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Children with acute myeloid leukemia (AML) commonly develop extramedullary disease (EMD), which comprises central nervous system (CNS) lesions and myeloid sarcoma (MS). In this retrospective analysis, we aimed to determine the effect of EMD on the outcomes of allogeneic hematopoietic cell transplantation (HCT) in 678 pediatric patients with de novo AML (median age, 7 years; range, 0.3-15 years) between 2006 and 2016. We compared the outcomes between patients with (EMD group, n = 158; CNS lesion, n = 47, CNS lesion + MS, n = 9, and MS, n = 102) and without EMD at diagnosis (non-EMD group, n = 520). Survivors were followed for a median of 4.5 years, and the 4-year overall survival (OS) rates were 60.6% and 56.4% in the EMD and non-EMD groups, respectively (P = 0.60). No significant differences in OS were observed with respect to the EMD site, except bone lesions, which were associated with poor OS after HCT in a non-remission status. A multivariate analysis revealed that EMD did not affect the outcomes of HCT. In conclusion, the study findings suggest that EMD should not be considered a poor prognostic factor in HCT for children with AML.

Pediatric acute myeloid leukemia (AML) represents an aggressive disease and is the leading cause of childhood leukemic mortality. The genomic landscape of pediatric AML has been recently mapped and redefined thanks to large-scale sequencing efforts. Today, understanding how to incorporate the growing list of genetic lesions into a risk stratification algorithm for pediatric AML is increasingly challenging given the uncertainty regarding the prognostic impact of rare lesions. Here we review some uncommon cytogenetic lesions to be considered for inclusion in the high-risk groups of the next pediatric AML treatment protocols. We describe their main clinical characteristics, biological background and outcome. We also provide some suggestions for the management of these rare but challenging patients and some novel targeted therapeutic options.

BACKGROUND: In addition to treatment response, cytogenetic and molecular aberrations are the most important prognostic factors in children with de novo acute myeloid leukemia (AML). However, little is known about cytogenetics at the time of relapse.METHODS: This international study analyzed the prognostic value of cytogenetic profiles and karyotypic changes in pediatric relapsed AML in relation to the probability of event-free (pEFS) and overall survival (pOS). For this purpose, cytogenetic reports from all patients registered on the Relapsed AML 2001/01 Study were reviewed and classified.RESULTS: Cytogenetic information at relapse was available for 403 (71%) of 569 registered patients. Frequently detected aberrations at relapse were t(8;21)(q22;q22) (n = 60) and inv(16)(p13.1q22)/t(16;16)(p13.1;q22) (n = 24), both associated with relatively good outcome (4-year pOS 59% and 71%, respectively). Monosomy 7/7q-, t(9;11)(p22;q23), t(10;11)(p12;q23), and complex karyotypes were associated with poor outcomes (4-year pOS 17%, 19%, 22%, and 22%, respectively). Of 261 (65%) patients for whom cytogenetic data were reliable at both diagnosis and relapse, pEFS was inferior for patients with karyotypic instability (n = 128, 49%), but pOS was similar. Unstable karyotypes with both gain and loss of aberrations were associated with inferior outcome. Early treatment response, time to relapse, and cytogenetic profile at time of relapse were the most important prognostic factors, both outweighing karytoypic instability per se.CONCLUSION: The cytogenetic subgroup at relapse is an independent risk factor for (event-free) survival. Cytogenetic assessment at the time of relapse is of high importance and may contribute to improved risk-adapted treatment for children with relapsed AML.

Although the 5-year survival rates in pediatric acute myeloid leukemia (AML) have improved over the last decades, there is a high relapse rate for Pediatric AML patients. In the present study, we mainly combine PCA with the LASSO technique to identify prognostic markers for Pediatric AML patients coming from the NCI TARGET database. Three key genes (EEF1A1, RPLP2, RPL19) associated with poor prognosis of pediatric AML has been screened by both PCA and LASSO Cox regression analysis. Simultaneously, we developed a risk score model to predict the prognosis of pediatric AML, according to risk scores, the patients were divided into high‐ and low‐risk groups based on the median risk score. Kaplan–Meier survival analysis indicated that Pediatric AML patients with the high-risk group have a poorer survival rate than those with a low‐risk group (p

To evaluate the outcome and prognostic significance of CEBPA mutations among pediatric acute myeloid leukemia (AML) from TARGET dataset. A total of 1803 pediatric patients who were diagnosed with AML were classified into two groups based on the CEBPA status by using a retrospective cohort study method from September 1996 to December 2016. The incidence of CEBPA mutations was 18%. CEBPA mutations were significantly associated with elder age (p

Simple Summary The outcome of pediatric AML improved considerably worldwide during the past few decades. Hereby, we summarize the therapeutic results of pediatric AML patients registered between 2012 and 2019 in Hungary. As compared to our previous results, improvement was registered in event-free (EFS) and overall (OS) survival, which can be attributed to the application of contemporary diagnostic and therapeutic guidelines, advanced supportation, and higher efficacy of hematopoietic stem cell transplantation. Between 2016 and 2019, a statistically significant increment of 2-year EFS was confirmed over the period between 2012 and 2015. The most prominent progress was observed in acute promyelocytic leukemia (APL). Multidimensional flow cytometry made possible the prompt introduction of ATRA in two cases with M3v, who also represent the first pediatric APL patients in Hungary to be treated with arsenic-trioxide. Besides joining multinational pediatric AML treatment groups, our future aims include the introduction of centralized treatment centers and diagnostic facilities. Abstract Outcome measures of pediatric acute myeloid leukemia (AML) improved considerably between 1990 and 2011 in Hungary. Since 2012, efforts of the Hungarian Pediatric Oncology-Hematology Group (HPOG) included the reduction in the number of treatment centers, contemporary diagnostic procedures, vigorous supportation, enhanced access to hematopoietic stem cell transplantation (HSCT), and to targeted therapies. The major aim of our study was to evaluate AML treatment results of HPOG between 2012 and 2019 with 92 new patients registered (52 males, 40 females, mean age 7.28 years). Two periods were distinguished: 2012–2015 and 2016–2019 (55 and 37 patients, respectively). During these periods, 2 y OS increased from 63.6% to 71.4% (p = 0.057), and the 2 y EFS increased significantly from 56.4% to 68.9% (p = 0.02). HSCT was performed in 37 patients (5 patients received a second HSCT). We demonstrate advances in the diagnosis and treatment of acute promyelocytic leukemia (APL) in two cases. Early diagnosis and follow-up were achieved by multidimensional flow cytometry and advanced molecular methods. Both patients were successfully treated with all-trans retinoic acid and arsenic-trioxide, in addition to chemotherapy. In order to meet international standards of pediatric AML management, HPOG will further centralize treatment centers and diagnostic facilities and join efforts with international study groups.

Background The optimal number of chemotherapy courses for low-risk (LR) pediatric acute myeloid leukemia (AML) is not known. Objective To compare outcomes for four (21.6 g/m2 cytarabine) versus five (45.6 g/m2 cytarabine) chemotherapy courses for LR-AML using data from Children's Oncology Group (COG) AAML0531 and AAML1031. Methods We compared relapse risk (RR), disease-free survival (DFS), and overall survival (OS), and the differential impact in LR subgroups for patients receiving four versus five chemotherapy courses. Cox (OS and DFS) and risk (RR) regressions were used to estimate hazard ratios (HR) to compare outcomes. Results A total of 923 LR-AML patients were included; 21% received five courses. Overall, LR-AML patients who received four courses had higher RR (40.9% vs. 31.4%; HR = 1.40, 95% confidence interval [CI]: 1.06-1.85), and worse DFS (56.0% vs. 67.0%; HR = 1.45, 95% CI: 1.10-1.91). There was a similar decrement in OS though it was not statistically significant (77.0% vs. 83.5%; HR = 1.45, 95% CI: 0.97-2.17). Stratified analyses revealed the detrimental effects of cytarabine dose de-escalation to be most pronounced in the LR-AML subgroup with uninformative cytogenetic/molecular features who were minimal residual disease (MRD) negative after the first induction course (EOI1). The absolute decrease in DFS with four courses for patients with favorable cytogenetic/molecular features and positive MRD was similar to that observed for patients with uninformative cytogenetic/molecular features and negative MRD at EOI1, though not statistically significant. Conclusions Our results support de-escalation of cytarabine exposure through the elimination of a fifth chemotherapy course only for LR-AML patients who have both favorable cytogenetic/molecular features and negative MRD after the first induction cycle.

