outcomes. As patients with non-DS-AMKL have extremely poor outcomes, even with haplo-HSCT, a combination of novel therapies is urgently needed.

Analysis 33 patients of non-DS-AMKL with or without acquired trisomy 21 from multiple centers and compared to 118 AML patients

BACKGROUND

Acute megakaryoblastic leukemia (AMKL) without Down syndrome (non-DS-AMKL) usually a worse outcome than DS-AMKL. Acquired trisomy 21(+21) was one of the most common cytogenetic abnormalities in non-DS-AMKL. Knowledge of the difference in the clinical characteristics and prognosis between non-DS-AMKL with +21 and those without +21 is limited.

OBJECTIVE

Verify the clinical characteristics and prognosis of non-DS-AMKL with +21.

METHOD

We retrospectively analyzed 33 non-DS-AMKL pediatric patients and 118 other types of AML, along with their clinical manifestations, laboratory data, and treatment response.

RESULTS

Compared with AMKL without +21, AMKL with +21 has a lower platelet count (44.04 ± 5.01G/L) at onset (P > 0.05). Differences in remission rates between AMKL and other types of AML were not significant. Acquired trisomy 8 in AMKL was negatively correlated with the long-term OS rate (P < 0.05), while +21 may not be an impact factor. Compared with the other types of AML, AMKL has a younger onset age (P < 0.05), with a mean of 22.27 months. Anemia, hemorrhage, lymph node enlargement, lower white blood cell, and complex karyotype were more common in AMKL (P < 0.05). AMKL has a longer time interval between onset to diagnosis (53.61 ± 71.15 days) (P < 0.05), and patients with a diagnosis delay ≥3 months always presented as thrombocytopenia or pancytopenia initially.

CONCLUSIONS

Due to high heterogeneity, high misdiagnosis rate, and myelofibrosis, parts of AMKL may take a long time to be diagnosed, requiring repeated bone marrow punctures. Complex karyotype was common in AMKL. +21 may not be a promising indicator of a poor prognosis.

Understanding WT1 Alterations and Expression Profiles in Hematological Malignancies

WT1 is a true chameleon, both acting as an oncogene and tumor suppressor. As its exact role in leukemogenesis is still ambiguous, research with model systems representing natural conditions surrounding the genetic alterations in WT1 is necessary. In a cohort of 59 leukemia/lymphoma cell lines, we showed aberrant expression for WT1 mRNA, which does not always translate into protein levels. We also analyzed the expression pattern of the four major WT1 protein isoforms in the cell lines and primary AML blasts with/without WT1 mutations and demonstrated that the presence of mutations does not influence these patterns. By introduction of key intronic and exonic sequences of WT1 into a lentiviral expression vector, we developed a unique tool that can stably overexpress the four WT1 isoforms at their naturally occurring tissue-dependent ratio. To develop better cellular model systems for WT1, we sequenced large parts of its gene locus and also other important myeloid risk factor genes and revealed previously unknown alterations. Functionally, inhibition of the nonsense-mediated mRNA decay machinery revealed that under natural conditions, the mutated WT1 alleles go through a robust degradation. These results offer new insights and model systems regarding the characteristics of WT1 in leukemia and lymphoma.

Pediatric Hematopathology in the Era of Advanced Molecular Diagnostics: What We Know and How We Can Apply the Updated Classifications

Pediatric hematologic malignancies often show genetic features distinct from their adult counterparts, which reflect the differences in their pathogenesis. Advances in the molecular diagnostics including the widespread use of next-generation sequencing technology have revolutionized the diagnostic workup for hematologic disorders and led to the identification of new disease subgroups as well as prognostic information that impacts the clinical treatment. The increasing recognition of the importance of germline predisposition in various hematologic malignancies also shapes the disease models and management. Although germline predisposition variants can occur in patients with myelodysplastic syndrome/neoplasm (MDS) of all ages, the frequency is highest in the pediatric patient population. Therefore, evaluation for germline predisposition in the pediatric group can have significant clinical impact. This review discusses the recent advances in juvenile myelomonocytic leukemia, pediatric acute myeloid leukemia, B-lymphoblastic leukemia/lymphoma, and pediatric MDS. This review also includes a brief discussion of the updated classifications from the International Consensus Classification (ICC) and the 5th edition World Health Organization (WHO) classification regarding these disease entities.

Pediatric Non-Down Syndrome Acute Megakaryoblastic Leukemia With Unusual Immunophenotype

Acute megakaryoblastic leukemia (AMKL) is a rare subtype of acute myeloid leukemia (AML) characterized by abnormal megakaryoblasts expressing platelet-specific surface antigens. 4%-16% of childhood AMLs are AMKL. Childhood AMKL is usually associated with Down syndrome (DS). It is 500 times more common in patients with DS when compared to the general population. In contrast, non-DS-AMKL is much rarer. We describe a case of de novo non-DS-AMKL in a teenage girl child who presented with a history of excessive tiredness, fever, abdominal pain for three months, and vomiting for four days. She had lost appetite, and weight. On examination she was pale; there was no clubbing, hepatosplenomegaly or lymphadenopathy. There were no dysmorphic features or neurocutaneous markers. Laboratory tests showed bicytopenia (Hb: 6.5g/dL, total WBC count: 700/µL, platelet count: 216,000/ µL, Reticulocyte %: 0.42) and 14% blasts on the peripheral blood smear. Platelet clumps and anisocytosis were also noted. Bone marrow aspirate showed a few hypocellular particles with dilute cell trails but showed 42% blasts. Mature megakaryocytes showed marked dyspoiesis. Flow cytometry on bone marrow aspirate showed myeloblasts and megakaryoblasts. Karyotyping showed 46 XX. Hence, a final diagnosis of non-DS-AMKL was established. She was treated symptomatically. However, she was discharged on request. Interestingly, the expression of erythroid markers such as CD36 and lymphoid markers like CD7 is usually seen in DS-AMKL and not in non-DS-AMKL. AMKL is treated with AML-directed chemotherapies. Although complete remission rates are similar to other AML subtypes, overall survival is only about 18-40 weeks.

