Treatment of Pediatric Acute Lymphoblastic Leukemia: A Historical Perspective

Acute lymphoblastic leukemia (ALL) is the most common disease in pediatric oncology. The history of developmental therapeutics for ALL began in the 1960s with the repetition of "unreliable" medical interventions against this lethal disease. By the 1990s, the development of multi-agent chemotherapy and various types of supportive care rendered ALL treatable. Highly sophisticated, molecular, diagnostic techniques have enabled highly accurate prediction of the relapse risk, and the application of risk-adapted treatments has increased the survival rate in the standard-risk group to nearly 100% in most European nations and North America. Incorporation of state-of-the-art, molecularly targeted agents and novel treatments, including cell and immunotherapy, is further improving outcomes even in the high-risk group. On the other hand, the financial burden of treating children with ALL has increased, imperiling the availability of these diagnostic and treatment strategies to patients in low- and middle-income countries (LMICs). The fundamental treatment strategy, consisting of corticosteroid and classical cytotoxic therapy, has achieved fairly good outcomes and should be feasible in LMICs as well. The present review will discuss the history of developmental therapeutics for childhood ALL in various countries through an extensive literature review with the aim of proposing a model for a treatment backbone for pediatric ALL. The discussion will hopefully benefit LMICs and be useful as a base for future clinical trials of novel treatments.

Clinical significance of end of induction measurable residual disease monitoring in B-cell acute lymphoblastic leukemia: A single center experience

The assessment of measurable residual disease (MRD) has emerged as a powerful prognostic tool for both pediatric and adult acute lymphoblastic leukemia (ALL). This retrospective study aimed to evaluate the prognostic relevance of the end of induction MRD in B-cell acute lymphoblastic leukemia (B ALL) patients. The study included 481 patients who underwent treatment for B ALL between August 2012 and March 2019 and had their MRD at the end of induction assessed by flow cytometry. Baseline demographic characteristics were collected from the patient's clinical records. Event free survival (EFS) and relapse free survival (RFS) were calculated using Kaplan-Meier analysis and survival estimates were compared using the log-rank test. End of induction MRD and baseline karyotype were the strongest predictors of EFS and RFS on multivariate analysis. The EFS was inversely related to the MRD value and the outcomes were similar in patients without morphological remission at the end of induction and patients in remission with MRD ≥1.0%. Even within the subgroups of ALL based on age, karyotype, BCR::ABL1 translocation and the treatment protocol, end of induction MRD positive patients had poor outcomes compared to patients who were MRD negative. The study outcome would help draft end of induction MRD-based treatment guidelines for the management of B ALL patients.

Evaluation of factors leading to poor outcomes for pediatric acute lymphoblastic leukemia in Mexico: a multi-institutional report of 2,116 patients

Background and aims

Pediatric acute lymphoblastic leukemia (ALL) survival rates in low- and middle-income countries are lower due to deficiencies in multilevel factors, including access to timely diagnosis, risk-stratified therapy, and comprehensive supportive care. This retrospective study aimed to analyze outcomes for pediatric ALL at 16 centers in Mexico.

Methods

Patients <18 years of age with newly diagnosed B- and T-cell ALL treated between January 2011 and December 2019 were included. Clinical and biological characteristics and their association with outcomes were examined.

Results

Overall, 2,116 patients with a median age of 6.3 years were included. B-cell immunophenotype was identified in 1,889 (89.3%) patients. The median white blood cells at diagnosis were 11.2.5 × 103/mm3. CNS-1 status was reported in 1,810 (85.5%), CNS-2 in 67 (3.2%), and CNS-3 in 61 (2.9%). A total of 1,488 patients (70.4%) were classified as high-risk at diagnosis. However, in 52.5% (991/1,889) of patients with B-cell ALL, the reported risk group did not match the calculated risk group allocation based on National Cancer Institute (NCI) criteria. Fluorescence in situ hybridization (FISH) and PCR tests were performed for 407 (19.2%) and 736 (34.8%) patients, respectively. Minimal residual disease (MRD) during induction was performed in 1,158 patients (54.7%). The median follow-up was 3.7 years. During induction, 191 patients died (9.1%), and 45 patients (2.1%) experienced induction failure. A total of 365 deaths (17.3%) occurred, including 174 deaths after remission. Six percent (176) of patients abandoned treatment. The 5-year event-free survival (EFS) was 58.9% ± 1.7% for B-cell ALL and 47.4% ± 5.9% for T-cell ALL, while the 5-year overall survival (OS) was 67.5% ± 1.6% for B-cell ALL and 54.3% ± 0.6% for T-cell ALL. The 5-year cumulative incidence of central nervous system (CNS) relapse was 5.5% ± 0.6%. For the whole cohort, significantly higher outcomes were seen for patients aged 1-10 years, with DNA index >0.9, with hyperdiploid ALL, and without substantial treatment modifications. In multivariable analyses, age and Day 15 MRD continued to have a significant effect on EFS.

Conclusion

Outcomes in this multi-institutional cohort describe poor outcomes, influenced by incomplete and inconsistent risk stratification, early toxic death, high on-treatment mortality, and high CNS relapse rate. Adopting comprehensive risk-stratification strategies, evidence-informed de-intensification for favorable-risk patients and optimized supportive care could improve outcomes.

Anthracycline-Free Protocol for Favorable-Risk Childhood ALL: A Noninferiority Comparison Between Malaysia-Singapore ALL 2003 and ALL 2010 Studies

PURPOSE

To investigate whether, for children with favorable-risk B-cell precursor ALL (BCP-ALL), an anthracycline-free protocol is noninferior to a modified Berlin-Frankfurt-Muenster ALL-IC2002 protocol, which includes 120 mg/m² of anthracyclines.

PATIENTS AND METHODS

Three hundred sixty-nine children with favorable-risk BCP-ALL (age 1-9 years, no extramedullary disease, and no high-risk genetics) who cleared minimal residual disease (≤0.01%) at the end of remission induction were enrolled into Ma-Spore (MS) ALL trials. One hundred sixty-seven standard-risk (SR) patients (34% of Malaysia-Singapore ALL 2003 study [MS2003]) were treated with the MS2003-SR protocol and received 120 mg/m² of anthracyclines during delayed intensification while 202 patients (42% of MS2010) received an anthracycline-free successor protocol. The primary outcome was a noninferiority margin of 1.15 in 6-year event-free survival (EFS) between the MS2003-SR and MS2010-SR cohorts.

RESULTS

The 6-year EFS of MS2003-SR and MS2010-SR (anthracycline-free) cohorts was 95.2% ± 1.7% and 96.5% ± 1.5%, respectively (P = .46). The corresponding 6-year overall survival was 97.6% and 99.0% ± 0.7% (P = .81), respectively. The cumulative incidence of relapse was 3.6% and 2.6%, respectively (P = .42). After adjustment for race, sex, age, presenting WBC, day 8 prednisolone response, and favorable genetic subgroups, the hazard ratio for MS2010-SR EFS was 0.98 (95% CI, 0.84 to 1.14; P = .79), confirming noninferiority. Compared with MS2003-SR, MS2010-SR had significantly lower episodes of bacteremia (30% v 45.6%; P = .04) and intensive care unit admissions (1.5% v 9.5%; P = .004).

CONCLUSION

In comparison with MS2003-SR, the anthracycline-free MS2010-SR protocol is not inferior and was less toxic as treatment for favorable-risk childhood BCP-ALL.

Impact of Age on Overall Survival Among Children With Wilms Tumor: A Population-based Registry Analysis

OBJECTIVES

International trials have reported conflicting findings on whether the association between age and worse overall survival (OS) among children with Wilms tumor (WT) is due to age as an independent prognostic factor or the observation of more advanced disease at older ages. We sought to further elucidate this relationship using a population-based registry analysis.

METHODS

The Surveillance, Epidemiology, and End Results database was queried for all patients diagnosed with WT under the age of 20. The association between age and OS was assessed using multivariable Cox proportional hazards regression.

RESULTS

In this study, 3463 patients (54% female) were diagnosed with WT between 1975 and 2016. More advanced stage, larger primary tumor size, lymph node involvement, disease requiring radiotherapy, and omission of surgery were associated with worse OS ( P <0.05). More advanced stage, larger primary tumor size, and disease requiring radiotherapy were also associated with older age, whereas bilateral disease was associated with younger age ( P <0.001). On average, each year of age conferred an incremental hazard ratio (HR) of 1.07 (95% CI, 1.01 to 1.12, P =0.018) independent of relevant covariates. The rise in adjusted OS HR was most pronounced after the transitions in diagnosis age from 2 to 3 (HR age 3-15 vs. 0-2 1.77, 95% CI, 1.11 to 2.82, P =0.016) and from 15 to 16 (HR age 16-19 vs. 3-15 2.58, 95% CI, 1.06 to 6.25, P =0.036).

CONCLUSIONS

Diagnosis of pediatric WT at an older age was found to be independently associated with worse OS. Although additional prospective studies are warranted to examine tumor biology and other potential correlates, more aggressive treatment of older children based on age, especially as they approach early adulthood, may be considered in the multidisciplinary management of WT.

