High modal number and triple trisomies are highly correlated favorable factors in childhood B-cell precursor high hyperdiploid acute lymphoblastic leukemia treated according to the NOPHO ALL 1992/2000 protocols

Prognostic and Pharmacotypic Heterogeneity of Hyperdiploidy in Childhood ALL

PURPOSE

High hyperdiploidy, the largest and favorable subtype of childhood ALL, exhibits significant biological and prognostic heterogeneity. However, factors contributing to the varied treatment response and the optimal definition of hyperdiploidy remain uncertain.

METHODS

We analyzed outcomes of patients treated on two consecutive frontline ALL protocols, using six different definitions of hyperdiploidy: chromosome number 51-67 (Chr51-67); DNA index (DI; DI1.16-1.6); United Kingdom ALL study group low-risk hyperdiploid, either trisomy of chromosomes 17 and 18 or +17 or +18 in the absence of +5 and +20; single trisomy of chromosome 18; double trisomy of chromosomes 4 and 10; and triple trisomy (TT) of chromosomes 4, 10, and 17. Additionally, we characterized ALL ex vivo pharmacotypes across eight main cytotoxic drugs.

RESULTS

Among 1,096 patients analyzed, 915 had B-ALL and 634 had pharmacotyping performed. In univariate analysis, TT emerged as the most favorable criterion for event-free survival (EFS; 10-year EFS, 97.3% v 86.8%; P = .0003) and cumulative incidence of relapse (CIR; 10-year CIR, 1.4% v 8.8%; P = .002) compared with the remaining B-ALL. In multivariable analysis, accounting for patient numbers using the akaike information criterion (AIC), DI1.16-1.6 was the most favorable criterion, exhibiting the best AIC for both EFS (hazard ratio [HR], 0.45; 95% CI, 0.23 to 0.88) and CIR (HR, 0.45; 95% CI, 0.21 to 0.99). Hyperdiploidy and subgroups with favorable prognoses exhibited notable sensitivities to asparaginase and mercaptopurine. Specifically, asparaginase sensitivity was associated with trisomy of chromosomes 16 and 17, whereas mercaptopurine sensitivity was linked to gains of chromosomes 14 and 17.

CONCLUSION

Among different definitions of hyperdiploid ALL, DI is optimal based on independent prognostic impact and also the large proportion of low-risk patients identified. Hyperdiploid ALL exhibited particular sensitivities to asparaginase and mercaptopurine, with chromosome-specific associations.

Paediatric B lymphoblastic leukaemia with hyperdiploidy and a false-positive KMT2A fluorescence in situ hybridization result

The dramatic improvement in the event-free survival of paediatric B-lymphoblastic leukaemia (B-ALL) has led to risk-stratified treatment. Through a combination of clinical features, cytogenetic abnormalities and assessment of treatment response, patients are stratified to receive different intensities of therapy. The presence of high hyperdiploidy (>50 chromosomes) is considered a favourable genetic feature. Conversely, KMT2A fusion genes in B-ALL are associated with a poor prognosis, resulting in intensification of treatment. We present a seven-year-old female with B-ALL, a high hyperdiploid karyotype (56 chromosomes) and KMT2A rearrangement detected on FISH, but with no productive fusion identified. Single nucleotide polymorphism (SNP) array suggested the KMT2A rearrangement was due to chromosome 11 chromothripsis. Subsequent targeted RNA fusion panel and whole transcriptomic sequencing (mRNA-seq) did not detect an expressed KMT2A fusion. Differential expression analyses of the mRNA-seq data led to clustering of this case with other hyperdiploid cases, consistent with the hyperdiploid cytogenetic results. Given the additional intensity and potential toxicity of high-risk treatment, unusual findings by chromosome analysis, FISH and/or chromosomal microarray should prompt consideration of testing for a KMT2A fusion by another method to avoid misclassification.

Overview on Aneuploidy in Childhood B-Cell Acute Lymphoblastic Leukemia

Recent years have brought significant progress in the treatment of B-cell acute lymphoblastic leukemia (ALL). This was influenced by both the improved schemes of conventionally used therapy, as well as the development of new forms of treatment. As a consequence, 5-year survival rates have increased and now exceed 90% in pediatric patients. For this reason, it would seem that everything has already been explored in the context of ALL. However, delving into its pathogenesis at the molecular level shows that there are many variations that still need to be analyzed in more detail. One of them is aneuploidy, which is among the most common genetic changes in B-cell ALL. It includes both hyperdiploidy and hypodiploidy. Knowledge of the genetic background is important already at the time of diagnosis, because the first of these forms of aneuploidy is characterized by a good prognosis, in contrast to the second, which is in favor of an unfavorable course. In our work, we will focus on summarizing the current state of knowledge on aneuploidy, along with an indication of all the consequences that may be correlated with it in the context of the treatment of patients with B-cell ALL.

Emerging molecular subtypes and therapies in acute lymphoblastic leukemia

Tremendous strides have been made in the molecular and cytogenetic classification of acute lymphoblastic leukemia based on gene expression profiling data, leading to an expansion of entities in the recent International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias and 2022 WHO Classification of Tumours: Haematolymphoid Tumors, 5th edition. This increased diagnostic and therapeutic complexity can be overwhelming, and this review compares nomenclature differences between the ICC and WHO 5th edition publications, compiles key features of each entity, and provides a diagnostic algorithmic approach. In covering B-lymphoblastic leukemia (B-ALL), we divided the entities into established (those present in the revised 4th edition WHO) and novel (those added to either the ICC or WHO 5th edition) groups. The established B-ALL entities include B-ALL with BCR::ABL1 fusion, BCR::ABL1-like features, KMT2A rearrangement, ETV6::RUNX1 rearrangement, high hyperdiploidy, hypodiploidy (focusing on near haploid and low hypodiploid), IGH::IL3 rearrangement, TCF3::PBX1 rearrangement, and iAMP21. The novel B-ALL entities include B-ALL with MYC rearrangement; DUX4 rearrangement; MEF2D rearrangement; ZNF384 or ZNF362 rearrangement, NUTM1 rearrangement; HLF rearrangement; UBTF::ATXN7L3/PAN3,CDX2; mutated IKZF1 N159Y; mutated PAX5 P80R; ETV6::RUNX1-like features; PAX5 alteration; mutated ZEB2 (p.H1038R)/IGH::CEBPE; ZNF384 rearranged-like; KMT2A-rearranged-like; and CRLF2 rearrangement (non-Ph-like). Classification of T-ALL is complex with some variability in how the subtypes are defined in recent literature. It was classified as early T-precursor lymphoblastic leukemia/lymphoma and T-ALL, NOS in the WHO revised 4th edition and WHO 5th edition. The ICC added an entity into early T-cell precursor ALL, BCL11B-activated, and also added provisional entities subclassified based on transcription factor families that are aberrantly activated.