Haematopoietic cell transplantation for children with acute megakaryoblastic leukaemia without Down syndrome

Patients with acute megakaryoblastic leukaemia of Down syndrome (DS-AMKL) have an excellent survival rate; however, patients with non-DS-AMKL experience poor outcomes. Therefore, this study retrospectively analysed 203 children with non-DS-AMKL who underwent their first haematopoietic cell transplantation (HCT) from 1986 to 2015 using a nationwide Japanese HCT registry data to assess HCT outcomes for non-DS-AMKL. The 5-year overall survival (OS) and event-free survival (EFS) rates were 43% and 38% respectively. The 5-year OS rate was significantly higher for patients who underwent HCT in the first complete remission (CR1, 72%) than for those in the second CR (CR2, 23%) and non-CR (16%) (p < 0.001), and for those from a human leukocyte antigen (HLA)-matched (52%) than for those from an HLA-mismatched donor (27%) (p < 0.001). Multivariate analysis for OS revealed that HCT in CR2 and non-CR was a significant risk factor (hazard ratio, 5.86; 95% confidence interval, 3.56-9.53; p < 0.001). The 3-year EFS in patients who received HCT in CR1 using reduced-intensity conditioning (RIC, 35%) was significantly lower than in those using myeloablative conditioning (busulfan-based, 71%; total body irradiation-based, 58%) (p < 0.001). Risk stratification in patients with non-DS-AMKL should be established to determine HCT indication in CR1.

t(1;7;22)(p13;q21;q13) is a novel 3-way variant of t(1;22)(p13;q13) neonatal acute megakaryoblastic leukemia: A case report

Acute megakaryoblastic leukemia (AMKL) is a rare disease, occurring mostly in infants and young children. The chromosomal translocation t(1;22)(p13;q13), resulting in the RBM15-MKL1 fusion gene, is a recurrent and diagnostic translocation in infants with AMKL. The present case report describes a case of a newborn girl, without Down's syndrome, with congenital AMKL. At birth, the infant had hepatosplenomegaly and the peripheral blood count revealed anemia, thrombopenia and leukocytosis, with 28% blasts. Immunophenotyping demonstrated blasts positive for CD34, CD61 and CD42b. Karyotyping of these blasts (R-banding) showed a hitherto unreported chromosomal translocation, t(1;7;22)(p13;q21;q13), a 3-way variant of the t(1;22)(p13;q13) variant. Fluorescent in situ hybridization analysis confirmed the presence of the RBM15-MKL1 fusion gene.

Unmanipulated haploidentical hematopoietic stem cell transplantation for pediatric de novo acute megakaryoblastic leukemia without Down syndrome in China: A single-center study

Background

AMKL without DS is a rare but aggressive hematological malignant disease in children, and it is associated with inferior outcomes. Several researchers have regarded pediatric AMKL without DS as high-risk or at least intermediate-risk AML and proposed that upfront allogenic hematopoietic stem cell transplantation (HSCT) in first complete remission might improve long-term survival.

Patients and method

We conducted a retrospective study with twenty-five pediatric (< 14 years old) AMKL patients without DS who underwent haploidentical HSCT in the Peking University Institute of Hematology, Peking University People's Hospital from July 2016 to July 2021. The diagnostic criteria of AMKL without DS were adapted from the FAB and WHO: ≥ 20% blasts in the bone marrow, and those blasts expressed at least one or more of the platelet glycoproteins: CD41, CD61, or CD42. AMKL with DS and therapy related AML was excluded. Children without a suitable closely HLA-matched related or unrelated donor (donors with more than nine out of 10 matching HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ loci), were eligible to receive haploidentical HSCT. Definition was adapted from international cooperation group. All statistical tests were conducted with SPSS v.24 and R v.3.6.3.

Results

The 2-year OS was 54.5 ± 10.3%, and the EFS was 50.9 ± 10.2% in pediatric AMKL without DS undergoing haplo-HSCT. Statistically significantly better EFS was observed in patients with trisomy 19 than in patients without trisomy 19 (80 ± 12.6% and 33.3 ± 12.2%, respectively, P = 0.045), and OS was better in patients with trisomy 19 but with no statistical significance (P = 0.114). MRD negative pre-HSCT patients showed a better OS and EFS than those who were positive (P < 0.001 and P = 0.003, respectively). Eleven patients relapsed post HSCT. The median time to relapse post HSCT was 2.1 months (range: 1.0-14.4 months). The 2-year cumulative incidence of relapse (CIR) was 46.1 ± 11.6%. One patient developed bronchiolitis obliterans and respiratory failure and died at d + 98 post HSCT.

Conclusion

AMKL without DS is a rare but aggressive hematological malignant disease in children, and it is associated with inferior outcomes. Trisomy 19 and MRD negative pre-HSCT might contribute to a better EFS and OS. Our TRM was low, haplo-HSCT might be an option for high-risk AMKL without DS.

Lineage switch in a pediatric patient with KMT2A-MLLT3 from acute megakaryoblastic leukemia to T cell acute lymphoblastic leukemia at the fourth relapse after allo-HSCT: with literature review

We present a patient with acute megakaryoblastic leukemia (AMKL) harboring KMT2A-MLLT3 that converted to T cell acute lymphoblastic leukemia (T-ALL) at her fourth relapse. A 4-year-old girl developed AMKL with multiple swollen lymph nodes. She exhibited several recurrences in the bone marrow and died of septic shock after her fourth relapse. Bone marrow cells at the initial diagnosis and at all four relapses had the same KMT2A-MLLT3 fusion transcript. She also developed a somatic mutation (c.7177C > T p.Q2393X) of NOTCH1 at the fourth relapse. This sequential phenotypic and cytogenetic study may yield valuable insights into the mechanism of AMKL to T-ALL lineage switch and possible implications for treatment selection.

