Core Binding Factor Acute Myeloid Leukemia Patients Research Articles

Prevalence and Prognosis of Secondary Genetic Aberrations Among Patients With Core Binding Factor Acute Myeloid Leukemia: A Mitelman Database Analysis.

Core binding factor acute myeloid leukemia (CBF-AML) comprises t(8;21) and inv(16) and usually has a favorable prognosis. However, a wide spectrum of secondary genetic aberrations has been shown to be associated with worse outcomes with respect to overall survival (OS) and relapse. We aimed to identify secondary molecular and chromosomal aberrations within each group of CBF-AML, i.e., t(8;21) and inv(16), and to evaluate their prognosis with OS. Using the Mitelman Database of Chromosome Aberrations and Gene Fusions in Cancer, we analyzed 193 cases of CBF-AML reported between 2011 and 2021. We conducted a survival analysis to determine the 5-year OS, and we conducted univariate and multivariate Cox regression to identify independent genetic factors related to OS. Among the 193 cases with CBF-AML, structural and numerical chromosome rearrangements were 25.9% and 40.9%, respectively, and secondary genetic mutations were 54.9%. The 5-year OS for the presence of del(7) and trisomy 22 was significantly worse. NRAS mutations had a worse 5-year OS in the t(8;21) group in the univariate analysis but showed no significant difference in the multivariate analysis. CBF-AML has heterogeneous cytogenetic characteristics but no difference in the 5-year OS between the inv(16) and t(8;21) groups. Finally, the presence of del(7), trisomy 22 and NRAS mutations showed a potential prognostic impact in CBF-AML patients. Secondary genetic findings may need to be identified to determine its association to a worse prognosis, and in the future develop better targeted therapies in patients with CBF-AML.

Molecular Relapse after First-Line Intensive Therapy in Patients with Core-Binding Factor and NPM1-Mutated Acute Myeloid Leukemia - a Filo Study

Background: Patients with Core-Binding Factor (CBF) and NPM1-mutated acute myeloid leukemia (AML) are considered as favorable or intermediate-risk according to the European LeukemiaNet (ELN) 2022 classification and allogeneic hematopoietic cell transplantation (HCT) is usually not considered in those achieving first complete remission (CR) with good molecular response. Close molecular monitoring by quantitative PCR has been widely implemented over time and approximately 30% of patients will experience molecular relapse. However, there is no recommendation on how to manage these patients due to the lack of data from large patient series or clinical trials. In this study, we retrospectively analyzed the outcome of CBF or NPM1-mutated AML patients who had MRD monitoring after having achieved first CR. Methods: All CBF and NPM1-mutated AML patients, aged 18-60 years, who had MRD molecular monitoring (RT-qPCR of RUNX1-RUNXT1 or CBFB-MYH1 transcripts or classical NPM1 mutations) after first-line therapy including induction therapy with daunorubicin/idarubicin and cytarabine followed by intermediate or high-dose cytarabine consolidation, without allogeneic HCT in first CR, were included. MRD measurements were generally performed every three months during follow-up for 24 months in either bone marrow (BM) or peripheral blood (PB). Molecular relapse was defined according to ELN recommendations (Heuser M, Blood 2021) as a conversion from MRD negativity to positivity or an increase in MRD copy numbers >1 log between two positive samples. Results: Between 2010 and 2019, 303 patients from 9 centers with newly diagnosed CBF or NPM1-mutated AML ( RUNX1-RUNX1T1, 19%; CBFB-MYH11, 27%; NPM1, 53%) and available MRD monitoring after first-line therapy were included. Among these patients, 153 (51%) never relapsed, 95 (31%) had molecular relapse, with a median of 326 days (interquartile range [IQR]: 276-438) from initial diagnosis, and 55 (18%) had upfront morphologic relapse (i.e., without prior molecular relapse detected), with a median of 388 days (IQR: 280-559). Patients with molecular and upfront morphologic relapse had higher white blood cell (WBC) count at diagnosis (12 vs. 22 vs. 30 G/l in those without relapse, molecular relapse, and morphological relapse, respectively, P=0.003) and were more likely to have a FLT3-ITD mutation (7% vs. 25% vs. 19%, respectively, P=0.001). In addition, patients with upfront morphologic relapse had a lower log-reduction of MRD during first-line treatment (4.90 vs. 4.93 vs. 3.77, respectively, P=0.009) and were more likely to have CR with positive MRD at the end of treatment in peripheral blood (2% vs. 16% vs. 32%, respectively, P<0.001). Overall survival (OS) was significantly different according to whether patients never relapsed, had molecular relapse, or had upfront morphological relapse (three-year OS of 100% vs. 75% vs. 60%, P<0.001; Figure A). Among the 95 patients with molecular relapse, 53 (56%) received preemptive therapy (median of 48 days [IQR:24-68] from molecular relapse to treatment initiation) and 42 (44%) progressed to morphologic relapse before treatment was initiated (median of 58 days [IQR:36-134] from molecular to morphologic relapse). Patients who received preemptive therapy had a better OS than those who received salvage therapy after having progressed from molecular to morphologic relapse, and those who had upfront morphologic relapse (78% vs. 51% vs. 51% at three years, respectively, P=0.01; Figure B). Preemptive therapy included upfront allogeneic HCT (n=19), intensive chemotherapy (n=21), and non-intensive therapy (n=13) with different OS rates that did not reach statistical significance (92% vs. 79% vs. 58% at three years for upfront allogeneic HCT, intensive chemotherapy, and less intensive therapy, respectively, P=0.09). Conclusion: Up to 30% of patients with CBF or NPM1-mutated AML experienced molecular relapse in our cohort and more than 50% of them received preemptive therapy. Patients treated preemptively at molecular relapse had a better OS than those treated with active disease. Although these results need to be confirmed in larger studies, it supports molecular monitoring during follow-up to start preemptive therapy before overt morphologic relapse. Other techniques for MRD monitoring are urgently needed for AML patients who cannot be monitored by qPCR.

