Prospective analysis of TEL/AML1-positive patients treated on Dana-Farber Cancer Institute Consortium Protocol 95-01

Outcomes in patients with ETV6::RUNX1 or high-hyperdiploid B-ALL treated in the St. Jude Total Therapy XV/XVI studies

ABSTRACT

Children with ETV6::RUNX1 or high-hyperdiploid B-cell acute lymphoblastic leukemia (B-ALL) have favorable outcomes. The St. Jude (SJ) classification considers these patients low risk, regardless of their National Cancer Institute (NCI) risk classification, except when there is slow minimal residual disease (MRD) response or central nervous system/testicular involvement. We analyzed outcomes in children (aged 1-18.99 years) with these genotypes in the SJ Total XV/XVI studies (2000-2017). Patients with ETV6::RUNX1 (n = 222) or high-hyperdiploid (n = 296) B-ALL had 5-year event-free survival (EFS) of 97.7% ± 1.1% and 94.7% ± 1.4%, respectively. For ETV6::RUNX1, EFS was comparable between NCI standard-risk and high-risk patients and between SJ low-risk and standard-risk patients. Of the 40 NCI high-risk patients, 37 who received SJ low-risk therapy had excellent EFS (97.3% ± 2.8%). For high-hyperdiploid B-ALL, NCI high-risk patients had worse EFS than standard-risk patients (87.6% ± 4.5% vs 96.4% ± 1.3%; P = .016). EFS was similar for NCI standard-risk and high-risk patients classified as SJ low risk (96.0% ± 1.5% and 96.9% ± 3.2%; P = .719). However, EFS was worse for NCI high-risk patients than for NCI standard-risk patients receiving SJ standard/high-risk therapy (77.4% ± 8.2% vs 98.0% ± 2.2%; P = .004). NCI high-risk patients with ETV6::RUNX1 or high-hyperdiploid B-ALL who received SJ low-risk therapy had lower incidences of thrombosis (P = .013) and pancreatitis (P = .011) than those who received SJ standard/high-risk therapy. MRD-directed therapy yielded excellent outcomes, except for NCI high-risk high-hyperdiploid B-ALL patients with slow MRD response, who require new treatment approaches. Among NCI high-risk patients, 93% with ETV6::RUNX1 and 54% with high-hyperdiploid B-ALL experienced excellent outcomes with a low-intensity regimen. These trials were registered at www.clinicaltrials.gov as #NCT00137111 and #NCT00549848.

Acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is a haematological malignancy characterized by the uncontrolled proliferation of immature lymphoid cells. Over past decades, significant progress has been made in understanding the biology of ALL, resulting in remarkable improvements in its diagnosis, treatment and monitoring. Since the advent of chemotherapy, ALL has been the platform to test for innovative approaches applicable to cancer in general. For example, the advent of omics medicine has led to a deeper understanding of the molecular and genetic features that underpin ALL. Innovations in genomic profiling techniques have identified specific genetic alterations and mutations that drive ALL, inspiring new therapies. Targeted agents, such as tyrosine kinase inhibitors and immunotherapies, have shown promising results in subgroups of patients while minimizing adverse effects. Furthermore, the development of chimeric antigen receptor T cell therapy represents a breakthrough in ALL treatment, resulting in remarkable responses and potential long-term remissions. Advances are not limited to treatment modalities alone. Measurable residual disease monitoring and ex vivo drug response profiling screening have provided earlier detection of disease relapse and identification of exceptional responders, enabling clinicians to adjust treatment strategies for individual patients. Decades of supportive and prophylactic care have improved the management of treatment-related complications, enhancing the quality of life for patients with ALL.

Generation of a Zebrafish Knock-In Model Recapitulating Childhood ETV6::RUNX1-Positive B-Cell Precursor Acute Lymphoblastic Leukemia

Approximately 25% of children with B-cell precursor acute lymphoblastic leukemia (pB-ALL) harbor the t(12;21)(p13;q22) translocation, leading to the ETV6::RUNX1 (E::R) fusion gene. This translocation occurs in utero, but the disease is much less common than the prevalence of the fusion in newborns, suggesting that secondary mutations are required for overt leukemia. The role of these secondary mutations remains unclear and may contribute to treatment resistance and disease recurrence. We developed a zebrafish model for E::R leukemia using CRISPR/Cas9 to introduce the human RUNX1 gene into zebrafish etv6 intron 5, resulting in E::R fusion gene expression controlled by the endogenous etv6 promoter. As seen by GFP fluorescence at a single-cell level, the model correctly expressed the fusion protein in the right places in zebrafish embryos. The E::R fusion expression induced an expansion of the progenitor cell pool and led to a low 2% frequency of leukemia. The introduction of targeted pax5 and cdkn2a/b gene mutations, mimicking secondary mutations, in the E::R line significantly increased the incidence in leukemia. Transcriptomics revealed that the E::R;pax5mut leukemias exclusively represented B-lineage disease. This novel E::R zebrafish model faithfully recapitulates human disease and offers a valuable tool for a more detailed analysis of disease biology in this subtype.

Stem cell mutations, associated cancer risk, and consequences for regenerative medicine

Mutation accumulation in stem cells has been associated with cancer risk. However, the presence of numerous mutant clones in healthy tissues has raised the question of what limits cancer initiation. Here, we review recent developments in characterizing mutation accumulation in healthy tissues and compare mutation rates in stem cells during development and adult life with corresponding cancer risk. A certain level of mutagenesis within the stem cell pool might be beneficial to limit the size of malignant clones through competition. This knowledge impacts our understanding of carcinogenesis with potential consequences for the use of stem cells in regenerative medicine.

The Landscape of Secondary Genetic Rearrangements in Pediatric Patients with B-Cell Acute Lymphoblastic Leukemia with t(12;21)

The most frequent chromosomal rearrangement in childhood B-cell acute lymphoblastic leukemia (B-ALL) is translocation t(12;21)(p13;q22). It results in the fusion of the ETV6::RUNX1 gene, which is active in the regulation of multiple crucial cellular pathways. Recent studies hypothesize that many translocations are influenced by RAG-initiated deletions, as well as defects in the RAS and NRAS pathways. According to a "two-hit" model for the molecular pathogenesis of pediatric ETV6::RUNX1-positive B-ALL, the t(12;21) translocation requires leukemia-causing secondary mutations. Patients with ETV6::RUNX1 express up to 60 different aberrations, which highlights the heterogeneity of this B-ALL subtype and is reflected in differences in patient response to treatment and chances of relapse. Most studies of secondary genetic changes have concentrated on deletions of the normal, non-rearranged ETV6 allele. Other predominant structural changes included deletions of chromosomes 6q and 9p, loss of entire chromosomes X, 8, and 13, duplications of chromosome 4q, or trisomy of chromosomes 21 and 16, but the impact of these changes on overall survival remains unclarified. An equally genetically diverse group is the recently identified new B-ALL subtype ETV6::RUNX1-like ALL. In our review, we provide a comprehensive description of recurrent secondary mutations in pediatric B-ALL with t(12;21) to emphasize the value of investigating detailed molecular mechanisms in ETV6::RUNX1-positive B-ALL, both for our understanding of the etiology of the disease and for future clinical advances in patient treatment and management.