Pediatric non–Down’s syndrome acute megakaryoblastic leukemia patients in China: A single center's real-world analysis

Non-Down’s syndrome acute megakaryocytic leukemia (non-DS-AMKL) is a subtype of childhood acute myeloid leukemia (AML), whose prognosis, prognostic factors and treatment recommendations have not yet to be defined in children. We conducted a retrospective study with 65 newly diagnosed non-DS-AMKL children from August 2003 to June 2020 to investigate the clinical impact of factors and clinical outcome. Among all 65 patients, 47 of them were treated at our center who received three different regimens due to time point of admission (CAMS-another, CAMS-2009 and CAMS-2016 protocol), and the efficacy were compared. Patients with newly diagnosed non-DS-AMKL accounted for 7.4% of pediatric AML cases. The median age of the patients was 18 months at diagnosis, and over 90% of them were under three-years-old. The overall survival (OS) rates were 33.3% ± 1.7%, 66.7% ± 24.4% and 74.2% ± 4.0% for three groups (CAMS-another, CAMS-2009 and CAMS-2016 regimen), respectively. In CAMS-2016 group, the complete remission (CR) rate after induction was 67.7% (21/31), while the total CR rate after all phases of chemotherapy was 80.6% (25/31). The 2-year survival probability did not significantly improve in patients underwent HSCT when compared with non-HSCT group (75.0% ± 4.7% vs. 73.9% ± 4.6%, p=0.680). Those who had a “dry tap” during BM aspiration at admission had significantly worse OS than those without “dry tap” (33.3% ± 8.6% vs. 84.0% ± 3.6%, p=0.006). Moreover, the results also revealed that patients with CD34+ had significantly lower OS (50.0% ± 6.7% vs. 89.5% ± 3.5%, p=0.021), whereas patients with CD36+ had significantly higher OS than those who were negative (85.0% ± 4.0% vs. 54.5% ± 6.6%, p=0.048). In conclusion, intensive chemotherapy resulted in improved prognosis of non-DS-AMKL children and subclassification may base on “dry tap” and immunophenotypic. Although some progress has been made, outcomes of non-DS-AMKL children remain unsatisfactory, especially in HSCT group, when compared with other AML types.

Targeting cyclin-dependent kinases 4/6 inhibits survival of megakaryoblasts in acute megakaryoblastic leukaemia

Acute megakaryoblastic leukaemia (AMKL) is characterized by expansion of megakaryoblasts, which are hyper-proliferative cells that fail to undergo differentiation. Insight to the cell-cycle regulation revealed important events in early or late megakaryocytes (MKs) maturation; the cyclin-dependent kinases 4 and 6 (CDK4/6) have been reported to participate in the development of progenitor megakaryocytes, mainly by promoting cell cycle progression and DNA polyploidization. However, it remains unclear whether the continuous proliferation, but not differentiation, of megakaryoblasts is related to an aberrant regulation of CDK4/6 in AMKL. Here, we found that CDK4/6 were up regulated in patients with AMKL, and persistently maintained at a high level during the differentiation of abnormal megakaryocytes in vitro, according to a database and western blot. Additionally, AMKL cells were exceptionally reliant on the cell cycle regulators CDK4 or 6, as blocking their activity using an inhibitor or short hairpin RNA (shRNA) significantly reduced the proliferation of 6133/MPL megakaryocytes, reduced DNA polyploidy, induced apoptosis, decreased the level of phosphorylated retinoblastoma protein (p-Rb), and activation of caspase 3. Additionally, CDK4/6 inhibitors and shRNA reduced the numbers of leukemia cells in the liver and bone marrow (BM), alleviated hepatosplenomegaly, and prolonged the survival of AMKL-transplanted mice. These results suggested that blocking the activity of CDK4/6 may represent an effective approach to control megakaryoblasts in AMKL.

Interactive Video Games as a Method to Increase Physical Activity Levels in Children Treated for Leukemia

Despite the beneficial effect of exercise, children treated for cancer do not engage in sufficient physical activity. It is necessary to search for attractive forms of physical activity, including interactive video games (IVGs). The aim of this study was to verify the effectiveness of the rehabilitation model developed by the authors based on the use of IVGs in children undergoing leukemia treatment. The study included a group of 21 children aged 7–13 years (12 boys, 9 girls) undergoing treatment for acute lymphoblastic leukemia (ALL) (n = 13) and acute myeloid leukemia (AML) (n = 8). The children were randomly assigned to an intervention group and a control group. To assess the level of cardiorespiratory fitness (CRF), each child participated in a Cardiopulmonary Exercise Test. Daily physical activity was assessed using the HBSC questionnaire. The study also used the Children’s Effort Rating Table Scale (CERT) to assess the intensity of physical effort. The children in the intervention group participated in 12 sessions of. The study participants managed to complete all stages of a progressive training program, which confirmed the feasibility of such physical effort by patients with cancer. Pediatric patients reported that the IVG training required a light to moderate physical effort despite high values of energy expenditure (EE).

High EVI1 Expression Predicts Adverse Outcomes in Children With De Novo Acute Myeloid Leukemia

Background

A high ecotropic viral integration site 1 (EVI1) expression (EVI1^high) is an independent prognostic factor in adult acute myeloid leukemia (AML). However, little is known of the prognostic value of EVI1^high in pediatric AML. This study aimed to examine the biological and prognostic significance of EVI1^high in uniformly treated pediatric patients with AML from a large cohort of seven centers in China.

Methods

A diagnostic assay was developed to determine the relative EVI1 expression using a single real-time quantitative polymerase chain reaction in 421 newly diagnosed pediatric AML patients younger than 14 years from seven centers in southern China. All patients were treated with a uniform protocol, but only 383 patients were evaluated for their treatment response. The survival data were included in the subsequent analysis (n = 35 for EVI1^high, n = 348 for EVI1^low).