Phagocyte-related S100 proteins and cytokines in acute lymphoblastic leukemia and their prognostic value

In this retrospective cohort study, we evaluated the level of biomarkers of inflammation like phagocyte-related S100 proteins and a panel of cytokines in 128 children with pre-B ALL and 22 with T-ALL. The biomarkers were evaluated at diagnosis and during antileukemic therapy (day 29 and after six months) and we evaluated their correlation with basic laboratory values. Further, for the children with pre-B ALL, we evaluated whether the biomarkers could predict the outcome of ALL expressed as minimal residual disease (MRD), relapse, and death.The levels of S100A9, S100A12, IL-1beta, IL-12p70, IL-13, IL-17, IL-18, and MPO serum levels increased significantly as chemotherapy was initiated. The difference was most pronounced for S100A9 and S100A12, which had strong positive correlations with the neutrophil counts. In contrast, TNF-alpha, IL-6, IL-10, CCL-2, MMP-3, and CD25 serum levels decreased after chemotherapy. Although none of these biomarkers appear to be an independent predictor of outcomes, in predictive models with MRD as the outcome, AUC increased from 76% (95% CI 68-84%) when using initial risk group stratification alone to 83% (95% CI 73-91%) in a multivariate predictive model including initial risk group stratification and the biomarkers S100A12, TNF-alpha, and IL-10.

The KMT2A recombinome of acute leukemias in 2023

Chromosomal rearrangements of the human KMT2A/MLL gene are associated with de novo as well as therapy-induced infant, pediatric, and adult acute leukemias. Here, we present the data obtained from 3401 acute leukemia patients that have been analyzed between 2003 and 2022. Genomic breakpoints within the KMT2A gene and the involved translocation partner genes (TPGs) and KMT2A-partial tandem duplications (PTDs) were determined. Including the published data from the literature, a total of 107 in-frame KMT2A gene fusions have been identified so far. Further 16 rearrangements were out-of-frame fusions, 18 patients had no partner gene fused to 5'-KMT2A, two patients had a 5'-KMT2A deletion, and one ETV6::RUNX1 patient had an KMT2A insertion at the breakpoint. The seven most frequent TPGs and PTDs account for more than 90% of all recombinations of the KMT2A, 37 occur recurrently and 63 were identified so far only once. This study provides a comprehensive analysis of the KMT2A recombinome in acute leukemia patients. Besides the scientific gain of information, genomic breakpoint sequences of these patients were used to monitor minimal residual disease (MRD). Thus, this work may be directly translated from the bench to the bedside of patients and meet the clinical needs to improve patient survival.

Associations of T-Cell Receptor Repertoire Diversity with L-Asparaginase Allergy in Childhood Acute Lymphoblastic Leukemia

Asparaginase is a critical component of therapy for childhood acute lymphoblastic leukemia (ALL), but it is commonly associated with allergy, which results in morbidity and poorer outcomes. The underlying basis of this allergy is undoubtedly immune-mediated, but the exact components of T-cell immunity have yet to be characterized. We performed longitudinal TCR sequencing of 180 bone marrow samples from 67 children with B-ALL treated as part of the Ma-Spore-ALL-2010 trial, and we evaluated the associations of TCR profile with asparaginase hypersensitivity, with functional validation of asparaginase activity in a separate cohort of 113 children. We found that a more diverse and dynamically changing TCR repertoire was associated with increased risk of clinical hypersensitivity and decreased L-asp activity. Allergic patients had a higher proportion of infrequent clonotypes, as well as a significantly lower degree of shared clonotypes amongst the cohort. Allergic patients also had significantly higher longitudinal variability of clonotypes across timepoints, where a higher dissimilarity between diagnosis and week 5 represented an 8.1-fold increased risk of an allergic event. After an allergy had occurred, there was shaping and convergence of the TCR repertoire towards a common antigen. Understanding the immunological basis of T-cell responses in allergy lays the groundwork for developing predictive biomarkers or strategies to mediate this common toxicity in childhood ALL.

Impact of minimal residual disease on relapse in childhood acute lymphoblastic leukemia: Lessons learnt from a tertiary cancer center in India

Prognostic predictive value of end of induction minimal residual disease (EOI-MRD) is well established in acute lymphoblastic leukemia (ALL). We evaluated the factors likely to affect EOI-MRD positivity (>0.01%) by flow cytometry and relapse in different BFM-95 (Berlin-Frankfurt-Munich) risk groups among children and adolescents. In this retrospective study, data of 223 newly diagnosed patients with ALL was analyzed. Association between demographic and pretreatment characteristics with EOI-MRD was assessed. Risk factors for relapse were analyzed using univariate and multivariate Cox regression. Proportion of the SR (standard risk), MR (moderate risk), and HR (high risk) patients was 18.8%, 60.9%, 20.3%, respectively. Positive EOI-MRD among these risk groups was observed in 11.9%, 18.3%, and 55.5% patients respectively (p value <.01%). MRD positivity was more likely to be associated with older age (>10 years) and BFM-HR patients (p value .0008 and <.0001). Thirty-four (15.2%) patients relapsed in the whole cohort. On univariate analysis, statistically significant factors for RFS (relapse-free survival) included hyperleukocytosis, high-risk cytogenetics, NCI (National Cancer Institute) high risk, poor day-8 prednisolone response, BFM-HR and positive EOI-MRD status. Of all these only EOI-MRD retained its impact by multivariate analysis. Positive EOI-MRD significantly predicted relapse in BFM-MR with 5-year RFS of 88.0% and 68.4% (p value .02). Five-year RFS of EOI-MRD negative and positive groups were 86.4% and 65.5%, respectively (p value .004). EOI-MRD is a powerful tool to predict relapse in children and adolescent with ALL especially in BFM-MR. Application of MRD in HR patients needs to be redefined in conjunction with other variables.

Recent progress in pediatric lymphoblastic leukemia

The probability of long-term survival for children with lymphoblastic leukemia has improved dramatically over recent decades, mainly owing to advances in genomic analysis techniques, which have improved our understanding of the nature of leukemic cells and prognostic prediction based on the evaluation of precise treatment response. Risk-adjusted chemotherapy based on these advances has simultaneously reduced relapse rates and minimized complications. In addition, recent genomic analyses have deepened our understanding of the pathogenesis of leukemia and revealed the involvement of germline variations in the clinical course of leukemia treatment. Additionally, advances in minimal residual disease assays and the introduction of immunotherapy are expected to further improve therapeutic analyses. Further advances in clinical and translational research are anticipated to improve survival to 100% in a healthy state.

A Review of CAR-T Therapy in Pediatric and Young Adult B-Lineage Acute Leukemia: Clinical Perspectives in Singapore

Approximately 10-15% of pediatric B-cell acute lymphoblastic leukemia (B-ALL) are high risk at diagnosis or relapsed/ refractory. Prior to the availability of chimeric antigen receptor T-cell (CAR-T) in Singapore and the region, the treatment options for these paediatric and young adults are conventional salvage chemotherapy or chemo-immunotherapy regimens as a bridge to allogeneic total body irradiation-based hematopoietic stem cell transplantation (allo-HSCT). This results in significant acute and long-term toxicities, with suboptimal survival outcomes. Finding a curative salvage therapy with fewer long-term toxicities would translate to improved quality-adjusted life years in these children and young adults. In this review, we focus on the burden of relapsed/refractory pediatric B-ALL, the limitations of current strategies, the emerging paradigms for the role of CAR-T in r/r B-ALL, our local perspectives on the health economics and future direction of CAR-T therapies in pediatric patients.

Accounting for treatment during the development or validation of prediction models

Clinical prediction models are widely used to predict adverse outcomes in patients, and are often employed to guide clinical decision-making. Clinical data typically consist of patients who received different treatments. Many prediction modeling studies fail to account for differences in patient treatment appropriately, which results in the development of prediction models that show poor accuracy and generalizability. In this paper, we list the most common methods used to handle patient treatments and discuss certain caveats associated with each method. We believe that proper handling of differences in patient treatment is crucial for the development of accurate and generalizable models. As different treatment strategies are employed for different diseases, the best approach to properly handle differences in patient treatment is specific to each individual situation. We use the Ma-Spore acute lymphoblastic leukemia data set as a case study to demonstrate the complexities associated with differences in patient treatment, and offer suggestions on incorporating treatment information during evaluation of prediction models. In clinical data, patients are typically treated on a case by case basis, with unique cases occurring more frequently than expected. Hence, there are many subtleties to consider during the analysis and evaluation of clinical prediction models.

Sequential Approach to Improve the Molecular Classification of Childhood Acute Lymphoblastic Leukemia

Identification of specific leukemia subtypes is a key to successful risk-directed therapy in childhood acute lymphoblastic leukemia (ALL). Although RNA sequencing (RNA-seq) is the best approach to identify virtually all specific leukemia subtypes, the routine use of this method is too costly for patients in resource-limited countries. This study enrolled 295 patients with pediatric ALL from 2010 to 2020. Routine screening could identify major cytogenetic alterations in approximately 69% of B-cell ALL (B-ALL) cases by RT-PCR, DNA index, and multiplex ligation-dependent probe amplification. STIL-TAL1 was present in 33% of T-cell ALL (T-ALL) cases. The remaining samples were submitted for RNA-seq. More than 96% of B-ALL cases and 74% of T-ALL cases could be identified based on the current molecular classification using this sequential approach. Patients with Philadelphia chromosome-like ALL constituted only 2.4% of the entire cohort, a rate even lower than those with ZNF384-rearranged (4.8%), DUX4-rearranged (6%), and Philadelphia chromosome-positive (4.4%) ALL. Patients with ETV6-RUNX1, high hyperdiploidy, PAX5 alteration, and DUX4 rearrangement had favorable prognosis, whereas those with hypodiploid and KMT2A and MEF2D rearrangement ALL had unfavorable outcomes. With the use of multiplex ligation-dependent probe amplification, DNA index, and RT-PCR in B-ALL and RT-PCR in T-ALL followed by RNA-seq, childhood ALL can be better classified to improve clinical assessments.