Comparative Study for Haplo, MSD and MUD Allo-Hcts for Core-Binding Factor AML Patients in CR2: A Study from the Global Committee and the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Background Although core-binding factor acute myeloid leukemia (CBF-AML) generally has a favorable prognosis, relapse occurs in ~40% of cases. Allogeneic hematopoietic cell transplantation (allo-HCT) is recommended when patients achieve second complete remission (CR2). However, transplant outcomes and donor preference for these patients remain unclear. We compared in an EBMT global multi-center registry-based analysis the outcomes following allo-HCT using either haploidentical donors (HAPLO), matched siblings donors (MSD), or 10/10 matched unrelated donors (MUD). Methods Data from 865 de novo adult CBF AML patients in CR2 receiving allo-HCT in 227 EBMT centers from 2010-2022 were analyzed. Transplants from mismatched UD (<10/10), umbilical cord blood or grafts with ex-vivo manipulation were excluded. Univariate analyses and Cox regression models were used. Results Results from 329 MSD, 374 MUD, and 162 HAPLO HCTs were analyzed. For the entire cohort, median age was 43y (range: 18-76). Inv(16)/CBFBMYH11 was detected in 503 patients (58%) and t(8;21)/RUNX1-RUNX1T1 was detected in 362 patients (42%). Peripheral blood was the major graft source (86.1%), and myeloablative conditioning was used for the majority (60.1%) of all allo-HCTs. Female-to-male transplants were more common in the MSD group (25.5%) than in the HAPLO (19.8%) or MUD (14.2%) group, respectively (p<0.01). 83% of patients in the HAPLO group received post transplant cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis. Engraftment rates were higher in the MSD (98.8%) and MUD (98.9%) than in the HAPLO (94.9%) group (p<0.01). Original disease was the major cause of death for the MSD and MUD cohorts, while in the HAPLO group, it was infection. On univariate analysis, HAPLO HCT was associated with a higher 2-year non-relapse mortality (NRM) (MSD 17.1%, MUD 15.3%, HAPLO 25.7%). The 180-day cumulative incidence of grade II-IV acute GVHD was higher in HAPLOs (14.8%) than in MSD (6.8%) or MUD (7.9%) recipients, respectively . No significant difference was observed among the three cohorts for 2-year leukemia-free survival (LFS), overall survival (OS) and GVHD-free/relapse free survival (GRFS). CBF-AML with inv(16) was associated with lower relapse incidence RI (18.1%) than with t(8;21) (28.3%), which contributed to better OS (75.7% vs 59.8% at 2 years), LFS (65.8% vs 51.2%) and GRFS (50.8% vs 38.5%) . Older patient age i.e., above the median age, was associated with a higher NRM (22.4% vs 13.3%) and a lower OS (63.8% vs 74.8%) than younger age i.e., below the median age. Peripheral blood grafts were associated with higher incidences of chronic GVHD (41.5% vs 25.8%) and extensive cGVHD (21.6% vs 9.7%) than bone marrow grafts. On multivariate analysis, no significant difference was observed among HAPLO, MSD and MUD allo-HCTs on NRM. HAPLO HCT was associated with lower RI compared to MSD (hazard ratio [HR]=0.56, 95% CI 0.32-0.97; p<0.05) and MUD (HR=0.57, 95% CI: 0.33-0.99, p<0.05) while there was no significant differences between the 3 types of donors on LFS, OS and GRFS. CBF-AML with t(8;21) was associated with both higher RI (HR=1.79, 95% CI 1.3-2.47; p<0.01) and higher NRM (HR=1.58, 95% CI 1.1-2.27; p<0.01) than CBF-AML with inv(16), which led to worse LFS, OS and GRFS. Higher age (per 10 year) was associated with higher risk of NRM (HR=1.29, 95% CI 1.11-1.5; p<0.01) and worse OS (HR=1.13, 95% CI 1.01-1.27; p=0.03). Conclusions For CBF-AML patients in CR2, haploidentical HCTs were associated with a lower RI compared to MSD and MUD allo-HCTs. HAPLO achieved similar LFS, OS and GRFS to MSD or MUD, respectively. In addition, CBF AML with inv(16) had better outcomes than with t(8;21) after allo-HCT.

Residual Mast Cells Can Explain Persistent Molecular Positivity in Difference from Normal Flow Cytometric-Defined MRD Negative Core Binding Factor AML