Results

EVI1^high was found in 9.0% of all 421 pediatric patients with de novo AML. EVI1^high was predominantly found in acute megakaryoblastic leukemia (FAB M7), MLL rearrangements, and unfavorable cytogenetic aberrance, whereas it was mutually exclusive with t (8; 21), inv (16)/t (16; 16), CEBPA, NPM1, or C-KIT mutations. In the univariate Cox regression analysis, EVI1^high had a significantly adverse 5-year event-free survival (EFS) and overall survival (OS) [hazard ratio (HR) = 1.821 and 2.401, p = 0.036 and 0.005, respectively]. In the multivariate Cox regression analysis, EVI1^high was an independent prognostic factor for the OS (HR = 2.447, p = 0.015) but not EFS (HR = 1.556, p = 0.174). Furthermore, EVI1^high was an independent adverse predictor of the OS and EFS of patients with MLL rearrangements (univariate analysis: HR = 9.921 and 7.253, both p < 0.001; multivariate analysis: HR = 7.186 and 7.315, p = 0.005 and 0.001, respectively). Hematopoietic stem cell transplantation (HSCT) in first complete remission (CR1) provided EVI1^high patients with a tendential survival benefit when compared with chemotherapy as a consolidation (5-year EFS: 68.4% vs. 50.8%, p = 0.26; 5-year OS: 65.9% vs. 54.8%, p = 0.45).

Conclusion

It could be concluded that EVI1^high can be detected in approximately 10% of pediatric AML cases. It is predominantly present in unfavorable cytogenetic subtypes and predicts adverse outcomes. Whether pediatric patients with EVI1^high AML can benefit from HSCT in CR1 needs to be researched further.

Recommendations for Diagnosis and Treatment of Children with Transient Abnormal Myelopoiesis (TAM) and Myeloid Leukemia in Down Syndrome (ML-DS)

Children with Down syndrome are at a high risk of developing transient abnormal myelopoiesis (TAM; synonym: TMD) or myeloid leukemia (ML-DS). While most patients with TAM are asymptomatic and go into spontaneous remission without a need for therapy, around 20% of patients die within the first six months due to TAM-related complications. Another 20-30% of patients progress from TAM to ML-DS. ML-DS patients are particularly vulnerable to therapy-associated toxicity, but the prognosis of relapsed ML-DS is extremely poor - thus, ML-DS therapy schemata must strive for a balance between appropriate efficacy (to avoid relapses) and treatment-related toxicity. This guideline presents diagnostic and therapeutic strategies for TAM and ML-DS based on the experience and results of previous clinical studies from the BFM working group, which have helped reduce the risk of early death in symptomatic TAM patients using low-dose cytarabine, and which have achieved excellent cure rates for ML-DS using intensity-reduced treatment protocols.

[Clinical features and prognosis of pediatric acute megakaryocytic leukemia]

OBJECTIVE

To study the clinical features and prognosis of children with acute megakaryocytic leukemia (AMKL) and the clinical effect of acute myeloid leukemia 03 (AML03) regimen for the treatment of pediatric AMKL.

METHODS

The clinical data were collected from 47 children with AMKL who were diagnosed from May 2011 to December 2019. The treatment outcomes and prognostic factors were analyzed. The Kaplan-Meier method and the log-rank test were used for survival analysis.

RESULTS

Among the 47 children with AMKL, 22 with non-Down syndrome-AMKL were treated by the AML03 regimen, with a median follow-up time of 11.4 months. For the 22 non-Down syndrome-AMKL patients, the remission rate of bone marrow cytology was 85% and the negative rate of minimal residual disease (MRD) was 79% after induction Ⅱ, with a 2-year overall survival (OS) rate of (50±13)% and a 2-year event-free survival (EFS) rate of (40±12)%. The group with positive immunophenotypic marker CD56 had significantly lower 2-year EFS and OS rates than the group with negative CD56 (P < 0.05). The group without remission of bone marrow cytology after induction Ⅱ had significantly lower 2-year EFS and OS rates than the group with remission (P < 0.05). The group with positive MRD after induction Ⅱ had a significantly lower 2-year EFS rate than the group with negative MRD (P < 0.05). There was no significant difference in 2-year OS and EFS rates between the patients with transplantation and those without transplantation (P > 0.05).

CONCLUSIONS

Children with AMKL tend to have a low remission rate and a poor prognosis. Positive immunophenotypic marker CD56, bone marrow cytology during early treatment response, and MRD results are important factors influencing the prognosis. Allogeneic hematopoietic stem cell transplantation has no significant effect on the prognosis of AMKL.

Outcome of pediatric acute myeloid leukemia (AML) in low- and middle-income countries: a systematic review of the literature

Introduction: Survival rates of pediatric acute myeloid leukemia (AML) in low- and middle-income countries (LMICs) seem extremely poor, and the available literature on the matter is scarce. Accordingly, there is a limited understanding of poor treatment outcomes seen in this population.Areas covered: We provide an overview of the available literature with respect to treatment outcomes of pediatric AML in LMICs yielding poor outcomes compared to high-income countries. Moreover, treatment outcomes vary markedly between LMICs. In addition, there is a wide variation among studies in how treatment outcomes are reported and analyzed.Expert opinion: The substantially inferior treatment outcomes of pediatric AML in LMICs emphasize the unprecedented importance of global initiatives and international collaborations to improve the survival of these patients. A coordinated approach is necessary to carry out country-specific situational analyses. These analyses will result in operational plans on how to structurally implement childhood cancer registries, align healthcare infrastructure, build on capacities, and provide universal health coverage in LMICs. In addition, we strongly recommend that, in the future, LMICs document, analyze, and publish pediatric AML treatment outcomes in a more structured and uniform manner.

Outcome and Prognostic Features in Pediatric Acute Megakaryoblastic Leukemia Without Down Syndrome: A Retrospective Study in China

BACKGROUND

Acute megakaryoblastic leukemia (AMKL) is a biologically heterogeneous subtype of acute myeloid leukemia that originates from megakaryocytes. Patients with AMKL with non-Down syndrome (DS) had a poorer prognosis. However, clear prognostic indicators and treatment recommendations for this subgroup remain controversial.

