INTRODUCTION:Infection causes significant morbidity and mortality in pediatric acute myeloid leukemia (pAML). This study describes the incidence and risk factors of bloodstream infection (BSI) and invasive fungal infection (IFI) in pAML. METHODS:A retrospective chart review was performed of patients treated according to the ANLL-97/AML-12 (N = 116), AML-15 (N = 60), or DB AML-01 (N = 67) protocols between 1998 and 2014. Cumulative incidence was analyzed for infectious outcomes (any BSI, viridans group streptococci [VGS-BSI], Gram-negative rod [GNR-BSI], IFI). Risk factors were analyzed in multivariable models. Recurrent event analyses were performed to evaluate whether previous infection(s) were related to subsequent infection. RESULTS:The cumulative incidence of any BSI was 78%, VGS-BSI 35%, GNR-BSI 15%, and IFI 11% through Day 150. Incidence of GNR-BSI decreased over time; AML-15 hazard ratio ([HR] 0.37, 95% confidence interval [CI]: 0.14-0.98, p = 0.045) and DB AML-01 (HR 0.42, 95% CI: 0.18-0.97, p = 0.042) compared to ANLL-97/AML-12. White blood cell counts ≥20 × 109/L at diagnosis and older age were associated with lower infection risk. Recurrent event analyses showed a higher risk of subsequent BSI for patients who had two or more prior BSIs. CONCLUSION:Despite efforts to improve supportive care in pAML, only GNR-BSI cumulative incidence declined over time. Future studies should continue working toward decreasing the incidence of infection while maintaining treatment efficacy.

Abstract Background: Bone marrow (BM) aspirates during and after induction chemotherapy are established but cumbersome prognostic tools for assessing treatment response in pediatric acute myeloid leukemia (AML) (Creutzig 2014, Abrahamsson 2011, Kern 2003). Peripheral blood blast clearance (PBBC) assessment by morphology has shown prognostic value in adult AML and might offer a cost-effective, easily accessible alternative, especially in low-resource settings (Manabe 2008, Arellano 2012). Its utility in pediatric AML is not well-established. This study investigates early PBBC as a predictor of treatment response and outcomes in pediatric AML. Methods: Data on pediatric patients with de novo AML treated according to the NOPHO-DBH AML-2012 protocol were prospectively obtained. Participating countries included Belgium, Denmark, Israel, Latvia, The Netherlands, Norway and Sweden. The first 5 days of induction therapy consisted of etoposide, followed by 7 days of low-dose cytarabine and mitoxantrone or liposomal daunorubicin. Peripheral blood (PB) was assessed by morphology at the time of diagnosis, daily in the first week, and thrice weekly until D22 or until complete clearance of blasts occurred. BM at day 22 (D22) was assessed by morphology and flow cytometry. A receiver operating characteristic (ROC) analysis was performed to evaluate the predictive power of the number of days from starting chemotherapy to complete PBBC. The time to PBBC and rate of PBBC, defined as the daily percentage of peripheral blood blast count cleared from diagnosis to the last assessment, were correlated with BM response on D22, complete remission status (CR), refractory disease (RD), event-free survival (EFS), and overall survival (OS). Flow cytometry based measurable residual disease (flow-MRD) negativity was defined as the absence of detectable leukemic cells in the BM (<0.01%). Results: Between March 2013 and February 2023, a total of 319 patients were included, 241 of whom were eligible for analysis, due to missing or incomplete data (n=78). Day 9 after initiation of chemotherapy was identified as the most discriminating cut-off point for predicting BM D22 response (predicted probability of 89.3%; P<0.001). Patients who achieved PBBC ≤9 days were classified as early PBBC (n=159; 66%), while those with blast clearance >9 days were classified as delayed PBBC (n=82; 34%). For 217 patients (due to missing data in 24 cases), the rate of PBBC could be calculated, and a discriminative cut-off value of 11% was identified (predicted probability of 84%, P<0.001). Patients were categorized into a high rate of PBBC (>11%; n=132) and low rate of PBBC (≤11%; n=85). Early PBBC and a high PBBC rate were associated with favorable BM responses (<5% leukemic cells) on D22 (86.7% vs. 68.4%, P<0.001; and 88.1% vs. 67.1%, P=0.001, respectively). No poor responders with ≥15% leukemic cells in BM on D22 were observed in the early PBBC group. Early PBBC and high PBBC rate were associated with higher flow-MRD negative rates on D22 (53.7% vs. 37.5%, P=0.027 and 51.9% vs. 38.4%, P=0.028). There was no significant association with RD or EFS in either group. Five-year OS was significantly higher in the early PBBC and high PBBC rate group (84.2% vs. 72.6%, P=0.02; and 86.5% vs. 73.7%, P=0.021, respectively). Conclusion: Early PBBC is a promising, non-invasive prognostic marker of treatment response and outcome in pediatric AML. Its simplicity and cost-effectiveness make it particularly advantageous for low-resource settings.

