An effective chemotherapeutic regimen for acute myeloid leukemia and myelodysplastic syndrome in children with Down's syndrome

Survival outcomes of myeloid leukemia associated with Down syndrome and de novo acute myeloid leukemia in children: Experience from a single tertiary center in Thailand

Few studies have reported the survival outcomes of myeloid leukemia associated with Down syndrome (DS) in resource-limited countries. This study aimed to compare characteristics and survival outcomes of children with acute myeloid leukemia (AML) between those with and without DS in Thailand. The medical records of AML patients aged 0-15 years treated in a major tertiary center in Southern Thailand between October 1978 and December 2019 were reviewed retrospectively. The overall (OS) and event-free survivals (EFS) rates were calculated using the Kaplan-Meier method. A total of 362 AML patients were included, of which 41 (11.3%) had DS. The mean age at diagnosis of the DS patients was 2.5 ± 1.9 years and most of them (90.2%) were under the age of five. The DS patients had lower initial white blood cell counts and peripheral blasts compared to the non-DS patients. The AML-M7 subtype was more common in the DS than in the non-DS patients (80.5% vs. 9.1%, p < 0.01, respectively). The 5-year OS and EFS rates of the DS patients were lower compared to the non-DS patients (12.9% vs. 20.5%, p = 0.05 and 13.7% vs. 18.4%, p = 0.03, respectively). DS patients had a significantly higher rate of early and treatment-related deaths compared to non-DS patients (30.3% vs. 13.5%, p < 0.01 and 39.4% vs. 19.5%, p = 0.02, respectively). Over the study period, there were a decrease in early death rate and an increase in survival rates of DS patients, which suggests that chemotherapy regimens and supportive care have improved over time.

Clonal Myeloproliferative Disorders in Patients with Down Syndrome-Treatment and Outcome Results from an Institution in Argentina

Children with Down syndrome (DS) are at an increased risk of developing clonal myeloproliferative disorders. The balance between treatment intensity and treatment-related toxicity has not yet been defined. We analyzed this population to identify risk factors and optimal treatment. This single-center retrospective study included 78 DS patients <16 years-old with Transient Abnormal Myelopoiesis (TAM, n = 25), Acute Myeloblastic Leukemia (DS-AML, n = 41) of which 35 had classical Myeloid Leukemia associated with DS (ML-DS) with megakaryoblastic immunophenotype (AMKL) and 6 sporadic DS-AML (non-AMKL). Patients with DS-AML were treated according to four BFM-based protocols. Classical ML-DS vs. non-DS-AMKL were compared and the outcome of ML-DS was analyzed according to treatment intensity. Only four patients with TAM required cytoreduction with a 5-year Event-Free Survival probability (EFSp) of 74.4 (±9.1)%. DS-AML treatment-related deaths were due to infections, with a 5-year EFSp of 60.6 (±8.2)%. Megakaryoblastic immunophenotype was the strongest good-prognostic factor in univariate and multivariate analysis (p = 0.000). When compared ML-DS with non-DS-AMKL, a better outcome was associated with a lower relapse rate (p = 0.0002). Analysis of administered treatment was done on 32/33 ML-DS patients who achieved CR according to receiving or not high-dose ARA-C block (HDARA-C), and no difference in 5-year EFSp was observed (p = 0.172). TAM rarely required treatment and when severe manifestations occurred, early intervention was effective. DS-AML good outcome was associated with AMKL with a low relapse-rate. Even if treatment-related mortality is still high, our data do not support the omission of HDARA-C in ML-DS since we observed a trend to detect a higher relapse rate in the arm without HDARA-C.

Clinical and biological aspects of myeloid leukemia in Down syndrome

Children with Down syndrome are at an elevated risk of leukemia, especially myeloid leukemia (ML-DS). This malignancy is frequently preceded by transient abnormal myelopoiesis (TAM), which is self-limited expansion of fetal liver-derived megakaryocyte progenitors. An array of international studies has led to consensus in treating ML-DS with reduced-intensity chemotherapy, leading to excellent outcomes. In addition, studies performed in the past 20 years have revealed many of the genetic and epigenetic features of the tumors, including GATA1 mutations that are arguably associated with all cases of both TAM and ML-DS. Despite these advances in understanding the clinical and biological aspects of ML-DS, little is known about the mechanisms of relapse. Upon relapse, patients face a poor outcome, and there is no consensus on treatment. Future studies need to be focused on this challenging aspect of leukemia in children with DS.

Epidemiology of Acute Leukemia among Children with Down Syndrome in Korea

Purpose

Children with Down syndrome (DS) show a higher risk of acute leukemia than those without DS. In this study, we investigated the nationwide incidence of acute leukemia among children with DS and compared their epidemiologic characteristics with those of children with acute leukemia but without DS.

Materials and Methods

Using the National Health Insurance Service database, we selected patients with acute leukemia aged 0–19 years at diagnosis between 2007 and 2016.

Results

Among the 4,697 children with acute leukemia, 54 (1.1%) had DS. The median incidence rate of leukemia with DS by year was 1.3% (range, 0.2% to 2.0%). Sixteen patients with acute lymphoblastic leukemia (ALL; 29.6%) and 36 with acute myeloid leukemia (AML; 66.7%) had DS. The DS group showed younger age at diagnosis than the non-DS group, and diagnosis of AML was more frequent in the DS group than in the non-DS group (3 years vs. 9 years, p < 0.001; 66.7% vs. 32.4%, p < 0.001, respectively). The 5-year overall survival was comparable between the DS and non-DS groups (88.0% vs. 81.9%, p=0.375). Among all the Koreans born between 2007 and 2008, the incidences of acute leukemia, ALL, and AML were 49.25, 20.75, and 163.38 times higher, respectively, in the DS group than in the non-DS group.

Conclusion

Our findings support the fact that the incidence of acute leukemia is higher among patients with DS than among those without DS in Korea. However, the DS and non-DS groups in this study had a comparable overall survival rate.

Characteristics and outcomes of children with acute myeloid leukemia and Down syndrome who are ineligible for clinical trials due to severe comorbidities

BACKGROUND

High survival rates of 80-90% have been reported in recent clinical trials of reduced-intensity chemotherapies for children with acute myeloid leukemia and Down syndrome (AML-DS). However, a certain number of children with AML-DS have complicating comorbidities, including congenital heart disease (CHD), and are therefore ineligible for enrolment in clinical trials.

METHODS

We retrospectively analyzed the clinical characteristics and outcomes of children with AML-DS who were excluded from Japanese clinical trials conducted between 2000 and 2015.