This prospective study aimed to compare the pattern of mitochondrial deoxyribonucleic acid D-loop (mt-DNA D-loop) variations in 41 paired samples of de novo pediatric acute myeloid leukemia (AML) (baseline vs. relapse) patients by Sanger's sequencing. Mean mt-DNA D-loop variation was 10.1 at baseline as compared with 9.4 per patients at relapse. In our study, 28 (68.3%) patients showed change in number of variations from baseline to relapse, 11 (26.8%) patients showed increase, 17 (41.6%) patients showed decrease, and 7 (17.1%) patients who suffered a relapse had a gain at position T489C. No statistically significant difference was observed in the mutation profile of mt-DNA D-loop region from baseline to relapse in the evaluated population of pediatric AML.

Introduction Objectives were used to describe guardian proxy‐report and child self‐report quality of life (QoL) during chemotherapy for pediatric acute myeloid leukemia (AML) patients. Methods Patients enrolled on the phase 3 AML trial AAML1031 who were 2‐18 years of age with English‐speaking guardians were eligible. Instruments used were the PedsQL Generic Core Scales, Acute Cancer Module, and Multidimensional Fatigue Scale. Assessments were obtained at the beginning of Induction 1 and following completion of cycles 2‐4. Potential predictors of QoL included the total number of nonhematological grade 3‐4 Common Terminology Criteria for Adverse Event (CTCAE) submissions. Results There were 505 eligible guardians who consented to participate and 348 of their children provided at least one self‐report assessment. The number of submitted CTCAE toxicities was significantly associated with worse physical health summary scores (β ± standard error (SE) −3.00 ± 0.69; P

The treatment for pediatric acute myeloid leukemia (AML) has not changed significantly over the past 3 decades, yet outcomes have improved with cure rates increasing from 30% to over 60% of all newly diagnosed children over this period. This improvement in survival has been attributed to both treatment intensification and improved supportive care over the decades, although the precise impact of each remains unknown.We retrospectively analyzed a unique cohort of 276 patients with de novo AML diagnosed in childhood, all treated with the same chemotherapy protocol over a 25-year period from 1986 to 2012.The contemporary cohort (2000-2012), compared with the historical cohort (1986-1999) had significantly improved overall survival (75% vs. 50%; hazard ratio, 2.17; 95% confidence interval, 1.15-2.93), lower disease-related mortality (38% vs. 19%, P=0.02) and were significantly more likely to receive an allogeneic transplant after relapse (stem cell transplantation [SCT], 73% vs. 12%; P0.0001). Allogeneic transplant postrelapse was associated with a significantly improved survival across the entire cohort (overall survival 50% for allogeneic SCT vs. 12% for autologous or none, P0.0001). There was no significant difference between the contemporary and historical cohorts in treatment-related mortality (13% vs. 7%, P=0.42) or relapse rates after induction (50% in older cohort vs. 40% in recent era, P=0.25), suggesting consistency of induction treatment efficacy and toxicity across the 2 periods.This data suggests improved survival in pediatric AML in the modern era has predominantly resulted from changes in treatment after relapse, including increased use of allogeneic SCT.

Improvement in outcomes of children with acute myeloid leukemia (AML) is attributed to several refinements in clinical management. We evaluated treatment outcomes of Taiwanese pediatric AML patients in the past 20 years. Overall, 860 de novo AML patients aged 0–18 years and registered in the Childhood Cancer Foundation of R.O.C during January 1996–December 2019 were included. Survival analysis was performed to identify factors that improved treatment outcomes. Regardless of treatment modalities used, patients during 2008–2019 had better 5-year event-free survival (EFS) and overall survival (OS) rates than patients during 1996–2007. For patients received the TPOG-AML-97A treatment, only 5-year OS rates were significantly different between patients diagnosed before and after 2008. Patients with RUNX1–RUNX1T1 had similar relapse-free survival rates, but 5-year OS rates were better during 2008–2019. However, the survival of patients who received hematopoietic stem-cell transplantations (HSCT) did not differ significantly before and after 2008. For patients without relapse, the 5-year OS improved during 2008–2019. Non-relapse mortality decreased annually, and cumulative relapse rates were similar. In conclusion, 5-year EFS and OS rates improved during 2008–2019, though intensities of chemotherapy treatments were similar before and after 2008. Non-relapse mortality decreased gradually. Further treatment strategies including more intensive chemotherapy, novel agents’ use, identification of high-risk patients using genotyping and minimal residual disease, early intervention of HSCT, and antibiotic prophylaxis can be considered for future clinical protocol designs in Taiwan.

Introduction: A systematic review was performed to assess the prognostic value of Measurable Residual Disease (MRD) during treatment, for relapse and overall survival in pediatric acute myeloid leukemia (AML). Areas covered: A systematic search of available literature was performed to identify original full-text articles concerning MRD as prognostic for relapse and survival in pediatric AML. Thirteen studies were included, and in all studies, MRD positivity during treatment was associated with worse clinical outcome. MRD positivity was significantly associated with a higher probability of relapse in eleven studies. However, MRD negativity does not exclude the possibility of relapse in pediatric AML, while positivity early during therapy does not exclude cure. Expert opinion: MRD positivity during treatment has emerged as the most powerful prognostic factor in pediatric AML concerning relapse and overall survival and is useful for risk-group adapted treatment. Future studies should identify the optimal time-point(s) for MRD measurements and the optimal technique, to further improve its prognostic significance.

Objective Long non‐coding RNA microvascular invasion in hepatocellular carcinoma (lnc‐MVIH) is correlated with unfavorable prognosis in several malignancies, while limitedly studied in pediatric acute myeloid leukemia (AML). This study aimed to investigate the correlation of lnc‐MVIH with disease features, response to induction therapy, and survival in pediatric AML patients. Methods A total of 129 de novo pediatric AML patients who were retrospectively analyzed and 60 children with non‐malignant hematological diseases who underwent bone marrow examination were reviewed as controls. Bone marrow mononuclear cells (BMMCs) were isolated from all participants to detect lnc‐MVIH expression by reverse transcription‐quantitative polymerase chain reaction. The complete remission status after 1 course of induction therapy, event‐free survival, and overall survival of pediatric AML patients were recorded. Results Lnc‐MVIH was upregulated in pediatric AML patients compared with controls (p, Objective: Long non‐coding RNA microvascular invasion in hepatocellular carcinoma (lnc‐MVIH) is correlated with unfavorable prognosis in several malignancies, while limitedly studied in pediatric acute myeloid leukemia (AML). This study aimed to investigate the correlation of lnc‐MVIH with disease features, response to induction therapy and survival in pediatric AML patients. Methods: A total of 129 de novo pediatric AML patients were retrospectively analyzed and 60 children with non‐malignant hematologic diseases underwent bone marrow examination were reviewed as controls. Bone marrow mononuclear cells (BMMCs) were isolated from all participants to detect lnc‐MVIH expression by reverse transcription quantitative polymerase chain reaction. The complete remission status after 1 course of induction therapy, event‐free survival and overall survival of pediatric AML patients were recorded. Results: Lnc‐MVIH was upregulated in pediatric AML patients compared with controls (p

