Acute megakaryoblastic leukemia in children and adolescents, excluding Down's syndrome: improved outcome with intensified induction treatment

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.

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.

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.

AMKL chimeric transcription factors are potent inducers of leukemia

Acute megakaryoblastic leukemia in patients without Down syndrome is a rare malignancy with a poor prognosis. RNA sequencing of fourteen pediatric cases previously identified novel fusion transcripts that are predicted to be pathological including CBFA2T3-GLIS2, GATA2-HOXA9, MN1-FLI and NIPBL-HOXB9. In contrast to CBFA2T3-GLIS2, which is insufficient to induce leukemia, we demonstrate that the introduction of GATA2-HOXA9, MN1-FLI1 or NIPBL-HOXB9 into murine bone marrow induces overt disease in syngeneic transplant models. With the exception of MN1, full penetrance was not achieved through the introduction of fusion partner genes alone, suggesting that the chimeric transcripts possess a unique gain-of-function phenotype. Leukemias were found to exhibit elements of the megakaryocyte erythroid progenitor gene expression program, as well as unique leukemia-specific signatures that contribute to transformation. Comprehensive genomic analyses of resultant murine tumors revealed few cooperating mutations confirming the strength of the fusion genes and their role as pathological drivers. These models are critical for both the understanding of the biology of disease as well as providing a tool for the identification of effective therapeutic agents in preclinical studies.

Collaborative Efforts Driving Progress in Pediatric Acute Myeloid Leukemia

Diagnosis, treatment, response monitoring, and outcome of pediatric acute myeloid leukemia (AML) have made enormous progress during the past decades. Because AML is a rare type of childhood cancer, with an incidence of approximately seven occurrences per 1 million children annually, national and international collaborative efforts have evolved. This overview describes these efforts and includes a summary of the history and contributions of each of the main collaborative pediatric AML groups worldwide. The focus is on translational and clinical research, which includes past, current, and future clinical trials. Separate sections concern acute promyelocytic leukemia, myeloid leukemia of Down syndrome, and relapsed AML. A plethora of novel antileukemic agents that have emerged, including new classes of drugs, are summarized as well. Finally, an important aspect of the treatment of pediatric AML--supportive care--and late effects are discussed. The future is bright, with a wide range of emerging innovative therapies and with more and more international collaboration that ultimately aim to cure all children with AML, with fewer adverse effects and without late effects.

Neonatal Acute Megakaryoblastic Leukemia Presenting with Leukemia Cutis and Multiple Intracranial Lesions Successfully Treated with Unrelated Cord Blood Transplantation

Neonatal acute megakaryoblastic leukemia (AMKL) without Down syndrome (DS) is an extremely rare disorder. We report of a one-day-old male infant without DS who developed AMKL with leukemia cutis and right facial nerve palsy. Magnetic resonance imaging of the patient's brain revealed multiple intracranial tumors. A biopsy specimen of the skin lesion was suggestive of AMKL, but the bone marrow leukemic cells were less than 5% of the marrow nucleated cells. The skin and intracranial lesions had spontaneously regressed within one and a half months, but the patient's anemia and thrombocytopenia gradually worsened and the leukemic cells in the bone marrow gradually increased to more than 20% of the nucleated cells. In addition, multiple intracranial lesions reappeared at 72 days of life. We diagnosed the patient with AMKL, and chemotherapy followed by unrelated cord blood transplantation after a reduced-intensity conditioning regimen resulted in sustained complete remission. At present, the patient is well, and he has demonstrated normal development for five years.

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.

The biology of pediatric acute megakaryoblastic leukemia

Acute megakaryoblastic leukemia (AMKL) comprises between 4% and 15% of newly diagnosed pediatric acute myeloid leukemia patients. AMKL in children with Down syndrome (DS) is characterized by a founding GATA1 mutation that cooperates with trisomy 21, followed by the acquisition of additional somatic mutations. In contrast, non-DS-AMKL is characterized by chimeric oncogenes consisting of genes known to play a role in normal hematopoiesis. CBFA2T3-GLIS2 is the most frequent chimeric oncogene identified to date in this subset of patients and confers a poor prognosis.