Clonal origin and development of high hyperdiploidy in childhood acute lymphoblastic leukaemia

High hyperdiploid acute lymphoblastic leukemia (HeH ALL), one of the most common childhood malignancies, is driven by nonrandom aneuploidy (abnormal chromosome numbers) mainly comprising chromosomal gains. In this study, we investigate how aneuploidy in HeH ALL arises. Single cell whole genome sequencing of 2847 cells from nine primary cases and one normal bone marrow reveals that HeH ALL generally display low chromosomal heterogeneity, indicating that they are not characterized by chromosomal instability and showing that aneuploidy-driven malignancies are not necessarily chromosomally heterogeneous. Furthermore, most chromosomal gains are present in all leukemic cells, suggesting that they arose early during leukemogenesis. Copy number data from 577 primary cases reveals selective pressures that were used for in silico modeling of aneuploidy development. This shows that the aneuploidy in HeH ALL likely arises by an initial tripolar mitosis in a diploid cell followed by clonal evolution, in line with a punctuated evolution model.

[Clinical features and prognosis of high hyperdiploid childhood acute lymphoblastic leukemia: a multicenter retrospective analysis in Fujian Province, China]

OBJECTIVES

To study the clinical features and prognosis of high hyperdiploid (HHD) childhood acute lymphoblastic leukemia (ALL).

METHODS

A retrospective analysis was performed on the medical data of 1 414 children who were newly diagnosed with ALL and were admitted to five hospitals in Fujian Province of China from April 2011 to December 2020. According to karyotype, they were divided into two groups: HHD (n=172) and non-HHD (n=1 242). The clinical features and treatment outcome were compared between the two groups, and the factors influencing the prognosis were further explored.

RESULTS

Among the 1 414 children with ALL, 172 (12.16%) had HHD. Compared with the non-HHD group, the HHD group had significantly lower proportions of children with risk factors for poor prognosis at diagnosis (age of onset ≥10 years or <1 year, white blood cell count ≥50×109/L, and T-cell phenotype) or positive fusion genes (TEL-AML1, BCR-ABL1, E2A-PBX1, and MLL gene rearrangement) (P<0.05). The HHD group had a significantly higher proportion of children with minimal residual disease (MRD) <0.01% at the end of induction chemotherapy (P<0.05). The 10-year event-free survival (EFS) rate and overall survival (OS) rate in the HHD group were significantly higher than those in the non-HHD group (P<0.05). The univariate analysis showed that the number of chromosomes of 58-66, trisomy of chromosome 10, trisomy of chromosome 17, bone marrow MRD <1% on day 15 or 19 of induction chemotherapy, and bone marrow MRD <0.01% on day 33 or 46 of induction chemotherapy were associated with a higher EFS rate (P<0.05), and trisomy of chromosome 10 was associated with a higher OS rate (P<0.05). The multivariate Cox analysis showed that trisomy of chromosome 17 was closely associated with a high EFS rate (P<0.05).

CONCLUSIONS

The ALL children with HHD have few risk factors for poor prognosis at diagnosis and often have good prognosis. The number of chromosomes and trisomy of specific chromosomes are associated with prognosis in these children.

Hyperdiploidy: the longest known, most prevalent, and most enigmatic form of acute lymphoblastic leukemia in children

Hyperdiploidy is the largest genetic entity B-cell precursor acute lymphoblastic leukemia in children. The diagnostic hallmark of its two variants that will be discussed in detail herein is a chromosome count between 52 and 67, respectively. The classical HD form consists of heterozygous di-, tri-, and tetrasomies, whereas the nonclassical one (usually viewed as "duplicated hyperhaploid") contains only disomies and tetrasomies. Despite their apparently different clinical behavior, we show that these two sub-forms can in principle be produced by the same chromosomal maldistribution mechanism. Moreover, their respective array, gene expression, and mutation patterns also indicate that they are biologically more similar than hitherto appreciated. Even though in-depth analyses of the genomic intricacies of classical HD leukemias are indispensable for the elucidation of the disease process, the ensuing results play at present surprisingly little role in treatment stratification, a fact that can be attributed to the overall good prognoses and low relapse rates of the concerned patients and, consequently, their excellent treatment outcome. Irrespective of this underutilization, however, the detailed genetic characterization of HD leukemias may, especially in planned treatment reduction trials, eventually become important for further treatment stratification, patient management, and the clinical elucidation of outcome data. It should therefore become an integral part of all upcoming treatment studies.

Clonal heterogeneity and rates of specific chromosome gains are risk predictors in childhood high-hyperdiploid B-cell acute lymphoblastic leukemia

B‐cell acute lymphoblastic leukemia (B‐ALL) is the commonest childhood cancer. High hyperdiploidy (HHD) identifies the most frequent cytogenetic subgroup in childhood B‐ALL. Although hyperdiploidy represents an important prognostic factor in childhood B‐ALL, the specific chromosome gains with prognostic value in HHD‐B‐ALL remain controversial, and the current knowledge about the hierarchy of chromosome gains, clonal heterogeneity and chromosomal instability in HHD‐B‐ALL remains very limited. We applied automated sequential‐iFISH coupled with single‐cell computational modeling to identify the specific chromosomal gains of the eight typically gained chromosomes in a large cohort of 72 primary diagnostic (DX, n = 62) and matched relapse (REL, n = 10) samples from HHD‐B‐ALL patients with either favorable or unfavorable clinical outcome in order to characterize the clonal heterogeneity, specific chromosome gains and clonal evolution. Our data show a high degree of clonal heterogeneity and a hierarchical order of chromosome gains in DX samples of HHD‐B‐ALL. The rates of specific chromosome gains and clonal heterogeneity found in DX samples differ between HHD‐B‐ALL patients with favorable or unfavorable clinical outcome. In fact, our comprehensive analyses at DX using a computationally defined risk predictor revealed low levels of trisomies +18+10 and low levels of clonal heterogeneity as robust relapse risk factors in minimal residual disease (MRD)‐negative childhood HHD‐B‐ALL patients: relapse‐free survival beyond 5 years: 22.1% versus 87.9%, P < 0.0001 and 33.3% versus 80%, P < 0.0001, respectively. Moreover, longitudinal analysis of matched DX‐REL HHD‐B‐ALL samples revealed distinct patterns of clonal evolution at relapse. Our study offers a reliable prognostic sub‐stratification of pediatric MRD‐negative HHD‐B‐ALL patients.