Cytogenetics and Molecular Genetics in Pediatric Acute Lymphoblastic Leukemia (ALL) and Its Correlation with Induction Outcomes

Arathi SrinivasanAims  The aim was to study cytogenetics and molecular genetic profile in pediatric B-acute lymphoblastic leukemia (ALL) and correlate it with induction outcomes. Subjects and Methods  A retrospective study of cytogenetics and molecular genetics of 98 children with B-cell ALL from January 2013 to May 2018 was done. Cytogenetics and molecular genetics were done in the bone marrow using multiplex reverse transcription polymerase chain reaction and G-banded karyotyping, respectively. Minimal residual disease (MRD) assessment was done at the end of induction by flowcytometry. Results  Of the 98 children, 83 (84.6%) had evaluable cytogenetics, with 11 (13.25%) being abnormal karyotypes. Of the 11 abnormal karyotypes, seven children (8.4%) had hyperdiploidy, one had hypodiploidy, and three had miscellaneous findings. In molecular genetics, TEL-AML1 (ETV6/RUNX1)[t(12;21)] was the most common fusion gene abnormality (12.2% [12/98]), followed by E2A-PBX1 [t(1;19)] (5%), BCR/ABL1 [t(9;22)] (3%), and MLL-AF4 [t(4;11)] (1%). All the 98 children attained morphologic remission at the end of induction. All children with hyperdiploidy (7/7) attained remission and MRD negativity, but one expired during maintenance chemotherapy of disseminated tuberculosis. The child with hypodiploidy was MRD-positive. Three (25%) children with t (12;21) were MRD-positive. All children with Ph + ALL, t(1:19), and t(4;11) were MRD-negative. Fifty-two children had no detected abnormalities, six of whom had MRD positivity (11.5%). Conclusion  Cytogenetic and molecular genetic subgrouping prognosticates ALL outcomes. Although 25% of TEL-AML + children had MRD positivity, larger studies are required to validate the same. End-of-induction MRD outcomes did not correlate with chromosomal aberrations.

Impact of high-risk cytogenetics on outcomes for children and young adults receiving CD19-directed CAR T-cell therapy

Chimeric antigen receptor (CAR) T-cell therapy can induce durable remissions of relapsed/refractory B-acute lymphoblastic leukemia (ALL). However, case reports suggested differential outcomes mediated by leukemia cytogenetics. We identified children and young adults with relapsed/refractory CD19+ ALL/lymphoblastic lymphoma treated on 5 CD19-directed CAR T-cell (CTL019 or humanized CART19) clinical trials or with commercial tisagenlecleucel from April 2012 to April 2019. Patients were hierarchically categorized according to leukemia cytogenetics: High-risk lesions were defined as KMT2A (MLL) rearrangements, Philadelphia chromosome (Ph+), Ph-like, hypodiploidy, or TCF3/HLF; favorable as hyperdiploidy or ETV6/RUNX1; and intermediate as iAMP21, IKZF1 deletion, or TCF3/PBX1. Of 231 patients aged 1 to 29, 74 (32%) were categorized as high risk, 28 (12%) as intermediate, 43 (19%) as favorable, and 86 (37%) as uninformative. Overall complete remission rate was 94%, with no difference between strata. There was no difference in relapse-free survival (RFS; P = .8112), with 2-year RFS for the high-risk group of 63% (95% confidence interval [CI], 52-77). There was similarly no difference seen in overall survival (OS) (P = .5488), with 2-year OS for the high-risk group of 70% (95% CI, 60-82). For patients with KMT2A-rearranged infant ALL (n = 13), 2-year RFS was 67% (95% CI, 45-99), and OS was 62% (95% CI, 40-95), with multivariable analysis demonstrating no increased risk of relapse (hazard ratio, 0.70; 95% CI, 0.21-2.90; P = .7040) but a higher proportion of relapses associated with myeloid lineage switch and a 3.6-fold increased risk of all-cause death (95% CI, 1.04-12.75; P = .0434). CTL019/huCART19/tisagenlecleucel are effective at achieving durable remissions across cytogenetic categories. Relapsed/refractory patients with high-risk cytogenetics, including KMT2A-rearranged infant ALL, demonstrated high RFS and OS probabilities at 2 years.

[Clinical features and prognosis of ETV6-RUNX1-positive childhood B-precursor acute lymphocyte leukemia]

Objective: To investigate the clinical features and prognosis of ETV6-RUNX1-positive childhood B-precursor acute lymphocyte leukemia (B-ALL) . Methods: The clinical data of 927 newly diagnosed children with B-ALL admitted to the Fujian Medical University Union Hospital from April 2011 to May 2020 were retrospectively analyzed. According to the results of ETV6-RUNX1 gene, the patients were divided into ETV6-RUNX1(+) and ETV6-RUNX1(-) groups. The clinical features and prognosis between the two groups were compared. Among the 182 children with ETV6-RUNX1(+), 144 patients received the Chinese Childhood Leukemia Collaborative Group (CCLG) -ALL 2008 protocol (CCLG-ALL 2008 group) and 38 received the China Childhood Cancer Collaborative Group (CCCG) -ALL2015 protocol (CCCG-ALL 2015 group) . The efficacy, serious adverse effects (SAE) incidence, and treatment-related mortality (TRM) of the two groups were also compared. Results: Of the 927 B-ALL patients, 189 (20.4% ) were ETV6-RUNX1(+). The proportion of patients with risk factors (age ≥10 years or <1 year, white blood cell count ≥50×10(9)/L) in the ETV6-RUNX1(+) group was significantly lower than that in the ETV6-RUNX1(-) group (P=0.000, 0.001, respectively) , while the proportion of patients with good early response (good response to prednisone, d15 or d19 MRD <1% , and d33 or d46 MRD<0.01% in induction chemotherapy) in the ETV6-RUNX1(+) group was significantly higher than that in the ETV6-RUNX1(-) group (P=0.028, 0.004, respectively) . The 5-year EFS and OS of the ETV6-RUNX1(+) group were significantly higher than those of the ETV6-RUNX1(-) group (EFS: 89.8% vs 83.2% , P=0.003; OS: 90.2% vs 86.3% , P=0.030) . The incidence of infection-related SAE and TRM was significantly higher than that of CCCG-ALL 2015 group. A statistical difference was observed between the incidence of infection-related SAE of the two groups (27.1% vs 5.3% , P=0.004) , but no difference in TRM (4.9% vs 0, P=0.348) . Conclusion: ETV6-RUNX1(+)B-ALL children have fewer risk factors at diagnosis, better early response, lower recurrence rate, and good prognosis than that of ETV6-RUNX1(-)B-ALL children. Reducing the intensity of chemotherapy appropriately can lower the infection-related SAE and TRM and improve the long-term survival in this subtype.

Prognostic Value and Outcome for ETV6/RUNX1-Positive Pediatric Acute Lymphoblastic Leukemia: A Report From the South China Children's Leukemia Group

PURPOSE

To analyzed the outcome of ETV6/RUNX1-positive pediatric acute B lymphoblastic leukemia (B-ALL) with the aim of identifying prognostic value.