Go with the Flow—Early Assessment of Measurable Residual Disease in Children with Acute Lymphoblastic Leukemia Treated According to ALL IC-BFM2009

Simple Summary

Monitoring of residual disease is a very important aspect of modern treatment approaches in many types of cancer. In acute leukemias in both children and adults, molecular and cytometric methods are used to assess the burden of leukemia at different points during therapy. Residual disease measured at the end of induction was shown to be the strongest predictor of outcome. Analyzing the outcomes of children with acute lymphoblastic leukemia (ALL), we aimed to establish the most informative cut-off and time point of assessment. Applying only the measurement of residual disease by flow cytometry along with genotypic findings, we managed to identify patients with a poor prognosis. Although new precise, molecular techniques as the next generation sequencing strategy are approaching daily clinical practice, flow cytometry is still a reliable, standardized method of residual disease detection. We may say ‘go with the flow’; thus, the assessment of residual disease by multiparametric flow cytometry is a proper method for the management of ALL patients according to risk-adapted therapies.

Abstract

Measurable residual disease (MRD) is a well-known tool for the evaluation of the early response to treatment in patients with acute lymphoblastic leukemia (ALL). In respect to predicting the relapse the most informative cut-off and time point of MRD measurement during therapy were evaluated in our study. Between 1 January 2013 and 31 December 2019, multiparametric flow cytometry (MFC) MRD was measured in the bone marrow of 140 children with ALL treated according to the ALL IC-BFM2009 protocol. The MRD cut-off of 0.1% and day 33, end of induction, were the most discriminatory for all patients. Patients with negative MRD on day 15 and 33 had a higher 5-year overall survival—OS (100%) and a higher relapse-free survival—RFS rate (97.6%) than those with positive levels of MRD (≥0.01%) at both time points (77.8% and 55.6%, p = 0.002 and 0.001, respectively). Most patients with residual disease below 0.1% on day 15 exhibit hyperdiploidy or ETV6-RUNX1 in ALL cells. Measurement of MRD at early time points can be used with simplified genetic analysis to better identify low and high-risk patients, allowing personalized therapies and further improvement in outcomes in pediatric ALL.

Reduced Dose Intensity of Daunorubicin During Remission Induction for Low-Risk Patients With Acute Lymphoblastic Leukemia: A Retrospective Cohort Study of the Chinese Children’s Cancer Group

It is urgently necessary to reduce the adverse effects of chemotherapy while maintaining their cure high rates for children with acute lymphoblastic leukemia (ALL). The present study aimed to determine whether the dose intensity of daunorubicin during the remission-induction phase could be reduced for low-risk patients with ALL. A total of 2396 eligible patients, who participated in CCCG-ALL-2015 study and were provisionally assigned to the low-risk group, were included and divided into single-dose group and double-dose group according to the dosage of daunorubicin during the remission-induction phase. For patients with ETV6-RUNX1 positive ALL or hyperdiploidy ALL, there were no significant differences in outcomes between the two groups. For other patients, the 5-year event-free survival rate was significantly better and the 5-year cumulative risk of any relapse was significantly lower in the double-dose group compared with the single-dose group. Both the 5-year overall survival rate and the risk of early deaths were not significantly different between the two groups. Our results suggested that only B-lineage ALL patients with ETV6-RUNX1 positivity or hyperdiploidy who achieved an early negative minimal residual disease status were suitable candidates for dosage reduction of daunorubicin during the remission-induction phase.

Digital PCR for Minimal Residual Disease Quantitation Using Immunoglobulin/T-Cell Receptor Gene Rearrangements in Acute Lymphoblastic Leukemia: A Proposed Analytic Algorithm

In minimal residual disease (MRD), where there are exceedingly low target copy numbers, digital PCR (dPCR) can improve MRD quantitation. However, standards for dPCR MRD interpretation in acute lymphoblastic leukemia are lacking. Here, for immunoglobulin/T-cell receptor-based MRD, we propose an objective, statistics-based analytic algorithm. In 161 postinduction samples from 79 children with acute lymphoblastic leukemia, MRD was performed by dPCR and real-time quantitative PCR (qPCR) using the same markers and primer-probe sets. The dPCR raw data were analyzed by using an automated algorithm. dPCR and qPCR results were highly concordant (P < 0.0001): 98% (50 of 51) of qPCR positive were positive by dPCR, whereas 95% (61 of 64) of qPCR negative results were also negative by dPCR. For MRD quantitation, both qPCR and dPCR were tightly correlated (R² = 0.94). Using more DNA (1 μg × 7 versus 630 ng × 3), dPCR improved sensitivity of MRD quantitation by one log₁₀ (median MRD positive cutoff 1.6 × 10^-5). With dPCR, 83% (29 of 35) of positive-not-quantifiable results by qPCR could be assigned positive/negative MRD status. Seven replicates of tested samples and negative controls were optimal. Compared with qPCR, dPCR could improve MRD sensitivity by one log₁₀. We proposed an automatable, statistics-based algorithm that minimized interoperator variance for dPCR MRD.

Risk-adapted modulation through de-intensification of cancer treatments: an ESMO classification

BACKGROUND

The landscape of clinical trials testing risk-adapted modulations of cancer treatments is complex. Multiple trial designs, endpoints, and thresholds for non-inferiority have been used; however, no consensus or convention has ever been agreed to categorise biomarkers useful to inform the treatment intensity modulation of cancer treatments.

METHODS

An expert subgroup under the European Society for Medical Oncology (ESMO) Precision Medicine Working Group shaped an international collaborative project to develop a classification system for biomarkers used in the cancer treatment de-intensification, based on a tiered approach. A group of disease-oriented clinical, translational, methodology and public health experts, and patients' representatives provided an analysis of the status quo, and scanned the horizon of ongoing clinical trials. The classification was developed through multiple rounds of expert revisions and inputs.

RESULTS

The working group agreed on a univocal definition of treatment de-intensification. Evidence of reduction in the dose-density, intensity, or cumulative dose, including intermittent schedules or shorter treatment duration or deletion of segment(s) of the standard regimens, compound(s), or treatment modality must be demonstrated, to define a treatment de-intensification. De-intensified regimens must also portend a positive impact on toxicity, quality of life, health system burden, or financial toxicity. ESMO classification categorises the biomarkers for treatment modulation in three tiers, based on the level of evidence. Tier A includes biomarkers validated in prospective, randomised, non-inferiority clinical trials. The working group agreed that in non-inferiority clinical trials, boundaries are highly dependent upon the disease scenario and endpoint being studied and that the absolute differences in the outcomes are the most relevant measures, rather than relative differences. Biomarkers tested in single-arm studies with a threshold of non-inferiority are classified as Tier B. Tier C is when the validation occurs in prospective-retrospective quality cohort investigations.

CONCLUSIONS

ESMO classification for the risk-guided intensity modulation of cancer treatments provides a set of evidence-based criteria to categorise biomarkers deemed to inform de-intensification of cancer treatments, in risk-defined patients. The classification aims at harmonising definitions on this matter, therefore offering a common language for all the relevant stakeholders, including clinicians, patients, decision-makers, and for clinical trials.

JACLS ALL-02 SR protocol reduced-intensity chemotherapy produces excellent outcomes in patients with low-risk childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. As overall cure rates of childhood ALL have improved, reduction of overall treatment intensity while still ensuring excellent outcomes is imperative for low-risk patients. We report the outcomes of patients treated following the standard-risk protocol from the prospective Japan Association of Childhood Leukemia Study (JACLS) ALL-02 study, which was conducted between 2002 and 2008 for patients with newly diagnosed ALL aged 1-18 years. Of 1138 patients with B-cell precursor ALL, 388 (34.1%) were allocated to this protocol. Excellent outcomes were achieved despite the overall treatment intensity being lower than that of most contemporary protocols: 4 years event-free survival (EFS) was 92.3% and 4 years overall survival 98.2%. Patients with high hyperdiploidy (HHD) involving triple trisomy (trisomy of chromosomes 4, 10, and 17) or ETV6-RUNX1 had even better outcomes (4 years EFS 97.6% and 100%, respectively). Unique characteristics of this protocol include a selection of low-risk patients with a low initial WBC count and good early treatment response and reduction of cumulative doses of chemotherapeutic agents while maintaining dose density. In Japan, we are currently investigating the feasibility of this protocol while incorporating minimal residual disease into the patient stratification strategy.

Association of Genetic Ancestry With the Molecular Subtypes and Prognosis of Childhood Acute Lymphoblastic Leukemia

IMPORTANCE

Racial and ethnic disparities persist in the incidence and treatment outcomes of childhood acute lymphoblastic leukemia (ALL). However, there is a paucity of data describing the genetic basis of these disparities, especially in association with modern ALL molecular taxonomy and in the context of contemporary treatment regimens.

OBJECTIVE

To evaluate the association of genetic ancestry with childhood ALL molecular subtypes and outcomes of modern ALL therapy.

DESIGN, SETTING, AND PARTICIPANTS

This multinational, multicenter genetic association study was conducted from March 1, 2000, to November 20, 2020, among 2428 children and adolescents with ALL enrolled in frontline trials from the United States, South East Asia (Singapore and Malaysia), and Latin America (Guatemala), representing diverse populations of European, African, Native American, East Asian, and South Asian descent. Statistical analysis was conducted from February 3, 2020, to April 19, 2021.

MAIN OUTCOMES AND MEASURES

Molecular subtypes of ALL and genetic ancestry were comprehensively characterized by performing RNA sequencing. Associations of genetic ancestries with ALL molecular subtypes and treatment outcomes were then evaluated.