PATIENTS AND METHODS

Herein, we performed a retrospective study on 40 patients (age ≤ 18 years) with non-Down syndrome AMKL at our institution. We assessed the effect of different prognostic factors, such as their cytogenetic abnormalities, early treatment response, and the role of hematopoietic stem cell transplantation (HSCT) as post-remission treatment on the outcomes.

RESULTS

The complete remission (CR) rate of the patients was 57.9% and 81.1%, respectively, at the end of induction therapy 1 and 2. The overall survival (OS) and event-free survival rates at 2 years were 41% ± 13% and 41% ± 10%, respectively. An analysis of the cytogenetic features showed that patients with +21 or hyperdiploid (> 50 chromosomes) had significantly better OS than those in other cytogenetic subgroups (P_log-rank = .048 and P_log-rank = .040, respectively). Besides cytogenetics, an excellent early treatment response (CR and minimal residual disease < 1% after induction therapy 1) also provided a significant survival benefit in univariate analysis in our study. However, multivariate analysis indicated that allogeneic HSCT was the only independent prognostic marker (relative risk, 11.192; 95% confidence interval, 2.045-61.241; P = .005 for OS and relative risk, 5.400; 95% confidence interval, 1.635-17.832; P = .006 for event-free survival, respectively).

CONCLUSION

AMKL in patients with non-Down syndrome has a poor outcome. With poor OS but CR rates comparable with other acute myeloid leukemia subtypes, allogenic HSCT may be a better option for post-remission therapy than conventional chemotherapy, especially for those having a poor response to induction therapy.

Exposure of Patient-Derived Mesenchymal Stromal Cells to TGFB1 Supports Fibrosis Induction in a Pediatric Acute Megakaryoblastic Leukemia Model

Bone marrow fibrosis (BMF) is a rare complication in acute leukemia. In pediatrics, it predominantly occurs in acute megakaryoblastic leukemia (AMKL) and especially in patients with trisomy 21, called myeloid leukemia in Down syndrome (ML-DS). Defects in mesenchymal stromal cells (MSC) and cytokines specifically released by the myeloid blasts are thought to be the main drivers of fibrosis in the bone marrow niche (BMN). To model the BMN of pediatric patients with AMKL in mice, we first established MSCs from pediatric patients with AMKL (n = 5) and ML-DS (n = 9). Healthy donor control MSCs (n = 6) were generated from unaffected children and adolescents ≤18 years of age. Steady-state analyses of the MSCs revealed that patient-derived MSCs exhibited decreased adipogenic differentiation potential and enrichment of proliferation-associated genes. Importantly, TGFB1 exposure in vitro promoted early profibrotic changes in all three MSC entities. To study BMF induction for longer periods of time, we created an in vivo humanized artificial BMN subcutaneously in immunodeficient NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice, using a mixture of MSCs, human umbilical vein endothelial cell, and Matrigel. Injection of AMKL blasts as producers of TGFB1 into this BMN after 8 weeks induced fibrosis grade I/II in a dose-dependent fashion over a time period of 4 weeks. Thus, our study developed a humanized mouse model that will be instrumental to specifically examine leukemogenesis and therapeutic targets for AMKL blasts in future. IMPLICATIONS: TGFB1 supports fibrosis induction in a pediatric AMKL model generated with patient-derived MSCs. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/18/10/1603/F1.large.jpg.

Downregulation of MIR100HG Induces Apoptosis in Human Megakaryoblastic Leukemia Cells

Long noncoding ribonucleic acids (lncRNAs) are ribonucleic acid (RNA) molecules longer than 200 nucleotides without protein-coding capacity. Several studies have shown that lncRNAs play a pivotal role in the initiation, maintenance, and progression of acute myeloid leukemia (AML), which could make them a promising candidate in the diagnosis and treatment of leukemia. Acute Megakaryoblastic leukemia (AMKL) is a rare form of AML with a poor prognosis and low survival. It has been reported that lncRNA MIR100HG is involved several types of malignancies. In the present study, MIR100HG was downregulated in a human acute megakaryoblastic leukemia cell line (M-07e) using Antisense LNA GapmeRs. In order to assess the expression level of MIR100HG, cell viability, apoptosis, and necrosis (late apoptosis), quantitative reverse transcription polymerase chain reaction (qRT-PCR), Methyl-thiazol Tetrazolium assay, AnnexinV, and propidium iodide staining was performed at different time points after the transfection. In addition, the expression level of TGFβ was evaluated by qRT-PCR. Our results revealed that inhibition of MIR100HG might serve as a new method for inhibition of the proliferation of AMKL cells and therefore, could be a promising approach in medicine for targeted therapy in AMKL.

RNA-Binding Proteins in Acute Leukemias

Acute leukemias are genetic diseases caused by translocations or mutations, which dysregulate hematopoiesis towards malignant transformation. However, the molecular mode of action is highly versatile and ranges from direct transcriptional to post-transcriptional control, which includes RNA-binding proteins (RBPs) as crucial regulators of cell fate. RBPs coordinate RNA dynamics, including subcellular localization, translational efficiency and metabolism, by binding to their target messenger RNAs (mRNAs), thereby controlling the expression of the encoded proteins. In view of the growing interest in these regulators, this review summarizes recent research regarding the most influential RBPs relevant in acute leukemias in particular. The reported RBPs, either dysregulated or as components of fusion proteins, are described with respect to their functional domains, the pathways they affect, and clinical aspects associated with their dysregulation or altered functions.