Acute myeloid leukemia (AML) accounts for 15% to 20% of childhood leukemias. Because of high-intensive therapy, up to 5% of patients suffer from treatment-related mortality (TRM). Abdominal complications are frequent, however, literature on this subject is sparse. We aimed to characterize severe abdominal pain (AP) and hyperbilirubinemia experienced by pediatric AML patients treated according to the Nordic Society of Pediatric Hematology and Oncology (NOPHO)-AML 2004 protocol (n=313). Patients were censored at hematopoietic stem cell transplantation and relapse. Toxicity information was collected prospectively. Additional information was requested retrospectively from the treating centers. Sixteen episodes of hyperbilirubinemia and 107 episodes of AP were reported. The treating centers deemed infection (30%) and typhlitis (18%) as the most frequent causes of AP. Six patients developed appendicitis (2%). Patients experiencing concurrent AP and sepsis had a high risk of TRM (36%, n=4). Eighty percent of episodes with hyperbilirubinemia fulfilled the European Society for Bone and Marrow Transplantation criteria for sinusoidal obstruction syndrome. In conclusion, abdominal complications were frequent with infection considered the predominate cause. Most patients with hyperbilirubinemia fulfilled the criteria for sinusoidal obstruction syndrome. AML treatment might be associated with appendicitis. Patients suffering from concurrent AP and sepsis had a high risk of TRM indicating that high awareness of abdominal complications is essential to reduce mortality, especially during sepsis.

Acute myeloid leukemia (AML) is the second most common pediatric leukemia, with a survival rate of 70%. In this retrospective study, we evaluated the treatment outcomes of pediatric AML among 144 patients diagnosed between 2000 and 2013. After induction, 80.6% of patients achieved complete remission (CR). The 5-year overall survival (OS) and event-free survival (EFS) rates were 58.8 ± 4.2% and 49.8 ± 4.2%, respectively. Based on the response to induction therapy, the 5-year OS was 66.9 ± 5.7% in patients with CR (p &lt, 0.001). Ninety-nine patients with CR after induction therapy were examined, and their 5-year OS and EFS were 66.4 ± 4.9% and 56.3 ± 5.1%, respectively. The 5-year OS rates according to treatment were 59.9 ± 7.4% in the chemotherapy group and 72.3 ± 6.3% in the hematopoietic stem cell transplantation (HSCT) group (p = 0.089). The EFS was 50.1 ± 7.4% in the chemotherapy group and 61.7 ± 6.9% in the HSCT group (p = 0.098). OS and EFS according to cytogenetics were insignificant. Our findings confirmed that the response to induction treatment was important for survival and HSCT had no significant survival benefits compared with those of chemotherapy. Moreover, many early induction deaths under the age of 2 years were observed.

Pediatric acute myeloid leukemia (AML) is a heterogeneous disease that requires a multifaceted treatment approach. Although outcomes for low-risk AML have improved significantly over recent decades, high-risk AML continues to be associated with an adverse prognosis. Recent advances in molecular diagnostics, risk stratification, and supportive care have contributed to improvements in outcomes in pediatric AML. Targeted approaches, for example, the use of tyrosine kinase inhibitors to treat FLT3-ITD AML, offer promise and are currently undergoing clinical investigation in pediatric patients. New approaches to hematopoietic stem cell transplantation, including the use of haploidentical donors, are significantly expanding donor options for patients with high-risk AML. This review provides an overview of recent advances in the treatment of pediatric AML that are likely to have clinical impact and reshape the standard of care.

A 15-year-old male presented with fatigue and weight loss for 1 month, petechiae and bruising for 2 weeks. He was diagnosed with concurrent new acute myeloid leukemia and coronavirus disease 2019. He was febrile and chest computed tomography scan showed ground glass opacities. Fever resolved after 4 days. Polymerase chain reaction test for coronavirus disease 2019 became negative after 2 days. Induction chemotherapy was initiated on day 8 and was complicated by multisystem inflammatory syndrome in children. The multisystem inflammatory syndrome in children was managed with symptomatic treatment and continued chemotherapy. Patient recovered and end of induction bone marrow showed remission of the leukemia.

Normal karyotype acute myeloid leukemia (NK-AML) constitutes 20–25% of pediatric AML and detailed molecular analysis is essential to unravel the genetic background of this group. Using publicly available sequencing data from the TARGET-AML initiative, we investigated the mutational landscape of NK-AML in comparison with abnormal karyotype AML (AK-AML). In 164 (97.6%) of 168 independent NK-AML samples, at least one somatic protein-coding mutation was identified using whole-genome or targeted capture sequencing. We identified a unique mutational landscape of NK-AML characterized by a higher prevalence of mutated CEBPA, FLT3, GATA2, NPM1, PTPN11, TET2, and WT1 and a lower prevalence of mutated KIT, KRAS, and NRAS compared with AK-AML. Mutated CEBPA often co-occurred with mutated GATA2, whereas mutated FLT3 co-occurred with mutated WT1 and NPM1. In multivariate regression analysis, we identified younger age, WBC count ≥50 × 109/L, FLT3-internal tandem duplications, and mutated WT1 as independent predictors of adverse prognosis and mutated NPM1 and GATA2 as independent predictors of favorable prognosis in NK-AML. In conclusion, NK-AML in children is characterized by a unique mutational landscape which impacts the disease outcome.

Background: Acute myeloid leukemia (AML) and hyperleukocytosis are related to an unfavorable prognosis. The impact of hyperleukocytosis on the prognosis of pediatric AML has not been fully explained so far. We aimed to assess the clinical characteristics and prognosis of pediatric AML with hyperleukocytosis, referred to as white blood cell (WBC) count ≥50×109/L. Methods: A total of 307 newly diagnosed non-acute promyelocytic leukemia patients were continuously enrolled at our center from October 2005 to September 2015. 81 patients with initial leukocyte counts ≥50×109/L. The baseline demographic and clinical characteristics of AML patients were compared. Progression-free survival (PFS) and overall survival (OS) were documented. Results: Hyperleukocytosis occurred in 26.38% of AML patients, and FAB M5 subtype (n=41, 50.62%) and FLT3-ITD mutations (n=16, 19.75%) had a high proportion in AML and hyperleukocytosis. Overall mortality was significantly higher in patients with hyperleukocytosis than patients without hyperleukocytosis (50.62% vs. 35.84%, P=.020). Patients with hyperleukocytosis had a lower 10-year PFS and OS rates than those without hyperleukocytosis (44.4%±9.4% vs. 59.7%±5.5%, P=.041; 49.4%±9.4% vs. 64.2%±5.4%, P=.051, respectively). There were similar PFS and OS rates between the subgroups of patients with WBC count 50-100×109/L and WBC count ≥100×109/L (43.8%±13.3% vs. 44.9%±12.3%, P=.507; 46.9%±13.3% vs. 51.0%±12.3%, P=.907, respectively). In all patients with hyperleukocytosis, male and FAB M5 subtype patients had a significantly inferior survival, while CBF-AML had a better survival. Conclusions: A WBC count greater than 50×109/L at onset was a critical predictive adverse factor in pediatric AML.