RESULTS

Among the participants in the study, 1340 of 2318 (57.8%) were male, and the mean (SD) age was 7.8 (5.3) years. Of 21 ALL subtypes identified, 8 were associated with ancestry. East Asian ancestry was positively associated with the frequency of somatic DUX4 (odds ratio [OR], 1.30 [95% CI, 1.16-1.45]; P < .001) and ZNF384 (OR, 1.40 [95% CI, 1.18-1.66]; P < .001) gene rearrangements and negatively associated with BCR-ABL1-like ALL (OR, 0.79 [95% CI, 0.66-0.92]; P = .002) and T-cell ALL (OR, 0.80 [95% CI, 0.71-0.90]; P < .001). By contrast, occurrence of CRLF2 rearrangements was associated with Native American ancestry (OR, 1.48 [95% CI, 1.29-1.69]; P < .001). When the percentage of Native American ancestry increased, ETV6-RUNX1 fusion became less frequent (OR, 0.80 [95% CI, 0.70-0.91]; P < .001), with the opposite trend observed for ETV6-RUNX1-like ALL. There was a marked preponderance of T-cell ALL in children of African descent compared with those with a high percentage of Native American ancestry (African: OR, 1.22 [95% CI, 1.07-1.37]; P = .003; Native American: OR, 0.53 [95% CI, 0.40-0.67]; P < .001). African ancestry was also positively associated with the prevalence of TCF3-PBX1 (OR, 1.49 [95% CI, 1.25-1.76]; P < .001) and negatively associated with DUX4 rearrangements (OR, 0.70 [95% CI, 0.48-0.93]; P = .01) and hyperdiploidy (OR, 0.77 [95% CI, 0.68-0.86]; P < .001). African and Native American ancestries as continuous variables were both associated with poorer event-free survival (for every 25% increase in ancestry: hazard ratio [HR], 1.2; 95% CI, 1.1-1.4; P = .001 for African ancestry; HR, 1.3; 95% CI, 1.0-1.6; P = .04 for Native American ancestry) and overall survival (for every 25% increase in ancestry: HR, 1.2; 95% CI, 1.1-1.5; P = .01 for African ancestry; HR, 1.4; 95% CI, 1.0-1.8; P = .03 for Native American ancestry). Even after adjusting for biological subtypes and clinical features, Native American and African ancestries remained associated with poor prognosis.

CONCLUSIONS AND RELEVANCE

This study suggests that ALL molecular subtypes and prognosis are associated with genetic ancestry, potentially pointing to a genetic basis for some of the racial and ethnic disparities in ALL. Therefore, molecular subtype-driven treatment individualization is needed to help address racial and ethnic gaps in outcomes.

High-throughput sequencing of peripheral blood for minimal residual disease monitoring in childhood precursor B-cell acute lymphoblastic leukemia: A prospective feasibility study

BACKGROUND

Minimal residual disease (MRD) measured on end-of-induction bone marrow (BM) is the most important biomarker for guiding therapy in pediatric acute lymphoblastic leukemia (ALL). Due to limited sensitivity of current approaches, peripheral blood (PB) is not a reliable source for identifying patients needing treatment changes. We sought to determine if high-throughput sequencing (HTS) (next-generation sequencing) of rearranged immunoglobulin and T-cell receptor genes can overcome this and be used to measure MRD in PB.

PROCEDURE

We employed a quantitative HTS approach to accurately measure MRD from one million cell equivalents of DNA from 17 PB samples collected at day 29 after induction therapy in patients with precursor B-cell ALL. We compared these results to the gold-standard real-time PCR result obtained from their paired BM samples, median follow-up 49 months.

RESULTS

With the increased sensitivity, detecting up to one abnormal cell in a million normal cells, we were able to detect MRD in the PB by HTS in all those patients requiring treatment intensification (MRD ≥ 0.005% in BM).

CONCLUSION

This is proof of principle that using the increased sensitivity of HTS, PB can be used to measure MRD and stratify children with ALL. The method is cost effective, rapid, accurate, and reproducible, with inherent advantages in children. Importantly, increasing the frequency testing by PB as opposed to intermittent BM sampling may allow extension of the dynamic range of MRD, giving a more complete picture of the kinetics of disease remission while improving relapse prediction and speed of detection.

Assessment of Minimal Residual Disease in Childhood Acute Lymphoblastic Leukemia: A Multicenter Study From Turkey

Assestment of minimal residual disease (MRD) in childhood acute lymphoblastic leukemia (ALL) is of utmost importance both for risk classification and tailoring of the therapy. The data of pediatric ALL patients that received treatment with Berlin-Frankfurt-Münster (BFM) protocols were retrospectively collected from 5 university hospitals in Turkey. Of the 1388 patients enrolled in the study 390 were treated according to MRD-based protocols. MRD assestment was with real time quantitative polymerase chain reaction (qPCR) in 283 patients and with multiparametric flow cytometry (MFC)-MRD in 107 patients. MRD monitoring had upstaged a total of 8 patients (2%) from intermediate risk group to high-risk group. Univariate analysis revealed age 10 years or above, prednisone poor response, PCR-MRD ≥10-3 on day 33 and on day 78 as poor prognostic factors affecting event-free survival (EFS). Detection of >10% blasts on day 15 with MFC (MFC-high-risk group) was not shown to affect EFS and/or overall survival (log-rank P=0.339). Multiple logistic regression analysis revealed PCR-MRD ≥10-3 on day 78 as the only poor prognostic factor affecting EFS (odds ratio: 8.03; 95% confidence interval: 2.5-25; P=0.000). It is very important to establish the infrastructure and ensure necessary standardization for both MRD methods for optimal management of children with ALL.

Life-threatening infections during treatment for acute lymphoblastic leukemia on the Malaysia-Singapore 2003 and 2010 clinical trials: A risk prediction model

AIM

Life-threatening infections significantly impact the care of children undergoing therapy for acute lymphoblastic leukemia (ALL) who are at risk of severe sepsis due to both host and treatment factors. Our aim was to develop a life-threatening infection risk prediction model that would allow remote rapid triage of patients to reduce time to first dose of antibiotics and sepsis-related mortality.

METHODS

A retrospective analysis of 2068 fever episodes during ALL therapy was used for model building and subsequent internal validation.

RESULTS

Three hundred and seventy-seven patients were treated for ALL in two institutions with comparable critical and supportive care resources. A total of 55 patients accounted for 71 admissions to the critical care unit for sepsis that led to eight septic deaths during a 16-year study period. A retrospective analysis of risk factors for sepsis enabled us to build a model focused on 13 variables that discriminated admissions requiring critical care well: area under the receiver operating characteristic curve of .82; 95% CI .76-.87, p<.001, and Brier score of .033. Significant univariate predictors included neutropenia, presence of symptoms of abdominal pain, diarrhea, fever during induction or steroid-based phases, and the lack of any localizing source of infection at time of presentation.

CONCLUSION

We have developed a risk prediction model that can reliably identify ALL patients undergoing treatment who are at a higher risk of life-threatening sepsis. Clinical applicability can potentially be extended to low-middle income settings, and its utility should be further studied in real-world settings.

Distinct clinical characteristics of DUX4- and PAX5-altered childhood B-lymphoblastic leukemia

Despite poor end-of-induction MRD, DUX4 B-ALL has excellent outcome.

PAX5alt B-ALL with IKZF1 codeletion is associated with poor outcome, which can be improved by treatment intensification.

Among the recently described subtypes in childhood B-lymphoblastic leukemia (B-ALL) were DUX4- and PAX5-altered (PAX5alt). By using whole transcriptome RNA sequencing in 377 children with B-ALL from the Malaysia-Singapore ALL 2003 (MS2003) and Malaysia-Singapore ALL 2010 (MS2010) studies, we found that, after hyperdiploid and ETV6-RUNX1, the third and fourth most common subtypes were DUX4 (n = 51; 14%) and PAX5alt (n = 36; 10%). DUX4 also formed the largest genetic subtype among patients with poor day-33 minimal residual disease (MRD; n = 12 of 44). But despite the poor MRD, outcome of DUX4 B-ALL was excellent (5-year cumulative risk of relapse [CIR], 8.9%; 95% confidence interval [CI], 2.8%-19.5% and 5-year overall survival, 97.8%; 95% CI, 85.3%-99.7%). In MS2003, 21% of patients with DUX4 B-ALL had poor peripheral blood response to prednisolone at day 8, higher than other subtypes (8%; P = .03). In MS2010, with vincristine at day 1, no day-8 poor peripheral blood response was observed in the DUX4 subtype (P = .03). The PAX5alt group had an intermediate risk of relapse (5-year CIR, 18.1%) but when IKZF1 was not deleted, outcome was excellent with no relapse among 23 patients. Compared with MS2003, outcome of PAX5alt B-ALL with IKZF1 codeletion was improved by treatment intensification in MS2010 (5-year CIR, 80.0% vs 0%; P = .05). In conclusion, despite its poor initial response, DUX4 B-ALL had a favorable overall outcome, and the prognosis of PAX5alt was strongly dependent on IKZF1 codeletion.