RESULTS

Twelve children (six males and six females) were identified and were ineligible for CHD (n = 8) and other comorbidities, including hyperleukocytosis complicated with coagulopathy, severe hemophagocytosis, pulmonary fibrosis, and hypoxic-ischemic encephalopathy (n = 1 each). The median age at the diagnosis was 14 months (range, 5 months to 11.5 years). Among all cases, 11 patients were treated with curative intent. Four patients were considered intolerant to intensive chemotherapy and received only low-dose cytarabine-based chemotherapy: three failed to achieve remission and died of disease, while one successfully achieved remission but eventually died of infection. Seven cases underwent regular-intensive chemotherapy for AML-DS: six were alive and in remission; one had relapsed disease. One patient who received the best supportive care died of disease. Finally, six patients remained in continuous complete remission, while six died. The 5-year overall survival rate was 51%.

CONCLUSIONS

The prognosis of AML-DS patients who received insufficient treatment due to severe complication was poor. The optimal dose intensity of curative chemotherapy for such cases should be explored.

Treatment results in children with myeloid leukemia of Down syndrome in Saudi Arabia: A multicenter SAPHOS leukemia group study

Despite the high incidence of Down syndrome (DS) in Arab countires, the incidence and outcomes of myeloid leukemia of DS (ML-DS) have not been studied. We evaluated 206 pediatric acute myeloid leukemia (AML) patients diagnosed between 2005 and 2012 and identified 31 (15%) ML-DS. The incidence of ML-DS was 48 per 100,000 compared to 0.6 per 100,000 for AML in non-DS children. Thus, patients with DS had 80-fold increased risk of ML-DS compared to AML in non-DS children. The median age at diagnosis was 1.8 years, male/female ratio was 1.2, majority (84%) of patients had FAB-M7 subtype, and the cytogenetic abnormalities were normal karyotype (constitutional trisomy 21) in 48%, additional trisomy in 23%, and other aberrations in 29%. Complete remission, cumulative incidences of relapse (CIR), toxic-death, and 5-year event-free survival (EFS) rates were 96.8%, 19.4%, 13.1%, and 67.7±8.4%; respectively. In the present study, multivariate analysis revealed favorable outcome (5-year EFS 86.7±8.8%) for patients with normal karyotype. The incidence and clinical characteristics of ML-DS in Saudi patients were comparable to other reports. However, there is a need to optimize risk stratification and treatment intensity to reduce CIR and toxic death rates to further improve outcomes of patients with ML-DS.

Anthracycline-Related Cardiotoxicity in Patients with Acute Myeloid Leukemia and Down Syndrome: A Literature Review

Pediatric patients with Down syndrome (DS) are at an increased risk of developing certain cancers. Specifically, patients with DS have a reported 10-20-fold increased risk of developing acute myeloid leukemia (AML). Anthracycline-based treatment regimens achieve good results in patients with DS and AML. It has been proposed that DS status constitutes a risk factor for the cardiotoxicity associated with the use of anthracyclines in the pediatric setting. However, published evidence pointing toward an increased risk of cardiotoxicity in patients with DS is relatively scarce and conflictive. This concise review compiles literature relating to the incidence of anthracycline-related cardiotoxicity in pediatric patients with DS. In general, reports from trials using anthracyclines at the maximum recommended dose showed increases in the incidence of anthracycline-related cardiotoxicity in patients with DS in comparison with trials that used anthracyclines at reduced doses. Evidence from the literature suggests that patients with DS can achieve favorable therapeutic outcomes after receiving treatment with reduced doses of anthracyclines to minimize the potential for cardiotoxicity. Further prospective trials, along with the available evidence, would assist the design of treatment protocols for patients with pediatric leukemias and DS.

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.

Reduced intensity conditioning in allogeneic stem cell transplantation for AML with Down syndrome

Allogeneic hematopoietic stem cell transplantation (HSCT) has not been widely used in patients with acute myeloid leukemia (AML) and Down syndrome (DS) due to fear of transplantation-related toxicity. A retrospective analysis of the outcome of allogeneic HSCT was conducted in 15 patients with AML and DS. The five patients transplanted with the reduced intensity conditioning (4 in complete remission (CR) and 1 in non-CR) had a significantly better survival rate than 10 patients transplanted with a conventional conditioning (4 in CR and 6 in non-CR) (3-year EFS (95% confidence interval): 80.0% (20.4-96.9%) vs. 10.0% (0.6%-35.8%), P = 0.039).

Continuous and high-dose cytarabine combined chemotherapy in children with down syndrome and acute myeloid leukemia: Report from the Japanese children's cancer and leukemia study group (JCCLSG) AML 9805 down study

BACKGROUND

The aim of the JCCLSG AML 9805 Down study was to evaluate the effect of continuous and high-dose cytarabine combined chemotherapy on the survival outcome of acute myeloid leukemia (AML) with Down syndrome (DS).

PROCEDURE

From May 1998 to December 2006, DS patients with newly diagnosed AML were enrolled. Remission induction therapy consisted of two courses of pirarubicin, vincristine, and continuous-dose cytarabine (AVC1). The patients who achieved complete remission (CR) after two courses of AVC1 were subsequently treated with mitoxantrone and continuous-dose cytarabine (MC), etoposide and high-dose cytarabine (EC) and pirarubicin, vincristine, and continuous-dose cytarabine (AVC2).

RESULTS

Twenty-four patients were enrolled. All patients were younger than 4 years and diagnosed as having acute megakaryoblastic leukemia. Twenty-one patients achieved CR. Three patients died during remission induction therapy due to serious infection. No toxic deaths were observed during remission. All but one patient maintained CR without serious complications. The 5-year overall and event-free survivals were 87.5%  ± 6.8% and 83.1%  ± 7.7%, respectively.

CONCLUSIONS

Continuous and high-dose cytarabine combined chemotherapy with reduced intensity would be effective in DS children with AML.

Myeloid leukaemia in children with Down syndrome: report of the registry-based French experience between 1990 and 2003

AIM

To determine the epidemiology of myeloid leukaemia (ML) in children with Down syndrome (DS) and the efficacy of two approaches, low-dose cytarabine-based regimen (LDC) and standard-dose intensive chemotherapy (SD).

PROCEDURE

All children with Down syndrome aged from 2 months to 15 years with ML/myelodysplasia registered in the French registry between January 1990 and December 2003 were included.

RESULTS

Forty-four patients were included. The median age was 1.75 years. The French-America-British subtypes were as follows: M7: 24, M0: 6, M2: 5, M6: 2. Forty-three patients were treated with curative prospect, 20 patients with LDC regimen and 22 according to SD protocols, 1 was given the LDC regimen plus autologous stem-cell transplantation. The event-free survival (EFS) and overall survival (OS) at 5 years were 64.4% and 76.8%. At 5 years, OS in LDC and SD groups were 65% and 85.9% (P = 0.08). EFS were 45% and 80.3% respectively (P < 0.01).