Introduction: Core binding factor acute myeloid leukemia (CBF-AML) accounts for 30% of pediatric and 15% adult AMLs and is defined by fusions involving RUNX1 or CBFB. RT-PCR is commonly used to monitor measurable residual disease (MRD) in patients with CBF-AML. However, it has been reported that these fusions can be detected in patients during complete remission (CR) or after hematopoietic cell transplant (HCT). This raises the question of if these patients should be considered MRD positive, given they appear otherwise disease free. We utilized flow cytometric cell sorting and fluorescent in situ hybridization (FISH) to determine the source of persistent CBF fusions. Methods: Flow cytometry was used to isolate mast cells (CD117 bright/CD34 negative) from 13 patients with CBF-AML fusions (8 RUNX1:: RUNX1T1 and 5 CBFB:: MYH11) alongside progenitor cells (CD34+/CD117 heterogeneous, 12 patients) and T cells (CD3+, 11 patients) as available for FISH analysis. These patients were fusion positive by RT-PCR but had no evidence of MRD by difference from normal multidimensional flow cytometry (ΔN), the gold standard for determination of residual disease in Children's Oncology Group-sponsored clinical trials for AML. Cells were sorted from 6 additional patients with a history of RUNX1:: RUNX1T1 CBF-AML who were MRD negative by ΔN but without RT-PCR results available. Results: In 11/13 patients, the mast cell fraction was positive for the CBF fusion but all other sorted cell fractions tested were negative. In the remaining two specimens, all cell fractions were negative, likely due to FISH sensitivity compared to RT-PCR. Both CBF fusions exhibited the same pattern, with fusions detected only in the mast cell fractions (7 RUNX1:: RUNX1T1 and 4 CBFB:: MYH11). The additional 6 patients who were MRD negative by ΔN but without RT-PCR data followed the same pattern, with RUNX1:: RUNX1T1 detected by FISH in the mast cells (6/6 patients) and not in other sorted populations (5/6 patients sorted for progenitor and T cells). Two patients had a clinical history of CBF-AML and systemic mastocytosis (SM). ΔN revealed no evidence of residual AML but showed abnormal mast cells with expression of CD2 and CD25, consistent with abnormalities associated with SM. FISH analysis of sorted mast cells revealed the presence of the RUNX1:: RUNX1T1 fusion, while progenitor and T cells were both negative. In all other patients the mast cells showed no phenotypic abnormalities, demonstrating that CBF fusions can be detected in both phenotypically normal and abnormal mast cells in patients who are free of residual AML. Two patients with CBFB:: MYH11 fusions had specimens evaluated by FISH on sorted cells over a month apart where the fusion persisted only in the mast cells. Two patients with RUNX1:: RUNX1T1 fusions had serial specimens analyzed at 4 different timepoints. One patient had fusion positive mast cells for over 8 months after residual disease was last detected by ΔN. The other patient, who had previously undergone HCT, harbored fusion positive mast cells for 13 months. Both patients remained MRD negative by ΔN over the course of testing. Discussion: These data demonstrate that in CBF-AML, fusions can be detected exclusively in the mast cells of otherwise leukemia-free patients, resulting in positive RT-PCR results in the absence of any other disease pathology. These mast cells can be normal or abnormal and can persist after successful HCT. Given that these patients are free of disease by other measures, these fusion positive mast cells do not appear to contribute to AML pathogenesis. Additionally, this post-HCT fusion positive persistence demonstrates a potential clinical implication: if patients such as reported here are assessed pre-transplant using RT-PCR on unsorted specimens alone, they may not be considered candidates for HCT even though the fusion is confined to terminally differentiated cells and successful transplant can be achieved. For these reasons, while RT-PCR is a specific and accurate assay, caution is required for CBF-AML patients. Flow cytometry and cell sorting in combination with genetic testing, in this case FISH, protect against these mast cell driven positive results and provide an accurate assessment of disease status. These data highlight the importance of considering AML biology and combining multiple testing methods to monitor AML patients comprehensively and accurately.

Clinical impact of c-KIT and CEBPA mutations in 33 patients with corebinding factor (Non-M3) acute myeloid leukemia.

Corebinding factor acute myeloid leukemia (CBF-AML) is the most common cytogenetic subtype of pediatric AML. CBF-AML is associated with a relatively favorable outcome, although the relapse rate of approximately 40% indicates a high degree of clinical heterogeneity. The clinical impact of additional cytogenetic aberrations, including c-KIT and CEBPA mutations, in pediatric CBF-AML has not been well characterized, especially in the multi-ethnic region of Yunnan Province in China. In this study, we retrospectively analyzed the clinical features, gene mutations, and prognoses of 72 pediatric patients newly diagnosed with non-M3 AML in Kunming Children's Hospital, China, from January 1, 2015 to May 31, 2020. Of the 72 pediatric patients with AML, 46% (33/72) had CBF-AML. Thirteen patients with CBF-AML (39%) had c-KIT mutations, five (15%) had CEBPA mutations, and eleven (33.3%) had no other cytogenetic aberrations. The c-KIT mutations, resulting from single nucleotide substitutions and small insertions or deletions, occurred in exons 8 and 17. All of the CBF-AML-associated CEBPA mutations were single mutations and occurred in patients with RUNX1-RUNX1T1 fusion. We found no significant differences in the clinical data between CBF-AML patients with c-KIT or CEBPA mutations and CBF-AML patients without other aberrations, and no prognostic significance was established for these mutations. Our study is the first to report the clinical impact of c-KIT and CEBPA mutations in pediatric patients with non-M3 CBF-AML from the multi-ethnic Yunnan Province, China. c-KIT and CEBPA mutations occurred at a higher frequency in CBF-AML cases and were associated with unique clinical characteristics; however, no potential molecular prognostic markers were identified.