There is paucity of data on outcomes of MSD-HSCT in children with relapsed or high-risk AML from developing countries, which have unique challenges including adverse host factors and resource constraints. We retrospectively reviewed records of children (age ≤ 18 years) who underwent MSD-HSCT for AML at our center from 2009 to 2019 to evaluate clinical outcome and its predictors using Cox proportional hazards model. There were 46 children (36 boys and 10 girls) with mean age 10.7 ± 4.8 years. Indication for HSCT was relapsed AML in CR2 (n = 37), primary refractory (n = 3), or relapsed refractory disease (n = 3); high-risk (n = 1) or secondary (n = 2) AML in CR1. Five-year EFS and OS were 33.3 ± 7.2% and 36.3 ± 7.6%, respectively. On multivariate analysis, CR1 duration less than 12 months, presence of active disease at transplant, and use of bone marrow stem cell graft were associated with poorer EFS and OS. There was one (2.2%) TRM, while disease relapse occurred in 20/40 patients who underwent HSCT in remission. Though the 5-year EFS and OS were inferior to results reported from high-income countries, relapse (and not TRM) was the major cause of treatment failure. A well-sustained CR1, achievement of disease remission, and use of peripheral blood allograft seem imperative to a successful transplant. Targeted therapy along with HSCT may be the option for those with early relapse.

AIM The aim of this study was to evaluate the diagnostic and prognostic performance of miRNA-29a and miRNA-100 in pediatric acute myeloid leukemia (AML). PATIENTS AND METHODS In all, 73 children with diagnosed pediatric AML (based on standard morphologic, cytochemical, cytogenetic, immunologic, and molecular workup, and the French-American British classification) admitted to Children's Cancer Hospital Egypt (CCHE-57357), and 9 healthy age-matched and sex-matched controls were recruited for a case-control study. Gene expression levels of miRNA-29a and miRNA-100 were assessed using real-time quantitative RT-PCR. RESULTS When diagnosed, patients had a significantly higher expression of miRNA-100 as against controls (median [range]: 12.99 [0.92-851.38] vs. 0.26 [0.03-2.67], P

Background: Leukemia is the most common childhood cancer. Compared to acute lymphoblastic leukemia, which makes up 80% of pediatric leukemia cases, acute myeloid leukemia (AML) is rarer and has low...

Background microRNA-381 is dysregulated in a variety of cancers. However, its clinical significance in pediatric acute myeloid leukemia (AML) is still unclear. The purpose of this study was to detect the expression level of miR-381 in pediatric AML patients and to explore its potential clinical significance. Methods The levels of miR-381 in bone marrow and serum of 102 pediatric AML patients were measured by quantitative real-time polymorperase chain reaction (qRT-PCR). The diagnostic value of serum miR-381 in pediatric AML patients was evaluated by the receiver operating characteristic (ROC) curve. A Chi square test was used to analyze the relationship between serum miR-381 and the clinical characteristics of patients. Cox regression analysis and Kaplan–Meier evaluated the prognostic value of serum miR-381 in patients. Finally, the proliferation of the cells was analyzed by the CCK-8 assay. Results Compared with healthy controls, the levels of miR-381 in serum and bone marrow of pediatric AML patients were significantly decreased (P P P = 0.011) and poor relapse-free survival (log-rank test, P = 0.004). Cox regression analysis confirmed that reduced serum miR-381 was an independent predictor of poor prognosis in AML (HR = 3.794, 95% CI 1.3633–10.559, P = 0.011). In addition, low expression of miR-381 significantly reduced the proliferation of cells (P Conclusion All experimental results confirm that miR-381 has reduced bone marrow and serum expression in pediatric AML, and low levels of serum miR-381 have certain diagnostic and prognostic value in pediatric AML and may be a potential therapeutic target for AML.

Acute myeloid leukemia (AML) accounts for approximately 20% of all pediatric acute leukemias. The outcome of AML is still unsatisfactory. CD123 and CD200 were demonstrated to play important roles in hematological malignancies. The aim of this study was to investigate the impact of CD200 and CD123 overexpression and the influence of both proteins on the clinical presentation and disease outcome. Bone marrow (BM) samples from 89 pediatric AML patients were obtained at presentation and after therapy. Cells from the bulk population and from the leukemia stem cell (LSC) compartment were examined by multi parametric flow cytometry. In the bulk population, CD200 was positive in 64/89 (71.9) samples, CD123 was positive in 62/89 (69.7%) samples, and dual CD200 and CD123 positivity was observed in 54/89 (60.7%) samples. CD200/CD123 expressions were observed in LSCs in 64/60 samples respectively (71.9%/67.4%), and co-expressed in 51 samples (57.3%). CD200 was overexpressed in secondary AML (p 0.05). A multivariate analysis revealed that minimal residual disease (MRD) and lymphadenopathy were associated with CD200 overexpression. Moreover, lymphadenopathy, low platelet count, and MRD were independently associated with CD123 expression. The co-expression of CD200 and CD123 demonstrated a statistically significant relationship with unfavorable cytogenetic karyotypes and high total leucocyte count (TLC). The expression of CD200 and CD123 alone and together had an adverse impact on complete remission (CR), MRD positivity, and overall survival (OS). Cases with MRD on day 28 after induction displayed stable expression patterns of CD200 and CD123. CD200 and CD123 both had a negative influence on clinical presentation and treatment outcome, which remarkably worsened when both were concomitantly overexpressed. CD200 and CD123 can therefore be used as markers of MRD in AML and may also serve as therapeutic targets.

Acute promyelocytic leukemia (APL) is a rare disease accounting for only 5%−10% of pediatric acute myeloid leukemia (AML) and fewer than 1000 cases occur annually in the United States across all age groups. Characterized by t (15; 17), with a resultant PML-RARA gene fusion driving leukemia development, advances in therapy have improved outcomes for APL significantly in the past several decades, now making APL the most curable form of AML in both children and adults. Cure rates in APL are now comparable to pediatric B-lymphoid leukemias. The success of APL treatment is due, in part, to the breadth of understanding of the driver PML-RARA mutation as well as collaborative efforts to quickly introduce and maximize the benefit of new therapies. Here, we review the presentation, clinical features, pathogenesis, and treatment advances in pediatric APL.

Hyperleukocytosis (HL) is a laboratory abnormality commonly presented in patients with acute myeloid leukemia (AML). However, large cohort studies on the clinical significance of HL in pediatric AML are paucity. Moreover, the effect of stem cell transplantation in HL patients remains unknown. The clinical profiles of 885 pediatric patients with AML were downloaded from the TARGET dataset. HL was defined as an initial peripheral WBC count of ≥ 100 ×109/L. We analyzed the prevalence, clinical profile and prognosis of HL in these patients. The frequency of HL among all the pediatric AML was 22.6%. FMS-like tyrosine kinase 3/internal tandem duplication (FLT3/ITD) mutation and gene fusion of NUP98/NSD1 occurred with higher incidence in HL patients. Overall, HL was associated with a low induction complete remission rate, and high risk of induction death. Moreover, HL predicted a significantly inferior 5-year event-free survival (EFS) (P P = 0.059). However, compared with chemotherapy, stem cell transplantation had no significant effect on the survival of HL patients in terms of 5-year leukemia-free survival (P = 0.449) or OS (P = 0.447). Multivariate analysis revealed that HL was an independent prognosis factor for EFS (Hazard ratio:1.352, P = 0.013) but not for OS (Hazard ratio:1.225, P = 0.170) in pediatric AML. HL might predict inferior clinical outcome in pediatric AML. SCT is an effective therapy for AML, but it may have no better effect on the survival of patients with HL, compared to chemotherapy.

Despite advances in therapy over the past decades, overall survival for children with acute myeloid leukemia (AML) has not exceeded 70%. In this review, we highlight recent insights into risk stratification for patients with pediatric AML and discuss data driving current and developing therapeutic approaches.Advances in cytogenetics and molecular profiling, as well as improvements in detection of minimal residual disease after induction therapy, have informed risk stratification, which now relies heavily on these elements. The treatment of childhood AML continues to be based primarily on intensive, conventional chemotherapy. However, recent trials focus on limiting treatment-related toxicity through the identification of low-risk subsets who can safely receive fewer cycles of chemotherapy, allocation of hematopoietic stem-cell transplant to only high-risk patients and optimization of infectious and cardioprotective supportive care.Further incorporation of genomic and molecular data in pediatric AML will allow for additional refinements in risk stratification to enable the tailoring of treatment intensity. These data will also dictate the incorporation of molecularly targeted therapeutics into frontline treatment in the hope of improving survival while decreasing treatment-related toxicity.