The effects of idarubicin versus other anthracyclines for induction therapy of patients with newly diagnosed leukaemia

BACKGROUND

Anthracycline combined with cytarabine has been the standard for induction therapy of newly diagnosed acute myeloid leukaemia (AML) for several decades. Due to theoretical advantages, idarubicin (IDA) might be the most effective and tolerable anthracycline. However, there is no evidence that would definitively prove the superiority of IDA over other anthracyclines.

OBJECTIVES

To assess the efficacy and safety of IDA versus other anthracyclines in induction therapy of newly diagnosed AML.

SEARCH METHODS

We identified relevant randomised controlled trials (RCTs) by searching the Cochrane Central Register of Controlled Trials (The Cochrane Library 2014, Issue 8), MEDLINE (from 1946 to 3 August 2014), EMBASE (from 1974 to 3 August 2014), Chinese BioMedical Literature Database (1978 to 3 August 2014), relevant conference proceedings and databases of ongoing trials.

SELECTION CRITERIA

RCTs that compared IDA with other anthracyclines in induction therapy of newly diagnosed AML.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the quality of studies according to methodological standards of the Cochrane Collaboration. We estimated hazard ratios (HRs) for time-to-event data outcomes using the inverse variance method, and risk ratios (RRs) for dichotomous data outcomes using the Mantel-Haenszel method. We adopted a fixed-effect model and repeated the main meta-analysis by a random-effects model in a sensitivity analysis.

MAIN RESULTS

We identified 2017 references. Ultimately, 27 RCTs (including 22 two-armed RCTs and five three-armed RCTs) involving 9549 patients were eligible. The consolidation treatments adopted in the studies were comparable and had no impact on the results. Overall, the risk of bias of the studies was unclear to high.Eighteen RCTs (N = 6755) assessed IDA versus daunorubicin (DNR). The main meta-analyses showed that IDA compared with DNR prolonged overall survival (OS) (12 studies, 5976 patients; HR 0.90, 95% confidence interval (CI) 0.84 to 0.96, P = 0.0008; high quality of evidence) and disease-free survival (DFS) (eight studies, 3070 patients; HR 0.88, 95% CI 0.81 to 0.96, P = 0.004; moderate quality of evidence), increased complete remission (CR) rate (18 studies, 6692 patients; RR 1.04, 95% CI 1.01 to 1.07, P = 0.009; moderate quality of evidence), and reduced relapse rate (four studies, 1091 patients; RR 0.88, 95% CI 0.80 to 0.98, P = 0.02; moderate quality of evidence), although increased the risks of death on induction therapy (14 studies, 6349 patients; RR 1.18, 95% CI 1.01 to 1.36, P = 0.03; moderate quality of evidence) and grade 3/4 mucositis (five studies, 2000 patients; RR 1.22, 95% CI 1.04 to 1.44, P = 0.02; moderate quality of evidence). There was no evidence for difference in the risks of grade 3/4 cardiac toxicity (six studies, 2795 patients; RR 0.98, 95% CI 0.70 to 1.37, P = 0.91; moderate quality of evidence) and other grade 3/4 adverse events (AEs). None of the studies reported on quality of life (QoL).Eight RCTs (N = 2419) evaluated IDA versus mitoxantrone (MIT). The main meta-analyses showed that there was no evidence for difference between arms in OS (six studies, 2171 patients; HR 0.98, 95% CI 0.89 to 1.08, P = 0.69; high quality of evidence), DFS (four studies, 249 patients; HR 0.88, 95% CI 0.70 to 1.10, P = 0.26; low quality of evidence), CR rate (eight studies, 2411 patients; RR 0.97, 95% CI 0.92 to 1.03, P = 0.32;moderate quality of evidence), the risks of death on induction therapy (five studies, 2055 patients; RR 1.10, 95% CI 0.88 to 1.38, P = 0.39; moderate quality of evidence) and relapse (three studies, 328 patients; RR 0.99, 95% CI 0.80 to 1.22, P = 0.89; moderate quality of evidence). There was no evidence for difference in the risks of grade 3/4 cardiac toxicity (one study, 160 patients; RR 0.67, 95% CI 0.11 to 3.88, P = 0.65; low quality of evidence) and other grade 3/4 AEs. None of the studies reported on QoL.Two RCTs (N = 211) compared IDA with doxorubicin (DOX). Neither study assessed OS. One study showed that there was no evidence for difference in DFS (63 patients; HR 0.62, 95% CI 0.34 to 1.14, P = 0.12; low quality of evidence). The main meta-analysis for CR rate showed an improved CR rate with IDA (two studies, 187 patients; RR 1.28, 95% CI 1.03 to 1.59, P = 0.02; low quality of evidence). Neither study provided data for the risks of death on induction therapy and relapse. One trial showed that there was no evidence for difference in the risk of grade 3/4 cardiac toxicity (one study, 100 patients; RR 0.31, 95% CI 0.01 to 7.39, P = 0.47; very low quality of evidence). Neither study reported on QoL.Two RCTs (N = 1037) evaluated IDA versus zorubicin (ZRB). Neither study assessed OS. One trial showed that there was no evidence for difference in DFS (one study, 155 patients; HR 1.25, 95% CI 0.83 to 1.88, P = 0.29; low quality of evidence). The main meta-analyses for CR and death on induction therapy both showed that there was no evidence for difference (CR rate: two studies, 964 patients; RR 1.04, 95% CI 0.96 to 1.13, P = 0.31; low quality of evidence. risk of death on induction therapy: two studies, 964 patients; RR 0.75, 95% CI 0.50 to 1.13, P = 0.17; moderate quality of evidence). Neither study reported the risks of relapse and grade 3/4 cardiotoxicity. One trial showed that IDA reduced the risk of grade 3/4 mucositis. Neither study reported on QoL.