Curing the Curable: Managing Low-Risk Acute Lymphoblastic Leukemia in Resource Limited Countries

Although childhood acute lymphoblastic leukemia (ALL) is curable, global disparities in treatment outcomes remain. To reduce these global disparities in low-middle income countries (LMIC), a paradigm shift is needed: start with curing low-risk ALL. Low-risk ALL, which accounts for >50% of patients, can be cured with low-toxicity therapies already defined by collaborative studies. We reviewed the components of these low-toxicity regimens in recent clinical trials for low-risk ALL and suggest how they can be adopted in LMIC. In treating childhood ALL, the key is risk stratification, which can be resource stratified. NCI standard-risk criteria (age 1–10 years, WBC < 50,000/uL) is simple yet highly effective. Other favorable features such as ETV6-RUNX1, hyperdiploidy, early peripheral blood and bone marrow responses, and simplified flow MRD at the end of induction can be added depending on resources. With limited supportive care in LMIC, more critical than relapse is treatment-related morbidity and mortality. Less intensive induction allows early marrow recovery, reducing the need for intensive supportive care. Other key elements in low-toxicity protocol designs include: induction steroid type; high-dose versus low-dose escalating methotrexate; judicious use of anthracyclines; and steroid pulses during maintenance. In summary, the first effective step in curing ALL in LMIC is to focus on curing low-risk ALL with less intensive therapy and less toxicity.

Treatment of children with acute lymphoblastic leukemia in Cambodia

We report a retrospective analysis of 110 unselected pediatric patients with acute lymphoblastic leukemia (ALL) treated during 2015-2017 in a charity-funded public institution in Cambodia with a reduced intensity ALL-Moscow Berlin (MB)-91 protocol. No patient abandoned treatment. Sixty-three patients (57%) were high risk (HR). Seventy-two patients (65.5%) reached complete remission (CR) on day 36. The 3-year event-free survival (EFS) and overall survival (OS) was 34.9% (50.5% for standard risk [SR]). Most deaths resulted from infections (40 [53.3%]) and bleeding (15 [20%]). With further selective reduction of treatment intensity and access to platelet infusion, leukemia therapy is justified in this setting.

Genetic Alterations in Childhood Acute Lymphoblastic Leukemia: Interactions with Clinical Features and Treatment Response

Acute lymphoblastic leukemia (ALL) is the most common cancer among children. This aggressive cancer comprises multiple molecular subtypes, each harboring a distinct constellation of somatic, and to a lesser extent, inherited genetic alterations. With recent advances in genomic analyses such as next-generation sequencing techniques, we can now clearly identify >20 different genetic subtypes in ALL. Clinically, identifying these genetic subtypes will better refine risk stratification and determine the optimal intensity of therapy for each patient. Underpinning each genetic subtype are unique clinical and therapeutic characteristics, such as age and presenting white blood cell (WBC) count. More importantly, within each genetic subtype, there is much less variability in treatment response and survival outcomes compared with current risk factors such as National Cancer Institute (NCI) criteria. We review how this new taxonomy of genetic subtypes in childhood ALL interacts with clinical risk factors used widely, i.e., age, presenting WBC, IKZF1del, treatment response, and outcomes.

Toward the Cure of Acute Lymphoblastic Leukemia in Children in China

This study explored results of therapy of children with acute lymphoblastic leukemia (ALL) in China, recent progress, and challenges. Included are a survey of therapy outcomes of ALL in Chinese children nationwide, comparison of these data with global ALL therapy outcomes, analyses of obstacles to improving outcomes, and suggestions of how progress can be achieved. Therapy outcomes at many Chinese pediatric cancer centers are approaching those of resource-rich countries. However, nationwide outcomes still need improvement. Obstacles include suboptimal clinical trials participation, children without adequate health care funding, human resource shortages, especially physicians expert in pediatric hematology and oncology, and social-economic disparities. We suggest how these obstacles have been and continue to be remedied including expanded access to protocol-based therapy, improved supportive care, health care reforms, recruitment of trained personnel, and international collaborations. China has made substantial progress treating children with ALL. We envision even better outcomes in the near future.

Practical Considerations for Using RNA Sequencing in Management of B-Cell Acute Lymphoblastic Leukemia: Malaysia-Singapore Acute Lymphoblastic Leukemia-Sequencing 2020 Implementation Strategy

Despite the immense genetic heterogeneity of B-cell acute lymphoblastic leukemia (ALL), RNA sequencing (RNA-Seq) could comprehensively interrogate its genetic drivers, assigning a specific molecular subtype in >90% of patients. However, study groups have only started to use RNA-Seq. For broader clinical use, technical, quality control, and appropriate performance validation are needed. We describe the development and validation of an RNA-Seq workflow for subtype classification, TPMT/NUDT15/TP53 variant discovery, and IGH disease clone identification for Malaysia-Singapore ALL sequencing (ALL-Seq) 2020. We validated this workflow in 377 patients in our preceding Malaysia-Singapore ALL-Seq 2003/Malaysia-Singapore ALL-Seq 2010 studies and proposed the quality control measures for RNA quality, library size, sequencing, and data analysis using the International Organization for Standardization 15189 quality and competence standard for medical laboratories. Compared with conventional methods, we achieved >95% accuracy in oncogene fusion identification, digital karyotyping, and TPMT and NUDT15 variant discovery. We found seven pathogenic TP53 mutations, confirmed with Sanger sequencing, which conferred a poorer outcome. Applying this workflow prospectively to the first 21 patients in Malaysia-Singapore ALL-Seq 2020, we identified the genetic drivers and IGH disease clones in >90% of patients with concordant TPMT, NUDT15, and TP53 variants using PCR-based methods. The median turnaround time was 12 days, which was clinically actionable. In conclusion, RNA-Seq workflow could be used clinically in management of B-cell ALL patients.

Genomic Analyses of Pediatric Acute Lymphoblastic Leukemia Ph+ and Ph-Like-Recent Progress in Treatment

Pediatric acute lymphoblastic leukemia (ALL) with t(9;22)(q34;q11.2) is a very rare malignancy in children. Approximately 3-5% of pediatric ALL patients present with the Philadelphia chromosome. Previously, children with Ph+ had a poor prognosis, and were considered for allogeneic stem cell transplantation (allo-HSCT) in their first remission (CR1). Over the last few years, the treatment of childhood ALL has significantly improved due to standardized research protocols. Hematopoietic stem cell transplantation (HSCT) has been the gold standard therapy in ALL Ph+ patients, but recently first-generation tyrosine kinase inhibitor (TKI)-imatinib became a major milestone in increasing overall survival. Genomic analyses give the opportunity for the investigation of new fusions or mutations, which can be used to establish effective targeted therapies. Alterations of the IKZF1 gene are present in a large proportion of pediatric and adult ALL Ph+ cases. IKZF1 deletions are present in ~15% of patients without BCR-ABL1 rearrangements. In BCR-ABL1-negative cases, IKZF1 deletions have been shown to have an independent prognostic impact, carrying a three-fold increased risk of treatment failure. The prognostic significance of IKZF1 gene aberrations in pediatric ALL Ph+ is still under investigation. More research should focus on targeted therapies and immunotherapy, which is not associated with serious toxicity in the same way as classic chemotherapy, and on the improvement of patient outcomes. In this review, we provide a molecular analysis of childhood ALL with t(9;22)(q34;q11.2), including the Ph-like subtype, and of treatment strategies.

Testicular involvement of acute lymphoblastic leukemia in children and adolescents: Diagnosis, biology, and management

Acute lymphoblastic leukemia (ALL) in children and adolescents can involve the testes at diagnosis or upon relapse. The testes were long considered pharmacologic sanctuary sites, presumably because of the blood-testis barrier, which prevents the entry of large-molecular-weight compounds into the seminiferous tubule. Patients with testicular involvement were historically treated with testicular irradiation or orchiectomy. With the advent of contemporary intensive chemotherapy, including high-dose methotrexate, vincristine/glucocorticoid pulses, and cyclophosphamide, testicular leukemia present at diagnosis can be eradicated, with the risk of testicular relapse being 2% or lower. However, the management of testicular leukemia is not well described in the recent literature and remains relevant in low- and middle-income countries where testicular relapse is still experienced. Chemotherapy can effectively treat late, isolated testicular B-cell ALL relapses without the need for irradiation or orchiectomy in patients with an early response and thereby preserve testicular function. For refractory or early-relapse testicular leukemia, newer treatment approaches such as chimeric antigen receptor-modified T (CAR-T) cell therapy are under investigation. The control of testicular relapse with CAR-T cells and their penetration of the blood-testis barrier have been reported. The outcome of pediatric ALL has been improved remarkably by controlling the disease in the bone marrow, central nervous system, and testes, and such success should be extended globally. LAY SUMMARY: Acute lymphoblastic leukemia (ALL) in children and adolescents can involve the testes at diagnosis or upon relapse. Modern intensive chemotherapy has largely eradicated testicular relapse in high-income countries. Consequently, most current clinicians are not familiar with how to manage it if it does occur, and testicular relapse continues to be a significant problem in low- and middle-income countries that have not had access to modern intensive chemotherapy. The authors review the historical progress made in eradicating testicular ALL and use the lessons learned to make recommendations for treatment.

Reduced-intensity therapy for pediatric lymphoblastic leukemia: impact of residual disease early in remission induction

Legacy data show that ∼40% of children with acute lymphoblastic leukemia (ALL) were cured with limited antimetabolite-based chemotherapy regimens. However, identifying patients with very-low-risk (VLR) ALL remains imprecise. Patients selected based on a combination of presenting features and a minimal residual disease (MRD) level <0.01% on day 19 of induction therapy had excellent outcomes with low-intensity treatment. We investigated the impact of MRD levels between 0.001% and <0.01% early in remission induction on the outcome of VLR ALL treated with a low-intensity regimen. Between October of 2011 and September of 2015, 200 consecutive patients with B-precursor ALL with favorable clinicopathologic features and MRD levels <0.01%, as assessed by flow cytometry in the bone marrow on day 19 and at the end of induction therapy, received reduced-intensity therapy. The 5-year event-free survival was 89.5% (± 2.2% standard error [SE]), and the overall survival was 95.5% (± 1.5% SE). The 5-year cumulative incidence of relapse (CIR) was 7% (95% confidence interval, 4-11%). MRD levels were between 0.001% and <0.01% on day 19 in 29 patients. These patients had a 5-year CIR that was significantly higher than that of patients with undetectable residual leukemia (17.2% ± 7.2% vs 5.3% ± 1.7%, respectively; P = .02). Our study shows that children with VLR ALL can be treated successfully with decreased-intensity therapy, and it suggests that the classification criteria for VLR can be further refined by using a more sensitive MRD assay.