Biologically, Acute myeloid leukemia (AML) is highly heterogenous. AML with cup-like blast morphology variant has been reported to have important role in risk group stratification and treatment implications. In pediatric age group, this morphology and its clinical implication is rarely discussed. Although this morphology variant is not stated in World Health Organization (WHO) classification of Tumours of Haematopoietic and Lymphoid Tissues, it is associated with poor outcome from the association with other features. A 10- year old girl diagnosed to have AML with this morphology variant is reported in this study. Her laboratory features were hyperleucocytosis, high D-dimer, and blasts morphology of cup-like cells and few mimic the bilobed features of acute promyelocytic leukemia (APML). Further investigation showed clinical and laboratory features similar to what had been reported before in adults, including the presence of adverse marker of Fms-like tyrosine kinase 3 (FLT3) mutation. She was treated with chemotherapy, following which the bone marrow examination documented marrow in remission. Unfortunately, she succumbed to the disease complication from sepsis and marrow failure after few months of diagnosis. Haemato-morphologists might consider this unique morphological recognition and correlate it with other findings, including molecular testing for proper clinical evaluation. The blast feature and haematological findings could predict the clinical behaviour of this type of AML and guide the patient management. This morphological variant serves an important role especially if molecular testing is not available in some parts of the world or at the time of presentation when the result is still pending.

Pediatric patients with acute myeloid leukemia (AML) are at high risk of invasive fungal infection (IFI). In adult patients, the D-index, which reflects the duration and intensity of neutropenia, was reported as a predictive factor of IFI after induction therapy for AML. The aim of this study was to assess whether the D-index is a predictive factor for IFI in pediatric AML. We define the D-index as the area over the neutrophil curve during neutropenia. Ninety-two courses of chemotherapy performed for 24 consecutive patients with AML undergoing chemotherapy at Sapporo Hokuyu Hospital between April 2007 and March 2017 were analyzed. We also evaluated the utility of the cumulative D-index (c-D-index) from the start of neutropenia until the clinical manifestation of IFI in these patients. The D-index and c-D-index were compared between courses with and without IFI episodes. The median D-index and c-D-index in 6 courses with IFI episodes were 12,816 (range 9500-27,412) and 7250 (range 3987-16,273), respectively, which was not statistically higher than the median D-index [10,127 (range 3788-20,897)] in 86 courses without IFI episodes (P = 0.081 and P = 0.108, respectively). Unlike in adult cases, neither the D-index nor c-D-index reflected the risk of IFI in pediatric AML.

Pediatric acute myeloid leukemia (AML) is the deadliest malignancy in children. Despite maximally intensive therapy, inclusive of chemotherapy and hematopoietic stem cell transplant, approximately 20% of patients experience recurrent disease. These patients are also burdened with treatment-related toxicities. Significant improvements in survival in pediatric AML patients necessitate the incorporation of rational targeted therapies with reduced toxicity. Recent studies demonstrate that PRMT5 knockout or inhibition in syngeneic mouse models of KMT2A (MLL) rearranged leukemic cells increased disease latency (Serio et al., Oncogene, 37:450, 2018; Kaushik et al., Leukemia, 32:499, 2018), indicating that PRMT5 is a potential therapeutic target in pediatric AML. However, there are no reports testing the efficacy of PRMT5 in PDX models of pediatric AML. We evaluated the preclinical efficacy of C220, a potent and selective PRMT5 inhibitor (PRMT5i) (Pastore et al., Cancer Discovery, 10:1742, 2020) in three distinct patient-derived xenograft (PDX) models of KMT2A rearranged AML. Based on the model used for the study, 3-5 million AML cells were injected intravenously in NSG-B2m mice. Disease progression was monitored by evaluating the percentage of human cells in mouse peripheral blood at periodic intervals by flow cytometry. At 2-3 weeks post transplantation, when human cells were detectable in peripheral blood, mice were randomly assigned to control (n=4-5) or treatment (n=2) groups. C220 was administered daily p.o. at a dose of 15 mg/kg for seven days with a break of two days. Mice were dosed with 2-3 additional cycles (indicated in the figure by shaded areas) based on their health status. Mice were monitored daily for experimental endpoints that included body condition score and human cell percentages in peripheral blood. Kaplan-Meier survival plots were generated based on the time when mice were euthanized because they met experimental endpoints. Chronic dosing of C220 prolonged survival and delayed the rise in percentage of human AML cells in mouse peripheral blood in all 3 PDX models (Fig. 1B, D, F). In the NTPL-146 model (KMT2A-MLLT1 fusion), a 135-day improvement in median survival was observed with C220-treatment (Fig. 1A). In the DF-2 (KMT2A-MLLT10 fusion) and DF-5 (KMT2A-MLLT4 fusion) models, which showed a faster engraftment compared to NTPL-146, there was a 5.5-day and 18-day improvement in median survival respectively (Fig. 1C, E). The improvement in median survival was statistically significant in all models (*P Figure 1 Figure 1. Disclosures Gopalakrishnapillai: Geron: Research Funding. Zhang: Prelude Therapeutics: Current Employment. Ruggeri: Prelude Therapeutics: Current Employment, Current equity holder in publicly-traded company. Scherle: Prelude Therapeutics: Current Employment, Current equity holder in publicly-traded company. Barwe: Prelude Therapeutics: Research Funding.

