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Background Since pediatric cancer drug development is a global enterprise, we sought to provide an overview of the landscape of intercontinental clinical trials in pediatric oncology opened over the last decade. Methods ClinicalTrials.gov was systematically searched to identify all clinical therapeutic trials which opened between 2010 and 2020 and recruited pediatric patients (, Intercontinental collaboration is alarmingly rare in childhood cancer trials, despite the rare disease setting and despite pediatric clinical research being inevitably a global enterprise. Barriers to collaboration should be identified and met with specific solutions to accelerate urgently needed drug development for children and adolescents with cancer.

Comparison of treatment strategies in de novo pediatric acute lymphoblastic leukemia (ALL) requires standardized measures of efficacy. Key parameters that define disease-related events, including complete remission (CR), treatment failure (TF; not achieving CR), and relapse (loss of CR) require an updated consensus incorporating modern diagnostics. We collected the definitions of CR, TF, and relapse from recent and current pediatric clinical trials for the treatment of ALL, including the key components of response evaluation (timing, anatomic sites, detection methods, and thresholds) and found significant heterogeneity, most notably in the definition of TF. Representatives of the major international ALL clinical trial groups convened to establish consensus definitions. CR should be defined at a time point no earlier than at the end of induction and should include the reduction of blasts below a specific threshold in bone marrow and extramedullary sites, incorporating minimal residual disease (MRD) techniques for marrow evaluations. TF should be defined as failure to achieve CR by a prespecified time point in therapy. Relapse can only be defined in patients who have achieved CR and must include a specific threshold of leukemic cells in the bone marrow confirmed by MRD, the detection of central nervous system leukemia, or documentation of extramedullary disease. Definitions of TF and relapse should harmonize with eligibility criteria for clinical trials in relapsed/refractory ALL. These consensus definitions will enhance the ability to compare outcomes across pediatric ALL trials and facilitate development of future international collaborative trials.

Background: ABL-class fusion genes other than BCR–ABL1 have been identified in approximately 3% of children with newly diagnosed acute lymphocytic leukaemia, and studies suggest that leukaemic cells carrying ABL-class fusions can be targeted successfully by tyrosine-kinase inhibitors. We aimed to establish the baseline characteristics and outcomes of paediatric patients with ABL-class fusion B-cell acute lymphocytic leukaemia in the pre-tyrosine-kinase inhibitor era. Methods: This multicentre, retrospective, cohort study included paediatric patients (aged 1–18 years) with newly diagnosed ABL-class fusion (ABL1 fusion-positive, ABL2 fusion-positive, CSF1R fusion-positive, and PDGFRB fusion-positive) B-cell acute lymphocytic leukaemia enrolled in clinical trials of multidrug chemotherapy done between Oct 3, 2000, and Aug 28, 2018, in which tyrosine-kinase inhibitors had not been given as a first-line treatment. Patients from 14 European, North American, and Asia-Pacific study groups of the Ponte di Legno group were included. No patients were excluded, and patients were followed up by individual study groups. Through the Ponte di Legno group, we collected data on the baseline characteristics of patients, including IKZF1, PAX5, and CDKN2A/B deletion status, and whether haematopoietic stem cell transplantation (HSCT) had been done, as well as treatment outcomes, including complete remission, no response, relapse, early death, and treatment-related mortality, response to prednisone, and minimal residual disease (MRD) at end of induction therapy. 5-year event-free survival and 5-year overall survival were estimated by use of Kaplan-Meier methods, and the 5-year cumulative incidence of relapse was calculated by use of a competing risk model. Findings: We identified 122 paediatric patients with newly diagnosed ABL-class fusion B-cell acute lymphocytic leukaemia (77 from European study groups, 25 from North American study groups, and 20 from Asia-Pacific study groups). 64 (52%) of 122 patients were PDGFRB fusion-positive, 40 (33%) were ABL1 fusion-positive, ten (8%) were CSF1R fusion-positive, and eight (7%) were ABL2 fusion-positive. In all 122 patients, 5-year event-free survival was 59·1% (95% CI 50·5–69·1), 5-year overall survival was 76·1% (68·6–84·5), and the 5-year cumulative incidence of relapse was 31·0% (95% CI 22·4–40·1). MRD at the end of induction therapy was high (≥10−2 cells) in 61 (66%) of 93 patients, and most prevalent in patients with ABL2 fusions (six [86%] of 7 patients) and PDGFRB fusion-positive B-cell acute lymphocytic leukaemia (43 [88%] of 49 patients). MRD at the end of induction therapy of 10−2 cells or more was predictive of an unfavourable outcome (hazard ratio of event-free survival in patients with a MRD of ≥10−2 vs those with a MRD of