Prognostic impact of minimal residual disease at the end of consolidation in NCI standard-risk B-lymphoblastic leukemia: A report from the Children's Oncology Group

The 5-year disease-free survival (DFS) of National Cancer Institute (NCI) high-risk (HR) B-lymphoblastic leukemia (B-ALL) patients with end of induction (EOI) minimal residual disease (MRD) ≥0.1% and end of consolidation (EOC) MRD ≥0.01% is 39 ± 7%, warranting consideration of hematopoietic stem cell transplant (HSCT). However, the impact of EOC MRD in NCI standard-risk (SR) B-ALL patients using COG regimens is unknown. We found that SR patients with MRD ≥0.01% at both EOI and EOC have a 4-year DFS/overall survival (OS) of 72.9 ± 19.0%/91.7 ± 10.8% versus 90.7 ± 2.9%/95.5 ± 2.0% (p = .0019/.25) for those with EOI MRD ≥0.01% and EOC MRD <0.01%. These data suggest that routine use of HSCT may not be warranted in EOC MRD ≥0.01% SR patients.

Validation of a PCR-Based Next-Generation Sequencing Approach for the Detection and Quantification of Minimal Residual Disease in Acute Lymphoblastic Leukemia and Multiple Myeloma Using gBlocks as Calibrators

Detection of minimal residual disease (MRD) to guide therapy has been a standard practice in treatment of childhood acute lymphoblastic leukemia (ALL) for decades. In multiple myeloma (MM), a clear correlation is found between absence of MRD and longer survival. Quantitative allele-specific oligonucleotide (qASO)-PCR is the standard molecular method for MRD detection in these hematologic malignant tumors. However, this technique has some drawbacks that can be overcome by next-generation sequencing (NGS). In this study, NGS is validated as an alternative method for qASO-PCR for MRD detection in both ALL and MM. MRD results obtained by NGS and qASO-PCR were compared in 59 and 39 bone marrow samples of 33 and 14 patients with ALL and MM, respectively. Our results indicate that the use of gBlocks as calibrators makes the NGS approach a powerful tool to quantify MRD. With an input of 400 ng of DNA (corresponding to approximately 7 × 10⁴ cells), a limit of detection of 0.01% can be achieved. The specificity of the NGS-MRD technique was 100%, and a correlation with qASO-PCR for quantifiable MRD results of 0.93 and 0.91 was found in ALL and MM, respectively. Especially for MM, the higher applicability (100%) of the NGS-MRD protocol, compared with qASO-PCR (57%), was clearly demonstrated. These results demonstrate that NGS is an even better alternative to qASO-PCR.

Re-Emergence of Minimal Residual Disease Detected by Flow Cytometry Predicts an Adverse Outcome in Pediatric Acute Lymphoblastic Leukemia

Purpose

While the role of minimal residual disease (MRD) assessment and the significance of achieving an MRD-negative status during treatment have been evaluated in previous studies, there is limited evidence on the significance of MRD re-emergence without morphological relapse in acute lymphoblastic leukemia (ALL). We sought to determine the clinical significance of MRD re-emergence in pediatric ALL patients.

Methods

Between 2005 and 2017, this study recruited 1126 consecutive patients newly diagnosed with ALL. Flow cytometry was performed to monitor MRD occurrence during treatment.

Results

Of 1030 patients with MRD-negative results, 150 (14.6%) showed MRD re-emergence while still on morphological complete remission (CR). Patients with white blood cell counts of ≥50 × 10⁹/L (p = 0.033) and MRD levels of ≥0.1% on day 33 (p = 0.012) tended to experience MRD re-emergence. The median re-emergent MRD level was 0.12% (range, 0.01–10.00%), and the median time to MRD re-emergence was 11 months (range, <1–52 months). Eighty-five (56.6%) patients subsequently developed relapse after a median of 4.1 months from detection of MRD re-emergence. The median re-emergent MRD level was significantly higher in the relapsed cohort than in the cohort with persistent CR (1.05% vs. 0.48%, p = 0.005). Of the 150 patients, 113 continued to receive chemotherapy and 37 underwent transplantation. The transplantation group demonstrated a significantly higher 2-year overall survival (88.7 ± 5.3% vs. 46.3 ± 4.8%, p < 0.001) and cumulative incidence of relapse (23.3 ± 7.4% vs. 64.0 ± 4.6%, p < 0.001) than the chemotherapy group.

Conclusions

MRD re-emergence during treatment was associated with an adverse outcome in pediatric ALL patients. Transplantation could result in a significant survival advantage for these patients.

Molecular basis of ETV6-mediated predisposition to childhood acute lymphoblastic leukemia

There is growing evidence supporting an inherited basis for susceptibility to acute lymphoblastic leukemia (ALL) in children. In particular, we and others reported recurrent germline ETV6 variants linked to ALL risk, which collectively represent a novel leukemia predisposition syndrome. To understand the influence of ETV6 variation on ALL pathogenesis, we comprehensively characterized a cohort of 32 childhood leukemia cases arising from this rare syndrome. Of 34 nonsynonymous germline ETV6 variants in ALL, we identified 22 variants with impaired transcription repressor activity, loss of DNA binding, and altered nuclear localization. Missense variants retained dimerization with wild-type ETV6 with potentially dominant-negative effects. Whole-transcriptome and whole-genome sequencing of this cohort of leukemia cases revealed a profound influence of germline ETV6 variants on leukemia transcriptional landscape, with distinct ALL subsets invoking unique patterns of somatic cooperating mutations. 70% of ALL cases with damaging germline ETV6 variants exhibited hyperdiploid karyotype with characteristic recurrent mutations in NRAS, KRAS, and PTPN11. In contrast, the remaining 30% cases had a diploid leukemia genome and an exceedingly high frequency of somatic copy-number loss of PAX5 and ETV6, with a gene expression pattern that strikingly mirrored that of ALL with somatic ETV6-RUNX1 fusion. Two ETV6 germline variants gave rise to both acute myeloid leukemia and ALL, with lineage-specific genetic lesions in the leukemia genomes. ETV6 variants compromise its tumor suppressor activity in vitro with specific molecular targets identified by assay for transposase-accessible chromatin sequencing profiling. ETV6-mediated ALL predisposition exemplifies the intricate interactions between inherited and acquired genomic variations in leukemia pathogenesis.

Reduced intensity of early intensification does not increase the risk of relapse in children with standard risk acute lymphoblastic leukemia - a multi-centric clinical study of GD-2008-ALL protocol

Background

The prognosis of childhood acute lymphoblastic leukemia (ALL) is optimistic with a 5-year event-free survival (EFS) rate of 70–85%. However, the major causes of mortality are chemotherapy toxicity, infection and relapse. The Guangdong (GD)-2008-ALL collaborative protocol was carried out to study the effect of reduced intensity on treatment related mortality (TRM) based on Berlin-Frankfurt-Münster (BFM) 2002 backbone treatment. The study was designed to elucidate whether the reduced intensity is effective and safe for children with ALL.

Methods

The clinical data were obtained from February 28, 2008 to June 30, 2016. A total of 1765 childhood ALL cases from 9 medical centers were collected and data were retrospectively analyzed. Patients were stratified into 3 groups according to bone marrow morphology, prednisone response, age, genotype, and karyotype information: standard risk (SR), intermediate risk (IR) and high risk (HR). For SR group, daunorubicin was decreased in induction IA while duration was reduced in Induction Ib (2 weeks in place of 4 weeks). Doses for CAM were same in all risk groups - SR patients received one CAM, others got two CAMs.

Results

The 5-year and 8-year overall survival (OS), event-free survival (EFS) and cumulative incidence of relapse (CIR) were 83.5±0.9% and 83.1±1.0%, 71.9±1.1% and 70.9±1.2%, and 19.5±1.0% and 20.5±1.1%, respectively. The 2-year treatment-related mortality (TRM) was 5.2±0.5%. The 5-year and 8-year OS were 90.7±1.4% and 89.6±1.6% in the SR group, while the 5-year and 8-year EFS were 81.5±1.8% and 80.0±2.0%. In the SR group, 74 (15.2%) patients measured minimal residual disease (MRD) on Day 15 and Day 33 of induction therapy. Among them, 7 patients (9.46%) were MRD positive (≥ 0.01%) on Day 33. The incidence of relapse in the MRD Day 33 positive group (n=7) was 28.6%, while in the MRD Day 33 negative group (n=67) was 7.5% (p=0.129).

Conclusions

The results of GD-2008-ALL protocol are outstanding for reducing TRM in childhood ALL in China with excellent long term EFS. This protocol provided the evidence for further reducing intensity of induction therapy in the SR group according to the risk stratification. MRD levels on Day 15 and Day 33 are appropriate indexes for stratification.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07752-x.