B-cell acute lymphoblastic leukaemia: recent discoveries in molecular pathology, their prognostic significance, and a review of the current classification

Acute lymphoblastic leukaemia (ALL) remains a leading cause of non-traumatic death in children, and the majority of adults diagnosed will succumb to the disease. Recent advances in molecular biology and bioinformatics have enabled more detailed genomic analysis and a better understanding of the molecular biology of ALL. A number of recurrent genomic drivers have recently been described, which not only aid in diagnosis and prognostication, but also may offer opportunities for specific therapeutic targeting. The present review summarises B-ALL genomic pathology at diagnosis, including lesions detectable using traditional cytogenetic methods as well as those detected only through advanced molecular techniques.

Association of GATA3 Polymorphisms With Minimal Residual Disease and Relapse Risk in Childhood Acute Lymphoblastic Leukemia

BACKGROUND

Minimal residual disease (MRD) after induction therapy is one of the strongest prognostic factors in childhood acute lymphoblastic leukemia (ALL), and MRD-directed treatment intensification improves survival. Little is known about the effects of inherited genetic variants on interpatient variability in MRD.

METHODS

A genome-wide association study was performed on 2597 children on the Children's Oncology Group AALL0232 trial for high-risk B-cell ALL. Association between genotype and end-of-induction MRD levels was evaluated for 863 370 single nucleotide polymorphisms (SNPs), adjusting for genetic ancestry and treatment strata. Top variants were further evaluated in a validation cohort of 491 patients from the Children's Oncology Group P9905 and 6 ALL trials. The independent prognostic value of single nucleotide polymorphisms was determined in multivariable analyses. All statistical tests were 2-sided.

RESULTS

In the discovery genome-wide association study, we identified a genome-wide significant association at the GATA3 locus (rs3824662, odds ratio [OR] = 1.58, 95% confidence interval [CI] = 1.35 to 1.84; P = 1.15 × 10-8 as a dichotomous variable). This association was replicated in the validation cohort (P = .003, MRD as a dichotomous variable). The rs3824662 risk allele independently predicted ALL relapse after adjusting for age, white blood cell count, and leukemia DNA index (P = .04 and .007 in the discovery and validation cohort, respectively) and remained prognostic when the analyses were restricted to MRD-negative patients (P = .04 and .03 for the discovery and validation cohorts, respectively).

CONCLUSION

Inherited GATA3 variant rs3824662 strongly influences ALL response to remission induction therapy and is associated with relapse. This work highlights the potential utility of germline variants in upfront risk stratification in ALL.

Impaired condensin complex and Aurora B kinase underlie mitotic and chromosomal defects in hyperdiploid B-cell ALL

B-cell acute lymphoblastic leukemia (ALL; B-ALL) is the most common pediatric cancer, and high hyperdiploidy (HyperD) identifies the most common subtype of pediatric B-ALL. Despite HyperD being an initiating oncogenic event affiliated with childhood B-ALL, the mitotic and chromosomal defects associated with HyperD B-ALL (HyperD-ALL) remain poorly characterized. Here, we have used 54 primary pediatric B-ALL samples to characterize the cellular-molecular mechanisms underlying the mitotic/chromosome defects predicated to be early pathogenic contributors in HyperD-ALL. We report that HyperD-ALL blasts are low proliferative and show a delay in early mitosis at prometaphase, associated with chromosome-alignment defects at the metaphase plate leading to robust chromosome-segregation defects and nonmodal karyotypes. Mechanistically, biochemical, functional, and mass-spectrometry assays revealed that condensin complex is impaired in HyperD-ALL cells, leading to chromosome hypocondensation, loss of centromere stiffness, and mislocalization of the chromosome passenger complex proteins Aurora B kinase (AURKB) and Survivin in early mitosis. HyperD-ALL cells show chromatid cohesion defects and an impaired spindle assembly checkpoint (SAC), thus undergoing mitotic slippage due to defective AURKB and impaired SAC activity, downstream of condensin complex defects. Chromosome structure/condensation defects and hyperdiploidy were reproduced in healthy CD34+ stem/progenitor cells upon inhibition of AURKB and/or SAC. Collectively, hyperdiploid B-ALL is associated with a defective condensin complex, AURKB, and SAC.

Duplication 1q is highly correlated with poor prognosis in high hyperdiploid pediatric B-acute lymphoblastic leukemia

BACKGROUND

The role of structural abnormalities in high hyperdiploidy (HeH) has been debatable, with few studies that addressed recurrent translocations with concurrent HeH (t-HeH). We aimed at the characterization of HeH cases in pediatric B-acute lymphoblastic leukemia (B-ALL) patients with special emphasis on the structural abnormalities including t-HeH.

PATIENTS AND METHODS

Our study included all patients diagnosed with HeH over the period from January 2016 to April 2019 presenting to the Pediatric Oncology Department, National Cancer Institute, Cairo University.

RESULTS

Among 480 de novo B-ALL pediatric patients, HeH was detected in eighty (16.7%) cases with a median age of 5 years. t-HeH was identified in 17/480 (3.5%) cases: 9(1.9%) with t(12;21), 7(1.5%) with t(9;22), and 1(0.2%) with t(4;11). Duplication (1q) was the most prevalent structural abnormality in c-HeH (hyperdiploidy without recurrent translocations) (n = 12,15%). Children ≥10 years or presenting with white blood cells (WBC) ≥50 × 10⁹ /L) had an inferior 3 year-overall survival as compared to younger children (P = .003), and to lower WBC (P = .02). Duplication (1q) was an independent adverse parameter on the disease-free survival (DFS) of c-HeH patients (P = .004).