Background The aim of this study was to assess whether minimal residual disease (MRD) at the end of induction front-line treatment can serve as a surrogate endpoint for event-free survival (EFS) in childhood B-lineage acute lymphoblastic leukemia. Methods The analysis was based on individual data of 4830 patients from two large phase III trials that asked a randomized question on the effect of different corticosteroids (dexamethasone vs prednisone) during induction chemotherapy on EFS. The association between MRD classified in three ordered categories [negative = 0, low positive = (>0 and Results MRD at the end of induction was a poor surrogate for treatment effect on EFS at the trial level, with Rtrial2 = 0.09 (95% confidence interval [CI] = 0.00 to 0.29), whereas at the individual level it was strongly associated with EFS, with an odds ratio of 3.90 (95% CI = 3.35 to 4.44) of failure for patients with higher compared with lower MRD levels. Additional sensitivity and relevant subgroup analyses confirmed these findings at both trial- and patient-level association. Conclusions Although MRD is a robust biomarker highly predictive of outcome for individual patients, clinicians and regulatory bodies should be cautious in using early MRD response in the context of complex multiagent acute lymphoblastic leukemia therapy as an early surrogate endpoint to predict the effect of a randomized treatment intervention on long-term EFS.

Children with Down syndrome (DS) have an increased risk of B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). The prognostic factors and outcome of DS-ALL patients treated in contemporary protocols are uncertain. We studied 653 DS-ALL patients enrolled in 16 international trials from 1995 to 2004. Non-DS BCP-ALL patients from the Dutch Child Oncology Group and Berlin-Frankfurt- Münster were reference cohorts. DS-ALL patients had a higher 8-year cumulative incidence of relapse (26% ± 2% vs 15% ± 1%, P < .001) and 2-year treatment-related mortality (TRM) (7% ± 1% vs 2.0% ±

Purpose We sought to determine whether cranial radiotherapy (CRT) is necessary to prevent relapse in any subgroup of children with acute lymphoblastic leukemia (ALL). Patients and Methods We obtained aggregate data on relapse and survival outcomes for 16,623 patients age 1 to 18 years old with newly diagnosed ALL treated between 1996 and 2007 by 10 cooperative study groups from around the world. The proportion of patients eligible for prophylactic CRT varied from 0% to 33% by trial and was not related to the proportion eligible for allogeneic stem-cell transplantation in first complete remission. Using a random effects model, with CRT as a dichotomous covariate, we performed a single-arm meta-analysis to compare event-free survival and cumulative incidence of isolated or any CNS relapse and isolated bone marrow relapse in high-risk subgroups of patients who either did or did not receive CRT. Results Although there was significant heterogeneity in all outcome end points according to trial, CRT was associated with a reduced risk of relapse only in the small subgroup of patients with overt CNS disease at diagnosis, who had a significantly lower risk of isolated CNS relapse (4% with CRT v 17% without CRT; P = .02) and a trend toward lower risk of any CNS relapse (7% with CRT v 17% without CRT; P = .09). However, this group had a relatively high rate of events regardless of whether or not they received CRT (32% [95% CI, 26% to 39%] v 34% [95% CI, 19% to 54%]; P = .8). Conclusion CRT does not have an impact on the risk of relapse in children with ALL treated on contemporary protocols.