METHOD

A total of 2,530 pediatric patients who were diagnosed with B-ALL were classified into two groups based on the ETV6/RUNX1 status by using a retrospective cohort study method from February 28, 2008, to June 30, 2020, at 22 participating ALL centers.

RESULTS

In total, 461 (18.2%) cases were ETV6/RUNX1-positive. The proportion of patients with risk factors (age <1 year or ≥10 years, WB≥50×10⁹/L) in ETV6/RUNX1-positive group was significantly lower than that in negative group (P<0.001), while the proportion of patients with good early response (good response to prednisone, D15 MRD < 0.1%, and D33 MRD < 0.01%) in ETV6/RUNX1-positive group was higher than that in the negative group (P<0.001, 0.788 and 0.004, respectively). Multivariate analysis of 2,530 patients found that age <1 or ≥10 years, SCCLG-ALL-2016 protocol, and MLL were independent predictor of outcome but not ETV6/RUNX1. The EFS and OS of the ETV6/RUNX1-positive group were significantly higher than those of the negative group (3-year EFS: 90.11 ± 4.21% vs 82 ± 2.36%, P<0.0001, 3-year OS: 91.99 ± 3.92% vs 88.79 ± 1.87%, P=0.017). Subgroup analysis showed that chemotherapy protocol, age, prednisone response, and D15 MRD were important factors affecting the prognosis of ETV6/RUNX1-positive children.

CONCLUSIONS

ETV6/RUNX1-positive pediatric ALL showed an excellent outcome but lack of independent prognostic significance in South China. However, for older patients who have the ETV6/RUNX1 fusion and slow response to therapy, to opt for more intensive treatment.

[Efficacy and prognostic factors of the chemotherapy regimen of CCLG-ALL-2008 on pediatric acute lymphoblastic leukemia with ETV6-RUNX1 rearrangement]

Objective: To evaluate the predictive role of ETV6-RUNX1 fusion gene in protocol CCLG-ALL-2008 as well as identify the prognostic factors that influence the outcome of ALL with ETV6-RUNX1 fusion gene. Methods: One hundred and seventy-eight patients newly diagnosed with pediatric acute lymphoblastic leukemia with ETV6-RUNX1 rearrangement from April 2008 to April 2015 were enrolled in CCLG-ALL-2008. The follow up period ended in July 2018; we performed retrospective analyses of their data to determine the efficacy of the regimen and the prognostic factors. Results: The median age of the study population (178 pediatric patients) , including 100 boys and 78 girls was 4 (1-13) y, and the median white blood cell count at diagnosis was 9.46 (1.25-239.83) ×10(9)/L. Three patients died, and 1 was lost to follow up by the end of the first induction chemotherapy, resulting in an induced remission rate of 97.8% (174/178) . The cumulative incidence of relapse was 15.9% with a median follow up of 73.5 mon. Total 83.3% of the relapse cases were those of isolated bone marrow relapse, while 79.2% of the cases were those of late relapse. The median interval time between relapse and first complete remission was 35.5 mon (range, 1-62 months) . One of the 5 patients with early recurrence and 7 of the 19 with late recurrence cases survived. The 5-year-OS and 5-year-EFS of ETV6-RUNX1 positive children was (89.4±2.4) % and (82.1±6.9) %, respectively. The estimated 10-year-OS and 10-year-EFS of ETV6-RUNX1 positive children was (88.6±2.5) % and (77.3±4.0) %, respectively. The Kaplan-Meier method and Log-rank test were used to estimate and compare the survival. Univariate statistical analysis showed that poor prognostic factors that influenced survival included central nervous system state 2 at diagnosis, poor prednisone response, high risk, gene positivity after induction chemotherapy, as well as MRD positivity and gene positivity at the 12(th) week. In the multivariate analysis, only the central nervous system state 2 at diagnosis and MRD positivity at the 12(th) week were associated with the outcome. Conclusion: ETV6-RUNX1-positive ALL is a subgroup with a favorable prognosis as per the CCLG-ALL-2008 protocol. Patients with ETV6-RUNX1 should be given more intensive therapy, including hematopoietic stem cell transplantation when they are CNS2 at diagnosis or have high level of MRD at the 12(th) week after treatment.

Autophagy inhibition as a potential future targeted therapy for ETV6-RUNX1-driven B-cell precursor acute lymphoblastic leukemia

Translocation t(12;21), resulting in the ETV6-RUNX1 (or TEL-AML1) fusion protein, is present in 25% of pediatric patients with B-cell precursor acute lymphoblastic leukemia and is considered a first hit in leukemogenesis. A targeted therapy approach is not available for children with this subtype of leukemia. To identify the molecular mechanisms underlying ETV6-RUNX1-driven leukemia, we performed gene expression profiling of healthy hematopoietic progenitors in which we ectopically expressed ETV6-RUNX1. We reveal an ETV6-RUNX1-driven transcriptional network that induces proliferation, survival and cellular homeostasis. In addition, Vps34, an important regulator of autophagy, was found to be induced by ETV6-RUNX1 and up-regulated in ETV6-RUNX1-positive leukemic patient cells. We show that induction of Vps34 was transcriptionally regulated by ETV6-RUNX1 and correlated with high levels of autophagy. Knockdown of Vps34 in ETV6-RUNX1-positive cell lines severely reduced proliferation and survival. Inhibition of autophagy by hydroxychloroquine, a well-tolerated autophagy inhibitor, reduced cell viability in both ETV6-RUNX1-positive cell lines and primary acute lymphoblastic leukemia samples, and selectively sensitized primary ETV6-RUNX1-positive leukemia samples to L asparaginase. These findings reveal a causal relationship between ETV6-RUNX1 and autophagy, and provide pre-clinical evidence for the efficacy of autophagy inhibitors in ETV6-RUNX1-driven leukemia.

ETV6/RUNX1-positive childhood acute lymphoblastic leukemia (ALL): The spectrum of clonal heterogeneity and its impact on prognosis

The prognostic significance of the ETV6/RUNX1-fusion and of the accompanying aberrations is disputable; whether co-existing sub-clones are responsible for delayed MRD-clearance and thus, moderate outcome, remains to be clarified. We studied, in a paediatric cohort of 119 B-ALLs, the relation between the ETV6/RUNX1 aberration and the co-existing subclones with (a) presenting clinical/biological features, (b) early response to treatment(MRD) and (c) long-term outcome over a 12-year period. Patients were homogeneously treated according to BFM-based-protocols. 27/119 patients (22.7%) were ETV6/RUNX1-positive; 19/27 (70.4%) harbored additional genetic abnormalities while 9/19 (33.3%) presented with clonal heterogeneity. The most common abnormalities were del12p13 (37%), 3-6×21q22 (22.2%), del9p21 (18.5%) and 2-3xETV6/RUNX1 (18.5%). MRDd15-positivity (≥10-3) was detected in 44% of the cohort; the corresponding MRD among patients carrying subclones rises to 88.9%. Common features of all relapses were sub-clonal diversity, FCM-MRDd15-positivity and additional del(9p21) while there were no censored relapses among ETV6/RUNX1-positive patients with sole translocation and absence of additional aberrations, within a median follow-up time of 90 months. In our study, the presence of clonal heterogeneity and impaired FCM-MRD clearance among ETV6/RUNX1-positive patients, ultimately influenced prognosis. Longer follow-up is needed in order to further validate these initial results.