Emerging molecular subtypes and therapeutic targets in B-cell precursor acute lymphoblastic leukemia

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is characterized by genetic alterations with high heterogeneity. Precise subtypes with distinct genomic and/or gene expression patterns have been recently revealed using high-throughput sequencing technology. Most of these profiles are associated with recurrent non-overlapping rearrangements or hotspot point mutations that are analogous to the established subtypes, such as DUX4 rearrangements, MEF2D rearrangements, ZNF384/ZNF362 rearrangements, NUTM1 rearrangements, BCL2/MYC and/or BCL6 rearrangements, ETV6-RUNX1-like gene expression, PAX5alt (diverse PAX5 alterations, including rearrangements, intragenic amplifications, or mutations), and hotspot mutations PAX5 (p.Pro80Arg) with biallelic PAX5 alterations, IKZF1 (p.Asn159Tyr), and ZEB2 (p.His1038Arg). These molecular subtypes could be classified by gene expression patterns with RNA-seq technology. Refined molecular classification greatly improved the treatment strategy. Multiagent therapy regimens, including target inhibitors (e.g., imatinib), immunomodulators, monoclonal antibodies, and chimeric antigen receptor T-cell (CAR-T) therapy, are transforming the clinical practice from chemotherapy drugs to personalized medicine in the field of risk-directed disease management. We provide an update on our knowledge of emerging molecular subtypes and therapeutic targets in BCP-ALL.

Excellent Survival Outcomes of Pediatric Patients With Acute Myeloid Leukemia Treated With the MASPORE 2006 Protocol

PURPOSE

To determine the prognostic factors in pediatric patients with acute myeloid leukemia (AML) and to assess whether their outcomes have improved over time.

PATIENTS AND METHODS

Sixty-two patients with AML excluding acute promyelocytic leukemia were retrospectively analyzed. Patients in the earlier cohort (n = 36) were treated on the Medical Research Council (MRC) AML12 protocol, whereas those in the recent cohort (n = 26) were treated on the Malaysia-Singapore AML protocol (MASPORE 2006), which differed in terms of risk group stratification, cumulative anthracycline dose, and timing of hematopoietic stem-cell transplantation for high-risk patients.

RESULTS

Significant improvements in 10-year overall survival and event-free survival were observed in patients treated with the recent MASPORE 2006 protocol compared to the earlier MRC AML12 protocol (overall survival: 88.0% ± 6.5% vs 50.1% ± 8.6%, P = .002; event-free survival: 72.1% ± 9.0 vs 50.1% ± 8.6%, P = .045). In univariate analysis, patients in the recent cohort had significantly lower intensive care unit admission rate (11.5% vs 47.2%, P = .005) and numerically lower relapse rate (26.9% vs 50.0%, P = .068) compared to the earlier cohort. Multivariate analysis showed that treatment protocol was the only independent predictive factor for overall survival (hazard ratio = 0.21; 95% confidence interval, 0.06-0.73, P = .014).

CONCLUSION

Outcomes of pediatric AML patients have improved over time. The more recent MASPORE 2006 protocol led to significant improvement in long-term survival rates and reduction in intensive care unit admission rate.

The role of minimal residual disease in specific subtypes of pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a heterogeneous disease whose prognostic factors include minimal residual disease (MRD) and cytogenetic abnormalities. To explore the significance of MRD in ALL subtypes, we analyzed the outcomes of 1126 children treated with risk-stratified therapy based on sequential MRD monitoring. MRD distributions and treatment outcomes differed between distinct leukemia subtypes. Patients with ETV6-RUNX1 or hyperdiploidy had the best prognosis (5-year OS: 97 ± 1.5% and 89.2 ± 2.7%). However, hyperdiploidy patients with MRD ≥ 10% on day 15 had a higher risk of relapse (36.4%) than those with ETV6-RUNX1. TCF3-PBX1 patients had the fastest disease clearance (negative MRD rate on day 33: 92.1%), but the overall prognosis was intermediate (5-year OS: 82.5%). Patients with high-risk characteristics and ALL-T had inferior outcomes: even with undetectable MRD on day 33, cumulative incidence of relapse was 19.9% and 23.4%, respectively. Moreover, those with poor early-treatment response and detectable week-12 MRD had a worse prognosis. After adjusting for other risk factors, re-emergent MRD was the most significant adverse prognostic indicator overall. Sequential MRD measurement is important for MRD-guided therapy, and integration of MRD values at different timepoints based on leukemia subtype could allow for more refined risk stratification.

RAS-protein activation but not mutation status is an outcome predictor and unifying therapeutic target for high-risk acute lymphoblastic leukemia

Leukemias are routinely sub-typed for risk/outcome prediction and therapy choice using acquired mutations and chromosomal rearrangements. Down syndrome acute lymphoblastic leukemia (DS-ALL) is characterized by high frequency of CRLF2-rearrangements, JAK2-mutations, or RAS-pathway mutations. Intriguingly, JAK2 and RAS-mutations are mutually exclusive in leukemic sub-clones, causing dichotomy in therapeutic target choices. We prove in a cell model that elevated CRLF2 in combination with constitutionally active JAK2 is sufficient to activate wtRAS. On primary clinical DS-ALL samples, we show that wtRAS-activation is an obligatory consequence of mutated/hyperphosphorylated JAK2. We further prove that CRLF2-ligand TSLP boosts the direct binding of active PTPN11 to wtRAS, providing the molecular mechanism for the wtRAS activation. Pre-inhibition of RAS or PTPN11, but not of PI3K or JAK-signaling, prevented TSLP-induced RAS-GTP boost. Cytotoxicity assays on primary clinical DS-ALL samples demonstrated that, regardless of mutation status, high-risk leukemic cells could only be killed using RAS-inhibitor or PTPN11-inhibitor, but not PI3K/JAK-inhibitors, suggesting a unified treatment target for up to 80% of DS-ALL. Importantly, protein activities-based principal-component-analysis multivariate clusters analyzed for independent outcome prediction using Cox proportional-hazards model showed that protein-activity (but not mutation-status) was independently predictive of outcome, demanding a paradigm-shift in patient-stratification strategy for precision therapy in high-risk ALL.

Successful toxicity reduction during delayed intensification in the non-high-risk arm of Malaysia-Singapore Acute Lymphoblastic Leukaemia 2010 study

In non-high-risk (non-HR) patients, the Malaysia-Singapore Acute Lymphoblastic Leukaemia 2003 (MS2003) study achieved good outcomes. However, its delayed-intensification (DI) phase, comprising repeated blocks of protocol III (2003-PIII), was toxic and caused significant treatment delays. The successor MS2010 study attempted to lower DI toxicity by replacing myelosuppressive drugs (doxorubicin, cytarabine) with vincristine and asparaginase.

PATIENTS AND METHODS

We analysed 1748 admissions for fever in 315 Singapore children with non-HR acute lymphoblastic leukaemia (ALL) (MS2003, n = 183; MS2010, n = 132), comprising 76% of the total cohort (n = 413), to study the impact of these changes.

RESULTS

The new 2010-PVa which has no doxorubicin, was associated with significantly fewer hospitalisations due to fever (0.08 versus 0.30 admissions per block [A/blk], p < 0.001), as than 2003-PIIIa. Similarly in 2010-PIIIb and PVb, where one block of cytarabine was replaced by two doses of vincristine, admissions for fever were also fewer (0.47 versus 0.74 A/blk, p < 0.001) than in 2003-PIIIb. However, the addition of single doses of vincristine and asparaginase in 2010-PIIIa, even with a mandatory seven-day rest, led to more hospitalisations (0.45 A/blk, p < 0.001), increased risk of bacteraemia (relative-risk (RR) = 7.66, p = 0.005) and critical-care admissions (RR = 4.31, p = 0.13). Despite this, overall treatment-related mortality decreased from 2.7% to 0.8%. Taken together, the reduced phase delays allowed earlier completion of the intensive phase of treatment (standard risk: 38.1 versus 49.4 weeks, p < 0.001; intermediate risk: 50.9 versus 58.8 weeks, p < 0.001), while maintaining excellent 10-year event-free survival of 95.4% and overall survival of 96.2%.

CONCLUSIONS

In non-HR ALL, replacing doxorubicin/cytarabine with vincristine/asparaginase during some DI blocks is effective in reducing toxicity without compromising outcomes.

CLINICAL TRIAL INFORMATION

NCT0289464.

Results of two consecutive treatment protocols in Polish children with acute lymphoblastic leukemia

The aim of the study was to retrospectively compare the effectiveness of the ALL IC-BFM 2002 and ALL IC-BFM 2009 protocols and the distribution of risk groups by the two protocols after minimal residual disease (MRD) measurement as well as its impact on survival. We reviewed the medical records of 3248 patients aged 1-18 years with newly diagnosed ALL who were treated in 14 hemato-oncological centers between 2002 and 2018 in Poland. The overall survival (OS) of 1872 children with ALL treated with the ALL IC 2002 protocol was 84% after 3 years, whereas the OS of 1376 children with ALL treated with the ALL IC 2009 protocol was 87% (P < 0.001). The corresponding event-free survival rates were 82% and 84% (P = 0.006). Our study shows that the ALL IC-BFM 2009 protocol improved the results of children with ALL compared to the ALL IC-BFM 2002 protocol in Poland. This analysis confirms that MRD marrow assessment on day 15 of treatment by FCM-MRD is an important predictive factor.