Introduction The ETV6-ABL1 (TEL-ABL) fusion gene is a rare but recurrent genetic aberration found in various hematological malignancies in children and adults. Due to the inverse orientation of ETV6 (12p13) and ABL1 (9q34) an in-frame fusion cannot be produced by a simple balanced translocation and thus results from a complex rearrangement. Alternative splicing generates two fusion transcripts - type A and B without and with ETV6 exon 5, respectively. Both transcripts encode a constitutively active chimeric tyrosine kinase. The effect of ETV6-ABL1 on cellular proliferation, cell survival and transforming capacity mirrors that seen in BCR-ABL1-positive cases. There is a renewed interest in ETV6-ABL1 since the discovery of a "BCR-ABL1-like" (or "Ph-like") gene expression profile (GEP) among B-cell precursor (BCP) ALL cases lacking an established chromosomal abnormality (so-called "B-other ALL"). The BCR-ABL1-like GEP resembles the BCR-ABL1 GEP because both are driven by the activation of kinase signaling. In vitro studies suggest that many of these kinase fusions, including ETV6-ABL1, are sensitive to specific tyrosine kinase inhibitors (TKI), thus representing a promising and relevant therapeutic target, especially given the reported unfavorable prognosis of BCR-ABL1-like ALL. The aim of this study was to characterize the incidence, clinical features and genetic profile of ETV6-ABL1 leukemias with a focus on ALL as an example of a targetable kinase-activating lesion. Patients and methods The cohort totals 44 ETV6-ABL1 patients and comprises newly identified cases (n=9), published cases with additional new data (n=11) and cases with re-examined published data (n=24). Half of the patients (n=22) was diagnosed with ALL (13 children, 9 adults) while 22 had a myeloid malignancy (18 CML-like myeloproliferative neoplasm (MPN), 4 AML). Besides routine diagnostic examinations, we analyzed the presence of fusion transcript variants, genomic profile using MLPA and SNP-array, gene expression profile on microarrays and the presence of BCR-ABL1-like expression signature using quantitative PCR-based low density expression arrays. Results Systematic screening of >3500 cases revealed that ETV6-ABL1 is rare in childhood ALL (0.17% cases) and slightly more prevalent in adult ALL (0.38%). The equal number of MPN and ALL cases and the relative incidence of ALL and MPN in adulthood suggests ETV6-ABL1 is more common in MPN. The type B variant (including ETV6 exon 5) is the dominant transcript and its detection by PCR screening is a more reliable diagnostic approach than FISH with commercial probes for ETV6-RUNX1 and BCR-ABL1. In BCP ALL, ETV6-ABL1 fusion always localized to the der(12) whereas in T-ALL and myeloid cases the fusion localized to the der(9), der(12) or a third chromosome. The genomic profile of ETV6-ABL1 ALL resembled BCR-ABL1 and BCR-ABL1-like ALL with 80% cases having concurrent CDKN2A/B and IKZF1 deletions. The gene expression signature of ETV6-ABL1 ALL cases was more similar to BCR-ABL1 than BCR-ABL1-like principally due to low CRLF2 expression. Nonetheless, 11/12 ETV6-ABL1 ALL cases were classified as BCR-ABL1-like by a standardized qPCR-based expression array. Survival of ETV6-ABL1-positive ALL is 46% in children (6/13 alive) and 13% in adults (1/8 alive). While prognosis of childhood ALL patients responding well to initial treatment seems to be favorable (3/3 with end-induction MRD < 5x10e-5 are in the 1st remission >4 years from diagnosis), children with inferior response have very poor prognosis. Survival of MPN is 50% (9/18 alive) and depends on the disease status at diagnosis (chronic vs. blastic phase). Conclusion ETV6-ABL1 fusion occurs in lymphoid and myeloid leukemia. Its genomic and expression profile, spectrum of malignancies and clinical behavior resemble BCR-ABL1, including the unfavorable prognosis, particularly in acute leukemias. Systematic screening confirmed low frequency of ETV6-ABL1 fusion in ALL. Due to high false-negative rate of FISH, PCR diagnostics are recommended for systematic screening of ALL and FISH-negative CML-like MPN. Despite the generally poor outcome, childhood ALL cases with favorable early treatment response can be treated with standard modern therapeutic protocols. To improve prognosis of the others, early diagnostics of ETV6-ABL1 and treatment with TKI should be considered. Supported by grants IGA MZ NT/13170-4 and GAUK 694414. Disclosures Mullighan: Amgen: Honoraria; Incyte: Consultancy.