Pathogenesis of ETV6/RUNX1-positive childhood acute lymphoblastic leukemia and mechanisms underlying its relapse

ETV6/RUNX1 (E/R) is the most common fusion gene in childhood acute lymphoblastic leukemia (ALL). Multiple lines of evidence imply a “two-hit” model for the molecular pathogenesis of E/R-positive ALL, whereby E/R rearrangement is followed by a series of secondary mutations that trigger overt leukemia. The cellular framework in which E/R arises and the maintenance of a pre-leukemic condition by E/R are fundamental to the mechanism that underlies leukemogenesis. Accordingly, a variety of studies have focused on the relationship between the clones giving rise to the primary and recurrent E/R-positive ALL. We review here the most recent insights into the pathogenic mechanisms underlying E/R-positive ALL, as well as the molecular abnormalities prevailing at relapse.

Mechanism of ETV6-RUNX1 Leukemia

The t(12;21)(p13;q22) translocation is the most frequently occurring single genetic abnormality in pediatric leukemia. This translocation results in the fusion of the ETV6 and RUNX1 genes. Since its discovery in the 1990s, the function of the ETV6-RUNX1 fusion gene has attracted intense interest. In this chapter, we will summarize current knowledge on the clinical significance of ETV6-RUNX1, the experimental models used to unravel its function in leukemogenesis, the identification of co-operating mutations and the mechanisms responsible for their acquisition, the function of the encoded transcription factor and finally, the future therapeutic approaches available to mitigate the associated disease.

Outcome and Prognostic Factors for ETV6/RUNX1 Positive Pediatric Acute Lymphoblastic Leukemia Treated at a Single Institution in Korea

Purpose

ETV6/RUNX1 (+) acute lymphoblastic leukemia (ALL), which is the most common genetic subtype of pediatric ALL, has a favorable prognosis. In this study, we analyzed the outcome of ETV6/RUNX1 (+) ALL patients treated at our institution with the aim of identifying significant prognostic variables.

Materials and Methods

Sixty-three patients were diagnosed with ETV6/RUNX1 (+) ALL from 2005 to 2011. Prognostic variables studied included minimal residual disease (MRD) as detected by ETV6/RUNX1 (+) fusion, and the presence of additional cytogenetic abnormalities.

Results

The 5-year event-free survival was 84.1±4.6%, with 10 patients relapsing at a median of 28.3 months from diagnosis for a 5-year cumulative incidence of relapse of 15.9±4.6%. Multivariate analysis revealed that the presence MRD, as detected by real-time quantitative-polymerase chain reaction or fluorescence in situ hybridization for ETV6/RUNX1 fusion at end of remission induction, and the presence of additional structural abnormalities of 12p (translocations or inversions) negatively affected outcome. Despite treatment such as allogeneic hematopoietic cell transplantation, eight of the 10 relapsed patients died from disease progression for overall survival of 82.5±6.9%.

Conclusion

ETV6/RUNX1 (+) ALL may be heterogeneous in terms of prognosis, and variables such as MRD at end ofremission induction or additional structural abnormalities of 12p could define a subset of patients who are likely to have poor outcome.

Prognostification of ALL by Cytogenetics

Cytogenetic abnormalities in chromosomal number and structure are common in pediatric ALL and some have prognostic significance. One interesting association between cytogenetic status and treatment response involves the metabolism of methotrexate. Hyperdiploid lymphoblasts accumulate increased amounts of MTX and MTX polyglutamates, and they have higher basal apoptotic rates compared with leukemic cells with lower ploidy and normal cells. These characteristics may contribute to the better outcomes observed for patients with hyperdiploid lymphoblasts. A number of recurrent chromosomal abnormalities have been shown to have prognostic significance, especially in B-precursor ALL. Some chromosomal abnormalities are associated with more favorable outcomes, such as high hyperdiploidy (51-65 chromosomes) and the ETV6-RUNX1 fusion. Others are associated with a poorer prognosis, including the Philadelphia chromosome [t(9;22)], rearrangements of the MLL gene (chromosome 11q23), and intrachromosomal amplification of the AML1 gene (iAMP21).

Heterogeneity of Abnormal RUNX1 Leading to Clinicopathologic Variations in Childhood B-Lymphoblastic Leukemia

OBJECTIVES

Abnormalities of the RUNX1 gene in childhood B-acute lymphoblastic leukemia (B-ALL) are manifested by ETV6-RUNX1 or RUNX1 amplification. A detailed comparison between the two regarding clinicopathologic features with genetic analysis has not been performed previously. This parallel study assessed how different RUNX1 abnormalities affect the clinicopathology of B-ALL.

METHODS

We compared clinicopathologic factors, including age, sex, WBC count, cerebrospinal fluid (CSF) involvement, immunophenotype, and blast proliferation rate between B-ALL with RUNX1 amplification (10 cases) and B-ALL with ETV6-RUNX1 translocation (67 cases) in childhood B-ALL.

RESULTS

CD7 was often expressed in RUNX1 amplification but not in ETV6-RUNX1 (44% vs 0%, P = .0001) and appeared to correlate with CSF involvement in the former group (3/4 [75%]). CD13 was often detected in ETV6-RUNX1 with additional RUNX1 gain (38%) with an even higher frequency in double ETV6-RUNX1 translocation (77%), but was not detected in RUNX1 amplification (0%, P < .05). Children with RUNX1 amplification were older and more often CSF positive, while those with ETV6-RUNX1 were younger, more frequently had hyperleukocytosis, and had higher blast proliferation rates.

CONCLUSIONS

RUNX1 copy numbers seem to be proportional to the age of B-ALL onset and the frequency of CSF involvement, while RUNX1 amplification vs translocation causes aberrant expression of CD7 and CD13, respectively.

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.

Genomic ancestry and somatic alterations correlate with age at diagnosis in Hispanic children with B-cell acute lymphoblastic leukemia

Hispanic children have a higher incidence of acute lymphoblastic leukemia (ALL) than non-Hispanic whites but tend to be diagnosed at older ages. In genome-wide association studies, Native American ancestry and polymorphisms in six genes have been associated with ALL risk. In multivariable regression models, we investigated whether genomic ancestry, inherited risk SNPs, or acquired somatic alterations were associated with differences in age at diagnosis in Hispanic children with B-cell ALL. Genome-wide array data were used to estimate each participant's percent membership in the three Hispanic ancestral populations: Native American, African, and European. Each 20% increase in European ancestry was associated with a six month younger age at diagnosis (95% CI = 0.36-11.6 months, P = 0.037). Correspondingly, each 20% increase in Native American ancestry was associated with a six-month older age at diagnosis (P = 0.037). Both the TEL-AML1 translocation and high-hyperdiploidy were associated with younger age at diagnosis (24.4 months, P = 2.0 x 10(-4) and 12.4 months, P = 0.011, respectively), while CDKN2A and IKZF1 deletions were associated with older age at diagnosis (19.7 months, P = 7.0 x 10(-4) and 18.1 months, P = 0.012, respectively). No associations with age at diagnosis were observed for RAS mutation, PAX5 deletion or for known heritable risk alleles in IKZF1, CDKN2A, PIP4K2A, GATA3, ARID5B, or CEBPE. Because younger age at diagnosis is associated with improved treatment outcomes for children with ALL, the effect of European ancestry on ALL survival may be mediated by its effect on age at diagnosis, or by proxy, its association with more treatable molecular subtypes of ALL.