CONCLUSION

Children with DS can adequately tolerate SD chemotherapy with a significant superiority of EFS relative to LDC. We suggest that higher levels of cure can be obtained in DS-ML with SD chemotherapy including cytarabine and anthracyclines.

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.

High Erk-1 activation and Gadd45a expression as prognostic markers in high risk pediatric haemolymphoproliferative diseases

Studies on activated cell-signaling pathways responsible for neoplastic transformation are numerous in solid tumors and in adult leukemias. Despite of positive results in the evolution of pediatric hematopoietic neoplasias, there are some high-risk subtypes at worse prognosis. The aim of this study was to asses the expression and activation status of crucial proteins involved in cell-signaling pathways in order to identify molecular alterations responsible for the proliferation and/or escape from apoptosis of leukemic blasts. The quantitative and qualitative expression and activation of Erk-1, c-Jun, Caspase8, and Gadd45a was analyzed, by immunocytochemical (ICC) and western blotting methods, in bone marrow blasts of 72 patients affected by acute myeloid leukemia (AML), T-cell acute lymphoblastic leukemia (ALL) and stage IV non-Hodgkin Lymphoma (NHL). We found an upregulation of Erk-1, Caspase8, c-Jun, and Gadd45a proteins with a constitutive activation in 95.8%, 91.7%, 86.2%, 83.4% of analyzed specimens, respectively. It is worth noting that all AML patients showed an upregulation of all proteins studied and the high expression of GADD45a was associated to the lowest DFS median (p = 0.04). On univariate analysis, only Erk-1 phosphorylation status was found to be correlated with a significantly shorter 5-years DFS in all disease subgroups (p = 0.033) and the lowest DFS median in ALL/NHL subgroup (p = 0.04). Moreover, the simultaneous activation of multiple kinases, as we found for c-Jun and Erk-1 (r = 0.26; p = 0.025), might synergistically enhance survival and proliferation potential of leukemic cells. These results demonstrate an involvement of these proteins in survival of blast cells and, consequently, on relapse percentages of the different subgroups of patients.

Malignancy in children with trisomy 21

Patients with Down syndrome (DS) display a unique spectrum of malignancies, with a 10- to 20-fold higher risk of acute leukemias, and a markedly lower incidence of solid tumors. This review discusses the current understanding of the basis for this distinctive pattern of cancer incidence and the clinical and biologic features of the malignant disorders most frequent in DS individuals: transient myeloproliferative disease, acute megakaryoblastic leukemia, and acute lymphoblastic leukemia. We also review distinctive pharmacogenetic issues, highlighting the differential chemosensitivity and toxicity profiles of DS patients compared with the general population, and epidemiologic studies of protective and adverse environmental risk factors for the development of leukemia.

Transient abnormal myelopoiesis in a Down syndrome newborn followed by acute myeloid leukemia: identification of the same chromosomal abnormality in both stages

A transient abnormal myelopoiesis was observed in a newborn with Down syndrome. Cytogenetic study revealed multiple oligoclonal abnormalities: 47,XY,inv(6)(p23q21),+21c[3]/47,XY,der(7)t(1;7)(q25;p15),+21c[1]/47,XY,del(13)(q?),+21c[1]/47,XY,+21c[15]. Ten months after the patient achieved remission, the transient abnormal myelopoiesis evolved to an acute megakaryoblastic leukemia. Cytogenetic study revealed only a single clonal abnormality, 47,XY,der(7)t(1;7)(q25;p15),+21c, identical to one of the structural changes seen at birth. Sequence analysis of the GATA1 gene revealed a deletion-insertion mutation within the exon 2 introducing a stop codon after Arg 64. It may be that the der(7)t(1;7)(q25;p15) abnormality played some selective role in the development of acute megakaryoblastic leukemia in this patient. To our knowledge, the present case is unique in demonstrating a subclone with der(7)t(1;7)(q25;p15) evolving to acute leukemia.

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.

Cardiomyopathy in children with Down syndrome treated for acute myeloid leukemia: a report from the Children's Oncology Group Study POG 9421

PURPOSE

To determine the outcomes, with particular attention to toxicity, of children with Down syndrome (DS) and acute myeloid leukemia (AML) treated on Pediatric Oncology Group (POG) protocol 9421.

PATIENTS AND METHODS

Children with DS and newly diagnosed AML (n = 57) were prospectively enrolled onto the standard-therapy arm of POG 9421 and were administered five cycles of chemotherapy, which included daunorubicin 135 mg/m(2) and mitoxantrone 80 mg/m(2). Outcomes and toxicity were evaluated prospectively and were compared with the non-DS-AML cohort (n = 565). A retrospective chart review was performed to identify adverse cardiac events.

RESULTS

In the DS-AML group, 54 patients (94.7%) entered remission. One experienced induction failure and two died. Of the 54 who entered remission, three relapsed and six died as a result of other causes. The remission induction rate was similar in the non-DS-French-American-British (FAB) M7 (91.7%) and non-DS-non-M7 (89.3%) groups. The 5-year overall survival was significantly better in the DS-AML group (78.6%) than in the non-DS-M7 (36.3%) or the non-DS-non-M7 (51.8%) groups (P < .001). No age-related difference in 5-year, event-free survival was seen between patients younger than 2 years (75.8%) and those aged 2 to 4 years (78.3%). Symptomatic cardiomyopathy developed in 10 patients (17.5%) with DS-AML during or soon after completion of treatment; three died as a result of congestive heart failure.

CONCLUSION

The POG 9421 treatment regimen was highly effective in both remission induction and disease-free survival for patients with DS-AML. However, there was a high incidence of cardiomyopathy, which supports current strategies for dose reduction of anthracyclines in this patient population.