In contrast to patients with B cell precursor acute lymphoblastic leukemia (BCP-ALL), patients with acute myeloid leukemia (AML) have not yet benefited from recent advances in targeted immunotherapy. Repurposing immunotherapies that have been successfully used to target other hematological malignancies could, in case of a shared target antigen, represent a promising opportunity to expand the immunotherapeutic options for AML. Here, we evaluated the expression of CD19 in a large pediatric AML cohort, assessed the ex vivo AML killing efficacy of CD19-directed immunotherapies, and characterized the bone marrow immune microenvironment in pediatric AML, BCP-ALL, and non-leukemic controls. Out of 167 newly diagnosed de novo pediatric AML patients, 18 patients (11%) had CD19+ AML, with 61% carrying the translocation t(8;21)(q22;q22). Among CD19+ samples, we observed a continuum of CD19 expression levels on AML cells. In individuals exhibiting unimodal and high CD19 expression, the antigen was consistently present on nearly all CD34+CD38- and CD34+CD38+ subpopulations. In ex vivo AML-T cell co-cultures, blinatumomab demonstrated substantial AML killing, with an efficacy similar to BCP-ALL. In addition, CAR T cells could effectively eliminate CD19+ AML cells ex vivo . Furthermore, our immunogenomic assessment of the bone marrow immune microenvironment of newly diagnosed pediatric t(8;21) AML revealed that T- and NK cells had a less exhausted and senescent phenotype in comparison to pediatric BCP-ALL. Altogether, our study underscores the promise of CD19-directed immunotherapies for the treatment of pediatric CD19+ AML.### Competing Interest StatementThis work has been funded by a KIKA (329) program grant to O.H. Outside of the current work: C.M.Z.: Kura: Other: Institutional support for clinical trials; Gilead: Other: Institutional support for clinical trials; Novartis: Membership on an entity's Board of Directors or advisory committees; Syndax: Consultancy; Incyte: Consultancy; BMS: Consultancy; Kura Oncology: Consultancy; Jazz: Other: Institutional support for clinical trials; Gilead: Consultancy; Novartis: Consultancy; Daiichi Sankyo: Other: Institutional support for clinical trials; ITCC Hem Malignancies Committee: Other: Leadership or fiduciary role in other board, society, committee, or advocacy group, paid or unpaid; Chair Dutch MREC Society: Other: Leadership or fiduciary role in other board, society, committee, or advocacy group, paid or unpaid; Chair MREC Utrecht: Other: Leadership or fiduciary role in other board, society, committee, or advocacy group, paid or unpaid; Sanofi: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: Institutional support for clinical trials; Abbvie: Other: Institutional support for clinical trials; Pfizer: Other: Institutional support for clinical trials. O.H.: Roche: Research Funding; Syndax: Research Funding.

Annually, over 400,000 children develop cancer, with the majority living in low- and middle-income countries (LMICs). Survival rates in high-income countries (HICs; ≥75-80%) significantly exceed those in LMICs (<30%). Acute myeloid leukemia (AML) is a childhood cancer with high mortality rates in LMICs and is not included in the WHO's ‘six common and curable types of cancer’. This case report explores two pediatric AML cases in Kenya (LMIC) and the Netherlands (HIC), highlighting differences and similarities in both patient journeys. The first case is a 15-year-old Kenyan boy who initially experienced dizziness and fatigue. After repeated blood transfusions without a definitive diagnosis, AML was confirmed via bone marrow aspiration (BMA) 63 days later, and treatment followed the SIOP PODC AML guidelines for LMICs. The second case is a 6-year-old Dutch boy with fatigue and malaise. Initially diagnosed with post-viral bone marrow failure, a BMA performed 61 days after symptom onset revealed AML, and treatment followed the NOPHO-DBH AML-2012 protocol. Both patients faced frequent febrile neutropenia, managed per local guidelines, illustrating the balance between anti-cancer treatment and supportive care. Despite challenges, both boys completed treatment and are in complete remission. This case series highlights the potential for effective AML treatment in resource-constrained settings and underscores the need to address cancers beyond the ‘six common and curable types’.