CONCLUSIONS

Older age and WBC ≥ 50 × 10⁹ /L were adverse prognostic factors. Duplication (1q) is correlated with lower DFS in c-HeH patients. t-HeH has distinct patterns of chromosomal gain.

Evidence-based review of genomic aberrations in B-lymphoblastic leukemia/lymphoma: Report from the cancer genomics consortium working group for lymphoblastic leukemia

Clinical management and risk stratification of B-lymphoblastic leukemia/ lymphoma (B-ALL/LBL) depend largely on identification of chromosomal abnormalities obtained using conventional cytogenetics and Fluorescence In Situ Hybridization (FISH) testing. In the last few decades, testing algorithms have been implemented to support an optimal risk-oriented therapy, leading to a large improvement in overall survival. In addition, large scale genomic studies have identified multiple aberrations of prognostic significance that are not routinely tested by existing modalities. However, as chromosomal microarray analysis (CMA) and next-generation sequencing (NGS) technologies are increasingly used in clinical management of hematologic malignancies, these abnormalities may be more readily detected. In this article, we have compiled a comprehensive, evidence-based review of the current B-ALL literature, focusing on known and published subtypes described to date. More specifically, we describe the role of various testing modalities in the diagnosis, prognosis, and therapeutic relevance. In addition, we propose a testing algorithm aimed at assisting laboratories in the most effective detection of the underlying genomic abnormalities.

Is hyperdiploidy a favorable cytogenetics in adults with B-lymphoblastic leukemia?

Hyperdiploidy (chromosomal number 51-65) is a common cytogenetic abnormality in pediatric patients with B-lymphoblastic leukemia (B-ALL) and belongs to the favorable cytogenetic subgroup. Hyperdiploidy in adult B-ALL is much less common and its clinical significance has not been well studied. Among the 1205 patients with B-ALL (1018 adults and 187 children) from our institution, 78 had a hyperdiploid karyotype, including 45 (4.4%) adults and 33 (17.6%) children (P < 0.0001). Among the patients with hyperdiploid B-ALL, the adult group had a significantly inferior survival (similar to the patients with a normal karyotype) compared with the pediatric group (median survival: 42 months vs undefined, P = 0.0029). Hyperdiploidy in adults B-ALL tended to more frequently harbor structural abnormalities (two or more) than children (53% vs 33%). Two or more structural abnormalities in a hyperdiploidy correlated with an adverse survival in adult patients (33 months vs undefined, P = 0.0008), similar to the survival of patients with a complex karyotype. We conclude that hyperdiploidy in adults with B-ALL is less favorable and more commonly contains structural abnormalities comparing to pediatric patients. We suggest that hyperdiploidy with two or more structural abnormalities are best considered as a complex karyotype in adults with B-ALL.

Microarray testing as an efficient tool to redefine hyperdiploid paediatric B-cell precursor acute lymphoblastic leukaemia patients

The aim of our study was to characterize genetic alterations in a cohort of paediatric patients with B-cell progenitors (BCP-ALL) and a hyperdiploid karyotype. In our study, we analysed 55 childhood hyperdiploid BCP-ALL patients using single nucleotide polymorphism (SNP) microarray testing. The group consisted mostly of patients with the modal number of chromosomes between 54 and 58 (34 cases). Within this group, Trisomy 4 and Trisomy 10 (30 cases) were the most frequent cases. Additionally, a total of 93 structural abnormalities mainly affecting chromosomes 1, 6, 9, 12, and 17 as well as 68 copy number alterations (CNAs) were identified. The microarray testing revealed a loss of ETV6, IKZF1, CDKN2A/CDKN2B, PAX5, and RB1. Moreover, chromosomal abnormalities resulting in the loss of heterozygosity (LOH) were also observed. Currently, patients with hyperdiploidy constitute a genetically heterogeneous group, and therefore, it is insufficient to rely only on banding cytogenetic analysis for the identification of hyperdiploid karyotype. Microarray testing has been proven an effective and satisfactory tool for the analysis of molecular karyotypes and to redefine the prognostic criteria in hyperdiploid patients.

Updates in the Pathology of Precursor Lymphoid Neoplasms in the Revised Fourth Edition of the WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues

PURPOSE OF REVIEW

Acute lymphoblastic leukemias (ALL) are malignant disorders of immature B or T cells that occur characteristically in children, usually under the age of 6 (75%). Approximately 6000 new cases of ALL are diagnosed each year in the USA, 80-85% of which represent B-ALL forms. Most presentations of B-ALL are leukemic, whereas T-ALL presents with a mediastinal mass, with or without leukemic involvement. The revised fourth edition of the World Health Organization (WHO) classification (2017) has introduced some changes in both B and T-ALL. Here, we summarize the categories of lymphoblastic leukemia/lymphomas as defined by the WHO and recent developments in the understanding of this group of hematologic malignancy.

RECENT FINDINGS

Two provisional categories of B-ALL have now been identified including B-ALL, BCR-ABL1-like, and B-ALL with iAMP21. The Philadelphia chromosome-like B-ALL includes forms of the disease that shares the expression profiling of B-ALL with t(9;22) but lack such rearrangement. The second one shows amplification of part of the chromosome 21. Both entities are associated with worse prognosis. Within the T-ALL group, an early precursor T cell form has now been introduced as a provisional category. Such group demonstrates expression of stem cell and myeloid markers in conjunction with the T cell antigens. The current review summarizes the recent updates to the WHO classification.