The role of the proto-oncogene ETS2 in acute megakaryocytic leukemia biology and therapy

Acute myeloid leukemia (AML) in Down syndrome (DS) children has several unique features including a predominance of the acute megakaryocytic leukemia (AMkL) phenotype, higher event-free survivals compared to non-DS children using cytosine arabinoside (ara-C)/anthracycline-based protocols and a uniform presence of somatic mutations in the X-linked transcription factor gene, GATA1. Several chromosome 21-localized transcription factor oncogenes including ETS2 may contribute to the unique features of DS AMkL. ETS2 transcripts measured by real-time RT-PCR were 1.8- and 4.1-fold, respectively, higher in DS and non-DS megakaryoblasts than those in non-DS myeloblasts. In a doxycycline-inducible erythroleukemia cell line, K562pTet-on/ETS2, induction of ETS2 resulted in an erythroid to megakaryocytic phenotypic switch independent of GATA1 levels. Microarray analysis of doxycycline-induced and doxycycline-uninduced cells revealed an upregulation by ETS2 of cytokines (for example, interleukin 1 and CSF2) and transcription factors (for example, TAL1), which are key regulators of megakaryocytic differentiation. In the K562pTet-on/ETS2 cells, ETS2 induction conferred differences in sensitivities to ara-C and daunorubicin, depending on GATA1 levels. These results suggest that ETS2 expression is linked to the biology of AMkL in both DS and non-DS children, and that ETS2 acts by regulating expression of hematopoietic lineage and transcription factor genes involved in erythropoiesis and megakaryopoiesis, and in chemotherapy sensitivities.

Prospective study of a pirarubicin, intermediate-dose cytarabine, and etoposide regimen in children with Down syndrome and acute myeloid leukemia: the Japanese Childhood AML Cooperative Study Group

PURPOSE

To evaluate a less intensive chemotherapeutic regimen specifically designed for patients with Down syndrome (DS) and acute myeloid leukemia (AML), and to determine the prognostic factors for event-free survival.

PATIENTS AND METHODS

Seventy-two patients with AML-DS were treated with remission induction chemotherapy consisting of pirarubicin (25 mg/m2/d for 2 days), cytarabine (100 mg/m2/d for 7 days), and etoposide (150 mg/m2/d for 3 days). Patients received four courses of intensification therapy of the same regimen. Prophylaxis for CNS leukemia was not included.

RESULTS

All but two patients were younger than 4 years, and 67 of the 72 patients (93%) were diagnosed as acute megakaryoblastic leukemia (AMKL). Seventy of the 72 patients (97.2%) achieved a complete remission (CR), and the estimated 4-year event-free survival (EFS) rate was 83% +/- 9%. Nine patients relapsed, and one died as a result of pneumonia during CR. Multivariate analysis revealed that the presence of monosomy 7 was a greater risk factor of adverse outcome (odds ratio = 5.67; P = .027).

CONCLUSION

A less intensive chemotherapeutic regimen produces excellent outcomes in standard-risk AML-DS patient. Risk-oriented therapy should be considered for future trials in AML-DS.

Acute megakaryoblastic leukemia in Down syndrome

Children with Down syndrome (DS) have a 10- to 20-fold increased risk of developing acute leukemia. An estimated 10% of newborns with DS develop Transient Myeloproliferative Disease (TMD) or Transient Leukemia (TL), a clonal accumulation of megakaryoblasts that resolves spontaneously within months. Acute megakaryoblastic leukemia (AMKL) develops in approximately 20% of cases of TMD/TL by 4 years of age. Both the blasts of AMKL and TMD/TL in DS harbor somatic mutations of GATA1, an essential transcriptional regulator of megakaryocytic differentiation. The distinct phenotypes of megakaryoblastic leukemia in DS are a unique biological model of the incremental process of leukemic transformation.

Transcription factor GATA-1 and Down syndrome leukemogenesis

Mutations in transcription factors constitute one means by which normal hematopoietic progenitors are converted to leukemic stem cells. Recently, acquired mutations in the megakaryocytic regulator GATA1 have been found in essentially all cases of acute megakaryoblastic leukemia (AMkL) in children with Down syndrome and in the closely related malignancy transient myeloproliferative disorder. In all cases, mutations in GATA1 lead to the expression of a shorter isoform of GATA-1, named GATA-1s. Because GATA-1s retains both DNA binding zinc fingers, but is missing the N-terminal transactivation domain, it has been predicted that the inability of GATA-1s to regulate its normal class of megakaryocytic target genes is the mechanism by which mutations in GATA1 contribute to the disease. Indeed, several recent reports have confirmed that GATA-1s fails to properly regulate the growth of megakaryocytic precursors, likely through aberrant transcriptional regulation. Although the specific target genes of GATA-1 mis-regulated by GATA-1s that drive this abnormal growth remain undefined, multiple candidate genes have been identified via gene array studies. Finally, the inability of GATA-1s to promote expression of important metabolic genes, such as cytadine deaminase, likely contributes to the remarkable hypersensitivity of AMkL blasts to cytosine arabinoside. Future studies to define the entire class of genes dysregulated by mutations in GATA1 will provide important insights into the etiology of these malignancies.

Repetitive cycles of high-dose cytarabine are effective for childhood acute myeloid leukemia: long-term outcome of the children with AML treated on two consecutive trials of Tokyo Children's Cancer Study Group

BACKGROUND

Various methods of intensive chemotherapy have contributed to an improved survival in pediatric acute myeloid leukemia (AML). We here report the long-term results of the two consecutive trials of Tokyo Children's Cancer Study Group (TCCSG), incorporating repetitive use of high-dose cytarabine (HD-Ara-C) based combination chemotherapy in post-remission phase.

PROCEDURE

A total of 216 eligible children with newly diagnosed AML were treated in the two consecutive multi-center trials of TCCSG, M91-13 and M96-14, from August 1991 to September 1998. In M91-13 trial, patients received eight courses of intensive post-remission chemotherapy, including six HD-Ara-C containing courses, after remission-induction therapy. Autologous hematopoietic stem cell transplantation (HSCT) could be selected by physician's choice, and allogeneic HSCT was allocated if donor was available. In M96-14 trial, the last two HD-Ara-C courses were omitted from the chemotherapy arm.

RESULTS

The remission-induction rate was 88.8% and probability of 5-year Overall survival (OS) and event-free survival (EFS) were 62% (56-69% with 95% Confidence intervals (CIs)) and 56% (49-62%), respectively. Treatment-related mortality (TRM) was 7.8%. Among patients without Down syndrome (DS) or acute promyelocytic leukemia (APL), the presence of t(8;21) or inv(16) was a significant good prognostic factor both in the univariate and multivariate analyses. Children with DS (N = 10) and APL (N = 14) also showed a good survival exceeding 70% in 5 years.

CONCLUSIONS

These results suggest that repetitive use of HD-Ara-C was effective and safe for childhood AML. However, further optimization of AML therapy is required.