Outcomes of different therapies in acute myeloid leukemia patients with core-binding factor.

e19036 Background: Acute myeloid leukemia (AML) with RUNX1:RUNXT1 fusion or CBFB:MYH11 fusion is defined as core-binding factor AML (CBF-AML) and has been considered to show favorable prognosis. Methods: We conducted a retrospective analysis on previously untreated CBF-AML patients who received standard-dose induction therapies between Jan 2018 and Dec 2020 in our medical center. Patients were classified into 5 groups based on the induction regimens: VA, DA, IA, HAA, and DAV. The dosage of these regimens were determined as follows: VA, venetoclax 100mg d1,200mg d2, 400mg d3-28, Azacytidine 75mg/m2 d1-7; DA, daunorubicin 60mg/m2 d1-3, cytarabine 100mg/m2 d1-7; idarubicin 8-10mg/m2 d1-3, cytarabine 100mg/m2 d1-7; HAA, homoharringtonine 2mg/m2 d1-7, cytarabine 100mg/m2 d1-7, aclarubicin 12mg/m2 d1-7; DAV, daunorubicin 60mg/m2 d1-3, cytarabine 100mg/m2 d1-7, venetoclax 100mg d4, 200mg d5, 400mg d6-11. The response rate and survival data were analysed between these groups. Results: There’s a total of 106 CBF-AML patients involved, 85(80.2%) with RUNX1:RUNXT1 fusion and 21(19.8%) with CBFB:MYH11 fusion. The most common concomitant mutation was KIT (33%), and the most frequent hotspot mutation site was D816V in exon 17. The median age was 46 years ranging from 7 to 78, and 46.2% of the patients were male.Patients were classified into 5 groups based on the induction regimens, and there were 9 in VA group, 21 in HAA group, 23 in DA group, 38 in IA group, and 15 in DAV group. The CR rate of each group was 55.6%(VA), 87.0%(DA), 65.8%(IA), 90.4%(HAA), and 100%(DAV) respectively. Among the patients who received CR, patients in DAV group showed more pronounced decreasing of fusion gene levels (median 1450 fold) than other groups, while VA group had the slightest (median 8.9 fold). As to the survival, the median follow-up time was 15.2 months, and the median overall survival (OS) were not reached in all the groups. In the RUNX1:RUNXT1 fusion subgroup, DAV group showed significantly improved OS and event-free survival (EFS) than other groups, while VA groups was the worst. The median EFS were as follows: 3.5months(VA), not reached(HAA), 10.9months(DA), 7.9months(IA), and not reached(DAV) respectively. Conclusions: Our study demonstrated a promising therapeutic results of DAV regimen, and an unsatisfactory therapeutic results of VA regimen in CBF-AML. CBF-AML patients showed significantly improved CR rate, elimination of fusion genes, OS, and EFS when received intense chemotherapy, especially DAV and HAA regimen, than VA regimen. These results indicated that intense chemotherapy may be an optimal choice for CBF-AML.

The Prognostic Significance of c-KIT Mutations in Core Binding Factor Acute Myeloid Leukemia

BackgroundMany recurrent mutations are encountered in core binding factor acute myeloid leukemia (CBF-AML) which may affect the prognosis. Approximately 20 to 45% of CBF-AML patients have KIT mutations which are having poor prognosis and high incidence of relapse. There is still insufficient data to categorize the patients with c-kit mutation into which risk group and there is a debate around whether Tyrosine kinase inhibitors can decrease the relapse risk and improve the prognosis of those patients. Patients and MethodsThis study was conducted throughout a period of 3 years, where 102 CBF-AML were enrolled in our study. We analyzed the incidence of c-KIT exon 8 and 17 D816V mutations in CBF-AML patients and studied the prognosis. ResultsThe prevalence of CBF-AML was 102 of 989 (10.3%), 13.7% and 8.7% in pediatrics and adults’ groups respectively. c-KIT fragment mutation analysis revealed a mutant form in 27 of 102 (26.5%) patients. Exon 8 mutation was found in 4 of 40 pediatric and 2 of 62 adult patients, while exon 17 mutation was found in 9 of 40 pediatric and 12 of 62 adult patients. The c-KIT mutations was more common in t(8;21). There was no significant relationship between c-kit mutation and CR rates, while there was a significant inferior overall, disease free as well as progression free survival in the c-KIT mutant patients as compared to the wild group (P value .045, .036 and .024 respectively) in the pediatric group, however, this significance was not evident in the adults’ group. ConclusionAccording to our study, the results may suggest c-KIT mutation as a poor risk factor in pediatric CBF-AML.

Non-Age-Related Neoplastic Loss of Sex Chromosomecorrelated to Prolonged Survival in CBF-AML Patients in Real-World Clinical Setting