Measurable residual disease detection by high-throughput sequencing improves risk stratification for pediatric B-ALL

Early response to induction chemotherapy is an important prognostic factor in B-lymphoblastic leukemia (B-ALL). Here, we compare high-throughput sequencing (HTS) of IGH and TRG genes vs flow cytometry (FC) for measurable residual disease (MRD) detection at the end of induction chemotherapy in pediatric patients with newly diagnosed B-ALL. Six hundred nineteen paired pretreatment and end-of-induction bone marrow samples from Children's Oncology Group studies AALL0331 (clinicaltrials.gov #NCT00103285) (standard risk [SR]; with MRD by FC at any level) and AALL0232 (clinicaltrials.gov #NCT00075725) (high risk; with day 29 MRD <0.1% by FC) were evaluated by HTS and FC for event-free (EFS) and overall survival (OS). HTS and FC showed similar 5-year EFS and OS for MRD-positive and -negative patients using an MRD threshold of 0.01%. However, there was a high discordant rate with HTS identifying 55 (38.7%) more patients MRD positive at this threshold. These discrepant patients have worse outcomes than FC MRD-negative patients. In addition, the increased analytic sensitivity of HTS permitted identification of 19.9% of SR patients without MRD at any detectable level who had excellent 5-year EFS (98.1%) and OS (100%). The higher analytic sensitivity and lower false-negative rate of HTS improves upon FC for MRD detection in pediatric B-ALL by identifying a novel subset of patients at end of induction who are essentially cured using current chemotherapy and identifying MRD at 0.01% in up to one-third of patients who are missed at the same threshold by FC.

Impact of cytogenetic abnormalities in adults with Ph-negative B-cell precursor acute lymphoblastic leukemia

Multiple cytogenetic subgroups have been described in adult Philadelphia chromosome (Ph)-negative B-cell precursor (BCP) acute lymphoblastic leukemia (ALL), often comprising small numbers of patients. In this study, we aimed to reassess the prognostic value of cytogenetic abnormalities in a large series of 617 adult patients with Ph-negative BCP-ALL (median age, 38 years), treated in the intensified Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL)-2003/2005 trials. Combined data from karyotype, DNA index, fluorescence in situ hybridization, and polymerase chain reaction screening for relevant abnormalities were centrally reviewed and were informative in 542 cases (88%), allowing classification in 10 exclusive primary cytogenetic subgroups and in secondary subgroups, including complex and monosomal karyotypes. Prognostic analyses focused on cumulative incidence of failure (including primary refractoriness and relapse), event-free survival, and overall survival. Only 2 subgroups, namely t(4;11)/KMT2A-AFF1 and 14q32/IGH translocations, displayed a significantly worse outcome in this context, still observed after adjustment for age and after censoring patients who received allogeneic stem cell transplantation (SCT) in first remission at SCT time. A worse outcome was also observed in patients with low hypodiploidy/near triploidy, but this was likely related to their higher age and worse tolerance to therapy. The other cytogenetic abnormalities, including complex and monosomal karyotypes, had no prognostic value in these intensive protocols designed for adult patients up to the age of 60 years.

Children with low-risk acute lymphoblastic leukemia are at highest risk of second cancers

BACKGROUND

The improved survival rates for childhood acute lymphoblastic leukemia (ALL) may be jeopardized by the development of a second cancer, which has been associated with thiopurine therapy.

PROCEDURE

We retrospectively analyzed three sequential Nordic Society of Paediatric Haematology and Oncology's protocols characterized by increasing intensity of thiopurine-based maintenance therapy. We explored the risk of second cancer in relation to protocols, risk group, thiopurine methyltransferase (TPMT) activity, ALL high hyperdiploidy (HeH), and t(12;21)[ETV6/RUNX1].

RESULTS

After median 9.5 years (interquartile range, 5.4-15.3 yrs) of follow-up, 40 of 3,591 patients had developed a second cancer, of whom 38 had non-high-risk B-cell precursor ALL. Patients with standard-risk ALL, who received the longest maintenance therapy, had the highest adjusted hazard of second cancer (hazard ratio [HR], intermediate vs. standard risk: 0.16, 95% CI: 0.06-0.43, P < 0.001; HR, high vs. standard risk: 0.09, 95% CI: 0.02-0.49, P = 0.006); no significant effects of protocol, age, or white blood cell count at diagnosis, ALL HeH, or t(12;21)[ETV6/RUNX1] were observed. A subset analysis on the patients with standard-risk ALL did not show an increased hazard of second cancer from either HeH or t(12;21) (adjusted HR 2.02, 95% CI: 0.69-5.96, P = 0.20). The effect of low TPMT low activity was explored in patients reaching maintenance therapy in clinical remission (n = 3,368); no association with second cancer was observed (adjusted HR 1.43, 95% CI: 0.54-3.76, P = 0.47).

CONCLUSIONS

The rate of second cancer was generally highest in patients with low-risk ALL, but we could not identify a subset at higher risk than others.

High hyperdiploid acute lymphoblastic leukemia (ALL)-A 25-year population-based survey of the Austrian ALL-BFM (Berlin-Frankfurt-Münster) Study Group

BACKGROUND

Approximately 30% of childhood acute lymphoblastic leukemia (ALL) cases are high hyperdiploid (HD). Despite their low relative recurrence risk, this group accounts for the overall largest relapse proportion.

PROCEDURE

To evaluate potential risk factors in our population-based cohort of patients with HD ALL enrolled in four Austrian ALL-BFM (Berlin-Frankfurt-Münster) studies from 1986 to 2010 (n = 210), we reviewed the clinical, laboratory, and cytogenetic data of the respective cases in relation to their outcome.

RESULTS

The 5-year event-free (EFS) and overall survival (OS) of the entire group was 83.1 ± 2.7% and 92.0 ± 1.9%, respectively. Univariate analysis revealed that trisomy 17 was significantly associated with a better EFS and OS, whereas trisomy 10 and a modal chromosome number (MCN) > 53 chromosomes were significantly associated with a better OS. Except for the latter, findings remained valid in multivariate analysis.

CONCLUSIONS

In line with previous studies, our retrospective analysis shows that MCN and specific trisomies are relevant prognostic indicators in an ALL-BFM cohort of patients with HD ALL. However, considering the current dominant role of minimal residual disease monitoring for prognostic stratification in ALL, including this particular subgroup, it is unlikely that this information is compelling enough to be utilized for refined risk classification in future ALL-BFM treatment protocols.