CD36 (thrombospondin receptor) expression in childhood acute megakaryoblastic leukemia: in vitro drug sensitivity and outcome

The outcome for children with acute megakaryoblastic leukemia (AMKL) remains poor, except for cases associated with Down syndrome (DS). This study compared immunophenotypic and drug sensitivity patterns of childhood AMKL cases with or without DS. All DS-AMKL cases showed high expression of CD36 and were very sensitive to cytarabine and daunorubicin in vitro. In children without DS, high expression of CD36 on AMKL blasts identified a sub-group with immunophenotypic and drug sensitivity patterns similar to that of DS AMKL. Among non-DS AMKL patients, CD36-high cases had a superior outcome compared with CD36-negative cases. CD36 expression in acute myeloid leukemia cases other than AMKL was not associated with increased in vitro drug sensitivity. CD36 expression in AMKL may be an indicator of megakaryoblast maturation and chemotherapy sensitivity.

Etoposide pharmacokinetics in children treated for acute myeloid leukemia

We studied the pharmacokinetics of etoposide in 45 children treated for newly diagnosed acute myeloid leukemia. Etoposide, 100 mg/m body surface area/24 h, was administered by 96-h continuous intravenous infusion. Concomitantly, the children received cytarabine 200 mg/m/24 h by intravenous infusion and 6-thioguanine 100 mg/m twice daily orally. Median total body clearance in children 0.5-1.8 (n=4) and 2.3-17.7 years old (n=36) without Down's syndrome was 17.1 and 17.6 ml/min/m, respectively (P=0.96). Five children with Down's syndrome had a median clearance of 13.6 ml/min/m (P=0.067 compared with non-Down's syndrome children). Eighteen of the children received a second identical treatment course 3-4 weeks later; there was a significant correlation between individual clearance values (rho=0.56; P=0.017). We found no significant correlation between etoposide pharmacokinetics and the remission rate or the relapse rate. In conclusion, our findings indicate that special dose-calculation guidelines for infants above 3 months old are not substantiated by age-dependent pharmacokinetics of etoposide. Down's syndrome children might be candidates for dose reduction if our data are confirmed in larger numbers of patients. Low course-to-course variability indicates that pharmacokinetically guided dosing of etoposide might be clinically relevant, if larger studies can demonstrate that this approach decreases toxicity or increases response rates.

Doxorubicin pharmacokinetics is correlated to the effect of induction therapy in children with acute myeloid leukemia

We studied the pharmacokinetics of doxorubicin in 41 children treated for newly diagnosed acute myeloid leukemia. Doxorubicin, 75 mg/m2 body surface area, was administered by constant i.v. infusion over 8 h. Four children with Down's syndrome (DS), 1.2-2.3 years old, had a median total body clearance of 523 ml/min/m2. The median clearance in non-DS children, 0.6-1.8 years old (n = 4) and 2.5-17.7 years old (n = 33), was 446 and 538 ml/min/m2, respectively. Patients who went into complete remission (CR) after induction therapy had a significantly higher median plasma concentration of doxorubicin than those who did not, 249 compared with 180 ng/ml, respectively (P = 0.036; analysis restricted to non-DS patients). Doxorubicin plasma concentration was an independent factor for CR, both in univariate (P = 0.031) and multivariate analysis including sex, age and white blood cell count at diagnosis (P = 0.021). Patients who reached CR had a significantly lower doxorubicin clearance than those who did not, 513 and 657 ml/min/m2, respectively (P = 0.017). In conclusion, doxorubicin plasma concentration and total body clearance during up-front treatment were correlated to the effect of induction therapy. Prospective studies should be performed to confirm the concentration-effect relationship and explore the possibility of therapeutic monitoring.

Optimal treatment intensity in children with Down syndrome and myeloid leukaemia: data from 56 children treated on NOPHO-AML protocols and a review of the literature

Children with Down syndrome (DS) and myeloid leukaemia have a significantly higher survival rate than other children, but they also experience considerable treatment-related toxicity. We analysed data on 56 children with DS who were treated on the Nordic Society for Paediatric Haematology and Oncology-acute myeloid leukaemia (NOPHO-AML)88 and NOPHO-AML93 protocols and reviewed the literature. In the dose-intensive NOPHO-AML88 protocol, 8 out of 15 patients (53%) experienced an event. In the less dose-intensive NOPHO-AML93 protocol, 7 out of 41 patients (17%) had an event. Therapy was reduced in 29 patients (52%) with in average 75% and 67% of the scheduled dose of anthracycline and cytarabine, respectively. Treatment-related death occurred in seven who all received full treatment. Relapse and resistant disease occurred at a similar rate in those receiving full and reduced treatment. Review of major series of myeloid leukaemia of DS showed no clear relationship between dose and survival; however, it appears that both a reduction in treatment dose and a less intensively timed treatment regimen improved the outcome. Further studies are needed to define the optimal regimen for treating myeloid leukaemia of DS.

Identification of novel genes with prognostic value in childhood leukemia using cDNA microarray and quantitative RT-PCR

The aim of this study was to identify genes distinctively expressed or suppressed in childhood leukemia with different prognoses, using cDNA microarray and quantitative reverse transcription-polymerase chain reaction (RT-PCR). The expression levels of the selected genes by cDNA microarray were quantified in primary leukemic blasts from 44 patients (acute lymphoblastic leukemia, 28; acute myelogenous leukemia (AML), 13; transient myeloproliferative disorder, 3). The expression levels of CDKN2C, CRADD, and IGFBP-2 genes were significantly associated with the event-free survival of the patients in AML. The present results suggest that a combination of cDNA microarray and quantitative RT-PCR may be useful to identify novel genes with prognostic value in childhood AML.

Treatment of childhood acute myeloid leukemia

Childhood acute myeloid leukemia is rare, but accounts for a significant number of malignancy-related deaths in this age group. However, the prognosis has improved over past decades, and survival rates of 60% and above have been reported. Still, this implies that more than a third of children and adolescents die from this disease. Moreover, treatment is intensive, and quality of life and late effects are worrying issues. Therefore, there is a need for further improved treatment of pediatric acute myeloid leukemia. This review describes several important developments in this respect, such as improved diagnostics, prognostic factors, subgroup-directed and tailored treatment, and targeted therapy. In addition, background information is provided and current treatment strategies are described, as well as the late effects of treatment. Most groups now have risk-group adapted protocols, with allogeneic stem cell transplantation often being reserved for the higher risk group. Even in these cases, the benefit of stem cell transplantation has not been demonstrated beyond reasonable doubt with current high-intensive chemotherapy. Similarly, the use of cranial irradiation for CNS prophylaxis and maintenance treatment does not seem to be indicated in general. Subgroup-directed treatment has become a reality for acute myeloid leukemia in young children with Down's syndrome and in acute promyelocytic leukemia. In addition to tailoring therapy according to biologic features and especially monitoring treatment by measurements of minimal residual disease, targeted therapy for subgroups with activating mutations in receptor tyrosine kinases will further optimize the treatment of pediatric acute myeloid leukemia. Together with the development of many novel agents that have different mechanisms of action than the currently available anticancer agents, and improved supportive care, it is realistic that the prognosis of acute myeloid leukemia in children and adolescents will improve further in the next 5-10 years.