IntroductionSince Core-binding factor acute myeloid leukemia (CBF-AML) is categorized as a favorable cytogenetic risk group, allogenic hematopoietic stem cell transplantation (HSCT) is generally not recommended during the first complete remission (CR1). However, approximately 30-50% of CBF-AML patients relapse, and about 50% of relapsed patients remain incurable. Therefore, in real-world clinical setting, the indication of HSCT even in CR1 is considered based on prognosis prediction and minimal residual disease (MRD) status. With respect to prognosis prediction by chromosomal abnormalities, the prognostic impact of loss of sex chromosome (LOS) in the patients with CBF-AML is still controversial. Previous studies suggest that the impact of LOS in predicting the prognosis of CBF-AML may depend on treatment strategies including HSCT. In addition, although CBF-AML develops LOS at a high rate of 20-40%, it is still unclear whether LOS is age-related or neoplastic.MethodsHokkaido Leukemia Net (HLN) is prospective cohort study collecting AML samples from hospitals of North Japan Hematology Study Group (NJHSG).Cases of CBF-AML that were registered in HLN from January 2010 to December 2019 were used for analysis in the present study. All the patients received either intensive or low-intensity chemotherapy. HSCT was performed at the discretion of the attending physicians even in CR1. Conventional cytogenetic analysis was performed at the time of diagnosis and after each treatment. FLT3-ITD and KIT exon17 mutations were analyzed using genome DNA template at the central laboratory. The results of genetic analysis were returned to physicians so that they could reflect the genetic result in their treatment choice. We evaluated the impacts of several factors including advanced age, poor response to chemotherapy, LOS, and KIT exon17 mutation on overall survival (OS) and relapse-free survival (RFS) in these patients. This study was conducted in compliance with ethical principles based on the Declaration of Helsinki and was approved by the institutional review board of Hokkaido University Hospital.ResultsA total 96 CBF-AML patients including 62 patients with RUNX1/RUNX1T1 and 34 patients with CBFβ/MYH11 were enrolled in the present study. Intensive induction chemotherapy using '7+3' cytarabine plus anthracycline and low-intensity induction chemotherapy were performed in 90 patients and 6 patients, respectively. In 90 patients who underwent intensive induction chemotherapy, the CR rate after one cycle of induction therapy was 73.3%. Total CR rate as the best response was 91.7% for all CBF-AML patients. HSCT in CR1 was performed in 15 patients (15.6%) at the discretion of the attending physician based on genetic alterations, poor response to chemotherapy, and sustained detection of MRD after chemotherapy. There was no significant difference in 5-year OS (RUNX1/RUNX1T1 64.9% vs CBFβ/MYH11 52.9%; P=0.546) or 5-year RFS (63.6% vs 53.3%; P=0.364) between the CBF subtypes. LOS was significantly more frequent in patients with RUNX1/RUNX1T1 than in patients with CBFβ/MYH11 (35.5% vs 5.9%; P=0.001). Multivariate analyses for 5-year OS in CBF-AML patients revealed that age of 50 years or older (HR: 3.46, 95% CI: 1.47-8.11, P=0.004) and receiving 2 or more induction cycles (HR: 3.55, 95% CI: 1.57-8.05, P=0.002) were independently associated with worse OS and that LOS was independently associated with better OS (HR: 0.09, 95% CI: 0.01-0.71, P=0.022). We next sought to clarify whether LOS was age-related or neoplastic based on the transition of chromosome results. All the 24 patients with LOS achieved CR, and chromosome analysis at CR showed a normal karyotype in all of the 21 patients for whom chromosome analysis was performed. In the remaining 3 patients, only FISH analysis for RUNX1/RUNX1T1 or CBFβ/MYH11 was performed. Furthermore, chromosome analysis showed mosaics of metaphase cells with and without t(8;21) in 9 patients at diagnosis. In all of those patients, metaphase cells without t(8;21) showed a normal karyotype.ConclusionIn our real-world clinical setting in which '7+3' induction was performed and the indication of HSCT was determined by prognostic factors and MRD status, LOS correlated to prolonged survival in CBF-AML patients. Furthermore, the transition of chromosome results revealed that LOS was not age-related physiological loss but part of neoplastic chromosomal abnormalities. [Display omitted] DisclosuresTeshima: CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding; Janssen Pharmaceutical K.K.: Other; Novartis International AG: Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Gentium/Jazz Pharmaceuticals: Consultancy; Takeda Pharmaceutical Company: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kyowa Kirin Co.,Ltd.: Honoraria, Research Funding; Astellas Pharma Inc.: Research Funding; Merck Sharp & Dohme: Membership on an entity's Board of Directors or advisory committees; TEIJIN PHARMA Limited: Research Funding; Nippon Shinyaku Co., Ltd.: Research Funding; Bristol Myers Squibb: Honoraria; Fuji pharma CO.,Ltd: Research Funding; Pfizer Inc.: Honoraria; Sanofi S.A.: Research Funding. Kondo: Astellas Pharma Inc.: Consultancy, Honoraria; Otsuka Pharmaceutical: Honoraria, Research Funding; Novartis Pharma KK: Honoraria; Bristol-Myers Squibb Company: Honoraria; Sumitomo Dainippon Pharma: Honoraria; Sanwa Kagaku Kenkyusho CO.,LTD: Consultancy.

Non-age-related neoplastic loss of sex chromosome correlated with prolonged survival in real-world CBF-AML patients.

In this real-world clinical study, in which we determined eligibility for allogenic hematopoietic stem cell transplantation by prognostic factors and minimal residual disease status, we retrospectively evaluated cytogenetic, genetic, and clinical features in 96 patients with core-binding factor acute myeloid leukemia (CBF-AML) including 62 patients with RUNX1/RUNX1T1 and 34 patients with CBFβ/MYH11. Multivariate analyses for 5-year overall survival (OS) in CBF-AML patients revealed that age of 50years or older (HR: 3.46, 95% CI 1.47-8.11, P = 0.004) and receiving 2 or more induction cycles (HR: 3.55, 95% CI 1.57-8.05, P = 0.002) were independently associated with worse OS and that loss of sex chromosome (LOS) was independently associated with better OS (HR: 0.09, 95% CI 0.01-0.71, P = 0.022). At the time of complete remission, all 21 karyotyped patients with LOS had a normal karyotype. Furthermore, in all 9 patients with LOS who had a mosaic of metaphase cells with and without t(8;21) or inv(16), the metaphase cells without t(8;21)/inv(16) showed a normal karyotype. These results proved that LOS was not age-related and physiological, but rather a neoplastic chromosomal abnormality.

Population Pharmacokinetics and Safety of Dasatinib in Chinese Children with Core-Binding Factor Acute Myeloid Leukemia.