Characterization of a novel acquired der(1)del(1)(p13p31)t(1;15)(q42;q15) in a high risk t(12;21)-positive acute lymphoblastic leukemia

The t(12;21)(p13;q22) with ETV6-RUNX1 fusion occurs in 25% of cases of B-cell precursor acute lymphoblastic leukemia (BCP-ALL); and is generally associated with favorable prognosis. However, 15-20% of the t(12;21)-positive cases are associated with high-risk disease due to for example slow early responses to therapy. It is well-known that development of overt leukemia in t(12;21)-positive ALL requires secondary chromosomal aberrations although the full spectrum of these cytogenetic alterations is yet unsettled, and also, how they may be associated with disease outcome. This report describes the case of an adolescent male with t(12;21)-positive ALL who displayed a G-banded karyotype initially interpreted as del(1)(p22p13) and del(15)(q15). The patient was treated according to NOPHO standard risk protocol at diagnosis, but had minimal residual disease (MRD) at 6,4% on day 29 as determined by flow cytometric immunophenotyping. Because of MRD level>0.1% he was then assigned as a high risk patient and received intensified chemotherapy accordingly. Further molecular cytogenetic studies and oligo-based aCGH (oaCGH) analysis characterized the acquired complex structural rearrangements on chromosomes 1 and 15, which can be described as der(1)del(1)(p13.1p31.1)t(1;15)(q42;q15) with concurrent deletions at 1q31.2-q31.3, 1q42.12-q43, and 15q15.1-q15.3. The unbalanced complex rearrangements have not been described previously. Extended locus-specific FISH analyses showed that the three deletions were on the same chromosome 1 homologue that was involved in the t(1;15), and that the deletion on chromosome 15 also was on the same chromosome 15 homologue as involved in the t(1;15). Together these findings show the great importance of the combined usage of molecular cytogenetic analyses and oaCGH analysis to enhance characterization of apparently simple G-banded karyotypes, and to provide a more complete spectrum of secondary chromosomal aberrations in high risk t(12;21)-positive BCP-ALLs.

Conserved hierarchical gain of chromosome 4 is an independent prognostic factor in high hyperdiploid pediatric acute lymphoblastic leukemia

BACKGROUND

High hyperdiploid (HeH) pre-B pediatric acute lymphoblastic leukemia (B-pALL) is known to be heterogeneous by prognosis, but the stratification principals according to conventional cytogenetic analysis (CCA) are equivocal.

PROCEDURE

Untreated bone marrow samples of 214 B-pALL patients were previously classified according to the modal numbers (iMN₈) based on the gains of the chromosomes 4, 6, 10, 14, 17, 18, 21, and X as revealed by consecutive and correlated 2×4 color interphase fluorescence in situ hybridization, and at least five years of follow up data were analyzed.

RESULTS

Data from 48 of the 53 HeH (iMN₈>50) B-pALL patients indicated that among the age, gender, WBC, and iMN₈ parameters, only the last was significantly associated with overall survival (pOS), which allowed the cases to be classified as iMN₈ 51-54 (75%) and iMN₈ ≥ 55 (95%). Among the specific chromosomal gains of +4, +4/+6, +4/+17 and +4/+18, the first exhibited the most significance in terms of beneficial outcomes. The better prognostic group according to the iMN₈ was associated with a significantly reduced complexity of the subclonal landscape. However, iMN₈ did not prove to be an independent variable but was instead overridden by isolated trisomy of chromosome 4.

CONCLUSIONS

These data indicate that the better outcomes in the HeH B-pALL group arose from the gain of a specific chromosome that always ranks at the same position in the sequential acquisition of the affected chromosomes.

Slower early response to treatment and distinct expression profile of childhood high hyperdiploid acute lymphoblastic leukaemia with DNA index < 1.16

Acute lymphoblastic leukaemias (ALL) with 51-67 chromosomes are defined as high hyperdiploid (HHD) and are generally associated with good prognosis. However, several studies show heterogeneity in HHD ALL and suggest that the favourable prognosis is associated rather with higher ploidy defined by DNA index (DNAi) ≥ 1.16 or with a presence of specific single or combined trisomies. HHD ALL with DNAi < 1.16 are only rarely studied separately. Using single nucleotide polymorphism array, we analysed 89 childhood HHD ALL patients divided into groups with lower (<1.16; n = 34) and higher (≥1.16; n = 55) DNAi. We assessed treatment response, presence of secondary aberrations, mutations in RAS pathway genes and CREBBP and also gene expression profile (GEP) to reveal differences between the two subgroups. Cases with 51-54 chromosomes had DNAi 1.1-1.16 and cases with 55-67 chromosomes had DNAi ≥ 1.16. The groups with lower and higher DNAi had distinct response to early treatment and distinct GEP. The better response of the group with higher DNAi was associated with specific trisomies (trisomy of chromosome 10 or combined with trisomies 4 and/or 17). Our results suggest that cytogenetically defined HHD ALL can in fact be divided into two biologically distinguishable subgroups and that DNAi 1.16 is a relevant value to separate between the two. © 2016 Wiley Periodicals, Inc.

Oligo-based aCGH analysis reveals cryptic unbalanced der(6)t(X;6) in pediatric t(12;21)-positive acute lymphoblastic leukemia

Secondary chromosomal aberrations are necessary for development of overt leukemia in t(12;21)/ETV6-RUNX1-positive acute lymphoblastic leukemia (ALL). Conventional cytogenetic analysis supplemented with locus-specific FISH analyses is gold standard to detect important clonal aberrations in this disease group. However, adequate chromosome banding analysis may often be hampered by poor chromosome morphology and banding patterns in pediatric ALL cases, which may hinder identification of possible clinical important additional chromosomal aberrations. We used oligo-based high-resolution aCGH (oaCGH) analysis as an adjunct tool to enhance conventional cytogenetic analysis in pediatric acute B-cell lymphoblastic leukemia in a prospective single center study during a 4-year period (2012-2015). In a consecutive series of 45 pediatric B-ALLs, we identified eight patients with t(12;21)/ETV6-RUNX1 fusion by FISH analysis. In three of the patients, oaCGH analysis revealed concurrent Xq duplication and 6q deletion, which was cryptic by G-banded analysis. FISH analyses with whole chromosome painting probes confirmed the imbalances and showed an unbalanced translocation der(6)t(X;6) in all three patients. A search in the literature revealed two additional pediatric patients with cryptic der(6)t(X;6) in t(12;21)-positive ALLs. No common break points on Xq or 6q could be determined between the five patients. This study highlights the importance of oaCGH analysis as an adjunct cytogenetic tool to detect cryptic chromosomal aberrations. Further, the study adds to understanding the full spectrum of secondary chromosomal aberrations in the very common t(12;21)-positive pediatric ALL disease group. We suggest that the unbalanced der(6)t(X;6), which is cryptic to conventional cytogenetics, is a non-random secondary event in this disease group. It might be that the specific combination of concurrent Xq duplication and 6q-deletion results in gain of possible oncogenes on Xq and loss of possible tumor suppressor genes on 6q that are important for the leukemic propagation of t(12;21)-positive hematopoietic cells in a subset of ALLs.