AUTHORS' CONCLUSIONS

Compared with DNR in induction therapy of newly diagnosed AML, IDA prolongs OS and DFS, increases CR rate and reduces relapse rate, although increases the risks of death on induction therapy and grade 3/4 mucositis. The currently available evidence does not show any difference between IDA and MIT used in induction therapy of newly diagnosed AML. There is insufficient evidence regarding IDA versus DOX and IDA versus ZRB to make final conclusions. Additionally, there is no evidence for difference on the effect of IDA compared with DNR, MIT, DOX or ZRB on QoL.

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

Despite recent advances in the treatment of children with acute megakaryoblastic leukemia (AMKL) using intensified treatment protocols, clear prognostic indicators, and treatment recommendations for this acute myeloid leukemia (AML) subgroup are yet to be defined. Here, we report the outcome of 97 pediatric patients with de novo AMKL (excluding Down syndrome [DS]) enrolled in the prospective multicenter studies AML-BFM 98 and AML-BFM 04 (1998-2014). AMKL occurred in 7.4 % of pediatric AML cases, at younger age (median 1.44 years) and with lower white blood cell count (mean 16.5 × 10⁹/L) as compared to other AML subgroups. With 60 ± 5 %, children with AMKL had a lower 5-year overall survival (5-year OS; vs. 68 ± 1 %, P_{log rank} = 0.038). Yet, we achieved an improved 5-year OS in AML-BFM 04 compared to AML-BFM 98 (70 ± 6 % vs. 45 ± 8 %, P_{log rank} = 0.041). Allogeneic hematopoietic stem cell transplantation in first remission did not provide a significant survival benefit (5-year OS 70 ± 11 % vs. 63 ± 6 %; P_Mantel-Byar = 0.85). Cytogenetic data were available for n = 78 patients. AMKL patients with gain of chromosome 21 had a superior 5-year OS (80 ± 9 %, P_{log rank} = 0.034), whereas translocation t(1;22)(p13;q13) was associated with an inferior 5-year event-free survival (38 ± 17 %, P_{log rank} = 0.04). However, multivariate analysis showed that treatment response (bone marrow morphology on day 15 and 28) was the only independent prognostic marker (RR = 4.39; 95 % CI, 1.97–9.78). Interestingly, GATA1-mutations were detected in six patients (11 %) without previously known trisomy 21. Thus, AMKL (excluding DS) remains an AML subgroup with inferior outcome. Nevertheless, with intensive therapy regimens, a steep increase in the survival rates was achieved.