Background Relapse free survival of pediatric AML remains only 60%. Current standard myelosuppressive therapy has been maximized, so novel therapies with minimal toxicities are needed to improve outcomes. Previously, we found atovaquone (AQ), an FDA-approved drug that treats pneumocystis jiroveci pneumonia (PJP), reduces AML burden - by suppressing oxidative phosphorylation (OXPHOS) - in xenograft mice. Clinically achievable concentrations of AQ for anti-PJP are 40-80µM, but the anti-leukemia effects are observed as low as 10µM (Stevens et al, Bld Adv, 2019). This makes AQ an ideal drug to incorporate into AML treatment. AQ is a daily administered oral medication, and plasma levels depend on patient compliance, absorption, and entero-hepatic recirculation, which can be compromised due to the patient population and adverse events (AE) of chemotherapy. Here we investigated the feasibility of incorporating AQ into standard pediatric AML treatment. Methods Patients with de novo AML were enrolled at two children's hospitals in the USA. Daily administration of AQ at established PJP prophylaxis dosing was combined with standard chemotherapy for AML, based on the Medical Research Council (MRC) backbone of cytarabine 100mg/m2 q12h x 10 days, and daunorubicin 50mg/m2/dose on days 1, 3, and 5. As it was unclear if our AQ dosing would provide adequate PJP prophylaxis, it was left to provider discretion to give additional PJP protection. AQ compliance, AEs (per NCI CTCAE v5), parent/caregiver ease of administration score (scale: 1-5, 1=very difficult, 5=very easy to administer) and peripheral blood/bone marrow pharmacokinetics (PK) were collected during Induction 1. Real time AQ plasma concentration results were not provided. To address feasibility of achieving adequate levels, all gastrointestinal (GI) AEs ≥ grade 2 were collected, in addition to grade 4 or greater AEs. Patients who took at least 85% of planned doses and missed less than 2 consecutive doses of AQ were eligible for analyses. Correlative biology studies assessed AQ induced apoptosis at 30uM, effects on OXPHOS and relevant signaling activities. Patient derived xenografts (PDX) were established and treated with AQ. This trial is registered with ClinicalTrials.gov (NCT03568994). Results A total of 26 pediatric AML patients enrolled (ages 8 months - 19.7 years, mean 10.7 years); 24 patients were evaluable for this study. Two patients had Grade ≥ 3 GI toxicities that prohibited enteral administration so they were excluded from AQ PK and ease of administration analyses. We found that 14/24 (58%) patients achieved plasma levels above the target anti-leukemia concentration (10µM) by day 11. At the end of induction, 19/24 (75%) patients achieved plasma levels above 10µM, but only 7/24 (29%) patients achieved adequate levels for PJP prophylaxis (40µM). Only 1 patient achieved levels above 40µM throughout the trial [FIG A]. Mean ease of administration score was 3.8. For the youngest patients (x ≤ 2.6years), the average score was 3.4 which was not significantly different from older patients (ANOVA, p > 0.05) [FIG B]. Ease of administration scores showed no association with plasma levels (Pearson's correlation, p > 0.05). Finally, correlative biology studies in patient samples demonstrated robust AQ-induced apoptosis, OXPHOS suppression, and prolonged survival in a PDX model receiving AQ [FIG C]. Conclusion Our data demonstrate the feasibility of combining AQ with traditional chemotherapy for pediatric AML. Patients of all ages were able to tolerate AQ and no AEs were attributable to AQ administration. The target anti-leukemic concentration of AQ in the plasma (> 10uM) was frequently achieved, but concentrations of > 40uM at standard dosing were rare. Low plasma levels of AQ did not correlate with the presence of GI related AEs or weight loss, so plasma levels should be monitored to ensure sufficient PJP prophylaxis. Our correlative biology results support suppression of OXPHOS as the primary mechanism of action by which AQ exerts its anti-leukemia effect, and AQ may be an active anti-leukemia agent for pediatric AML patients. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Introduction Together with considerable improvement in diagnostics and supportive care measures, treatment intensification has contributed to the improvement of pediatric acute myeloid leukemia (AML) survival outcomes. However, treatment-related toxicity is a consequence of intensified chemotherapy regimens, which has profound implications for both morbidity and mortality. Despite the known devastating impact of all types of toxicity on quality of life (QoL), studies presenting the different forms of non-infectious toxicity prevalent during the most recent Dutch pediatric AML protocols are lacking given that only prior protocols have been evaluated in this manner as of yet. Furthermore, the literature on non-infectious toxicity incidence in pediatric AML patients is relatively scarce. Therefore, the objectives of this study were to: 1) evaluate the cumulative incidence (C.I.) of severe, but non-lethal, non-infectious toxicity during AML treatment according to the last three consecutive protocols of the Dutch Childhood Oncology Group (DCOG), and 2) compare treatment-related toxicity frequencies between protocols. Methods A retrospective chart review was performed on 245 Dutch patients diagnosed with de novo AML (acute promyelocytic leukemia, myeloid leukemia of Down Syndrome, and secondary AML were excluded) and treated according to ANLL-97/AML-12 (1998-2005) n=118, AML-15 (2005-2010) n=60, or DB-AML-01 (2010-2013) n=67. Table 1 details protocol specifics, including drug dosages per course. Grade 3-4 toxicities, including hematological toxicity, cardiotoxicity, respiratory toxicity, mucositis, typhlitis, nephrotoxicity, hepatotoxicity, neurotoxicity, pain, allergic anaphylactic reaction, and elevation of alanineaminotransferase or bilirubin were defined according to Common Terminology Criteria for Adverse Event version 4.0, excluding infectious toxicity. Grade 5 toxicity (treatment-related mortality) was beyond the scope of this study. Intensive care unit (ICU) admission data was additionally assessed. Toxicity C.I.s were determined via competing events analyses. Relapse and death were considered competing events. Patients were censored at time of stem cell transplantation. Per-protocol comparisons were conducted via Chi-square test, due to lack of sufficient power required to calculate C.I.s. Results Median age at diagnosis was 6.0 years [interquartile range (IQR) 1.0-12.0], 58% were male. Mucositis was the most frequent form of non-hematological toxicity with a C.I. of 86.1% (standard error (S.E.) 3.5%), followed by hepatotoxicity (C.I. 27.4%, S.E. 2.9%), and respiratory toxicity (C.I. 24.6%, S.E. 3.0%) (Table 2). Eighty-three patients (C.I. 33.9%, S.E. 3.0%) were admitted to the ICU at least once, for a median of 6.0 days [IQR 2.0-15.0] (Table 2). Relatively more blood transfusions (both erythrocyte and thrombocyte) were administered to patients treated according to AML-15 (98.3%) and DB-AML-01 (97.0%) compared to AML-12 (86.4%) (p=0.01 and p=0.02, respectively). Relatively more patients suffered from severe mucositis during DB-AML-01 compared to AML-12 (43.4% vs. 25.4%, p=0.01). More patients treated according to AML-15 had bilirubin levels >3x upper limit of normal (ULN) compared to those treated according to AML-12 (13.3% vs. 3.4%, p=0.01). There were no differences in non-infectious toxicity frequency between AML-15 and DB-AML-01. Other forms of toxicity did not differ significantly between protocols. The percentage of patients admitted to the ICU at least once during treatment was 33.9% in AML-12, 26.7% in AML-15, and 40.3% in DB-AML-01. Conclusions The high incidence of severe short- and long-term toxicities during pediatric AML therapy poses substantial challenges for patients, families, and care providers. Mucositis was the most common form of non-hematological, non-infectious toxicity in the whole cohort and across all Dutch protocols. Toxicities were more prevalent during the more recent protocols (AML-15 and DB-AML-01) compared to AML-12. Therefore, our findings are important in that they substantiate the need to optimize pediatric AML care in a manner which decreases treatment-related toxicity and QoL impairment. High treatment-related morbidity rates stress the urge to improve supportive care and develop less toxic treatment, while maintaining efficacy. Figure 1 Figure 1. Disclosures Zwaan: Sanofi: Consultancy.

Background: From 1983, standardized therapeutic protocols for pediatric acute myeloid leukemia (AML) based on the BFM group experience were introduced in Poland. We retrospectively analyzed the results of pediatric AML treatment in Poland from 1983 to 2019 (excluding promyelocytic, therapy-related, biphenotypic, and Down syndrome AML). Methods: The study included 899 children suffering from AML treated with the following: AML-PPPLBC 83 (1983–1993, n = 187), AML-PPGLBC 94 (1994–1997, n = 74), AML-PPGLBC 98 (1998–2004, n = 151), AML-BFM 2004 Interim (2004–2015, n = 356), and AML-BFM 2012 (2015–2019, n = 131). Results: The probability of three-year overall survival was 0.34 ± 0.03, 0.37 ± 0.05, 0.54 ± 0.04, 0.67 ± 0.03, and 0.75 ± 0.05, event-free survival was 0.31 ± 0.03, 0.34 ± 0.05, 0.44 ± 0.04, 0.53 ± 0.03, and 0.67 ± 0.05, and relapse-free survival was 0.52 ± 0.03, 0.65 ± 0.05, 0.58 ± 0.04, 0.66 ± 0.03, and 0.78 ± 0.05, respectively, in the subsequent periods. A systematic reduction of early deaths and deaths in remission was achieved, while the percentage of relapses decreased only in the last therapeutic period. Surprisingly good results were obtained in the group of patients treated with AML-BFM 2012 with unfavorable genetic abnormalities like KMT2A-MLLT10/t(10, 11)(p12, q23) and DEK-NUP214/t(6, 9)(p23, q24), while unsatisfactory outcomes were found in the patients with FLT3-ITD. Conclusions: The use of standardized, systematically modified therapeutic protocols, with the successive consideration of genetic prognostic factors, and advances in supportive care led to a significant improvement in AML treatment outcomes over the last 40 years.