A prospective study of the natural history of transient leukemia (TL) in neonates with Down syndrome (DS): Children's Oncology Group (COG) study POG-9481

A unique transient leukemia (TL) has been described in newborns with Down syndrome (DS; or trisomy 21 mosaics). This leukemia has a high incidence of spontaneous remission; however, early death and subsequent development of acute megakaryoblastic leukemia (AMKL) have been reported. We prospectively evaluated 48 infants with DS and TL to determine the natural history and biologic characteristics of this disease, identify the clinical characteristics associated with early death or subsequent leukemia, and assess the incidence of subsequent leukemia. Blast cells associated with TL in DS infants exhibited FAB M(7) morphology and phenotype. Most infants (74%) had trisomy 21 (or mosaicism) as the only cytogenetic abnormality in the blast cells. Most children were able to spontaneously clear peripheral blasts (89%), normalize blood counts (74%), and maintain a complete remission (64%). Early death occurred in 17% of infants and was significantly correlated with higher white blood cell count at diagnosis (P < .001), increased bilirubin and liver enzymes (P < .005), and a failure to normalize the blood count (P = .001). Recurrence of leukemia occurred in 19% of infants at a mean of 20 months. Development of leukemia was significantly correlated with karyotypic abnormalities in addition to trisomy 21 (P = .037). Ongoing collaborative clinical studies are needed to determine the optimal role of chemotherapy for infants at risk for increased mortality or disease recurrence and to further the knowledge of the unique biologic features of this TL.

Differential gene expression, GATA1 target genes, and the chemotherapy sensitivity of Down syndrome megakaryocytic leukemia

Children with Down syndrome (DS) with acute megakaryocytic leukemia (AMkL) have very high survival rates compared with non-DS AMkL patients. Somatic mutations identified in the X-linked transcription factor gene, GATA1, in essentially all DS AMkL cases result in the synthesis of a shorter (40 kDa) protein (GATA1s) with altered transactivation activity and may lead to altered expression of GATA1 target genes. Using the Affymetrix U133A microarray chip, we identified 551 differentially expressed genes between DS and non-DS AMkL samples. Transcripts for the bone marrow stromal-cell antigen 2 (BST2) gene, encoding a transmembrane glycoprotein potentially involved in interactions between leukemia cells and bone marrow stromal cells, were 7.3-fold higher (validated by real-time polymerase chain reaction) in the non-DS compared with the DS group. Additional studies confirmed GATA1 protein binding and transactivation of the BST2 promoter; however, stimulation of BST2 promoter activity by GATA1s was substantially reduced compared with the full-length GATA1. CMK sublines, transfected with the BST2 cDNA and incubated with HS-5 bone marrow stromal cells, exhibited up to 1.7-fold reduced cytosine arabinoside (ara-C)-induced apoptosis, compared with mock-transfected cells. Our results demonstrate that genes that account for differences in survival between DS and non-DS AMkL cases may be identified by microarray analysis and that differential gene expression may reflect relative transactivation capacities of the GATA1s and full-length GATA1 proteins.

Chromosome 7 abnormalities in acute megakaryoblastic leukemia associated with Down syndrome

A 2-year-old girl with Down syndrome (DS) developed acute megakaryoblastic leukemia (AMKL) following a transient myeloproliferative disorder (TMD). The blast cells showed an altered karyotype of 47,XX,r(7),+21c. Serial cytogenetic studies during the course of the illness showed rapid stepwise clonal chromosome changes, including a ring chromosome 7, associated with treatment refractoriness. We reviewed 10 published cases of Down syndrome-related AMKL (DS-AMKL) showing chromosome 7 abnormalities and found that these changes do not carry the same prognostic weight as for non-DS children. For DS-AMKL, therefore, other prognostic factors besides clonal cytogenetic changes need to be identified for planning optimal therapy.

Acute leukaemia in children with Down syndrome: a population-based Nordic study

To determine the epidemiology and outcome of children with Down syndrome (DS) diagnosed with acute leukaemia in the Nordic countries, data registered in the Nordic Society of Paediatric Haematology and Oncology (NOPHO) population-based leukaemia registry were analysed. Of 3494 children with acute leukaemia diagnosed between July 1984 and December 2001, 136 patients (3.9%) with DS were identified. 2.1% of the children with acute lymphoid leukaemia (ALL) and 14.0% of the children with acute myeloid leukaemia (AML) had DS. In ALL, DS patients had similar age and sex distribution and no major differences in blood counts compared with non-DS children. None of the DS patients had T cell leukaemia. Outcome was inferior to that of non-DS children and treatment results did not improve over time. In AML, DS patients showed a significant female predominance and all but one were <5 years old. DS patients with AML had significantly lower platelet and white blood cell counts and two-thirds were type M7 as according to the French-American-British classification. None of the patients <5 years of age had typical AML cytogenetic aberrations. Outcome was far better in the DS group. DS patients treated for AML after 1992 had an excellent outcome (probability of event-free survival, 83 +/- 6%). The high proportion of female DS patients with AML is unexplained. The differing treatment results in AML versus ALL need further evaluation and represent a challenge for the coming years.

GATA1, cytidine deaminase, and the high cure rate of Down syndrome children with acute megakaryocytic leukemia

Down syndrome children with acute megakaryocytic leukemia (AMkL) have higher cure rates than non-Down syndrome acute myeloid leukemia (AML) patients treated with cytosine arabinoside (ara-C). Megakaryoblasts from Down syndrome AML patients are more sensitive in vitro to ara-C than cells from non-Down syndrome AML patients. Somatic mutations in the GATA1 transcription factor have been detected exclusively and almost uniformly in Down syndrome AMkL patients, suggesting a potential linkage to the chemotherapy sensitivity of Down syndrome megakaryoblasts. Stable transfection of wild-type GATA1 cDNA into the Down syndrome AMkL cell line CMK resulted in decreased (8- to 17-fold) ara-C sensitivity and a threefold-lower generation of the active ara-C metabolite ara-CTP compared with that for mock-transfected CMK cells. High intracellular levels of uridine arabinoside (ara-U) (an inactive ara-C catabolite generated by cytidine deaminase) and cytidine deaminase transcripts were detected in GATA1-transfected CMK sublines, whereas no ara-U was detected in mock-transfected cells. Cytidine deaminase transcripts were a median 5.1-fold (P = .002) lower in Down syndrome megakaryoblasts (n = 16) than in blast cells from non-Down syndrome patients (n = 56). These results suggest that GATA1 transcriptionally upregulates cytidine deaminase and that the presence or absence of GATA1 mutations in AML blasts likely confers differences in ara-C sensitivities due to effects on cytidine deaminase gene expression, which, in turn, contributes to the high cure rate of Down syndrome AMkL patients.