A comprehensive international consensus on the cytogenetic risk -group strati fication of KMT2A -rearranged ( KMT2A -r) pediatric acute myeloid leukemia (AML) is lacking. This retrospective (2005-2016) International Berlin-Frankfurt-M & uuml;nster Study Group study on 1256 children with KMT2A -r AML aims to validate the prognostic value of established recurring KMT2A fusions and additional cytogenetic aberrations (ACAs) and to de fine additional, recurring KMT2A fusions and ACAs, evaluating their prognostic relevance. Compared with our previous study, 3 additional, recurring KMT2A -r groups were de fined: Xq24/ KMT2A :: SEPT6 , 1p32/ KMT2A :: EPS15 , and 17q12/t(11;17)(q23;q12). Across 13 KMT2A -r groups, 5-year event-free survival probabilities varied signi ficantly (21.8%-76.2%; P < .01). ACAs occurred in 46.8% of 1200 patients with complete karyotypes, correlating with inferior overall survival (56.8% vs 67.9%; P < .01). Multivariable analyses con firmed independent associations of 4q21/ KMT2A :: AFF1 , 6q27/ KMT2A :: AFDN , 10p12/ KMT2A :: MLLT10 , 10p11.2/ KMT2A :: ABI1 , and 19p13.3/ KMT2A :: MLLT1 with adverse outcomes, but not those of 1q21/ KMT2A :: MLLT11 and trisomy 19 with favorable and adverse outcomes, respectively. Newly identi fied ACAs with independent adverse prognoses were monosomy 10, trisomies 1, 6, 16, and X, add(12p), and del(9q). Among patients with 9p22/ KMT2A :: MLLT3 , the independent association of French-American- British -type M5 with favorable outcomes was con firmed, and those of trisomy 6 and measurable residual disease at end of induction with adverse outcomes were identi fied. We provide evidence to incorporate 5 adverse -risk KMT2A fusions into the cytogenetic risk - group strati fication of KMT2A -r pediatric AML, to revise the favorable -risk classi fication of 1q21/ KMT2A :: MLLT11 to intermediate risk, and to re fine the risk -strati fication of 9p22/ KMT2A :: MLLT3 AML. Future studies should validate the associations between the newly identi fied ACAs and outcomes and unravel the underlying biological pathogenesis of KMT2A fusions and ACAs.

Background: t(8;21) acute myeloid leukemia (AML) is one of the most frequent subtypes of leukemia in pediatric patients with overall favorable outcome. Yet, the backbone of treatment mainly relies on intensive chemotherapy with 15% relapse rate. To further improve treatment outcomes, targeted/immune-based therapies are urgently needed. However, identification of novel immunotherapy targets exclusively expressed on AML cells has been challenging. Aims: The t(8;21) AML subtype has been shown to express varying levels of CD19 and this led us to question whether CD19 targeting immunotherapies approved for acute lymphoblastic leukemia (ALL) and mixed phenotype acute leukemia (MPAL) can be repurposed in CD19+ pediatric AML as well. Methods: We first assessed the incidence and outcome of CD19 positivity in pediatric AML patients by performing a retrospective medical records study on cytogenetic, flow cytometry and outcome data. Pediatric patients in the Dutch NOPHO-DBH AML-2012 cohort, diagnosed between January 2012 and October 2022 were included. Next, to determine if CD19+ AML cells could be killed by T-cells engaged through blinatumomab, a CD3xCD19 bispecific antibody, we used an ex-vivo co-culture system. Our system comprised t(8;21) patient-derived xenograft (PDX) cells, grown on mesenchymal stem cell (MSC) feeders in an in-house optimized cell culture medium supporting the survival and proliferation of AML cells, and varying ratios of CD3+ T-cells from healthy donors. Activation markers in T-cells and killing efficiency in AML population were determined in presence and absence of blinatumomab by flow cytometry. Results: In total, 167 AML patients were analyzed. Of these, 18 (10.8%) were positive for CD19 based on diagnostic flow cytometry data. In CD19+ patients, 11 carried t(8;21), one patient had t(1;11), one had t(9;11), two had t(16;21), and for 3 patients the cytogenetic data were unknown. The median age of the CD19+ patients was 10.5 years, and 77.8% were male. All CD19+ patients achieved complete remission (CR) within two induction courses of chemotherapy. Five patients had a relapse (27.8%), and one patient died (5.6%). Four of these patients were CD19+ in their relapse (80%). The 5-year event-free (EFS) and overall survival (OS) were 65.0% and 85.7%. Next, we assessed the response of t(8;21) patient-derived cells towards CD19 bispecific antibodies. The t-distributed stochastic neighbor embedding (tSNSE) plots showed homogenous CD19 expression in both CD34+ (immature) and CD11b+ and/or CD15+ (more differentiated) subpopulations, suggesting that both immature and more mature AML cells could be irradicated by blinatumomab activated T-cells. Accordingly, in co-culture of T-cells (Effectors) with AML (Target) cells at a ratio of 1:1 and 1:10 E:T, 85% and 50% killing of AML cells were observed respectively in the presence of blinatumomab after 48 hours, while in the absence of blinatumomab, the killing% was negligible. T-cell activation markers CD137, CD69, and CD25 increased substantially following co-culture of AML cells and T-cells with blinatumomab, suggesting that the bispecific antibody-mediated T-cell activation results in the observed AML cell killing. Summary/Conclusion: CD19 positivity can be exploited as an immunotherapy target in t(8;21) pediatric AML. Our data elucidates the efficacy of blinatumomab in eradicating AML cells, thus supporting clinical evaluation of its safety and efficacy in this pediatric AML subtype. Keywords: Immune therapy, Acute myeloid leukemia, AML1-ETO, Pediatric