New and emerging prognostic and predictive genetic biomarkers in B-cell precursor acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a heterogeneous disease at the genetic level. Chromosomal abnormalities are used as diagnostic, prognostic and predictive biomarkers to provide subtype, outcome and drug response information. t(12;21)/ETV6-RUNX1 and high hyper-diploidy are good-risk prognostic biomarkers whereas KMT2A(MLL) translocations, t(17;19)/TCF3-HLF, haploidy or low hypodiploidy are high-risk biomarkers. t(9;22)/BCR-ABL1 patients require targeted treatment (imatinib/dasatinib), whereas iAMP21 patients achieve better outcomes when treated intensively. High-risk genetic biomarkers are four times more prevalent in adults compared to children. The application of genomic technologies to cases without an established abnormality (B-other) reveals copy number alterations which can be used either individually or in combination as prognostic biomarkers. Transcriptome sequencing studies have identified a network of fusion genes involving kinase genes -ABL1,ABL2,PDGFRB,CSF1R,CRLF2,JAK2 and EPOR in-vitro and in-vivo studies along with emerging clinical observations indicate that patients with a kinase-activating aberration may respond to treatment with small molecular inhibitors like imatinib/dasatinib and ruxolitinib. Further work is required to determine the true frequency of these abnormalities across the age spectrum and the optimal way to incorporate such inhibitors into protocols. In conclusion, genetic biomarkers are playing an increasingly important role in the management of patients with ALL.

Patterns and frequencies of acquired and constitutional uniparental isodisomies in pediatric and adult B-cell precursor acute lymphoblastic leukemia

Single nucleotide polymorphism (SNP) arrays are increasingly being used in clinical routine for genetic analysis of pediatric B-cell precursor acute lymphoblastic leukemias (BCP ALL). Because constitutional DNA is not readily available as a control at the time of diagnosis, it is important to be able to distinguish between acquired and constitutional aberrations in a diagnostic setting. In the present study we focused on uniparental isodisomies (UPIDs). SNP array analyses of 143 pediatric and 38 adult B-cell precursor acute lymphoblastic leukemias and matched remission samples revealed acquired whole chromosome or segmental UPIDs (wUPIDs, sUPIDs) in 32 cases (18%), without any age- or gender-related frequency differences. Acquired sUPIDs were larger than the constitutional ones (mean 35.3 Mb vs. 10.7 Mb; P < 0.0001) and were more often terminally located in the chromosomes (69% vs. 4.5%; P < 0.0001). Chromosomes 3, 5, and 9 were most often involved in acquired wUPIDs, whilst recurrent acquired sUPIDs targeted 6p, 9p, 9q, and 14q. The majority (56%) of sUPID9p was associated with homozygous CDKN2A deletions. In pediatric ALL, all wUPIDs were found in high hyperdiploid (51-67 chromosomes) cases and an extended analysis, also including unmatched diagnostic samples, revealed a higher frequency of wUPID-positivity in higher modal number (56-67 chromosomes) than in lower modal number (51-55 chromosomes) high hyperdiploid cases (34% vs. 11%; P = 0.04), suggesting different underlying mechanisms of formation of these subtypes of high hyperdiploidy. © 2016 Wiley Periodicals, Inc.

Sequential and hierarchical chromosomal changes and chromosome instability are distinct features of high hyperdiploid pediatric acute lymphoblastic leukemia

BACKGROUND

Pathogenesis of the non-random accumulation of extra chromosomes in the low and high hyperdiploid (HeL, HeH) pre-B pediatric acute lymphoblastic leukemia (B-pALL) is largely unknown, and has been clarified with respect only to tetrasomic chromosomes. We analyzed the hierarchy of changes in chromosome number and chromosomal instability, as well as clonal heterogeneity and evolution, in the untreated bone marrow cell samples from 214 B-pALL patients.

PROCEDURE

Applying relocation, 2 × 4 color interphase fluorescence in situ hybridization was used to detect copy number alterations (CNAs) of the most commonly involved chromosomes, 4, 6, 10, 14, 17, 18, 21, and X. This approach allowed us to acquire a dataset correlated for all eight parameters.

RESULTS

Based on chromosome number, an average of 6.9 and 10.2, whereas according to unique constellation 15.3 and 26.7 subclones could be identified in the HeL and HeH subgroups, respectively. Cluster analysis revealed the order of CNAs to chromosomes was highly conserved, and network analysis indicated changes in chromosome number were sequential for 80-90% of all numerical aberrations. Significant chromosome instability was revealed in both subgroups of leukemia.

CONCLUSIONS

Data generated using this new approach indicate that chromosomal instability, which causes heterogeneity in the subclonal landscape, and the sequential changes to chromosome numbers, are both determining factors in the pathomechanism of the hyperdiploid B-pALL. These new observations could prompt research into the mitotic machinery of leukemic cells to identify new therapeutic targets for treating this disease.

MLLT10 and IL3 rearrangement together with a complex four-way translocation and trisomy 4 in a patient with early T-cell precursor acute lymphoblastic leukemia: A case report

Cytogenetic classification of acute lymphoblastic leukemia (ALL) is primarily based on numerical and structural chromosomal abnormalities. In T-cell ALL (T-ALL), chromosomal rearrangements are identified in up to 70% of the patients while the remaining patients show a normal karyotype. In the present study, a 16-year-old male was diagnosed with T-precursor cell ALL and a normal karyotype after standard GTG-banding, was studied retrospectively (>10 years after diagnosis) in frame of a research project by molecular approaches. In addition to molecular cytogenetics, multiplex ligation-dependent probe amplification (MLPA) and high resolution array-comparative genomic hybridization (aCGH) were also applied. Thus, the following yet unrecognized balanced chromosomal aberrations were detected: der(3)t(3;5)(p23;q31.1), der(5)t(3;5)(p23;q35.3), der(5)t(5;10)(q31.1;p12.3) and der(10)t(5;10)(q35.3;p12.3). The oncogene MLLT10 was involved in this rearrangement as was the IL3 gene; in addition, trisomy 4 was present. All of these clonal aberrations were found in 40% of the cells. Even if this complex karyotype would have been identified at the time of diagnosis, most likely no other protocol of anticancer therapy (ALL-BFM 95) would have been applied. Three months after the end of a successful 2-year treatment, the patient suffered from isolated bone marrow relapse and died of sepsis during ALL-REZ-BFM protocol treatment.