Purpose In a previous analysis of 326 children with Philadelphia chromosome (Ph) –positive acute lymphoblastic leukemia (ALL) treated between 1986 and 1996, hematopoietic stem-cell transplantation from HLA-matched related donors, but not from unrelated donors, offered a superior outcome than chemotherapy alone. To evaluate the impact of recent improvements in chemotherapy and transplantation, we performed a similar analysis on patients treated in the following decade. Patients and Methods We analyzed 610 patients with Ph-positive ALL treated between 1995 and 2005 without tyrosine kinase inhibitor therapy. The median follow-up duration was 6.3 years. Results Complete remission was achieved in 89% of patients. The 7-year event-free survival and overall survival rates were superior in the present cohort compared with the previous cohort (32.0% ± 2.0% v 25.0% ± 3.0, respectively, P = .007; and 44.9% ± 2.2% v 36.0% ± 3.0%, respectively, P = .017). Compared with chemotherapy alone, transplantation with matched related donors or unrelated donors in first remission (325 patients) showed an advantage with increasing follow-up, suggesting greater protection against late relapses (hazard ratio at 5 years, 0.37; P < .001). In the multivariate Cox regression analysis accounting for treatment (transplantation v no transplantation), age, leukocyte count, and early response had independent impact on treatment outcome. Conclusion Clinical outcome of children and adolescents with Ph-positive ALL has improved with advances in transplantation and chemotherapy. Transplantations with matched related donors and unrelated donors were equivalent and offered better disease control compared with chemotherapy alone. Age, leukocyte count, and early treatment response were independent prognostic indicators. The results of this study will serve as a historical reference to evaluate the therapeutic impact of tyrosine kinase inhibitors on the outcome of Ph-positive ALL.

The Eleventh International Childhood Acute Lymphoblastic Leukemia Workshop Report: Ponte di Legno, Italy, 6–7 May 2009

Acute lymphoblastic leukemia (ALL) in infants less than one year of age is characterized by a high frequency of rearrangements of the MLL gene (MLL-R) and poor prognosis. Infants with no MLL rearrangements (MLL-G) have a better outcome than those with MLL-R. To better understand the association of chromosomal abnormalities and outcome among MLL-G infants, we carried out a detailed cytogenetic investigation of patients from two infant ALL trials: Interfant-99 and Children’s Oncology Group (COG)-P9407. Among 162 MLL-G patients, an abnormal karyotype was detected in 90/128 (70%) patients with a successful result. They were categorised according to cytogenetic risk group (good, intermediate and poor) as previously defined for childhood ALL. Compared with childhood ALL (1-18 years) using data from the UKALL97/99 treatment trial, the frequency of good risk cytogenetic abnormalities among MLL-G infants was significantly lower (12% v 60%, p It is well established that MLL-R infants are younger than their MLL-G counterparts. Classification of MLL-G patients by cytogenetic risk group showed further correlation with age. The majority of cytogenetic good risk and all poor risk patients were >9 months old, whereas half of the cytogenetic intermediate risk patients were Low FLT3 expression has been associated with an excellent outcome in infants with ALL treated on COG-P9407, and the majority (10/11) of cases with low expression were MLL-G. However, low FLT3 expression was not simply a reflection of MLL-G status, as 7 MLL-G patients had high FLT3 expression. We have shown that low expression in MLL-G patients is not associated with a particular cytogenetic risk group. Interestingly, none of the MLL-G patients with low expression had an event, whereas all 5 of the events occurred in the high expressers. We have confirmed a unique cytogenetic profile among infants with MLL-G ALL. We demonstrate that the MLL-G infants share the same cytogenetic abnormalities as older children with ALL, but the distribution of abnormalities differs. Generally infants with MLL-G ALL are older, have low FLT3 expression and have an improved outcome compared to their MLL-R counterparts. Despite small numbers of MLL-G infants, when classified into the same good, intermediate and poor risk cytogenetic subgroups as childhood ALL, their pattern of outcome was very similar to that observed in older children. However, their overall worse outcome likely reflects the differences in distribution of good and poor risk abnormalities: lower incidence of the good risk abnormality: high hyperdiploidy, absence of ETV6-RUNX1, and higher incidence of poor risk abnormalities. Nevertheless, these data suggest that some MLL-G infants, especially those with good risk cytogenetics, may benefit from treatment on childhood protocols, which are generally less intensive and less toxic than infant ALL regimens. Disclosures: No relevant conflicts of interest to declare.