Dasatinib, an orally administered Src-family kinase inhibitor, is combined with the standard chemotherapeutic regimen to enhance antineoplastic activity against core-binding factor acute myeloid leukemia (CBF-AML) in adults; however, limited data are available for use in children. In the present study, we studied the pharmacokinetics and safety of dasatinib in children. Dasatinib (60 or 80 mg/m2 once daily) was administered to 20 children with CBF-AML. Blood samples were collected and drug concentrations were quantified by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Population pharmacokinetic analysis and Monte-Carlo simulations were performed using NONMEM software, and safety analyses were assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 4.0 (NCT03844360). Twenty pediatric patients (3.3-14.4 years of age) were included, and a total of 40 dasatinib concentrations were available for population pharmacokinetic analysis. The mean (standard deviation) of the estimated area under the concentration-time curve extrapolated to steady state (AUCss) of dasatinib 60 and 80 mg/m2 was 366.1 (146.6) ng·h/mL and 425.3 (150.7) ng·h/mL, respectively. The majority of adverse events were grade 1/2 in severity, including thrombocytopenia, rash, and pain in the extremities. The estimated cumulative incidence of complete remission and complete molecular response were 95.0% and 75.5%, respectively. The population pharmacokinetics of orally administered dasatinib were evaluated in pediatric CBF-AML patients. The AUCss of dasatinib (80 mg/m2) in CBF-AML pediatric patients was similar to those of dasatinib (100 mg) in adult patients. Dasatinib is well-tolerated in pediatric patients with CBF-AML.

Clonal Interference of Signaling Mutations Holds Prognostic Relevance in Core Binding Factor (CBF) Acute Myeloid Leukemia (AML)

Context. Mutations affecting cytokine signal transduction genes (‘signaling’ genes) are frequent in CBF AML and increase the risk of relapse. Clonal heterogeneity heralds poor prognosis in many tumors. Clonal interference is a specific type of clonal heterogeneity defined by the coexistence of independent clones affecting a common pathway, and has been linked to resistance to selection pressures in bacteria and viruses (Hughes, Nat Rev Genet 2015). Single-cell data has shown that in CBF AML with several signaling mutations, these mutations occur in independent clones (Hirsch, Nat Comm 2015). We investigated the prognostic role of clonal interference of signaling mutations in intensively-treated CBF AML.Methods. Diagnostic bone marrow (BM) samples from CBF AML cases from 2 multicenter adult and pediatric trials underwent targeted high-throughput sequencing (HTS) in Lille (n=215) as reported (Duployez Blood 2016). Diagnostic samples from adult CBF AML cases referred to Munich Leukemia Laboratory were analyzed with an independent HTS platform, including previously published RUNX1 - RUNX1T1 cases (CBFA, Krauth, Leukemia 2014) and additional CBFB - MYH11 (CBFB) cases (n=230 in total). All analyses were stratified on the HTS platform. We defined the number of ‘signaling clones’ as the total number of variants found in signaling genes (KIT, FLT3, NRAS, KRAS, JAK2 and CBL) by HTS in each patient.Results. The study cohort included 445 patients (pts, M/F 251/194, median age 42y [IQR 24 - 54]) with CBFA (n=230) and CBFB (n=215) AML. Median WBC was 14.6 x109/L. Sequencing data for all 445 pts was available for 6 signaling genes, with the following mutations frequencies: KIT 31%, NRAS 29%, FLT3 16% (TKD 10%, ITD 5%, both 1%), KRAS 13%, CBL (2%) and JAK2 (1%). FLT3-TKD, NRAS and KRAS mutations were significantly more frequent in CBFA AML, and FLT3-ITD in CBFB AML. Recurrent co-mutations in genes covered in >90% of cases included TET2 (6%) and ASXL1 (5%). At least one mutation in KIT, NRAS, KRAS, FLT3, CBL or JAK2 was found in 293 (66%) pts, of whom 126 harbored clonal interference, defined as ≥2 signaling clones, because of mutations in different genes (n=76), different variants in one gene (n=27), or both (n=23, Figure A). Gene redundancy, defined as the presence of ≥2 variants in one gene, particularly affected NRAS (n=27/50 cases) and KIT (n=12/50).Among cases with at least one signaling clone, clonal interference was more frequent in CBFB AML (48% vs 36% in CBFA, p=0.025), but was not associated with age, gender, leukocytosis, or to mutations in ASXL1 or TET2 . Importantly, the total allelic burden of signaling clones was comparable in cases with and without clonal interference (p=0.2, Figure B).All pts were treated with different 7+3 based intensive chemotherapy regimens as previously published (Duployez Blood 2016, Krauth Leukemia 2014). Median follow-up was 4.7 years, 47 (11%) pts received an allogeneic transplant in first CR. Censoring at transplant did not change our results. Three-year event-free survival (EFS) was 59.8% (95% CI, 51.2 - 67.3) in pts with no signaling mutation, 60.0% (52.0 - 67.2) in pts with a single signaling clone, and 46.4% (37.2 - 55.2) in pts with clonal interference (p=0.001, Figure C). This difference in EFS was seen in CBFB and to a lesser extent in CBFA AML. Clonal interference increased the cumulative incidence of failure (hazard ratio [HR]=1.54 compared to pts with a single signaling clone; p=0.03) translating into a trend towards poorer overall survival (HR=1.55; p=0.07). Martingale residuals indicated that each additional signaling clone worsened EFS (HR=1.30; p<0.0001). Presence of gene redundancy (≥2 variants in one gene) predicted worse EFS (p=0.04; Figure D) independently of the number of mutated signaling genes (p=0.10), further strengthening the adverse prognostic value of intratumoral heterogeneity in CBF AML. In a multivariate Cox model, clonal interference predicted a worse EFS (HR=2.32, p=0.002) independently of older age (p<0.0001), higher WBC (p<0.0001), CBF subtype (CBFA vs CBFB, p=0.004), and total allelic burden of signaling clones (p=0.13).Conclusion. Our results in a large cohort of CBF AML patients demonstrate that presence of two or more genetic lesions in recurrently mutated cytokine signaling genes predicts poor prognosis in CBF AML independently of clinical features. Our analyses suggest that clonal interference contributes to chemoresistance in AML. [Display omitted] DisclosuresItzykson:Janssen: Research Funding; Novartis: Research Funding. Fasan:MLL Munich Leukemia Laboratory: Employment. Meggendorfer:MLL Munich Leukemia Laboratory: Employment. Jourdan:NOVARTIS: Consultancy, Honoraria. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