Highly sensitive detection of GATA1 mutations in patients with myeloid leukemia associated with Down syndrome by combining Sanger and targeted next generation sequencing

Myeloid leukemia associated with Down syndrome (ML-DS) is characterized by a predominance of acute megakaryoblastic leukemia, the presence of GATA1 mutations and a favorable outcome. Because DS children can also develop conventional acute myeloid leukemia with unfavorable outcome, detection of GATA1 mutations is important for diagnosis of ML-DS. However, myelofibrosis and the significant frequency of dry taps have hampered practical screening of GATA1 mutations using bone marrow (BM) samples. In response to those problems, 82 patients were enrolled in the Japanese Pediatric Leukemia/Lymphoma Study Group AML-D11 study. GATA1 mutations were analyzed by Sanger sequencing (SS) using genomic DNA (gDNA) from BM and cDNA from peripheral blood (PB) followed by targeted next-generation sequencing (NGS) using pooled diagnostic samples. BM and PB samples were obtained from 71 (87%) and 82 (100%) patients, respectively. GATA1 mutations were detected in 46 (56%) and 58 (71%) patients by SS using BM gDNA and PB cDNA, respectively. Collectively, GATA1 mutations were identified in 73/82 (89%) patients by SS. Targeted NGS detected GATA1 mutations in 74/82 (90%) patients. Finally, combining the results of SS with those of targeted NGS, GATA1 mutations were identified in 80/82 (98%) patients. These results indicate that SS using BM gDNA and PB cDNA is a rapid and useful method for screening for GATA1 mutations in ML-DS patients. Thus, a combination of SS and targeted NGS is a sensitive and useful method to evaluate the actual incidence and clinical significance of GATA1 mutations in ML-DS patients.

Mutated WT1, FLT3-ITD, and NUP98-NSD1 Fusion in Various Combinations Define a Poor Prognostic Group in Pediatric Acute Myeloid Leukemia

Acute myeloid leukemia is a life-threatening malignancy in children and adolescents treated predominantly by risk-adapted intensive chemotherapy that is partly supported by allogeneic stem cell transplantation. Mutations in the WT1 gene and NUP98-NSD1 fusion are predictors of poor survival outcome/prognosis that frequently occur in combination with internal tandem duplications of the juxta-membrane domain of FLT3 (FLT3-ITD). To re-evaluate the effect of these factors in contemporary protocols, 353 patients (<18 years) treated in Germany with AML-BFM treatment protocols between 2004 and 2017 were included. Presence of mutated WT1 and FLT3-ITD in blasts (n=19) resulted in low 3-year event-free survival of 29% and overall survival of 33% compared to rates of 45-63% and 67-87% in patients with only one (only FLT3-ITD; n=33, only WT1 mutation; n=29) or none of these mutations (n=272). Including NUP98-NSD1 and high allelic ratio (AR) of FLT3-ITD (AR ≥0.4) in the analysis revealed very poor outcomes for patients with co-occurrence of all three factors or any of double combinations. All these patients (n=15) experienced events and the probability of overall survival was low (27%). We conclude that co-occurrence of WT1 mutation, NUP98-NSD1, and FLT3-ITD with an AR ≥0.4 as triple or double mutations still predicts dismal response to contemporary first- and second-line treatment for pediatric acute myeloid leukemia.

Transient leukemia of Down syndrome

Childhood leukemia is mostly a "developmental accident" during fetal hematopoiesis and may require multiple prenatal and postnatal "hits". The World Health Organization defines transient leukemia of Down syndrome (DS) as increased peripheral blood blasts in neonates with DS and classifies this type of leukemia as a separate entity. Although it was shown that DS predisposes children to myeloid leukemia, neither the nature of the predisposition nor the associated genetic lesions have been defined. Acute myeloid leukemia of DS is a unique disease characterized by a long pre-leukemic, myelodysplastic phase, unusual chromosomal findings and a high cure rate. In the present manuscript, we present a comprehensive review of the literature about clinical and biological findings of transient leukemia of DS (TL-DS) and link them with the genetic discoveries in the field. We address the manuscript to the pediatric generalist and especially to the next generation of pediatric hematologists.

Infections in children with acute myeloid leukemia: increased mortality in relapsed/refractory patients

The aim of this nationwide study was to describe the epidemiology and profile of bacterial infections (BI), invasive fungal disease (IFD) and viral infections (VI) in patients with de novo and relapsed/refractory (rel/ref) acute myeloid leukemia (AML). Within the studied group of 250 children with primary AML, at least one infectious complication (IC) was diagnosed in 76.0% (n = 190) children including 85.1% (n = 504) episodes of BI, 8.3% (n = 49) - IFD and 6.6% (n = 39) - VI. Among 61 patients with rel/ref AML, at least one IC was found in 67.2% (n = 41) of children including 78.8% (n = 78) of BI, 14.1% (n = 14) of IFD and 7.1% (n = 7) of VI. In all AML patients, within BI Gram-negative strains were predominant. Half of these strains were multi-drug resistant. Characteristics of IFD and VI were comparable for de novo and rel/ref AML. The infection-related mortality was significantly higher, while survival from infection was significantly lower in patients with rel/ref disease.

Molecular features, prognosis, and novel treatment options for pediatric acute megakaryoblastic leukemia

INTRODUCTION

Acute megakaryoblastic leukemia (AMegL) is a rare hematological neoplasm most often diagnosed in children and is commonly associated with Down's syndrome (DS). Although AMegLs are specifically characterized and typically diagnosed by megakaryoblastic expansion, recent advancements in molecular analysis have highlighted the heterogeneity of this disease, with specific cytogenic and genetic alterations characterizing different disease subtypes. Areas covered: This review will focus on describing recurrent molecular variations in both DS and non-DS pediatric AMegL, their role in promoting leukemogenesis, their association with different clinical aspects and prognosis, and finally, their influence on future treatment strategies with a number of specific drugs beyond conventional chemotherapy already under development. Expert opinion: Deep understanding of the genetic and molecular landscape of AMegL will lead to better and more precise disease classification in terms of diagnosis, prognosis, and possible targeted therapies. Development of new therapeutic approaches based on these molecular characteristics will hopefully improve AMegL patient outcomes.