New Financial and Research Models for Pediatric Orphan Drug Development - Focus on the NCATS TRND Program

While there are approximately 7,000 identified human diseases considered as "rare" based on population prevalence or incidence, the cumulative impact runs into the millions of patients globally. Although the genetic underpinnings of more than 2,000 rare diseases have been elucidated, there remains a paucity of therapeutic options, frequently due to lack of commercial interest. Development programs suffer high attrition within the so-called "Valley of Death," in which the risks of scientific failure are still too high to justify the increasing development costs. This problem is common to any drug development campaign, but it is particularly exacerbated in the rare diseases, many of which arise in childhood. To stimulate development of therapeutics for these otherwise underserved patient populations, a number of regulatory incentives and research initiatives have been established. Extended patent protections, expedited regulatory reviews for qualified drug sponsors, and clinical trial grant support aim to foster interest in completing development programs. To stimulate researchers to embark on rare disease drug development campaigns, earlier-stage preclinical research resources have been created, as well, such as the Therapeutics for Rare and Neglected Diseases (TRND) program at the U.S. National Institutes of Health (NIH). TRND is a unique NIH program created to support drug development through formation of public-private partnerships. These partnerships leverage the robust biopharmaceutical industry experience of the TRND staff scientists and the deep disease area expertise of the collaborating partners. Each project adopted into the TRND portfolio aims to satisfy two broad goals: developing a novel therapy for a rare or otherwise neglected disease, and exploring ways to accelerate the drug development process overall so that lessons learned can be disseminated to the wider community undertaking translational research. This article discusses common obstacles and opportunities for therapeutic development, and provides examples of the types of projects TRND has undertaken across a broad range of pediatric rare disorders.

Prevalence of ETV6/RUNX1 Fusion Gene in Pediatric Patients with Acute Lymphoblastic Leukemia in Iran

OBJECTIVE

ETV6/RUNX1 (also known as TEL/AML1) is the most frequent gene fusion in childhood acute lymphoblastic leukemia (ALL). Sixty-three patients were enrolled in this study to explore the distribution of this gene in Iranian population.

METHODS

This study used 63 peripheral blood and bone marrow (PB/BM) samples from children with ALL. Immunophenotyping of PB and BM samples were performed using flow cytometry to illustrate the lineage. Moreover, reverse transcriptase polymerase chain reaction (RT-PCR) technique was used to amplify transcripts of leukemia-specific chromosome fusion gene ETV6/RUNX1 and to monitor the expression levels of the ETV6/RUNX1 in patients according to Van Dongen et al protocol.

FINDINGS

On the basis of French-American-British (FAB) classification, 47 individuals had ALL-L1. The incidence of ETV6/RUNX1 fusion gene in this study was 34.9%. The laboratory and clinical features of twenty two ETV6/RUNX1 positive ALL cases were similar to those of other studies. The most positive cases of ETV6/RUNX1 fusion gene had the early pre B ALL and pre B ALL immunophenotypes.

CONCLUSION

The ETV6/RUNX1 fusion gene is a common genetic anomaly in Iranian childhood ALL patients and the prevalence of the ETV6/RUNX1 fusion gene is similar to that of ALL patients in other countries. However early pre B cells were the most common type in studied patients.

Copy number genome alterations are associated with treatment response and outcome in relapsed childhood ETV6/RUNX1-positive acute lymphoblastic leukemia

The clinical heterogeneity among first relapses of childhood ETV6/RUNX1-positive acute lymphoblastic leukemia indicates that further genetic alterations in leukemic cells might affect the course of salvage therapy and be of prognostic relevance. To assess the incidence and prognostic relevance of additional copy number alterations at relapse of the disease, we performed whole genome array comparative genomic hybridization of leukemic cell DNA from 51 patients with first ETV6/RUNX1-positive relapse enrolled in and treated according to the relapse trials ALL-REZ of the Berlin-Frankfurt-Münster Study Group. Within this cohort of patients with relapsed ETV6/RUNX1-positive acute lymphoblastic leukemia, the largest analyzed for genome wide DNA copy number alterations to date, alterations were present in every ETV6/RUNX1-positive relapse and a high proportion of them occurred in recurrent overlapping chromosomal regions. Recurrent losses affected chromosomal regions 12p13, 6q21, 15q15.1, 9p21, 3p21, 5q and 3p14.2, whereas gains occurred in regions 21q22 and 12p. Loss of 12p13 including CDKN1B was associated with a shorter remission duration (P=0.009) and a lower probability of event-free survival (P=0.001). Distribution of X-chromosomal copy number alterations was gender-specific: whole X-chromosome loss occurred exclusively in females, gain of Xq only in males. Loss of the glucocorticoid receptor gene NR3C1 (5q31.3) was associated with a poor response to induction treatment (P=0.003), possibly accounting for the adverse prognosis of some of the ETV6/RUNX1-positive relapses.

STAT3 mediates oncogenic addiction to TEL-AML1 in t(12;21) acute lymphoblastic leukemia

STAT3 activity is necessary for TEL-AML1 leukemia maintenance. TEL-AML1 induces STAT3 activation via RAC1 and leading to induction of MYC expression.

Predicting relapse risk in childhood acute lymphoblastic leukaemia

Intensive multi-agent chemotherapy regimens and the introduction of risk-stratified therapy have substantially improved cure rates for children with acute lymphoblastic leukaemia (ALL). Current risk allocation schemas are imperfect, as some children are classified as lower-risk and treated with less intensive therapy relapse, while others deemed higher-risk are probably over-treated. Most cooperative groups previously used morphological clearance of blasts in blood and marrow during the initial phases of chemotherapy as a primary factor for risk group allocation; however, this has largely been replaced by the detection of minimal residual disease (MRD). Other than age and white blood cell count (WBC) at presentation, many clinical variables previously used for risk group allocation are no longer prognostic, as MRD and the presence of sentinel genetic lesions are more reliable at predicting outcome. Currently, a number of sentinel genetic lesions are used by most cooperative groups for risk stratification; however, in the near future patients will probably be risk-stratified using genomic signatures and clustering algorithms, rather than individual genetic alterations. This review will describe the clinical, biological, and response-based features known to predict relapse risk in childhood ALL, including those currently used and those likely to be used in the near future to risk-stratify therapy.