Results of CoALL 07-03 study childhood ALL based on combined risk assessment by in vivo and in vitro pharmacosensitivity

We conducted a clinical trial and report the long-term outcome of 773 children with acute lymphoblastic leukemia upon risk-adapted therapy accrued in trial CoALL 07-03 (from the Cooperative Study Group for Childhood Acute Lymphoblastic Leukemia). In a 2-step stratification, patients were allocated to receive either low- or high-risk treatment, based on initial white blood cell count, age, and immunophenotype. A second stratification was performed according to the results of in vitro pharmacosensitivity toward prednisolone, vincristine, and asparaginase (PVA score) and in vivo response after induction therapy (minimal residual disease [MRD]). Therapy was reduced for both risk groups in patients with a low PVA score or negative MRD result, and intensified in patients with a high PVA score. Overall outcome improved significantly compared with the predecessor CoALL 06-97 trial, with identical therapy backbone despite treatment reduction in 15.8% of patients (10-year probability of event-free survival, 83.5% vs 73.9%; overall survival, 90.7% vs 83.8%). Outcome for patients in the reduced treatment arms was superior to that of patients in the standard arms, associated with a profound reduction in frequency and severity of infectious complications. Importantly, we observed a lack of correlation between in vitro and in vivo drug response, as well as a lower predictive value of in vitro drug testing, reflecting an intrinsic limitation of this methodology that prevents its use for treatment stratification in future trials. In conclusion, it might be possible to reduce chemotherapy in children with acute lymphoblastic leukemia selected by stringent in vivo measurement of MRD without jeopardizing overall outcome.

Assessing changes in microstructural integrity of white matter tracts in children with leukaemia following exposure to chemotherapy

BACKGROUND

Intrathecal and intravenous chemotherapy, specifically methotrexate, might contribute to neural microstructural damage.

OBJECTIVE

To assess, by diffusion tensor imaging, microstructural integrity of white matter in paediatric patients with acute lymphoblastic leukaemia (ALL) following intrathecal and intravenous chemotherapy.

MATERIALS AND METHODS

Eleven children diagnosed with de novo ALL underwent MRI scans of the brain with diffusion tensor imaging (DTI) prior to commencement of chemotherapy and at 12 months after diagnosis, using a 3-tesla (T) MRI scanner. We investigated the changes in DTI parameters in white matter tracts before and after chemotherapy using tract-based spatial statistics overlaid on the International Consortium of Brain Mapping DTI-81 atlas. All of the children underwent formal neurodevelopmental assessment at the two study time points.

RESULTS

Whole-brain DTI analysis showed significant changes between the two time points, affecting several white matter tracts. The tracts demonstrated longitudinal changes of decreasing mean and radial diffusivity. The neurodevelopment of the children was near compatible for age at the end of ALL treatment.

CONCLUSION

The quantification of white matter tracts changes in children undergoing chemotherapy showed improving longitudinal values in DTI metrics (stable fractional anisotropy, decreasing mean and radial diffusivity), which are incompatible with deterioration of microstructural integrity in these children.

Isolated Central Nervous System Relapse Following Treatment Reduction in Low-risk Acute Lymphoblastic Leukemia at the Children's Cancer Center of Lebanon

The aim of this trial was to decrease the incidence of life-threatening infections by decreasing the dose and the duration of dexamethasone treatment during maintenance therapy. This was a prospective, nonrandomized trial of low-risk acute lymphoblastic leukemia patients 1 to 18 years of age who were treated at the Children's Cancer Center of Lebanon (CCCL). Patients consecutively diagnosed between 2002 and 2013 were divided into groups 1 and 2 receiving total dexamethasone doses of 1144 and 618 mg/m, respectively. A total of 84 patients were assigned to group 1 and 33 patients to group 2. The 5-year cumulative incidence of isolated central nervous system relapse increased from (n=0% [95% confidence interval: 0%-4.4%]) in group 1 to 9.1% [95% confidence interval: 3%-23%]; P=0.021) in group 2. Decreasing cumulative dose of dexamethasone for low-risk childhood acute lymphoblastic leukemia patients aiming to avoid serious viral infections led to a significant increase in isolated central nervous system relapse.

FPGS relapse-specific mutations in relapsed childhood acute lymphoblastic leukemia

Although the cure rate for childhood acute lymphoblastic leukemia (ALL) has exceeded 80% with contemporary therapy, relapsed ALL remains a leading cause of cancer-related death in children. Relapse-specific mutations can be identified by comprehensive genome sequencing and might have clinical significance. Applying whole-exome sequencing to eight triplicate samples, we identified in one patient relapse-specific mutations in the folylpolyglutamate synthetase (FPGS) gene, whose product catalyzes the addition of multiple glutamate residues (polyglutamation) to methotrexate upon their entry into the cells. To determine the prevalence of mutations of the FPGS mutations, and those of two important genes in the thiopurine pathway, NT5C2 and PRPS1, we studied 299 diagnostic and 73 relapsed samples in 372 patients. Three more FPGS mutants were identified in two patients, NT5C2 mutations in six patients, and PRPS1 mutants in two patients. One patient had both NT5C2 and PRPS1 mutants. None of these alterations were detected at diagnosis with a sequencing depth of 1000X, suggesting that treatment pressure led to increased prevalence of mutations during therapy. Functional characterization of the FPGS mutants showed that they directly resulted in decreased enzymatic activity, leading to significant reduction in methotrexate polyglutamation, and therefore likely contributed to drug resistance and relapse in these cases. Thus, besides genomic alterations in thiopurine metabolizing enzymes, the relapse-specific mutations of FPGS represent another critical mechanism of acquired antimetabolite drug resistance in relapsed childhood ALL.

Post-induction Measurable Residual Disease Using Multicolor Flow Cytometry Is Strongly Predictive of Inferior Clinical Outcome in the Real-Life Management of Childhood T-Cell Acute Lymphoblastic Leukemia: A Study of 256 Patients

Background: Measurable/minimal residual disease (MRD) status is suggested as a powerful indicator of clinical-outcome in T-cell lymphoblastic leukemia/lymphoma (T-ALL). Contrary to B-cell ALL, reports on T-ALL MRD are limited and mostly based on molecular methods, mainly from developed countries. Multicolor flow cytometry (MFC)-based T-ALL studies are very few. Clinically relevant cut-off levels and ideal time-point for MRD assessment are still inconclusive. In view of lack of T-ALL MRD data from the developing world, we evaluated the prognostic value of MFC-based post-induction (PI)-MRD assessment in T-ALL in the context of standard practice. Methods: We included 256 childhood-T-ALL patients (age < 15 years) treated with a modified-MCP841 protocol, which uses high-dose cytarabine during consolidation, as a part of standard hospital practice. MRD was studied using 10-color 11-antibody MFC with any level of detectable disease being considered positive. Post-induction (PI)-MRD was available in all patients, and post-consolidation (PC) MRD was available mostly in PI-MRD-positive patients (n = 88). Results: Three years cumulative-incidence-of-relapse (3years-CIR) in PI-MRD-positive patients was inferior to negative patients (46.3% vs. 18.4%). The median relapse-free-survival (RFS), event-free-survival (EFS) and overall-survival (OS) with hazard ratio (HR) of PI-MRD-positive patients were 21.4 months vs not reached (p < 0.0001, HR-4.7), 21.6 months vs. not-reached (p = 0.0003, HR-2.01) and 37.3 months vs. not reached (p = 0.026, HR-1.64) respectively. RFS, EFS and OS of patients with PI-MRD<0.01% (n = 17) were as inferior as PI-MRD ≥ 0.01% in comparison with MRD-negative patients with HR of 4.7 (p < 0.0001), 2.45 (p = 0.0003), and 2.5 (p = 0.029), respectively. Three-years-CIR of patients with hyperleukocytosis (≥100 × 109/L) was also higher (50.5 vs. 27.6%) with inferior RFS, EFS, and OS. Among PI-MRD-positive patients, 3years-CIR, RFS, EFS, and OS of PC-MRD-positive were also inferior to that of negative patients. On multivariate analysis any-level detectable PI-MRD and hyperleukocytosis remained independently associated with inferior RFS, EFS, and OS. A combination of PI-MRD-positive status and hyperleukocytosis identified the patients with the worst clinical outcomes. Conclusion: Detectable PI-MRD using MFC was found to be the strong predictive factor of inferior clinical outcome in T-ALL patients. The combination of PI-MRD status and hyperleukocytosis provides the most influential tool for the management of T-ALL in resource constrained settings from developing world.

Reduced-dose intensity therapy for pediatric lymphoblastic leukemia: long-term results of the Recife RELLA05 pilot study

Treatment-related mortality is common among children with acute lymphoblastic leukemia (ALL) treated in poor-resource settings. We applied a simplified flow cytometric assay to identify patients with precursor B-cell ALL (B-ALL) at very low risk (VLR) of relapse and treated them with a reduced-intensity treatment plan (RELLA05). VLR criteria include favorable presenting features (age ≥ 1 and < 10 years), white blood cell count of <50 ×109/L, lack of extramedullary leukemia, and minimal residual disease level of <0.01% on remission induction day 19. Except for 2 doses of daunorubicin, treatment of patients with VLR B-ALL consisted of a combination of agents with relatively low myelotoxicity profiles, including corticosteroids, vincristine, L-asparaginase, methotrexate, and 6-mercaptopurine. Cyclophosphamide, systemic cytarabine, and central nervous system radiotherapy were not used. Of 454 patients with ALL treated at the Instituto de Medicina Integral Professor Fernando Figueira in Recife, Brazil, between December 2005 and June 2015, 101 were classified as having VLR B-ALL. There were no cases of death resulting from toxicity or treatment abandonment during remission induction. At a median follow-up of 6.6 years, there were 8 major adverse events: 6 relapses, 1 treatment-related death (from septicemia) during remission, and 1 secondary myeloid leukemia. The estimated 5-year event-free and overall survival rates were 92.0% ± 3.9% and 96.0% ± 2.8%, respectively. The 5-year cumulative risk of relapse was 4.24% ± 2.0%. The treatment was well tolerated. Episodes of neutropenia were of short duration. Patients with B-ALL selected by a combination of presenting features and degree of early response can be successfully treated with a mildly myelosuppressive chemotherapy regimen.