The changing scenario of non-Down syndrome acute megakaryoblastic leukemia in children

Pediatric non-Down-syndrome acute megakaryoblastic leukemia (non-DS-AMKL) is a heterogeneous subtype of leukemia that has historically been associated with poor prognosis. Until the advent of large-scale genomic sequencing, the management of patients with non-DS-AMKL was very difficult due to the absence of reliable biological prognostic markers. The sequencing of large cohort of pediatric non-DS-AMKL samples led to the discovery of novel genetic aberrations, including high-frequency fusions, such as CBFA2T3-GLIS2 and NUP98-KDM5 A, as well as less frequent aberrations, such as HOX rearrangements. These new insights into the genetic landscape of pediatric non-DS-AMKL has allowed refining the risk-group stratification, leading to important changes in the prognostic scenario of these patients. This review summarizes the most important molecular pathogenic mechanisms of pediatric non-DS-AMKL. A critical discussion on how novel genetic abnormalities have refined the risk profile assessment and changed the management of these patients in clinical practice is also provided.

CBFA2T3-GLIS2-positive acute myeloid leukaemia. A peculiar paediatric entity

The scenario of paediatric acute myeloid leukaemia (AML), particularly non‐Down syndrome acute megakaryoblastic leukaemia (non‐DS‐AMKL), has been recently revolutionized by the advent of large‐scale, genomic sequencing technologies. In this changing landscape, a significantly relevant discovery has been represented by the identification of the CBFA2T3‐GLIS2 fusion gene, which is the result of a cryptic inversion of chromosome 16. It is the most frequent chimeric oncogene identified to date in non‐DS‐AMKL, although it seems not to be exclusively restricted to the French‐American‐British M7 subgroup. The CBFA2T3‐GLIS2 fusion gene characterizes a subtype of leukaemia that is specific to paediatrics, having never been identified in adults. It characterizes an extremely aggressive leukaemia, as the presence of this fusion is associated with a grim outcome in almost all of the case series reported, with overall survival rates ranging between 15% and 30%. Although the molecular basis that underlies this leukaemia subtype is still far from being completely elucidated, unique functional properties induced by CBFA2T3‐GLIS2 in the leukaemogenesis driving process have been recently identified. We here review the peculiarities of CBFA2T3‐GLIS2‐positive AML, describing its intriguing clinical and biological behaviour and providing some challenging targeting opportunities.

Using genomics to define pediatric blood cancers and inform practice

Over the past decade, there has been exponential growth in the number of genome sequencing studies performed across a spectrum of human diseases as sequencing technologies and analytic pipelines improve and costs decline. Pediatric hematologic malignancies have been no exception, with a multitude of next generation sequencing studies conducted on large cohorts of patients in recent years. These efforts have defined the mutational landscape of a number of leukemia subtypes and also identified germ-line genetic variants biologically and clinically relevant to pediatric leukemias. The findings have deepened our understanding of the biology of many childhood leukemias. Additionally, a number of recent discoveries may positively impact the care of pediatric leukemia patients through refinement of risk stratification, identification of targetable genetic lesions, and determination of risk for therapy-related toxicity. Although incredibly promising, many questions remain, including the biologic significance of identified genetic lesions and their clinical implications in the context of contemporary therapy. Importantly, the identification of germ-line mutations and variants with possible implications for members of the patient's family raises challenging ethical questions. Here, we review emerging genomic data germane to pediatric hematologic malignancies.

Clinical implications of molecular markers in acute myeloid leukemia

The recently updated World Health Organization (WHO) Classification of myeloid neoplasms and leukemia reflects the fact that research in the underlying pathogenic mechanisms of acute myeloid leukemia (AML) has led to remarkable advances in our understanding of the disease. Gene mutations now allow us to explore the enormous diversity among cytogenetically defined subsets of AML, particularly the large subset of cytogenetically normal AML. Despite the progress in unraveling the tumor genome, only a small number of recurrent mutations have been incorporated into risk-stratification schemes and have been proven to be clinically relevant, targetable lesions. We here discuss the utility of molecular markers in AML in prognostication and treatment decision making, specifically highlighting the aberrations included in the current WHO classification.

The Comparative Sensitivity of Immunohistochemical Markers of Megakaryocytic Differentiation in Acute Megakaryoblastic Leukemia

OBJECTIVES

Immunohistochemistry (IHC) staining of core biopsy sections often plays an essential role in the diagnosis of acute megakaryoblastic leukemia (AMKL). The goal of this study was to define the relative sensitivities of commonly used stains for markers of megakaryocytic differentiation.

METHODS

The sensitivities of IHC stains for CD42b, CD61, and von Willebrand factor (vWF) were compared in 32 cases of pediatric AMKL.

RESULTS

The sensitivities of CD42b, CD61, and vWF were 90.6%, 78.1% and 62.5%, respectively. When CD42b and CD61 were used together, the combined sensitivity increased to 93.6%. There were no cases in which vWF was positive when both CD42b and CD61 were negative.

CONCLUSIONS

CD42b can reliably be used as a solitary first-line marker for blasts of megakaryocytic lineage, whereas CD61 may be reserved for infrequent cases that are CD42b negative. There is no role for the routine use of vWF when CD42b and CD61 are available.

Acute megakaryoblastic leukemia (excluding Down syndrome) remains an acute myeloid subgroup with inferior outcome in the French ELAM02 trial

We report the outcome of 27 children with de novo acute megakaryoblastic leukemia (AMKL) (excluding Down syndrome) enrolled in the French multicenter prospective study ELAM02 (2005-2011). There was no difference in gender, initial leukocyte count, CNS involvement, and complete remission rate (88.9%), as compared to other acute myeloid leukemia (AML) subtypes. AMKL patients had a significantly poorer outcome (5-year overall survival 54% [CI 95% 33%-71%] than children with other AML subtypes (5-year overall survival 73% [CI 95% 68%-77%] p = 0.02). Gender, age, CNS leukemia, hyperleukocytosis, complete remission or cytogenetic subgroups were not significant prognostic factors of disease-free survival. AMKL (excluding Down syndrom) remains an AML subgroup with inferior outcome.