Acute Megakaryoblastic Leukemia with t(1;22) Mimicking Neuroblastoma in an Infant

Acute megakaryoblastic leukemia (AMKL) with t(1;22) (p13;q13) is an extremely rare subtype of acute myeloid leukemia that is almost always described in infants. t(1;22) (p13;q13)-positive AMKL with extramedullary infiltration has been previously reported only once in the literature. Herein, we report a 3-month-old infant presenting with a pelvic mass and pancytopenia suggesting neuroblastoma. Bone marrow evaluation revealed t(1;22)-positive AMKL that responded well to a regimen containing high-dose cytarabine.

Prognosis and management of acute myeloid leukemia in patients with Down syndrome

Children with Down syndrome (DS) are at a substantially increased risk to develop acute myeloid leukemia (AML). This increase in incidence is tempered, however, by favorable overall survival rates of approximately 80%, whereas survival for non-DS children with similar leukemic subtypes is <35%. In this review, the clinical studies that have contributed to this overall high survival will be presented and their individual successes will be discussed. Important issues including intensity of treatment regimens, the role of bone marrow transplants and prognostic indicators will be reviewed. In particular, the roles of high- vs low- vs very low-dose cytarabine will be discussed, as well as potential therapeutic options in the future and the direction of the field over the next 5 years. In summary, children with DS and AML should be treated with a moderate-intensity cytarabine-based regimen with curative intent.

Ploidy and clinical characteristics of childhood acute myeloid leukemia: A NOPHO-AML study

We report the first large series (n = 596) of pediatric acute myeloid leukemia (AML) focusing on modal numbers (MN) from the population-based NOPHO-AML trials. Abnormal karyotypes were present in 452 cases (76%) and numerical aberrations were present in 40% (n = 237) of all pediatric AML. Among patients with an abnormal karyotype, the MN 46 was most common (n = 251; 56%) of which 36 (8%) were pseudodiploid with numerical aberrations, followed by MN 47 (n = 80; 18%) and MN 43-45 (n = 48; 8%). No cases had MN less than 43. Hyperdiploid AML with MN 48-65 comprised 11% of all cases and was associated with early onset (median age 2 years), female sex (57%), and a dominance of acute megakaryoblastic leukemia (AMKL) (29%). Hypodiploidy constituted 8% of all AML and was associated with older age (median age 9 years), male predominance (60%), FAB M2 (56%), and t(8;21)(q22;q22) (56%) with loss of sex chromosomes. Inferior outcome was observed for hypodiploid cases (5-year event-free survival 40% and 5-year overall survival 40%) but did not reach statistical significance. Chromosomes were gained in a nonrandom pattern, where chromosomes 8, 21, 19, and 6 were the most commonly gained. In conclusion, based on MNs, two cytogenetic subgroups with characteristic clinical features are described; hypodiploidy found in 8% and associated with high median age, male sex, t(8;21)(q22;q22), and FAB M2 and possibly associated with inferior outcome (P = 0.13), and hyperdiploidy with MN 48-65 in 11% associated with early onset, female sex, and AMKL.

NUP98/JARID1A is a novel recurrent abnormality in pediatric acute megakaryoblastic leukemia with a distinct HOX gene expression pattern

Cytogenetic abnormalities and early response to treatment are the main prognostic factors in acute myeloid leukemia (AML). Recently, NUP98/NSD1 (t(5; 11)(q35; p15)), a cytogenetically cryptic fusion, was described as recurrent event in AML, characterized by dismal prognosis and HOXA/B gene overexpression. Using split-signal fluorescence in situ hybridization, other NUP98-rearranged pediatric AML cases were identified, including several acute megakaryoblastic leukemia (AMKL) cases with a cytogenetically cryptic fusion of NUP98 to JARID1A (t(11;15)(p15;q35)). In this study we screened 105 pediatric AMKL cases to analyze the frequency of NUP98/JARID1A and other recurrent genetic abnormalities. NUP98/JARID1A was identified in 11/105 patients (10.5%). Other abnormalities consisted of RBM15/MKL1 (n=16), CBFA2T3/GLIS2 (n=13) and MLL-rearrangements (n=13). Comparing NUP98/JARID1A-positive patients with other pediatric AMKL patients, no significant differences in sex, age and white blood cell count were found. NUP98/JARID1A was not an independent prognostic factor for 5-year overall (probability of overall survival (pOS)) or event-free survival (probability of event-free survival (pEFS)), although the 5-year pOS for the entire AMKL cohort was poor (42 ± 6%). Cases with RBM15/MLK1 fared significantly better in terms of pOS and pEFS, although this was not independent from other risk factors in multivariate analysis. NUP98/JARID1A cases were characterized by HOXA/B gene overexpression, which is a potential druggable pathway. In conclusion, NUP98/JARID1A is a novel recurrent genetic abnormality in pediatric AMKL.