Although survival in pediatric acute myeloid leukemia (AML) has increased considerably over the past decades, refractory disease and relapse rates remain high. Refractory and relapsed disease are difficult to treat, with overall survival rates less than 40-50%. Preventing relapse should, therefore, be one of the highest priorities. Current conventional chemotherapy regimens are hard to intensify due to associated toxic complications, hence more effective therapies that do not increase toxicity are needed. A promising targeted agent is the CD33-directed antibody-drug conjugate gemtuzumab ozogamicin (GO). Because CD33 is highly expressed on leukemic cells in the majority of AML patients, GO can be useful for a broad range of patients. Better relapse-free survival (RFS) after therapy including GO has been reported in several pediatric clinical trials; however, ambiguity about the clinical value of GO in newly diagnosed children remains. Treatment with GO in de novo AML patients aged ≥1 month, in combination with standard chemotherapy is approved in the United States, whereas in Europe, GO is only approved for newly diagnosed patients aged ≥15 years. In this review, we aimed to clarify the clinical value of GO for treatment of newly diagnosed pediatric AML patients. Based on current literature, GO seems to have additional value, in terms of RFS, and acceptable toxicity when used in addition to chemotherapy during initial treatment. Moreover, in KMT2A-rearranged patients, the clinical value of GO was even more evident. Also, we addressed predictors of response, being CD33 expression and SNPs, PgP-1 and Annexin A5. The near finalized intent-to-file clinical trial in the MyeChild consortium investigates whether fractionated dosing has additional value for pediatric AML, which may pave the way for a broader application of GO in pediatric AML.

The Pediatric Oncology in Developing Countries (PODC) committee of the International Society of Pediatric Oncology (SIOP) published a pediatric acute myeloid leukemia (AML)‐specific adapted treatment guideline for low‐ and middle‐income countries. We evaluated the outcomes of children with AML at a large Kenyan academic hospital before (period 1) and after (period 2) implementing this guideline.

Background and Significance The cure rate of pediatric acute myeloid leukemia (AML) has improved significantly; however, relapses still occur in up to 30% of the total patient population in high-income countries (HICs), and in an even higher percentage of patients in low- and middle-income countries (LMICs). Early treatment response, cytogenetics and minimal residual disease (MRD) are well-known prognostic factors for treatment outcome; however, sophisticated techniques for identifying prognostic factors are often lacking in LMICs, and are sometimes unsuccessful in HICs. Early treatment response assessed by a bone marrow (BM) aspirate on day 15 or day 22 (D22) (depending on the applicable protocol) after initiation of chemotherapy is a known prognostic factor for outcome in patients with pediatric AML, but does not allow modifications of the first induction chemotherapy course (Creutzig 2014, Abrahamsson 2011, Kern 2003). In both pediatric acute lymphoid leukemia (ALL) and adult AML, early peripheral blood blast clearance (PBBC) is a known early indicator of treatment response (Manabe 2008, Arellano 2012), whereas to the best of our knowledge, this has not yet been reported in pediatric AML. In this study, we evaluated the significance of time to complete PBBC, and rate of PBBC after initiation of chemotherapy, in relation to disease status in BM D22, as measure of early treatment response that has prognostic significance. Study Design and Methods Pediatric patients with AML, aged 0-18 years, that were treated according to the NOPHO-DBH AML-2012 protocol were included. The first 5 days of induction therapy consisted of etoposide, followed by 7 days of low-dose cytarabine and mitoxantrone or liposomal daunorubicin. Peripheral blood (PB) was assessed by morphology at the time of diagnosis, daily in the first week, and thrice weekly until D22 or until occurrence of complete clearance of blasts. BM D22 was assessed by morphology and flow cytometry. A receiver operating characteristic (ROC) analysis was performed to evaluate the predictive power of days from starting chemotherapy to complete PBBC. The correlation between time to complete PBBC and BM D22 results was analyzed using a logistic regression model. Multivariable logistic regression models were applied for the association after adjusting for effects of other covariates. Rate of PBBC was defined as the percentage of the absolute PB blast count on the day of diagnosis that cleared with each day of therapy, on average, until D22 or the day of complete PBBC. Results In total, 319 patients were included, out of whom 241 were eligible for analysis, and 78 not eligible due to missing or incomplete data. Day 9 after initiation of chemotherapy was identified as the most discriminating cut-off point for predicting BM D22 response. Patients were categorized into early PBBC (≤9 days; n=159) and delayed PBBC (>9 days; n=82) groups. Early PBBC was associated with having <5% AML cells in BM D22 as assessed by both morphology (OR 3.11; P=0.005) and flow cytometry (OR 2.73; P=0.041). Early PBBC also showed a much lower likelihood of having >15% AML cells in BM D22 by morphology (OR 0.08; P=0.002). None of the early PBBC patients had >15% AML cells in BM D22 by flow cytometry. For 217 patients (selection due to missing data [n=24]), the rate of PBBC could be calculated, and a discriminative cut-off value of 11% was identified. Patients were categorized into high rate of PBBC (>11%; n=132) and low rate of PBBC (≤11%; n=85). High rate of PBBC was associated with having <5% AML cells in BM D22 by flow cytometry (OR 4.30; P=0.007) and negative MRD status (OR 2.02; P=0.004), while also showing a strong association with a lower likelihood of >15% AML cells in BM D22 (OR 0.11; P=0.007) by morphology. None of the high rate PBBC patients had >15% AML cells in BM D22 by flow cytometry. Conclusion Both early complete PBBC and rate of PBBC after initiation of chemotherapy holds promise as prognostic marker for clinical outcome in pediatric AML, as it correlates significantly with BM D22 response. These findings may offer an early and easily accessible prognostic factor, particularly beneficial for LMICs, as well as for patients with unsuccessful MRD analyses.