Therapy reduction in patients with Down syndrome and myeloid leukemia: the international ML-DS 2006 trial

Reducing therapy intensity in the ML-DS 2006 trial did not impair the excellent prognosis in ML-DS compared with the historical control. Early treatment response and gain of chromosome 8 are independent prognostic factors.

Pediatric non-Down syndrome acute megakaryoblastic leukemia is characterized by distinct genomic subsets with varying outcomes

Acute megakaryoblastic leukemia (AMKL) is a subtype of acute myeloid leukemia (AML) in which cells morphologically resemble abnormal megakaryoblasts. While rare in adults, AMKL accounts for 4-15% of newly diagnosed childhood AML cases. AMKL in individuals without Down syndrome (non-DS-AMKL) is frequently associated with poor clinical outcomes. Previous efforts have identified chimeric oncogenes in a substantial number of non-DS-AMKL cases, including RBM15-MKL1, CBFA2T3-GLIS2, KMT2A gene rearrangements, and NUP98-KDM5A. However, the etiology of 30-40% of cases remains unknown. To better understand the genomic landscape of non-DS-AMKL, we performed RNA and exome sequencing on specimens from 99 patients (75 pediatric and 24 adult). We demonstrate that pediatric non-DS-AMKL is a heterogeneous malignancy that can be divided into seven subgroups with varying outcomes. These subgroups are characterized by chimeric oncogenes with cooperating mutations in epigenetic and kinase signaling genes. Overall, these data shed light on the etiology of AMKL and provide useful information for the tailoring of treatment.

Recurrent abnormalities can be used for risk group stratification in pediatric AMKL: a retrospective intergroup study

Genetic abnormalities and early treatment response are the main prognostic factors in acute myeloid leukemia (AML). Acute megakaryoblastic leukemia (AMKL) is a rare subtype of AML. Deep sequencing has identified CBFA2T3/GLIS2 and NUP98/KDM5A as recurrent aberrations, occurring in similar frequencies as RBM15/MKL1 and KMT2A-rearrangements. We studied whether these cytogenetic aberrations can be used for risk group stratification. To assess frequencies and outcome parameters of recurrent cytogenetic aberrations in AMKL, samples and clinical data of patients treated by the Associazione Italiana Ematologia Oncologia Pediatrica, Berlin-Frankfurt-Munster Study Group, Children's Oncology Group, Dutch Childhood Oncology Group, and the Saint Louis Hôpital were collected, enabling us to screen 153 newly diagnosed pediatric AMKL cases for the aforementioned aberrations and to study their clinical characteristics and outcome. CBFA2T3/GLIS2 was identified in 16% of the cases; RBM15/MKL1, in 12%; NUP98/KDM5A and KMT2A rearrangements, in 9% each; and monosomy 7, in 6%. These aberrations were mutually exclusive. RBM15/MKL1-rearranged patients were significantly younger. No significant differences in sex and white blood cell count were found. NUP98/KDM5A, CBFA2T3/GLIS2, KMT2A-rearranged lesions and monosomy 7 (NCK-7) independently predicted a poor outcome, compared with RBM15/MKL1-rearranged patients and those with AMKL not carrying these molecular lesions. NCK-7-patients (n = 61) showed a 4-year probability of overall survival of 35 ± 6% vs 70 ± 5% in the RBM15/MKL1-other groups (n = 92, P < .0001) and 4-year probability of event-free survival of 33 ± 6% vs 62 ± 5% (P = .0013), the 4-year cumulative incidence of relapse being 42 ± 7% and 19 ± 4% (P = .003), respectively. We conclude that these genetic aberrations may be used for risk group stratification of pediatric AMKL and for treatment tailoring.

Heterogeneous cytogenetic subgroups and outcomes in childhood acute megakaryoblastic leukemia: a retrospective international study

Comprehensive clinical studies of patients with acute megakaryoblastic leukemia (AMKL) are lacking. We performed an international retrospective study on 490 patients (age ≤18 years) with non-Down syndrome de novo AMKL diagnosed from 1989 to 2009. Patients with AMKL (median age 1.53 years) comprised 7.8% of pediatric AML. Five-year event-free (EFS) and overall survival (OS) were 43.7% ± 2.7% and 49.0% ± 2.7%, respectively. Patients diagnosed in 2000 to 2009 were treated with higher cytarabine doses and had better EFS (P = .037) and OS (P = .003) than those diagnosed in 1989 to 1999. Transplantation in first remission did not improve survival. Cytogenetic data were available for 372 (75.9%) patients: hypodiploid (n = 18, 4.8%), normal karyotype (n = 49, 13.2%), pseudodiploid (n = 119, 32.0%), 47 to 50 chromosomes (n = 142, 38.2%), and >50 chromosomes (n = 44, 11.8%). Chromosome gain occurred in 195 of 372 (52.4%) patients: +21 (n = 106, 28.5%), +19 (n = 93, 25.0%), +8 (n = 77, 20.7%). Losses occurred in 65 patients (17.5%): -7 (n = 13, 3.5%). Common structural chromosomal aberrations were t(1;22)(p13;q13) (n = 51, 13.7%) and 11q23 rearrangements (n = 38, 10.2%); t(9;11)(p22;q23) occurred in 21 patients. On the basis of frequency and prognosis, AMKL can be classified to 3 risk groups: good risk-7p abnormalities; poor risk-normal karyotypes, -7, 9p abnormalities including t(9;11)(p22;q23)/MLL-MLLT3, -13/13q-, and -15; and intermediate risk-others including t(1;22)(p13;q13)/OTT-MAL (RBM15-MKL1) and 11q23/MLL except t(9;11). Risk-based innovative therapy is needed to improve patient outcomes.