How I treat pediatric acute myeloid leukemia

Acute myeloid leukemia is a heterogeneous disease that accounts for approximately 20% of acute leukemias in children and adolescents. Despite the lack of targeted therapy for most subtypes and a dearth of new agents, survival rates have reached approximately 60% for children treated on clinical trials in developed countries. Most of the advances have been accomplished by better risk classification, the implementation of excellent supportive care measures, adaptation of therapy on the basis of each patient's response to therapy, and improvements in allogeneic hematopoietic stem cell transplantation. However, it is unlikely that further gains can be made through these measures alone. In this regard, high-resolution, genome-wide analyses have led to greater understanding of the pathogenesis of this disease and the identification of molecular abnormalities that are potential targets of new therapies. The development of molecularly targeted agents, some of which are already in clinical trials, holds great promise for the future.

Acute megakaryocytic leukemia (AMKL,FAB;M7) with Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is characterized by an accumulation of multiple congenital anomalies. Although patients with BWS are known to have a higher incidence of embryonal tumors, there has been no reports associated with acute leukemia. This report describes the case of a patient with BWS who developed Acute Megakaryocytic Leukemia (AMKL,FAB;M7). Because most patients with BWS present gigantism, the therapy-related toxicity of chemotherapy can be a very serious problem. This patient exhibited no therapy-related toxicity after chemotherapy, suggesting that acute leukemia with BWS may not require a reduction in dosage.

Acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous group of leukemias that result from clonal transformation of hematopoietic precursors through the acquisition of chromosomal rearrangements and multiple gene mutations. As a result of highly collaborative clinical research by pediatric cooperative cancer groups worldwide, disease-free survival has improved significantly during the past 3 decades. Further improvements in outcomes of children who have AML probably will reflect continued progress in understanding the biology of AML and the concomitant development of new molecularly targeted agents for use in combination with conventional chemotherapy drugs.

RUNX1 regulates phosphoinositide 3-kinase/AKT pathway: role in chemotherapy sensitivity in acute megakaryocytic leukemia

RUNX1 (AML1) encodes the core binding factor alpha subunit of a heterodimeric transcription factor complex which plays critical roles in normal hematopoiesis. Translocations or down-regulation of RUNX1 have been linked to favorable clinical outcomes in acute leukemias, suggesting that RUNX1 may also play critical roles in chemotherapy responses in acute leukemias; however, the molecular mechanisms remain unclear. The median level of RUNX1b transcripts in Down syndrome (DS) children with acute megakaryocytic leukemia (AMkL) were 4.4-fold (P < .001) lower than that in non-DS AMkL cases. Short hairpin RNA knockdown of RUNX1 in a non-DS AMkL cell line, Meg-01, resulted in significantly increased sensitivity to cytosine arabinoside, accompanied by significantly decreased expression of PIK3CD, which encodes the delta catalytic subunit of the survival kinase, phosphoinositide 3 (PI3)-kinase. Transcriptional regulation of PIK3CD by RUNX1 was further confirmed by chromatin immunoprecipitation and promoter reporter gene assays. Further, a PI3-kinase inhibitor, LY294002, and cytosine arabinoside synergized in antileukemia effects on Meg-01 and primary pediatric AMkL cells. Our results suggest that RUNX1 may play a critical role in chemotherapy response in AMkL by regulating the PI3-kinase/Akt pathway. Thus, the treatment of AMkL may be improved by integrating PI3-kinase or Akt inhibitors into the chemotherapy of this disease.