PURPOSE A previous study by the International Berlin-Frankfurt-Münster Study Group (I-BFM-SG) on childhood KMT2A-rearranged ( KMT2A-r) AML demonstrated the prognostic value of the fusion partner. This I-BFM-SG study investigated the value of flow cytometry-based measurable residual disease (flow-MRD) and evaluated the benefit of allogeneic stem-cell transplantation (allo-SCT) in first complete remission (CR1) in this disease. METHODS A total of 1,130 children with KMT2A-r AML, diagnosed between January 2005 and December 2016, were assigned to high-risk (n = 402; 35.6%) or non–high-risk (n = 728; 64.4%) fusion partner-based groups. Flow-MRD levels at both end of induction 1 (EOI1) and 2 (EOI2) were available for 456 patients and were considered negative (<0.1%) or positive (≥0.1%). End points were 5-year event-free survival (EFS), cumulative incidence of relapse (CIR), and overall survival (OS). RESULTS The high-risk group had inferior EFS (30.3% high risk v 54.0% non-high risk; P < .0001), CIR (59.7% v 35.2%; P < .0001), and OS (49.2% v 70.5%; P < .0001). EOI2 MRD negativity was associated with superior EFS (n = 413; 47.6% MRD negativity v n = 43; 16.3% MRD positivity; P < .0001) and OS (n = 413; 66.0% v n = 43; 27.9%; P < .0001), and showed a trend toward lower CIR (n = 392; 46.1% v n = 26; 65.4%; P = .016). Similar results were obtained for patients with EOI2 MRD negativity within both risk groups, except that within the non–high-risk group, CIR was comparable with that of patients with EOI2 MRD positivity. Allo-SCT in CR1 only reduced CIR (hazard ratio, 0.5 [95% CI, 0.4 to 0.8]; P = .00096) within the high-risk group but did not improve OS. In multivariable analyses, EOI2 MRD positivity and high-risk group were independently associated with inferior EFS, CIR, and OS. CONCLUSION EOI2 flow-MRD is an independent prognostic factor and should be included as risk stratification factor in childhood KMT2A-r AML. Treatment approaches other than allo-SCT in CR1 are needed to improve prognosis.

Bloodstream infections (BSIs), especially those caused by Gram-negative rods (GNR) and viridans group streptococci (VGS), are common and potentially life-threatening complications of pediatric acute myeloid leukemia (AML) treatment. Limited literature is available on prophylactic regimens. We retrospectively evaluated the effect of different antibacterial prophylaxis regimens on the incidence of febrile neutropenic (FN) episodes and bacterial BSIs. Medical records of children (0–18 years) diagnosed with de novo AML and treated at two Dutch centers from May 1998 to March 2021 were studied. Data were analyzed per chemotherapy course and consecutive neutropenic period. A total of 82 patients had 316 evaluable courses: 92 were given with single-agent ciprofloxacin, 138 with penicillin plus ciprofloxacin, and 51 with teicoplanin plus ciprofloxacin. The remaining 35 courses with various other prophylaxis regimens were not statistically compared. During courses with teicoplanin plus ciprofloxacin, significantly fewer FN episodes (43 vs. 90% and 75%; p < 0.0001) and bacterial BSIs (4 vs. 63% and 33%; p < 0.0001) occurred than with single-agent ciprofloxacin and penicillin plus ciprofloxacin, respectively. GNR and VGS BSIs did not occur with teicoplanin plus ciprofloxacin and no bacterial BSI-related pediatric intensive care unit (PICU) admissions were required, whereas, with single-agent ciprofloxacin and penicillin plus ciprofloxacin, GNR BSIs occurred in 8 and 1% (p = 0.004), VGS BSIs in 24 and 14% (p = 0.0005), and BSI-related PICU admissions were required in 8 and 2% of the courses (p = 0.029), respectively. Teicoplanin plus ciprofloxacin as antibacterial prophylaxis is associated with a lower incidence of FN episodes and bacterial BSIs. This may be a good prophylactic regimen for pediatric AML patients during treatment.

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.