Down syndrome, drug metabolism and chromosome 21

It has been recognized that chromosomal abnormalities in childhood leukemia, are linked to both leukemogenesis and segregate patients into prognostic treatment groups. This is best exemplified in cases of children with Down syndrome (DS), who have significantly higher risks of developing leukemia compared to non-DS children and distinctive treatment outcomes, particularly in cases of acute myeloid leukemia (AML). The high event-free survival (EFS) rates of DS AML patients and in particular, patients with megakaryocytic leukemia (AMkL), at least in part reflects an increased sensitivity to cytosine arabinoside (ara-C) secondary to increased expression of the chromosome 21-localized gene, cystathionine-beta-synthase, and potentially global mechanisms which increase the susceptibility of cells to undergo apoptosis. Somatic mutations of the X-linked transcription factor gene, GATA1, have been detected uniformly and exclusively in DS AMkL cases, which may lead to altered expression of GATA1 target genes and alter the metabolism of drugs including ara-C. Hyperdiploid acute lymphoblastic leukemia (ALL) cells with extra copies of chromosome 21, generate higher levels of the active methotrexate (MTX) metabolite, MTX polyglutamates. This is on account of increased intracellular transport of MTX via the reduced folate carrier (RFC) whose gene is localized to chromosome 21 and may also account for the increased MTX-associated toxicity of DS ALL patients. Microarray technology should lead to the identification of additional gene targets linked to the treatment response of specific cytogenetic leukemia subgroups.

A case of myelodysplastic syndrome with acquired monosomy 7 in a child with a constitutional t(1;19) and a mosaicism for trisomy 21

A 3-year-old patient presented with anemia, thrombocytopenia, and blasts in the peripheral blood. A bone marrow aspirate revealed a myelodysplastic syndrome (MDS). A mosaic abnormal female karyotype 46,XX, t(1;19)(q42; p13.1)c[12]/ 47,idem,+21c[3]/ 47,idem,-7,+21c,+mar[7] was obtained on G-banded metaphases from unstimulated bone marrow aspirate cell culture. To rule out constitutional abnormalities, we performed a cytogenetic analysis on the patient's phytohemagglutinin-stimulated peripheral blood and cultured skin fibroblasts. A karyotype of 46,XX,t(1;19) (q42;p13.1)c was found in all 20 peripheral lymphocytes analyzed, confirming the constitutional origin of the translocation. In addition, 5 out of 50 cells from two separate cultures of the skin fibroblasts contained an extra chromosome 21. The presence of two cell lines in multiple cultures indicates that the patient is a true low-level mosaic for trisomy 21. Because of the finding of monosomy 7 and a marker chromosome only in the trisomy 21 clone, we conclude that the leukemic clone arose from a hematopoietic precursor with constitutional trisomy 21. It is also possible that the t(1;19) played some role in the development of the MDS. Because acute myelogenous leukemia (AML) and MDS with Down syndrome (DS) have distinct biologic and clinical features, the identification of DS patients with a mild or normal phenotype in the AML/MDS population is of fundamental importance for clinical diagnosis and management.

Acute myeloid leukemia and Down syndrome evolution of modern therapy--state of the art review

Over the past decade, a series of clinical reports have described the experience of Down syndrome (DS) children treated for acute myeloid leukemia (AML). Whereas prior to the first reports in the early 1980's it was felt that DS children with AML had poor outcomes, these clinical trials concluded that DS had a better outcome than non-DS (NDS) children with AML. With these recent reports, it is clear that DS children have a better outcome utilizing less intensive chemotherapy regimens. They also tolerate the more intensive regimens less well than the NDS children. This review focuses upon the six multi-institutional reports that described the DS and AML experience in order to better ascertain the chemotherapy combinations that may be useful in the future for these children. Regimens of varying intensity have all had similar outcomes. In general, the remission rates are approximately 90% with event-free survival (EFS) approximating 70-80%. Most recently, the clinical trials have been large enough to explore prognostic factors specifically in the DS children. This has identified that the younger DS children fair significantly better than the older children. AML in DS is unique and these differences in comparison to NDS children are highlighted. The significantly better outcomes for DS children likely represents a combination of the unique AML seen in DS children and the heightened sensitivity to cytarabine that DS AML cells have. Future trials should focus on age-stratified approaches that exploit the greater sensitivity of DS AML to cytarabine.

Transient leukemia in newborns with Down syndrome

Children with Down syndrome (DS) have a 10- to 20-fold increased risk of developing leukemia, particularly acute megakaryocytic leukemia. Newborns with DS or trisomy 21 mosaicism may exhibit a particularly unique form of leukemia that historically has been associated with a high rate of spontaneous remission. This transient leukemia (TL) has been shown to be a clonal proliferation of blast cells exhibiting megakaryocytic features. Its true incidence remains to be determined. At presentation, many infants are clinically well with only an incidental finding of abnormal blood counts and circulating blasts in the peripheral blood. However, in approximately 20% of cases, the disease is severe and life-threatening, manifesting as hydrops faetalis, multiple effusions, and liver or multi-organ system failure resulting in death. Of those children who enter a spontaneous remission, 13-33% have been found to develop subsequent acute megakaryoblastic leukemia, usually within the first 3 years of life, which if left untreated is fatal. This unique TL of the DS newborn has been the subject of recent clinical cooperative group trials as well as many biological and genetic research efforts. We summarize here the known clinical, biological, and cytogenetic features of TL associated with DS.

[Acute leukemia in patients with Down syndrome]

BACKGROUND

Children with Down syndrome (DS) have a higher risk of acute leukemia than the remaining pediatric population. A favorable outcome of acute myeloid leukemia (AML) has recently been described in these patients whereas the prognosis of acute lymphoblastic leukemias (ALL) is similar to that in other children. The main cause of morbidity and mortality in children with Down syndrome are complications related to chemotherapy, leading to numerous modifications in treatment protocols.

OBJECTIVES

To characterize acute leukemias in children with Down syndrome in our center and determine their clinical outcome.