Identification of benzodiazepine Ro5-3335 as an inhibitor of CBF leukemia through quantitative high throughput screen against RUNX1-CBFβ interaction

Core binding factor (CBF) leukemias, those with translocations or inversions that affect transcription factor genes RUNX1 or CBFB, account for ~24% of adult acute myeloid leukemia (AML) and 25% of pediatric acute lymphocytic leukemia (ALL). Current treatments for CBF leukemias are associated with significant morbidity and mortality, with a 5-y survival rate of ~50%. We hypothesize that the interaction between RUNX1 and CBFβ is critical for CBF leukemia and can be targeted for drug development. We developed high-throughput AlphaScreen and time-resolved fluorescence resonance energy transfer (TR-FRET) methods to quantify the RUNX1-CBFβ interaction and screen a library collection of 243,398 compounds. Ro5-3335, a benzodiazepine identified from the screen, was able to interact with RUNX1 and CBFβ directly, repress RUNX1/CBFB-dependent transactivation in reporter assays, and repress runx1-dependent hematopoiesis in zebrafish embryos. Ro5-3335 preferentially killed human CBF leukemia cell lines, rescued preleukemic phenotype in a RUNX1-ETO transgenic zebrafish, and reduced leukemia burden in a mouse CBFB-MYH11 leukemia model. Our data thus confirmed that RUNX1-CBFβ interaction can be targeted for leukemia treatment and we have identified a promising lead compound for this purpose.

Excellent prognosis of late relapses of ETV6/RUNX1-positive childhood acute lymphoblastic leukemia: lessons from the FRALLE 93 protocol

BACKGROUND

The prognosis of patients with relapses of ETV6/RUNX1-positive acute lymphoblastic leukemia remains to be evaluated, particularly with regards to the frequency of late relapses. We performed a long-term, follow-up retrospective study to address the outcome of patients with ETV6/RUNX1-positive leukemia relapses.

DESIGN AND METHODS

Among the 713 children tested for ETV6/RUNX1 enrolled into the FRALLE 93 protocol, 43 ETV6/RUNX1-positive patients relapsed (19.4%). Most were initially stratified in the low or intermediate risk groups. The median follow-up after relapse was 54.2 months. All but three received second-line salvage therapy and 16 underwent allogeneic transplantation.

RESULTS

ETV6/RUNX1 had a strong effect on overall survival after relapse (3-year survival= 64.7% for positive cases versus 46.5% for negative cases) (P=0.007). The 5-year cumulative incidence of relapse was 19.4% and testes were more frequently involved in ETV6/RUNX1-positive relapses (P=0.04). In 81.4% of cases the relapses were late, early combined or isolated extramedullary relapses. The 5-year survival rate of patients with ETV6-RUNX1-positive acute lymphoblastic leukemia relapses reached 80.8% when the relapse occurred after 36 months (versus 31.2% when the relapse occurred earlier). In univariate analysis, female gender was associated with a poor survival, whereas site of relapse, age at diagnosis, leukocytosis and consolidation strategy had no effect. In multivariate analysis, only the duration of first remission remained associated with outcome.

CONCLUSIONS

We found an excellent outcome for patients with ETV6/RUNX1-positive leukemia relapses that occurred more than 36 months after diagnosis. The duration of first complete remission may, therefore, be a guide to define the treatment strategy for patients with relapsed ETV6/RUNX1- positive leukemia.

ETV6-RUNX1-positive childhood acute lymphoblastic leukemia: improved outcome with contemporary therapy

ETV6-RUNX1 fusion is the most common genetic aberration in childhood acute lymphoblastic leukemia (ALL). To evaluate whether outcomes for this drug-sensitive leukemia are improved by contemporary risk-directed therapy, we studied clinical features, response and adverse events of 168 children with newly diagnosed ETV6-RUNX1-positive ALL on St Jude Total Therapy studies XIIIA (N=36), XIIIB (N=38) and XV (N=94). Results were compared with 494 ETV6-RUNX1-negative B-precursor ALL patients. ETV6-RUNX1 was associated with age 1-9 years, pre-treatment classification as low risk and lower levels of minimal residual disease (MRD) on day 19 of therapy (P<0.001). Event-free survival (EFS) or overall survival (OS) did not differ between patients with or without ETV6-RUNX1 in Total XIIIA or XIIIB. By contrast, in Total XV, patients with ETV6-RUNX1 had significantly better EFS (P=0.04; 5-year estimate, 96.8±2.4% versus 88.3±2.5%) and OS (P=0.04; 98.9±1.4% versus 93.7±1.8%) than those without ETV6-RUNX1. Within the ETV6-RUNX1 group, the only significant prognostic factor associated with higher OS was the treatment protocol Total XV (versus XIIIA or XIIIB) (P=0.01). Thus, the MRD-guided treatment schema including intensive asparaginase and high-dose methotrexate in the Total XV study produced significantly better outcomes than previous regimens and demonstrated that nearly all children with ETV6-RUNX1 ALL can be cured.

Shortening infusion time for high-dose methotrexate alters antileukemic effects: a randomized prospective clinical trial

PURPOSE

To determine whether shortening the infusion duration of high-dose methotrexate (HDMTX; 1 g/m(2)) affects the in vivo accumulation of active methotrexate polyglutamates (MTXPG(1-7)) in leukemia cells and whether this differs among major acute lymphoblastic leukemia (ALL) subtypes.

METHODS

From June 2000 through October 2007, 356 children with ALL were randomly assigned to receive initial single-agent treatment with HDMTX (1 g/m(2)) as either a 24-hour infusion or a 4-hour infusion at two pediatric hospitals in the United States. The primary outcome measures were the accumulation of MTXPG(1-7) in leukemia cells and the antileukemic effects (eg, inhibition of de novo purine synthesis in bone marrow ALL cells, and decrease in circulating ALL cells).

RESULTS

The 24-hour infusion resulted in significantly higher amounts of MTXPG(1-7) in bone marrow leukemia cells (median: 1,695 v 1,150 pmol/10(9) cells, P = .0059), and better antileukemic effects. The 24-hour infusion had the greatest effect on MTXPG(1-7) accumulation in hyperdiploid ALL (median: 3,919 v 2,417 pmol/10(9) cells, P = .0038); T-cell ALL exhibited smaller differences in MTXPG(1-7) but greater antileukemic effects with the longer infusion (median decrease in leukemia cells: 88.4% v 51.8%, P = .0075). In contrast, infusion duration had no significant impact on MTXPG(1-7) accumulation or antileukemic effects in ALL with the t(12;21)/(ETV6-RUNX1) chromosomal translocation.

CONCLUSION

Shortening the infusion time of HDMTX reduces accumulation of active methotrexate in leukemia cells and decreases antileukemic effects, with differing consequences among major ALL subtypes.