AbstractBackgroundPediatric acute myeloid leukemia (AML) is a challenging disease to treat in low‐ and middle‐income countries (LMICs). Literature suggests that survival in LMICs is poorer compared with survival in high‐income countries (HICs).AimsThis study evaluates the outcomes of Kenyan children with AML and the impact of sociodemographic and clinical characteristics on outcome.Methods and ResultsA retrospective medical records study was performed at Moi Teaching and Referral Hospital (MTRH) in Eldoret, Kenya, between January 2010 and December 2018. Sociodemographic and clinical characteristics, and treatment outcomes were evaluated. Chemotherapy included two “3 + 7” induction courses with doxorubicin and cytarabine and two “3 + 5” consolidation courses with etoposide and cytarabine. Supportive care included antimicrobial prophylaxis with cotrimoxazole and fluconazole, and blood products, if available. Seventy‐three children with AML were included. The median duration of symptoms before admission at MTRH was 1 month. The median time from admission at MTRH to diagnosis was 6 days and to the start of AML treatment 16 days. Out of the 55 children who were started on chemotherapy, 18 (33%) achieved complete remission, of whom 10 (56%) relapsed. The abandonment rate was 22% and the early death rate was 46%. The 2‐year probabilities of event‐free survival and overall survival were 4% and 7%, respectively. None of the sociodemographic and clinical characteristics were significantly associated with outcome.ConclusionSurvival of Kenyan children with AML is dismal and considerably lower compared with survival in HICs. Strategies to improve survival should be put in place including better supportive care, optimization of the treatment protocol, and reduction of the abandonment rate and time lag to diagnosis with sooner start of treatment.

Abstract 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.

Abstract Introduction KMT2A-rearranged (KMT2A-r) acute myeloid leukemia (AML) is a heterogeneous genetic subgroup with a frequency of about 25% in children with AML. At the 62 nd ASH annual meeting last year, we reported on the differences in outcome of various KMT2A subgroups based on translocation partner and the significance of minimal residual disease (MRD) status during and after induction as a follow-up study of Balgobind et al., Blood 2009. The impact of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first complete remission (CR1) and the presence of additional cytogenetic aberrations (ACAs) on prognosis have not yet been described for our cohort. Methods Data on allo-HSCT in CR1 and the presence of ACAs of 1256 KMT2A-r de novo pediatric AML patients from 15 AML study groups affiliated with the I-BFM Study Group, diagnosed between 2005 and 2016, were retrospectively collected and studied. Karyotypes were reviewed and classified by two of the authors (RW&CH). Based on translocation partners, patients were classified to the KMT2A high-risk subgroup (6q27, 10p11.2, 10p12, 4q21, and 19p13.3) or non-high-risk subgroup (9p22, 19p13, 19p13.1, 1q21, Xq24, 17q21, 1p32, and 17q12). These two categories have been used to estimate a Cox model. Patients with unknown translocation partners were excluded from these analyses (n=126). Flow cytometry MRD levels at the end of induction course 1 (EOI1) and 2 (EOI2) <0.1% were considered negative, and levels ≥0.1% positive. Kaplan-Meier's methodology was used to estimate disease-free survival (DFS) and overall survival (OS). DFS was calculated from EOI1 for patients in CR to date of relapse or death/last follow-up. OS was calculated from the time of diagnosis to date of death/last follow-up. Two-sided P-values of ≤ .01 were considered statistically significant. Covariates with P-values ≤ .05 in univariate analyses were included in multivariate analyses; allo-HSCT in CR1 was included as a time-dependent covariate in the Cox model. MRD status at EOI2 was excluded from multivariate analyses as therapy could have been adjusted to the MRD status and the number of MRD positive patients was small. Results Of 1256 pediatric patients with KMT2A-r AML, data on HSCT in CR1 and ACAs were available for 1186 (94.4%) and 1204 patients (95.9%), respectively; 211 (17.8%) patients received HSCT in CR1 and ACAs were present in 601 (49.9%) patients. Compared with the KMT2A non-high-risk subgroup, patients in the KMT2A high-risk subgroup underwent HSCT in CR1 more often (23.8% vs 15.0%; P < .001). ACAs were borderline significantly more common in the KMT2A high-risk subgroup (54.1% vs 46.4%; P = .015). Univariate analysis of the probability of DFS (Table 1) showed that the KMT2A high-risk subgroup (HR 2.1; 95% CI, 1.7-2.5), age ≥10 years (HR 1.4; 95% CI, 1.2-1.7), and MRD ≥0.1 at EOI1 (HR 1.5; 95% CI, 1.1-1.9) were associated with DFS. HSCT in CR1 was a borderline significant prognostic factor (HR 0.7; 95% CI, 0.6-0.9). In a multivariate analysis for DFS (n=515) (Table 1), the KMT2A high-risk subgroup (HR 2.0; 95% CI, 1.6-2.6), MRD ≥0.1 at EOI1 (HR 1.7; 95% CI, 1.2-2.3), and HSCT in CR1 (HR 0.6; 95% CI, 0.4-0.9) were associated with DFS. Univariate analysis of the probability of OS (Table 1) showed that the KMT2A high-risk subgroup (HR 1.8; 95% CI, 1.5-2.2), age ≥10 years (HR 1.6; 95% CI 1.3-2.0), WBC ≥100 x10 9/L (HR 1.4; 95% CI, 1.1-1.7), the presence of ACAs (HR 1.4; 95% CI, 1.2-1.7), and MRD ≥0.1 at EOI1 (HR 2.1; 95% CI, 1.6-2.7) were associated with OS. HSCT in CR1 was not associated with OS. The effect of HSCT in CR1 was not significantly different between the KMT2A high-risk and non-high-risk subgroups. In a multivariate analysis for OS (n=557) (Table 1), the KMT2A high-risk subgroup (HR 1.9; 95% CI, 1.4-2.5), age ≥10 years (HR 1.5; 95% CI, 1.1-1.9), the presence of ACAs (HR 1.6; 95% CI, 1.2-2.1), and MRD positivity at EOI1 (HR 1.9; 95% CI, 1.4-2.5) were associated with OS. Conclusions In this cohort of KMT2A-r pediatric AML patients, the presence of ACAs at diagnosis was independently associated with inferior OS, but not with DFS. This may be due to the exclusion of refractory patients in DFS analysis, who were significantly more common in the group of patients with ACAs. Analysis has yet to be performed to distinguish karyotype complexity. In addition, allo-HSCT in CR1 was an independent predictor of improved DFS, but was not a prognostic factor for OS. Figure 1 Figure 1. Disclosures Abrahamsson: wedish Children´s Cancer Foundation. Research grants and 50% senior research position for clinical research on pediatric leukemia: Research Funding. Locatelli: Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Miltenyi: Speakers Bureau; Medac: Speakers Bureau; Jazz Pharamceutical: Speakers Bureau; Takeda: Speakers Bureau.