The Impact of Induction Treatment Response on the Prognosis of Pediatric Core Binding Factor-Acute Myeloid Leukemia Patients

To explore the impact of induction treatment response on the prognosis of pediatric core binding factor-acute myeloid leukemia (CBF-AML). The result of induce reaction and survival data of 157 pediatric CBF-AML patients in our hospital from September 2008 to December 2018 were retrospectively analyzed．The survival rate of the patients with different degrees of morphological remission after induction chemotherapy was comparative analyzed. Among the 157 children with CBF-AML, 113 (72.4%) patients achieved morphologic leukemia-free state (MLFS) after the first course of induction chemotherapy, 153 (98.1%) patients achieved MLFS after the second course of induction chemotherapy. The 5-year event-free survival (EFS) rate and 5-year overall survival (OS) rate of patients with non-remission (NR) status after the first course of induction of chemotherapy was significantly lower than the patients achieved MLFS and the patients achieved partial remission (PR). The 5-year EFS rate and 5-year OS rate of the patients with PR status after the second course of induction chemotherapy were lower than the patients achieved MLFS, but the difference was not statistically significant. Multivariable analyze showed that NR after the first course of induction chemotherapy and myeloid sarcoma were the independent risk factors affecting EFS of the patients. There were six patients with NR status after the first course of induction chemotherapy, in which all of them harbored t(8;21), three of them with sex chromosome deletion, two of them with myeloid sarcoma. NR status after the first course of induction chemotherapy was the independent risk factor affecting EFS and OS of CBF-AML patients, it can be taken as an indicator for higher risk stratification. PR status after the first course of induction chemotherapy may not be used as a diagnostic criterion for primary drug resistance.

Both the subtypes of KIT mutation and minimal residual disease are associated with prognosis in core binding factor acute myeloid leukemia: a retrospective clinical cohort study in single center.

Core binding factor acute myeloid leukemia (CBF-AML), including cases with KIT mutation, is currently defined as a low-risk AML. However, some patients have poor response to treatment, and the prognostic significance of KIT mutation is still controversial. This study aimed to explore the prognostic significance of different KIT mutation subtypes and minimal residual disease (MRD) in CBF-AML. We retrospectively evaluated continuous patients diagnosed with CBF-AML in our center between January 2014 and April 2019. Of the 215 patients, 147 (68.4%) and 68 (31.6%) patients were RUNX1-RUNX1T1- and CBFB-MYH11 positive, respectively. KIT mutations were found in 71 (33.0%) patients; of them, 38 (53.5%) had D816/D820 mutations. After excluding 10 patients who died or were lost to follow-up within a half year, 42.0% (n = 86) of the remaining 205 patients received allogeneic hematopoietic stem cell transplantation (allo-HSCT). An MRD > 0.1% at the end of two cycles of consolidation predicted relapse (P < 0.001). Multivariate analysis showed that D816 or D820 mutations and MRD > 0.1% at the end of two cycles of consolidation were independent adverse factors affecting relapse-free survival (RFS) and overall survival (OS). Allo-HSCT could improve RFS (74.4% vs. 34.6%, P < 0.001) and OS (78.1% vs. 52.3%, P = 0.002). In conclusion, high-risk CBF-AML patients must be identified before treatment. D816/D820 mutation, MRD > 0.1% at the end of two cycles of consolidation chemotherapy predicted poor survivals, and allo-HSCT can improve the survival of properly identified patients.

Double Genetic Hits and Subclonal Mosaicism in the Ras Signaling Pathway in Myeloid Neoplasia