Risk factors for relapse in childhood acute lymphoblastic leukemia: prediction and prevention

With current treatment regimens, survival rates for acute lymphoblastic leukemia (ALL) have improved dramatically since the 1980s, with current 5-year overall survival rates estimated at greater than 85%. This success was achieved, in part, through the implementation of risk-stratified therapy. Nevertheless, for a subgroup of patients (15-20%) with newly diagnosed ALL who will ultimately relapse, traditional risk assessment remains inadequate. The risk of relapse may be estimated on the basis of diagnostic features or early treatment response findings. Further progress in this field may thus come from refinement of predictive factors for relapse and treatment adaptation and from the identification of biological subsets of ALL patients who could benefit from specific target therapies. This article summarizes the aspects associated with the identification of predictive factors for relapse in childhood ALL and options available for prevention of disease recurrence.

An unusual case of high hyperdiploid childhood ALL with cryptic BCR/ABL1 rearrangement

Background

Both high hyperdiploidy (HeH) and the translocation t(9;22)(q34;q11) are recurrent abnormalities in childhood B-cell acute lymphoblastic leukemia (ALL) and both are used in current classification to define different genetic and prognostic subtypes of the disease. The coexistence of these two primary genetic aberrations within the same clone is very rare in children with ALL. Here we report a new case of a 17-year-old girl with newly diagnosed ALL and uncommon cytogenetic and clinical finding combining high hyperdiploidy and a cryptic BCR/ABL1 fusion and an inherited Charcot-Marie-Tooth neuropathy detected during the induction treatment.

Results

High hyperdiploid karyotype 51,XX,+X,+4,+14,+17,+21 without apparent structural aberrations was detected by conventional cytogenetic analysis and multicolor FISH. A cryptic BCR/ABL1 fusion, which was caused by the insertion of part of the ABL1 gene into the 22q11 region, was proved in HeH clone by FISH, RT-PCR and CGH-SNP array. In addition, an abnormal FISH pattern previously described as the deletion of the 3′BCR region in some BCR/ABL1 positive cases was not proved in our patient.

Conclusion

A novel case of extremely rare childhood ALL, characterized by HeH and a cryptic BCR/ABL1 fusion, is presented and to the best of our knowledge described for the first time. The insertion of ABL1 into the BCR region in malignant cells is supposed. Clearly, further studies are needed to determine the genetic consequences and prognostic implications of these unusual cases.

Evolutionary trajectories of hyperdiploid ALL in monozygotic twins

Identical twins have provided unique insights on timing or sequence of genetic events in acute lymphoblastic leukaemia (ALL). To date, this has mainly focused on ALL with MLL or ETV6-RUNX1 fusions, with hyperdiploid ALL remaining less well characterised. We examined three pairs of monozygotic twins, two concordant and one discordant for hyperdiploid ALL, for single-nucleotide polymorphism (SNP)-defined copy number alterations (CNAs), IGH/L plus TCR gene rearrangements and mutations in NRAS, KRAS, FLT3 and PTPN11 genes. We performed whole exome sequencing in one concordant twin pair. Potential 'driver' CNAs were low, 0-3 per case, and all were different within a pair. One patient had an NRAS mutation that was lacking from leukaemic cells of the twin sibling. By exome sequencing, there were 12 nonsynonymous mutations found in one twin and 5 in the other, one of which in SCL44A2 was shared or identical. Concordant pairs had some identical IGH/L and TCR rearrangements. In the twin pair with discordant hyperdiploid ALL, the healthy co-twin had persistent low level hyperdiploid CD19+ cells that lacked a CNA present in the ALL cells of her sibling. From these data, we propose that hyperdiploid ALL arises in a pre-B cell in utero and mutational changes necessary for clinical ALL accumulate subclonally and postnatally.

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.

Clinical and genetic features of pediatric acute lymphoblastic leukemia in Down syndrome in the Nordic countries

Background

Children with Down syndrome (DS) have an increased risk for acute lymphoblastic leukemia (ALL). Although previous studies have shown that DS-ALL differs clinically and genetically from non-DS-ALL, much remains to be elucidated as regards genetic and prognostic factors in DS-ALL.

Methods

To address clinical and genetic differences between DS-ALL and non-DS-ALL and to identify prognostic factors in DS-ALL, we ascertained and reviewed all 128 pediatric DS-ALL diagnosed in the Nordic countries between 1981 and 2010. Their clinical and genetic features were compared with those of the 4,647 B-cell precursor (BCP) ALL cases diagnosed during the same time period.

Results

All 128 DS-ALL were BCP ALL, comprising 2.7% of all such cases. The 5-year event-free survival (EFS) and overall survival (OS) were significantly (P = 0.026 and P = 0.003, respectively) worse for DS-ALL patients with white blood cell counts ≥50 × 10⁹/l. The age distributions varied between the DS and non-DS cases, with age peaks at 2 and 3 years, respectively; none of the DS patients had infant ALL (P = 0.029). The platelet counts were lower in the DS-ALL group (P = 0.005). Abnormal karyotypes were more common in non-DS-ALL (P < 0.0001), and there was a significant difference in the modal number distribution, with only 2% high hyperdiploid DS-ALL cases (P < 0.0001). The 5-year EFS and 5-year OS were significantly worse for DS-ALL (0.574 and 0.691, respectively) compared with non-DS-ALL (0.783 and 0.894, respectively) in the NOPHO ALL-1992/2000 protocols (P < 0.001).

Conclusions

The present study adds further support for genetic and clinical differences between DS-ALL and non-DS-ALL.