ETV6/RUNX1-positive relapses evolve from an ancestral clone and frequently acquire deletions of genes implicated in glucocorticoid signaling

Approximately 25% of childhood acute lymphoblastic leukemias carry the ETV6/RUNX1 fusion gene. Despite their excellent initial treatment response, up to 20% of patients relapse. To gain insight into the relapse mechanisms, we analyzed single nucleotide polymorphism arrays for DNA copy number aberrations (CNAs) in 18 matched diagnosis and relapse leukemias. CNAs were more abundant at relapse than at diagnosis (mean 12.5 vs 7.5 per case; P = .01) with 5.3 shared on average. Their patterns revealed a direct clonal relationship with exclusively new aberrations at relapse in only 21.4%, whereas 78.6% shared a common ancestor and subsequently acquired distinct CNA. Moreover, we identified recurrent, mainly nonoverlapping deletions associated with glucocorticoid-mediated apoptosis targeting the Bcl2 modifying factor (BMF) (n = 3), glucocorticoid receptor NR3C1 (n = 4), and components of the mismatch repair pathways (n = 3). Fluorescence in situ hybridization screening of additional 24 relapsed and 72 nonrelapsed ETV6/RUNX1-positive cases demonstrated that BMF deletions were significantly more common in relapse cases (16.6% vs 2.8%; P = .02). Unlike BMF deletions, which were always already present at diagnosis, NR3C1 and mismatch repair aberrations prevailed at relapse. They were all associated with leukemias, which poorly responded to treatment. These findings implicate glucocorticoid-associated drug resistance in ETV6/RUNX1-positive relapse pathogenesis and therefore might help to guide future therapies.

Recent research advances in childhood acute lymphoblastic leukemia

Recent progress in risk-adapted treatment for childhood acute lymphoblastic leukemia has secured 5-year event-free survival rates of approximately 80% and 5-year survival rates approaching 90%. With improved systemic and intrathecal chemotherapy, it is now feasible to omit safely in all patients prophylactic cranial irradiation, which was once a standard treatment. As high-resolution, genome-wide analyses of leukemic and normal host cells continue to identify novel subtypes of lymphoblastic leukemia and provide new insights into leukemogenesis, we can look forward to the time when all cases of this disease will be classified according to specific genetic abnormalities, some of which will yield "druggable" targets for more effective and less toxic treatments. Meanwhile, it is sobering to consider that a significant fraction of leukemia survivors will develop serious health problems within 30 years of their initial diagnosis. This underlines the need to introduce early countermeasures to reduce late therapy-related effects. The ultimate challenge is to gain a clear understanding of the factors that give rise to childhood leukemia in the first place, and enable preventive strategies to be devised and implemented.

Multiplex reverse transcription-polymerase chain reaction as diagnostic molecular screening of 4 common fusion chimeric genes in Taiwanese children with acute lymphoblastic leukemia

BACKGROUND

The classification of B-lineage acute lymphoblastic leukemia (ALL) by specific chromosomal translocations has prognostic implications for risk-directed therapy. Reverse transcription-polymerase chain reaction (RT-PCR) assay is a useful tool for detecting fusion transcripts from common chromosomal translocations of ALL cells.

METHODS

Multiplex RT-PCR and nested-PCR assays were used to detect ALL-type BCR-ABL1 transcripts of the t(9;22), TCF-PBX1 transcripts of t(1;19), the MLL-AF4 transcripts of t(4;11), and 2 variants of ETV6-RUNX1 of the cryptic t(12;21) in 148 leukemic samples upon diagnosis. The patients received risk-directed protocols of the Taiwan Pediatric Oncology Group-ALL-2002 that consisted of multiple chemotherapeutic agents of different intensities. Event-free survival (EFS) and overall survival (OS) rates were analyzed for genetic abnormalities detected by multiplex PCR and conventional cytogenetic analysis by the Kaplan-Meier method, and compared with the Mantel-Haenszel test. The Cox proportional hazards model was implemented to identify independent prognostic factors for EFS and OS.

RESULTS

In this cohort of Taiwanese children, the relative frequencies of the 4 translocations of B-lineage ALL were 8% with ALL-type t(9;22)/BCR-ABL1, 4% with (1;19)/TCF-PBX1, 2% with t(4;11)/MLL-AF4, and 17.6% with t(12;21)/ETV6-RUNX1. Patients with t(12;21)/ETV6-RUNX1 fusion, hyperdiploidy, and t(1;19)/TCF-PBX1 fusion had the most favorable outcomes, whereas those with the t(9;22)/BCR-ABL1 fusion or t(4;11) and other MLL gene rearrangement had poor prognosis (P<0.001 for EFS and OS). BCR-ABL1, MLL gene rearrangement, and very high-risk group were independent prognostic factors after Cox regression analysis.

CONCLUSIONS

The biological factors of leukemia cells are associated with treatment outcomes in childhood ALL. Multiplex RT-PCR assay is an efficient and sensitive diagnostic tool that may improve the ability to accurately and rapidly risk-stratify children with ALL.

Sequential monitoring of minimal residual disease in acute lymphoblastic leukemia: 7-year experience in a pediatric hematology/oncology unit

We evaluated minimal residual disease (MRD) in 91 children with acute lymphoblastic leukemia (ALL) by PCR amplification of clonal rearrangements, immunoglobulin (IgH; VDJ rearrangement, CDR3 region) and T-cell receptor (TCRdelta). Sequential monitoring of MRD was performed at different time points during and after chemotherapy and was correlated to patient outcome. In total, 792 bone marrow samples were assessed for MRD at the end of induction, and during and after treatment completion. MRD positivity at the end of induction was detected in 12% of patients and was associated with high incidence of relapse, 54.55% (p = 0.0002), at 5 years. On the other hand, 88% of patients were MRD-negative at the end of induction and the relapse rate at 5 years was very low, 5%. The frequency of MRD decreased to 16% in the first 6 months of chemotherapy; however, the incidence of relapse in MRD-positive patients remained high, 42.8%. After treatment completion (24-36 months from diagnosis), 32% patients were MRD-positive and the relapse rate was 36.5% (p = 0.0009). Our results indicated that monitoring of MRD constituted an essential prognostic marker, and detection of MRD particularly at the end of induction and after treatment completion was strongly predictive for patient outcome.

Expression and prognostic significance of the apoptotic genes BCL2L13, Livin, and CASP8AP2 in childhood acute lymphoblastic leukemia

Improved treatment of childhood acute lymphoblastic leukemia (ALL) depends on the identification of new molecular markers that are able to predict treatment response and clinical outcome. The development of impaired apoptosis in leukemic cells is one factor that may influence their response to treatment. We investigated the expression of three apoptosis related genes, BCL2L13, CASP8AP2, and Livin, as well as their prognostic significance, in a retrospective study of 90 pediatric ALL patients diagnosed between 1996 and 2007 in Taiwan. Univariant analysis revealed that high expression of BCL2L13 was associated with inferior event-free survival and overall survival (p<0.001 and 0.005, respectively). Multivariate analysis for EFS and OS demonstrated that high expression of BCL2L13 was an independent prognostic factor for childhood ALL in this ethnic group.

Prognosis of children with mixed phenotype acute leukemia treated on the basis of consistent immunophenotypic criteria

BACKGROUND

Mixed phenotype acute leukemia (MPAL) represents a diagnostic and therapeutic dilemma. The European Group for the Immunological Classification of Leukemias (EGIL) scoring system unambiguously defines MPAL expressing aberrant lineage markers. Discussions surrounding it have focused on scoring details, and information is limited regarding its biological, clinical and prognostic significance. The recent World Health Organization classification is simpler and could replace the EGIL scoring system after transformation into unambiguous guidelines.