METHODS AND RESULTS

Between 1990 and 2002, 214 children were diagnosed with acute leukemia at the Niño Jesus Hospital (40 with AML and 174 with ALL). Of these, eight children (3.8 %) had Down syndrome. AML (2/40) represented 5 % of myeloid leukemias and ALL (6/174) represented 3.4 % of lymphoblastic leukemias. The most frequent complication was hematologic toxicity due to chemotherapy, causing a high incidence of infections: pneumonia (5/8) and bacteriemia (5/8). In all patients, these complications led to treatment interruption or dose reduction. Two children died from treatment-related toxicity. Of these, one with AML developed fulminant sepsis due to Candida infection and the other, diagnosed with high risk ALL, died from multiorgan failure after high doses of methotrexate and ARA-C.

CONCLUSIONS

Patients with Down syndrome diagnosed with acute leukemia show a higher incidence of treatment-related complications, which affects their prognosis. Consequently, individualized treatment of these children in qualified units is essential.

Possibilities for tailored and targeted therapy in paediatric acute myeloid leukaemia

The clinical outcome of acute myeloid leukaemia (AML) in children has improved considerably using intensive chemotherapy and/or stem cell transplantation. This leads to cure in 50-70% of patients, and also results in significant morbidity and mortality. Hence, we need other ways to improve the cure rate. This review discusses possibilities for tailored therapy, reviewing in vitro cellular drug sensitivity data. The results provide suggestions regarding the adaptation of clinical protocols in certain AML subgroups, although further clinical studies will show whether this is effective. Secondly, we review type 1 genetic abnormalities (such as receptor tyrosine kinase mutations) that result in enhanced survival and proliferation of leukaemic cells, which can be detected in approximately 50% of paediatric AML samples, and are non-randomly associated with French-American-British type and cytogenetic subgroups. FLT3 internal tandem duplication is associated with poor clinical outcome, and may be used for risk-group stratification. The first results with small molecule inhibitors in adult AML do not suggest their use in children as yet. International collaboration is needed to further improve outcome by developing treatment protocols for subgroups of paediatric AML.

Increased age at diagnosis has a significantly negative effect on outcome in children with Down syndrome and acute myeloid leukemia: a report from the Children's Cancer Group Study 2891

PURPOSE

To determine the outcome of children with Down syndrome (DS) and acute myeloid leukemia (AML) receiving standard timing chemotherapy without bone marrow transplantation (BMT), with determination of prognostic factors.

PATIENTS AND METHODS

Children with DS and newly diagnosed AML or myelodysplasia were prospectively enrolled on Children's Cancer Group study 2891 (N = 161) and treated uniformly with four standard timing induction courses of dexamethasone, cytarabine arabinoside, 6-thioguanine, etoposide, daunorubicin (DCTER) followed by intensively timed high-dose cytarabine.

RESULTS

Children with DS were significantly younger at diagnosis than those without (median age, 1.8 v 7.5 years, respectively; P <.001), with more megakaryocytic leukemia (70% v 6%; P <.001). Higher complete remission rates (91%) were achieved in children with DS than among those without DS (75%; P <.001). Equivalent grade 3 to 4 toxicity (29% v 30%; P =.84) was seen, though children with DS had greater pulmonary toxicity (P <.01) during induction and mucositis during intensification (P =.12). Children with DS had significantly better 8-year event-free survival (EFS; 77% v 21% standard and 40% intensive induction; P <.0001). Multivariate analysis in children with DS revealed that only age at diagnosis of 2 years or older was a risk factor for greater relapse risk (odds ratio, 4.9; P =.006) and worse survival. Children between ages 0 to 2 years (n = 94) had a 6-year EFS of 86%; those from 2 to 4 years (n = 58), 70%; and those older than 4 years (n = 9), 28%. Remission failures were the primary reason for worse 6-year EFSs (1% in those 0 to 2 years v 14% if >2 years; P =.002).

CONCLUSION

Outcome for children with DS and AML is excellent with standard induction therapy, but declines with increasing age.

Chromosomal rearrangement in Down syndrome with acute myeloid leukemia

The incidence of acute leukemia in children with Down syndrome (DS) is high as compared to general population. Recent findings have demonstrated that DS children with acute myeloid leukemia (AML) have the highest event free survival rates with high dose cytosine arabinoside (Ara-C). We present 3 year-old DS female child with AML-M5, whose chromosomal analysis revealed constitutional t(21;21) alongwith del(5)(q31q33) and a unique translocation t(16;20)(q13;q12). After chemotherapy, child achieved complete clinical remission. Karyotype analysis of remission marrow showed disappearance of abnormal clone of der(20) t(16;20)(q13;q12), del(5q) indicating cytogenetic remission too. This case alongwith supportive literature indicate that pediatric DS-AML is a distinct biologic sub-group differs from that of non-DS-AML with respect to chemosensitivity.

Distinctive multidrug sensitivity and outcome of acute erythroblastic and megakaryoblastic leukemia in children with Down syndrome

We assessed the in vitro chemosensitivity of acute erythroblastic and megakaryoblastic leukemia cells from children with Down syndrome (DS) compared to non-DS children. We conducted in vitro tests using the MTT assay of bone marrow samples from 12 children with DS and 16 children without DS. Patients were newly diagnosed based on the morphology and expression of platelet-specific antigens. Induction failure occurred more frequently in the non-DS group (n = 4) than in the DS group (n = 0, P = .053). Children with DS had a superior event-free survival (EFS) probability of 0.750 at 4 years, compared to an EFS probability of 0.375 for non-DS children (P = .049). Blast cells from DS patients were significantly more sensitive to daunorubicin, melphalan, mitoxantrone, 4-hydroperoxy-cyclophosphamide, vincristine, etoposide, bleomycin, and pirarubicin than those from non-DS patients. Four of the 16 non-DS patients were found to have acquired an extra chromosome 21 in their leukemia cells: blasts from these patients also tended to have greater chemosensitivity than those from patients without an extra chromosome 21. Blast cells from DS patients are markedly sensitive to various drugs. These results suggest that the fragility of blast cells derived from DS patients may be related to an increased susceptibility to apoptosis.

Treatment of acute leukemia in children: recent advances and future challenges

Recently advances have been made in the treatment of acute leukemia in children, it is now possible to cure more than 70% of children with acute lymphoblastic leukemia. With the introduction of more intensive chemotherapy regimens in patients at higher risk of relapse and the identification of cases that could be less intensely treated to diminish long-term toxicity, it could be possible to improve these excellent results. In contrast, pediatric acute myeloid leukaemia seems to be a more heterogeneous disease and its response to conventional chemotherapy is not as uniform. Introduction of new and more efficacious therapies is necessary to improve the poor outcome, especially among patients with high-risk features.