Acute megakaryoblastic leukaemia (AMKL) in children: a comparison of AMKL with and without Down syndrome

To characterize childhood acute megakaryoblastic leukaemia (AMKL), we reviewed 45 children with AMKL diagnosed between 1986 and 2005 at Nagoya University Hospital and Japanese Red Cross Nagoya First Hospital. Twenty-four patients (53%) had AMKL associated with Down syndrome (DS-AMKL) and 21 (47%) had non-DS-AMKL. The median age of the DS-AMKL patients was 21 months (range, 8-38 months) and that of non-DS-AMKL patients was 15 months (range, 2-185 months). The morphology of blast cells was categorized into three groups according to the stage of megakaryocyte maturation. The blast cells were more immature in DS-AMKL than in non-DS-AMKL in terms of morphology and immunophenotyping. Cytogenetic abnormalities of leukaemic cells were classified into seven categories: normal karyotype including constitutional trisomy 21 in DS-AMKL; numerical abnormalities only; t(1;22)(p13;q13); 3q21q26 abnormalities; t(16;21)(p11;q22); -5/del(5q) and/or -7/del(7q); and other structural changes. The outcome of children with either DS-AMKL or non-DS-AMKL is excellent. The 10-year overall survival estimate was 79% [95% confidence interval (CI): 54-90] for DS-AMKL and 76% (95% CI: 58-91) for non-DS-AMKL (P = 0.81) with a median follow-up of 78 months (range, 20-243 months). Our study shows the diverse heterogeneity of childhood AMKL and the need for subclassification according to cytogenetic and morphological features.

Imaging findings of upper abdominal involvement by acute megakaryoblastic leukaemia

Acute megakaryoblastic leukaemia (AMKL), a relatively rare type of acute myeloid leukaemia, is characterized by frequent involvement of the liver, spleen and lymph nodes in addition to myelofibrosis in children. Diagnosis is difficult both clinically and pathologically, and the hepatic or lymph node involvement is not uncommonly misinterpreted as solid tumour. We report the imaging findings of upper abdominal involvement by AMKL in an infant. The hepatic lesion, initially suspected to be hepatoblastoma, showed a distinctive appearance on MRI suggesting its infiltrative nature. With the association of splenic lesion and lymphadenopathy, the imaging findings were considered indicative of a haematological disorder.

Acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous group of leukemias that result from clonal transformation of hematopoietic precursors through the acquisition of chromosomal rearrangements and multiple gene mutations. As a result of highly collaborative clinical research by pediatric cooperative cancer groups worldwide, disease-free survival has improved significantly during the past 3 decades. Further improvements in outcomes of children who have AML probably will reflect continued progress in understanding the biology of AML and the concomitant development of new molecularly targeted agents for use in combination with conventional chemotherapy drugs.

Treatment and prognostic impact of transient leukemia in neonates with Down syndrome

Approximately 10% of the neonates with Down syndrome (DS) exhibit a unique transient leukemia (TL). Though TL resolves spontaneously in most patients, early death and development of myeloid leukemia (ML-DS) may occur. Prognostic factors as well as treatment indication are currently uncertain. To resolve that issue, we prospectively collected clinical, biologic, and treatment data of 146 patients with TL. The 5-year overall survival (OS) and event-free survival (EFS) were 85% plus or minus 3% and 63% plus or minus 4%, respectively. Multivariate analysis revealed a correlation between high white blood cell (WBC) count, ascites, preterm delivery, bleeding diatheses, failure of spontaneous remission, and the occurrence of early death. Treatment with cytarabine (0.5-1.5 mg/kg) was administered to 28 patients with high WBC count, thrombocytopenia, or liver dysfunction. The therapy had a beneficial effect on the outcome of those children with risk factors for early death (5-year EFS, 52% +/- 12% vs 28% +/- 11% [no treatment]; P = .02). Multivariate analysis demonstrated its favorable prognostic impact. A total of 29 (23%) patients with TL subsequently developed ML-DS. Patients with ML-DS with a history of TL had a significantly better 5-year EFS (91% +/- 5%) than those without documented TL (70% +/- 4%), primarily due to a lower relapse rate. A history of TL may therefore define a lower-risk ML-DS subgroup. This study was registered at www.clinicaltrials.gov as no. NCT 00111345.