The purpose of this study was to evaluate the correlation of long non-coding RNA maternally expressed gene 3 (Lnc-MEG3) with disease features, treatment response, and survival in pediatric acute myeloid leukemia (AML) patients. Among 92 de novo pediatric AML patients (before treatment and after 1 course of induction) and 40 controls, bone marrow mononuclear cells were obtained. Then, Lnc-MEG3 expression was determined by reverse transcription quantitative polymerase chain reaction. After 1 course of standard induction therapy of pediatric AML patients, complete remission (CR) was assessed. Furthermore, event-free survival (EFS) and overall survival (OS) were determined according to follow-up data. Lnc-MEG3 was reduced in pediatric AML patients compared with controls. In pediatric AML patients, Lnc-MEG3 was correlated with French-American-Britain subtypes and lower Chinese Medical Association risk stratification, while it was not associated with cytogenetic features, FLT3-ITD mutation, CEBPA mutation, NPM1 mutation, WT1 mutation, or National Comprehensive Cancer Network risk stratification. After 1 course of treatment, Lnc-MEG3 exhibited an up-regulation trend. Furthermore, Lnc-MEG3 was of no difference before treatment between patients with and without CR, while elevated Lnc-MEG3 and change of Lnc-MEG3 after 1 course of treatment were associated with increased CR rate. Additionally, increased Lnc-MEG3 expression before treatment was associated with longer EFS but not OS, while enhanced Lnc-MEG3 expression after 1 course of treatment was correlated with both prolonged EFS and OS. Lnc-MEG3 may have clinical significance as a biomarker for assisting with disease management, treatment optimization, and prognosis improvement in pediatric AML patients.

INTRODUCTION: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapy for high-risk acute myeloid leukemia (AML).The preparative regimen consisting of busulfan and cyclophosphamide (BuCy) is considered as one of the classical myeloablative conditioning regimens (MAC); however, it is associated with significant early and long-term toxicities, leading to a high rate of transplant-related mortality (TRM). P urpose: To compare toxicities and outcomes of BuCy and FluBu12 conditioning in the pediatric population. Methods: We retrospectively analyzed 71 pediatric high-risk AML patients in CR1/2 (n=51, 71,8%) and R/R disease (n=20, 28,2%) received allo-HSCT from MSD (n=16, 22,5%), MUD (n=43, 60,6%) and Haplo donor (n=12, 16,9%). BuCy and FluBu conditioning regimens were used in 47 (66,2%) and 24 (33,8%) patients respectively. Median age was 6 years (0-17). GVHD prophylaxis was PTCy±CNI±m-TOR inhibitor in 32 (45%) or ATG±CNI in 39 (55%) patients. The primary end points were TRM, relapse-free survival (RFS), graft-versus-host disease (GVHD) free, relapse free survival (GRFS) and overall survival (OS). Secondary end points included neutrophil engraftment, sinusoidal obstruction syndrome (SOS), acute and chronic GVHD. Patient were censored at the time of death or last follow-up. Probabilities of OS, RFS and GRFS were estimated using Kaplan-Meier curves. TRM was defined as any death that occurred in the absence of disease relapse; relapse was a competing risk for this event. Results: Engraftment rate was 91% and 87,5% in patients received BuCy and FluBu, respectively (p=0,4). There was a trend to lower day 100 TRM after FluBu (4,1% vs 14,9% after BuCy, p=0,07). Overall survival at 2 years did not differ as well (BuCy 48,9%, FluBu 56%, p=0,5). BuCy showed borderline higher RFS at 2 years (70,2% vs 52%, p=0,06). The composite endpoint GRFS did not differ between two study cohorts being 31,8% and 29,2% at 2 years for BuCy and FluBu (p=0,7). We observed a tendency towards a higher incidence of III0-IV0 aGVHD and cGVHD following BuCy when compared with FluBu: 57,1% vs 41% (p=0,06) and 46,5% vs 28,5% respectively (p=0,2). No significant differences were found between the BuCy and FluBu groups in risk of SOS (6% and 8%, respectively). Conclusions: The optimal conditioning regimen for children with AML is still a matter of debate. Our results suggest that FluBu represents a valid myeloablative regimen, able to provide lower TRM, aGVHD and cGVHD. This conditioning might become an alternative approach in patients with a high risk of severe post-transplant complications. Disclosures No relevant conflicts of interest to declare.

Sensitive and specific detection of measurable residual disease (MRD) after treatment in pediatric acute myeloid leukemia (AML) is prognostic of relapse and is important for clinical decision making. Mutation-based methods are increasingly being used, but are hampered by the limited number of common driver gene mutations to target as clone markers. Additional targets would greatly increase MRD detection power. However, even in cases with many AML-defining mutations, it is the limited accuracy of current molecular methods which establishes the lower bounds of sensitivity. Here we describe an ultrasensitive approach for disease monitoring with personalized hybrid capture panels targeting hundreds of somatic mutations identified by whole genome sequencing (WGS), and using extremely accurate Duplex Sequencing (DS) in longitudinal samples. In a pilot cohort of 13 patients we demonstrate detection sensitivities several orders of magnitude beyond currently available single locus testing or less accurate sequencing. With multi-target panels, overall power for MRD detection is cumulative across sites. For example, if a patient has MRD at a true frequency of 1/30,000, sequencing a single mutant site to 10,000x molecular depth would be unlikely to detect MRD. However, sequencing 10 sites each to 10,000x would effectively total 100,000x informative site depth, increasing power to >95%. However, standard sequencing assays are insufficiently accurate to achieve this theoretical limit of detection (LOD). DS enables accurate detection of individual variants to Marrow aspirates were collected from 13 uniformly treated pediatric AML patients at time of diagnosis (TOD), during treatment (end of induction, EOI), in remission (end of therapy, EOT), and at relapse. 9/13 patients relapsed. DNA from TOD was analyzed by WGS. Germline variants were excluded and somatic single nucleotide variants (SNVs) were targeted by a custom probe panel designed for each patient. An average of 170 SNVs were targeted per patient (range 53-200). More than 90% of the SNVs were noncoding. Longitudinal samples were then analyzed with DS, which compares sequences from both strands of each DNA molecule to eliminate technical noise and reveal biological mutation signal with extreme accuracy and sensitivity. A median of 82% of WGS SNVs were validated by DS in the TOD DNA, and the vast majority of those were also present at relapse. Relapsers had more SNVs at diagnosis than non-relapsers. EOT samples were sequenced to an average Duplex molecular depth of 29,400x, with a maximum of 61,283x. The figure below shows time course plots tracking SNVs at diagnosis, EOT and relapse for 2 patients. Among mutations validated in TOD samples, a median of only 8 (5%) were detected per EOT sample (range 0-66 mutations). MRD was detected in 8/9 relapsers. Targeting 1 or even 10 SNVs would therefore have missed MRD in the majority of these patients. Among relapsers, median EOT SNV VAF was 0.069%. The lowest single VAF detected per EOT sample ranged from 0.036% to 0.002%. The presence of an SNV at diagnosis and relapse implies that it must truly be present at EOT, whether or not it is detected. Therefore, if a small minority of leukemic mutations are detected at EOT, the true overall MRD frequency is much lower than the LOD at any single site. In the only relapser where MRD was not detected, targeted SNVs were present at diagnosis and relapse, so additional sequencing depth at EOT would eventually reveal ultra-low frequency mutations. Among patients that did not relapse by the end of the study, median VAF at EOI (the latest time point DNA available) was 0.0258%. Therefore, non-relapsers have a lower median VAF at EOI than relapsers do even later at EOT, potentially indicating very early on that treatment is more successful. This study shows excellent performance of DS-based assays for detecting MRD with patient-specific panels. We have demonstrated that among large panels of validated somatic SNVs present at time of diagnosis, a median of 5% are identified at EOT in eventual relapsers. DS detected MRD in 8/9 patients, and at a median VAF well below the limit of detection of any other sequencing technology. Comprehensive personalized hybrid selection panels coupled with DS represents a powerful option for MRD monitoring in pediatric AML and potentially other cancers. Figure Disclosures Higgins: TwinStrand Biosciences: Current Employment. Lo:TwinStrand Biosciences: Current Employment. Hipp:TwinStrand Biosciences: Current Employment. Valentine:TwinStrand Biosciences: Current Employment. Williams:TwinStrand Biosciences: Current Employment. Radich:TwinStrand Biosciences: Research Funding. Salk:TwinStrand Biosciences: Current Employment.