DESIGN AND METHODS

Simple immunophenotypic criteria were used to classify all cases of childhood acute leukemia in order to provide therapy directed against acute lymphoblastic leukemia or acute myeloid leukemia. Prognosis, genotype and immunoglobulin/T-cell receptor gene rearrangement status were analyzed.

RESULTS

The incidences of MPAL were 28/582 and 4/107 for children treated with acute lymphoblastic leukemia and acute myeloid leukemia regimens, respectively. In immunophenotypic principal component analysis, MPAL treated as T-cell acute lymphoblastic leukemia clustered between cases of non-mixed T-cell acute lymphoblastic leukemia and acute myeloid leukemia, while other MPAL cases were included in the respective non-mixed B-cell progenitor acute lymphoblastic leukemia or acute myeloid leukemia clusters. Analogously, immunoglobulin/T-cell receptor gene rearrangements followed the expected pattern in patients treated as having acute myeloid leukemia (non-rearranged, 4/4) or as having B-cell progenitor acute lymphoblastic leukemia (rearranged, 20/20), but were missing in 3/5 analyzed cases of MPAL treated as having T-cell acute lymphobastic leukemia. In patients who received acute lymphoblastic leukemia treatment, the 5-year event-free survival of the MPAL cases was worse than that of the non-mixed cases (53+/-10% and 76+/-2% at 5 years, respectively, P=0.0075), with a more pronounced difference among B lineage cases. The small numbers of MPAL cases treated as T-cell acute lymphoblastic leukemia or as acute myeloid leukemia hampered separate statistics. We compared prognosis of all subsets with the prognosis of previously published cohorts.

CONCLUSIONS

Simple immunophenotypic criteria are useful for therapy decisions in MPAL. In B lineage leukemia, MPAL confers poorer prognosis. However, our data do not justify a preferential use of current acute myeloid leukemia-based therapy in MPAL.

Pharmacogenomic variations in treatment protocols for childhood acute lymphoblastic leukemia

OBJECTIVES

This retrospective study evaluates the role of pharmacogenomic determinants in the treatment of childhood acute lymphoblastic leukemia (ALL) in the Taiwanese population.

METHODS

A total of 105 childhood ALL patients received combined chemotherapy of different intensities based on risk-directed Taiwan Pediatric Oncology Group (TPOG)-ALL-93 protocols. Seventeen genetic polymorphisms in 13 pharmacogenomic targets were analyzed by PCR-based restriction fragment length polymorphism (RFLP) and sequence-specific oligonucleotide (SSO) probe hybridization. Pharmacogenomic polymorphisms were correlated with event-free survival (EFS) of patients, with confounding effects adjusted by multivariate regression.

RESULTS

Three polymorphic alleles in the multi-drug resistance 1 (MDR1) ABCB1 gene, and homozygotic MDR1 2677GG, 3435CC, and 2677G-3435C genotypes were highly associated with a significant reduction in EFS in those patients treated by the standard risk (SR) protocol (TPOG-ALL-93-SR). The hazard ratios were 6.8 (p = 0.01), 21.7 (p = 0.009), and 6.8 (p = 0.01), respectively.

CONCLUSIONS

Independent pharmacogenomic determinants associated with treatment outcome were identified in subsets of Taiwanese ALL patients.

Risk-adapted treatment of pediatric acute lymphoblastic leukemia

Optimal use of antileukemic agents and stringent application of risk-directed therapy in clinical trials have resulted in steady improvement in the outcome of children with acute lymphoblastic leukemia, with current cure rates exceeding 80% in developed countries. The intensity of treatment varies substantially among subsets of patients, as therapy is designed to reduce acute and long-term toxicity in low-risk groups while improving outcomes in poor risk groups by treatment intensification. Recent advances in genome-wide screening techniques, pharmacogenomic studies, and development of molecular therapeutics are ushering in an era of more refined personalized therapy.

Temporal changes in the incidence and pattern of central nervous system relapses in children with acute lymphoblastic leukaemia treated on four consecutive Medical Research Council trials, 1985-2001

Despite the success of contemporary treatment protocols in childhood acute lymphoblastic leukaemia (ALL), relapse within the central nervous system (CNS) remains a challenge. To better understand this phenomenon, we have analysed the changes in incidence and pattern of CNS relapses in 5564 children enrolled on four successive MRC-ALL trials between 1985 and 2001. Changes in the incidence and pattern of CNS relapses were examined and the relationship with patient characteristics assessed. Factors affecting post-relapse outcome were determined. Overall, relapses declined by 49%. Decreases occurred primarily in non-CNS and combined relapses with a progressive shift towards later (≥30 months from diagnosis) relapses (p<0·0001). Although isolated CNS relapses declined, the proportional incidence and timing of relapse remained unchanged. Age and presenting white cell count were risk factors for CNS relapse. On multivariate analysis, the time to relapse and the trial period influenced post-relapse outcomes. Relapse trends differed within biological subtypes. In ETV6-RUNX1 ALL, relapse patterns mirrored overall trends while in High Hyperdiploidy ALL, these appear to have plateaued over the latter two trial periods. Intensive systemic and intrathecal chemotherapy have decreased the overall CNS relapse rates and changed the patterns of recurrence. The heterogeneity of therapeutic response in the biological subtypes suggests room for further optimisation using currently available chemotherapy.

Long-term results of Dana-Farber Cancer Institute ALL Consortium protocols for children with newly diagnosed acute lymphoblastic leukemia (1985-2000)

The Dana-Farber Cancer Institute (DFCI) ALL Consortium has been conducting multi-institutional clinical trials in childhood ALL since 1981. The treatment backbone has included 20–30 consecutive weeks of asparaginase during intensification and frequent vincristine/corticosteroid pulses during the continuation phase. Between 1985–2000, 1457 children aged 0–18 years were treated on four consecutive protocols: 85-01 (1985–7), 87-01 (1987–91), 91-01 (1991–5) and 95-01 (1996–2000). The 10-year event-free survival (EFS) ± standard error by protocol was 77.9 ± 2.8% (85-01), 74.2± 2.3 (87-01), 80.8 ± 2.1% (91-01) and 80.5 ± 1.8% (95-01). Approximately 82% of patients treated in the 1980s and 88% treated in the 1990s were long-term survivors. Both EFS and overall survival (OS) rates were significantly higher for patients treated in the 1990s compared with the 1980s (p=0.05 and 0.01, respectively). On the two protocols conducted in the 1990s, EFS was 79–85% for T-ALL patients and 75–78% for adolescents (age 10–18 years). Results of randomized studies revealed that dexrazoxane prevented acute cardiac injury without adversely impacting EFS or OS in high-risk patients and frequently-dosed intrathecal chemotherapy was an effective substitute for cranial radiation in standard-risk patients. Current studies continue to focus on improving efficacy while minimizing acute and late toxicities.