Introduction Outcome of KMT2A-rearranged (KMT2A-r) pediatric AML (pAML) is in general poor with a 5-year probability of event-free survival (5y-pEFS) and overall survival (5y-pOS) of 44% and 56%, respectively (Balgobind et al., 2009). However, over the past decades, the heterogeneity of KMT2A-r pAML has emerged, showing differences in outcome between subgroups based on translocation partners. The predictive value of MRD in KMT2A-r pAML is undefined. This retrospective study aimed to confirm the outcome of pediatric KMT2A subgroups (Balgobind et al., 2009) in a more recent era and to study the significance of MRD status during and after induction. Methods Outcome and MRD data of 1257 KMT2A-rde novo pAML patients from 15 AML groups affiliated with the I-BFM-AML study group, diagnosed between 2005 and 2016 were retrospectively collected. Patients were assigned to KMT2A subgroups, or to the KMT2A-other group in case of unknown translocation partner. Flow cytometry MRD levels <0.1% were considered negative, and levels ≥0.1% positive. Kaplan-Meier methods were used to estimate probabilities of disease-free survival (pDFS), pEFS and pOS. Cox regression analyses were performed to study the independent impact of KMT2A subgroups and potentially prognostic factors: white blood cell count (WBC), age and MRD status. Results The 1257 patients were assigned to 13 KMT2A subgroups, or the KMT2A-other group. Two novel subgroups were identified: t(X;11)(q24;q23) (n=21, 2%) and t(1;11)(p32;q23) (n=12, 1%). The median age was 2.5 years (range, 0-18.9). The median WBC was 21.4 x 109/L (range, 0.2-727). Overall complete remission rate was 91%. The 5y-pEFS was 46% [SE, 2%] and the 5y-pOS was 62% [SE, 2%]. Differences across subgroups in 5y-pEFS (Figure 1) ranged from 24% [SE, 5%] to 76% [SE, 9%], and in 5y-pOS from 25% [SE, 13%] to 92% [SE, 8%] (both p<0.0001). The median follow-up time of patients at risk was 5 years. The subgroups t(10;11)(p12;q23) (HR 1.7, p<0.0001), t(6;11)(q27;q23) (HR 1.9, p<0.0001), t(4;11)(q21;q23) (HR 2.9, p=.003) and t(10;11)(p11.2;q23) (HR 2.7, p<0.0001), WBC of >100 x 10^9/L (HR 1.3, p=.006), and age >10y (HR 1.3, p=.005) were revealed as independent predictors of poor EFS. These factors also predicted OS. MRD data after induction course one were available for n=635 (MRD-positivity (range, 0.1-94) n=126, 20%) and after course two for n=527 (MRD-positivity (range, 0.1-88) n=51, 10%). In the four KMT2A poor-risk subgroups, MRD-positivity was not significantly more common after induction course one (p=.0232) or two (p=.066), compared with the other subgroups. MRD-positivity was associated with inferior 5y-pDFS after both induction course one (36% [SE, 4%] vs 48% [SE, 2%]; p=.002) and course two (28% [SE, 6%] vs 49% [SE, 2%]; p<0.0001) (Figure 2). Within the t(9;11)(p22;q23) subgroup, MRD-positivity after induction course one, and within the t(10;11)(p12;q23) subgroup after course two, was associated with inferior 5y-pDFS (36% [SE, 8%] vs 56% [SE, 4%]; p=.004, and 0% [SE, 0%] vs 35% [SE, 5%]; p<0.0001, respectively). After induction course one, the subgroups t(10;11)(p12;q23) (HR 1.7, p<0.0001) and t(10;11)(p11.2;q23) (HR 4.0, p<0.0001), and MRD-positivity (HR 1.5, p=.003) were revealed as independent predictors of poor DFS. After induction course two, the subgroups t(10;11)(p12;q23) (HR 1.8, p<0.0001), t(4;11)(q21;q23) (HR 4.9, p=.008) and t(10;11)(p11.2;q23) (HR 3.2, p<0.0001), MRD-positivity (HR 2.0, p<0.0001), and age >10y (HR 1.5, p=.002) were revealed as independent predictors of poor DFS. Within the group of patients with MRD-negativity after induction course two, the subgroups t(10;11)(p12;q23) and t(10;11)(p11.2;q23) were independent predictors of poor EFS (5y-pEFS 35%, HR 1.7, p=.003 and 5y-pEFS 18%, HR 2.7, p=.004, respectively). Conclusion Outcome for KMT2A-r pAML patients has improved slightly, but similar subgroups were identified as poor risk (Balgobind et al., 2009), including t(10;11)(p12;q23), t(10;11)(p11.2;q23) and t(6;11)(q27;q23). In our study, t(4;11)(q21;q23) was poor risk as well. These subgroups should be considered for high-risk pAML therapy protocols. The favorable risk of t(1;11)(q21;q23) could not be confirmed in our cohort. MRD status is highly predictive of outcome within KMT2A subgroups. In MRD-negative patients after induction course two, both t(10;11) KMT2A subgroups were associated with poor outcome. Disclosures Guest: Syndax Pharmaceuticals: Consultancy. Locatelli:Medac: Speakers Bureau; Miltenyi: Speakers Bureau; Bellicum Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceeutical: Speakers Bureau. Rubnitz:AbbVie Inc.: Research Funding. Kaspers: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; AbbVie: Ended employment in the past 24 months.