Intrachromosomal amplification of chromosome 21 (iAMP21) defines a distinct cytogenetic subgroup of childhood B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). To date, fluorescence in situ hybridisation (FISH), with probes specific for the RUNX1 gene, provides the only reliable detection method (five or more RUNX1 signals per cell). Patients with iAMP21 are older (median age 9 years) with a low white cell count. Previously, we demonstrated a high relapse risk when these patients were treated as standard risk. Recent studies have shown improved outcome on intensive therapy. In view of these treatment implications, accurate identification is essential. Here we have studied the cytogenetics and outcome of 530 iAMP21 patients that highlighted the association of specific secondary chromosomal and genetic changes with iAMP21 to assist in diagnosis, including the gain of chromosome X, loss or deletion of chromosome 7, ETV6 and RB1 deletions. These iAMP21 patients when treated as high risk showed the same improved outcome as those in trial-based studies regardless of the backbone chemotherapy regimen given. This study reinforces the importance of intensified treatment to reduce the risk of relapse in iAMP21 patients. This now well-defined patient subgroup should be recognised by World Health Organisation (WHO) as a distinct entity of BCP-ALL.

Gene expression profiling was performed on 97 cases of infant ALL from Children's Oncology Group Trial P9407. Statistical modeling of an outcome predictor revealed 3 genes highly predictive of event-free survival (EFS), beyond age and MLL status: FLT3, IRX2, and TACC2. Low FLT3 expression was found in a group of infants with excellent outcome (n = 11; 5-year EFS of 100%), whereas differential expression of IRX2 and TACC2 partitioned the remaining infants into 2 groups with significantly different survivals (5-year EFS of 16% vs 64%; P < .001). When infants with MLL-AFF1 were analyzed separately, a 7-gene classifier was developed that split them into 2 distinct groups with significantly different outcomes (5-year EFS of 20% vs 65%; P < .001). In this classifier, elevated expression of NEGR1 was associated with better EFS, whereas IRX2, EPS8, and TPD52 expression were correlated with worse outcome. This classifier also predicted EFS in an independent infant ALL cohort from the Interfant-99 trial. When evaluating expression profiles as a continuous variable relative to patient age, we further identified striking differences in profiles in infants less than or equal to 90 days of age and those more than 90 days of age. These age-related patterns suggest different mechanisms of leukemogenesis and may underlie the differential outcomes historically seen in these age groups.

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy and accounts for 25% of cancers that occur before 15 years of age and 19% among persons less than 20 years of age (Ries et al. 1999). Based on the most recent estimates from the Surveillance, Epidemiology and End Results (SEER) Program of the National Cancer Institute (NCI), there are about 3,000 cases of ALL diagnosed in the United States each year among persons less than 20 years of age. The incidence peaks at 80–90 cases/million at 2–3 years of age, begins to drop abruptly at age 5–6 years reaching a rate of about 20 cases/million at 8–11 years of age, and then gradually decreases to an annual rate of about 10 cases/million by 20 years of age.

Between 1995 and 2004, six International Childhood Acute Lymphoblastic Leukemia (ALL) Workshop have been held, and the completion of several collaborative projects has established the clinical relevance and treatment options for several specific genetic subtypes of ALL. This meeting report summarizes the data presented in the seventh meeting and the discussion.

‘Educational symposium on long-term results of large prospective clinical trials for childhood acute lymphoblastic leukemia (1985–2000)’