Background Cytogenetic and molecular aberrations are important prognostic factors in pediatric acute myeloid leukemia (AML). NUP98 translocations with more than 30 different partner genes have been identified in pediatric AML. The 2 most common fusions, NUP98-NSD1 and NUP98-KDM5A, have been shown to have distinct characteristics and are both associated with adverse outcomes. Although NUP98 fusions with less common fusion partners have been identified, the biological and clinical implications of these variants are unknown. Methods To determine the biological and clinical implications of the less common "other" NUP98 translocations (NUP98-X), we evaluated the clinical characteristics and transcriptome and genome sequencing data from 2396 children and young adults with AML within 4 consecutive Children's Cancer Group (CCG) and Children's Oncology Group (COG) trials CCG-2961, AAML03P1, AAML0531 and AAML1031. All NUP98-X translocations were confirmed by RNA sequencing. Results Of the 2396 patients screened, 164 patients (6.8%) had a NUP98 translocation. We identified 20 patients with a NUP98-X fusion (0.83%) and compared them with those with NUP98-NSD1 (n=110, 4.5%), NUP98-KDM5A(n=34, 1.4%), and a reference cohort without NUP98 translocations (n=2232). Translocation partners identified in the NUP98-X group were HOXA9 (n=4), HOXD13 (n=3), PHF15 (n=2), PHF23 (n=2), and single cases of BPTF, BRWD3, DDX10, HMGB3, HOXA13, KAT7, PRRX1, SET and TOP1. Besides the distinct characteristics of NUP98-NSD1 and NUP98-KDM5A, the NUP98-X group showed high inter-patient variance in clinical characteristics compared to our reference cohort. NUP98-X patients showed a clear bimodal age distribution with half of the patients being in the older age category and a similar number in the category We evaluated the impact of NUP98-X translocations in response to the initial induction therapy. The morphological complete remission (CR) rate after course 1 was 65% in the NUP98-X cohort versus 76% in the reference cohort (p=0.266). NUP98-NSD1 patients had an inferior CR rate (36%, p Conclusion NUP98-X translocated pediatric AML patients represent a rare cohort with a high variability in both translocation partners and other clinical characteristics. Despite this heterogeneity, the OS of these patients is comparable to high-risk pediatric AML patients, which justifies a high-risk stratification of these patients and emphasizes the need for developing new treatment strategies. Further research within large patient cohorts is needed to investigate the biologic and clinical characteristics of these rare translocations and potential differences between the different NUP98-X fusion partners. Disclosures Kaspers: AbbVie: Ended employment in the past 24 months; Helsinn Healthcare: Ended employment in the past 24 months; Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees; Janssen R&D: Ended employment in the past 24 months. Cooper:Celgene: Other: Spouse was an employee of Celgene (through August 2019).

Children with acute myeloid leukemia (AML) are at a particularly high risk for infectious complications related to the highly intensive chemotherapy. Infections leads to mortality and prolong hospitalization. The aim of the study is to evaluate the risk factors, infectious complications and assess outcome of febrile episodes during induction and consolidation chemotherapy courses in children with AML at the Pediatric Oncology Department, National Cancer Institute, Cairo University from January 2016 to December 2018. Infectious complications were evaluated retrospectively in 621 febrile episodes. Mortality from gram negative bacteremia was 29.9%, in febrile episodes with multidrug resistant gram negative bacteremia: Mortality was 39.2 % in febrile episodes with multidrug resistant gram negative bacteremia and septic shock. Mortality was 71.8 % (p value Sepsis and septic shock are major causes of mortality during chemotherapy-induced neutropenia. Thus, awareness of the presenting characteristics and prompt management is most important. Improved management of sepsis during neutropenia may reduce the mortality of pediatric Acute myeloid leukemia. It is Important to trace the risk factors that may affect the outcome of febrile episodes. Summary of Significant laboratory and clinical predictors of mortality Risk Factor Mortality p value Septic shock 55% 18 days 20.50% Start of antimicrobial in relation to start of chemotherapy < 16 days 33% Episodes: Not in remission 15.60% Risk factor Mortality p value CRP more than or equals 90 mg/l 24.4% Not significant ANC LESS THAN 500 29.9% 0.003 Hgb less than or equals to 7 g/dl 19.9% 0.633 Platelets less than 20000/cc 29.9% 0.299 Liver impairment (grades 3 and 4) 42.2% 0.025 Electrolyte imbalance (grades 3 and 4) 24.1% 0.003 Renal impairment 56.8% 0.025 Coagulopathy 41%

10032 Background: Pediatric acute myeloid leukemia (AML) is a rare disease with roughly 500 cases diagnosed in the United States each year and has had minimal improvement in clinical outcomes over recent decades. Novel treatment development to improve outcomes may be enhanced with an accompanying test for predicting treatment response. We previously demonstrated that an ex vivo drug sensitivity assay (DSA) can predict clinical response in myelodysplastic syndrome. Here we investigated the use of the DSA in pediatric AML patients, including a subset participating in a clinical trial of atovaquone. Atovaquone is an FDA-approved anti-parasitic drug that was associated with lower relapse rates in adult AML patients. Adding atovaquone and other standard of care combination treatments into the DSA, we investigated whether the assay, performed on pre-induction samples, correlated with measures of clinical response. Methods: We assayed pre-induction blood or bone marrow samples from 22 de novo pediatric AML patients diagnosed at Texas Children’s between 5/2015 and 10/2020 who consented to research (82% enrolled in clinical trial identifier NCT03568994). We subsetted this analysis to patients who received ADE (Cytarabine, Daunorubicin, Etoposide) (n = 20) induction, with the majority additionally receiving atovaquone (n = 16). For the DSA, samples were incubated with up to 25 compounds, including the treatment drug combinations and each of the compounds individually. After incubation, changes in tumor blast populations were assessed by flow cytometry. For each drug condition, drug sensitivity was calculated based on the number of blasts remaining after treatment. After quality control, downstream analyses were limited to 13 samples. Clinical response data, including minimal residual disease (MRD) percentage by flow cytometry and one year relapse-free survival, were correlated with the drug sensitivity results. Results: For the de novo subset analysis, we observed correlations between ex vivo drug sensitivity with both MRD percentage (r = 0.63) and one year relapse-free survival (RFS1, AUC = 0.92). The 3 patients with lowest ex vivo sensitivity had the highest MRD percentages (mean 21%). 2 of the 3 patients who did not achieve one year relapse-free survival had the lowest ex vivo sensitivity. Drug combination sensitivity correlated more with MRD and RFS1 than the single agents alone (single agent mean MRD r = 0.39). Conclusions: In our cohort, ex vivo DSA for ADE and atovaquone in pediatric AML cases correlated with both MRD and one year relapse-free survival. This suggests that clinical response in pediatric AML may be assessed prior to treatment using a DSA. This study also suggests that the DSA can be used to test drug combinations, and thus may be used for investigating novel treatment combinations. Further development of the DSA may benefit treatment decisions and prioritization of drug development.

A Children's Oncology Group study of nearly 1,000 pediatric acute myeloid leukemia (AML) cases reveals marked differences between the genomic landscapes of pediatric and adult AML and offers directions for future work.