Limited data are available on the incidence and impact of TP53 alterations and TP53 pathway deregulation in paediatric acute myeloid leukaemia (AML). We analysed TP53 alterations in bone marrow samples of 229 patients with de novo paediatric AML, and detected heterozygous missense exon mutations in two patients (1%) and 17p deletions of the TP53 gene in four patients (2%). These patients more frequently had complex karyotype (50% vs. 4%, P = 0·002) or adverse cytogenetic abnormalities, including complex karyotype (67% vs. 17%, P = 0·013), compared to TP53 wild-type. Differential expression of TP53 pathway genes was associated with poor survival, indicating a role for TP53 regulators and effector genes.

BACKGROUND:With the current more effective treatment regimens for pediatric acute myeloid leukemia (AML), research on early death (ED), treatment-related mortality (TRM), and toxicity becomes increasingly important. The aim of this study was to give an overview of the frequency, clinical features, and risk factors associated with ED and TRM in first complete remission (CR1) during the last three consecutive treatment protocols of the Dutch Childhood Oncology Group (DCOG) between 1998 and 2014. METHODS:Incidence and risk factors associated with ED and TRM in CR1 were retrospectively studied in 245 patients treated according to the Dutch ANLL-97/AML-12 (n = 118), AML-15 (n = 60), or DB AML-01 (n = 67) protocols. RESULTS:The incidence of ED was, respectively, 5.1%, 6.7%, and 3.0% excluding deaths before treatment (P = NS), and 7.4%, 11.1%, and 4.4% including deaths before the onset of treatment. Severe underweight at initial diagnosis was significantly associated with more frequent ED. When relapse was included as a competing risk, cumulative incidence of death in CR1 were 5.9%, 5.0%, and 4.6% for ANLL97, AML15, and DB01, respectively (P = NS). The most important cause of TRM included infectious and SCT-related complications. CONCLUSION:We report relatively stable rates of ED and TRM in CR1 in the latest completed DCOG protocols for newly diagnosed AML patients. The most important causes of TRM were SCT- or infection-related, warranting further evaluation and awareness.

ABSTRACT Introduction: Although the prognosis of pediatric acute myeloid leukemia (pAML) has improved, with current survival rates up to 75%, relapse rates remain high. Areas covered: The low number of patients, the heterogeneous genomic landscape of AML, novel diagnostic techniques, divergent available treatment protocols, and dose-limiting toxicity of conventional agents all contribute to the complexity of AML treatment. This review gives an overview of the current clinical challenges with respect to diagnostics, treatment, and supportive care in pAML. Expert commentary: Due to intensified treatment regimens and improved supportive care measures, the outcome for pAML patients has improved substantially over the past years. However, most treatment protocols still rely on conventional chemotherapeutic agents with significant toxicity. Although targeted therapies promise to reduce the need for high doses of conventional agents with a subsequent decrease in toxicity, the effectiveness of these strategies remains unsatisfactory today. International collaborations are needed in order to address the ongoing therapeutic challenges of reducing toxicity while increasing effectivity. Consensus on risk-group classification, a common chemotherapy backbone and evidence-based supportive care guidelines are necessary in this context, at the same time enabling intergroup studies on new agents in subgroups.