The high prevalence of oncogenic mutations in the RAS family genes including their down or upstream partners (e.g., NRAS, KRAS, PTPN11, RIT1α) has strong implication in abnormal Ras signaling in the pathogenesis of myeloid neoplasia (MN). For many years RAS mutations have been considered non-targetable. However, recently multiple targeted agents have been introduced as possible future therapies. While common in JMML, RAS mutations are rarely seen in adult MN as the ancestral event. Instead they serve as subclonal hits. To that end, the clinical impact of RAS mutations has been controversial: whereas some studies did not find prognostic impact, others demonstrated that these mutations may confer a poor prognosis. Nevertheless, molecular analysis of core binding factor AML patients showed the coexistence of RAS clones harboring independent hits targeting the same pathway. We stipulate that occurrence of RAS mutations is not random and reasoned that studying cases with multiple RAS mutant subclones may reveal distinct molecular or etio-pathologic background attracting the emergence of RAS mutations as a way to augment MYC activity as a ubiquitous pathway of clonal progression. In a review of a molecular collection of data of a cohort of MN patients (n=1876) including MDS (n=692), MDS/MPN (n=282), AML (pAML, 710; sAML, 192) we found RAS mutations in 21% (403/1876) of the patients. Among them we encountered a subgroup of patients (9%; 38/403) harboring multiple RAS mutations. These multiple hits affected PTPN11, NRAS, KRAS and RIT1-α. Most of these multiple RAS mutants represented a subclonal mosaicism rather than biallelic subclones as indicated by single cell DNA sequencing. Three patients were assessed serially (2 patients/ 2 time points and 1 patient/ 5 time points). In one case NRAS (VAF-24%) and PTPN11 (VAF-28%) were acquired at the time of AML evolution. In an MDS/MPN-U, NRAS/KRAS were both detected at diagnosis with a VAF of 1% and 12% each. Both clones increased over 2 years' time span with NRAS ramping to 43% and reaching KRAS (50%). In the 3rd case, samples were collected over a period of 5 years with NRAS and PTPN11 being detected only at the later time point (VAF of 5% and 15%, respectively). In contrast to competing RAS subclones in adults, our historical cohort of JMML showed that at least one RAS mutation was found in 89% (82/92) of the patients as ancestral events and in mutually exclusive manner while biallelic RAS mutations occurred in 15% (12/82) of the cohort. In adult MN, the most common subclonal mosaicism was encountered in NRAS/KRAS (63%; 24/38), while less fraction of patients had competing subclonal mutations in NRAS (26%; 10/38) or in KRAS (8%; 3/38). Most of these mutations were found in canonical sites (NRAS: G12D/S/A/C, G13D/R/V, Q61A/H/R; KRAS: G12D/A/R, G13D/R/V, A146P/T). Patients carrying RAS mutations had significantly higher WBCs (20.5 vs 7.2, P&amp;lt;.001) consistent with the role of RAS in proliferation, possibly via augmentation of MYC. Isolated chromosome 7 abnormalities were more common among RAS mutant carriers who otherwise showed less complex karyotypes. RAS mutations were mostly enriched in MDS/MPN (26%) while absent in sAML suggesting the impact of these lesions on OS but not on PFS. Analysis of clonal architecture showed that accumulation of RAS subclones was most commonly related to the presence TET2 (17% vs. 8%) and EZH2 (6% vs. 1%) compared to WT. At the time of AML evolution, the presence of RAS mutation did not correlate with OS (18 vs. 13 mo., P=0.07). However, median OS was shorter in MDS and MDS/MPN carrying multiple RAS mutations compared to WT (10 vs. 30 mo., P=0.005) again supporting the contention that these clones may be markers of non-progression-related mortality. In sum, our study supports the notion that ancestral RAS hits are common in childhood MN with a hereditary component whereby the progression is related to the acquisition of secondary hits in biallelic configuration. In contrast in adult and elderly MN, specific genetic background predisposes to RAS mutant mosaicism such as ancestral TET2 and EZH2 lesions and MPN features reflecting the direction of selection pressure towards accumulation of multiple RAS pathway hits. Lack of the gene/dose effect on progression indicates, that in contrast to the compound heterozygous RAS childhood diseases, RAS mutant mosaicism reflects branching rather than linear evolution mode. Disclosures Sekeres: Pfizer: Consultancy; Takeda/Millenium: Consultancy; BMS: Consultancy. Carraway:Abbvie: Other: Independent Advisory Committe (IRC); ASTEX: Other: Independent Advisory Committe (IRC); Takeda: Other: Independent Advisory Committe (IRC); Stemline: Consultancy, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; BMS: Consultancy, Other: Research support, Speakers Bureau; Novartis: Consultancy, Speakers Bureau. Saunthararajah:EpiDestiny: Consultancy, Current equity holder in private company, Patents &amp; Royalties: University of Illinois at Chicago. Patel:Alexion: Other: educational speaker. Maciejewski:Alexion, BMS: Speakers Bureau; Novartis, Roche: Consultancy, Honoraria.

AML-156: The Clinical Implications and Outcomes of RAS Mutatome in Core-Binding Factor Acute Myeloid Leukemia

<h3>Context</h3> The clonal architecture of <i>KRAS/NRAS</i> mutations (<i>RAS</i>^MT) in Core-Binding Factor AML (CBF-AML). <h3>Objective</h3> To dissect the impact of <i>RAS</i>^MT on CBF-AML. <h3>Design/Setting</h3> Clinical and molecular data and survival outcomes (OS) of the patients were collected at The Cleveland Clinic Foundation and Munich Leukemia Laboratory. <h3>Patients</h3> A cohort of 368 CBF-AML patients was identified, in whom inv(16) and t(8;21) represented 64% (n=237) and 36% (n=131) of the cases. Thirty-eight percent (141/368) carried <i>RAS</i>^MT (<i>KRAS</i>=22; <i>NRAS</i>=105) with 14 patients harboring both <i>KRAS/NRAS.</i> <h3>Main outcome measures</h3> Clinical and molecular characteristics and OS of <i>RAS</i>^MT CBF-AML. <h3>Results</h3> Leukopenia and anemia were significantly higher in <i>RAS</i>^MT and <i>RAS</i>^WT. <i>RAS</i>^MT had more +8 (14 <i>vs.</i> 7%) but less -Y (7 <i>vs.</i> 15%; <i>P</i>=0.02) and -X (2 <i>vs.</i> 7%; <i>P</i>=0.03) abnormalities. <i>RAS</i>^MT were less associated with <i>TET2</i>^MT (6 <i>vs.</i> 12%; <i>P</i>=0.02) and <i>KIT</i>^MT (9 <i>vs.</i> 31%; <i>P</i> < 0.0001). <i>DNMT3A</i>^MT was the most common dominant lesion, <i>KIT</i>^MT was the most frequent co-dominant mutation while <i>NPM1</i>^MT and <i>FLT3</i>^MT were the most subclonal hits in <i>RAS</i>^MT. <i>RAS</i>^MT associated with a neutral impact on OS (HR: 0.7; <i>P</i>=0.06) compared to <i>RAS</i>^WT. <i>KRAS/NRAS</i> were dominant in 35%, co-dominant in 5%, and secondary hits in 60% of <i>RAS</i>^MT cases. No effect on OS was observed per <i>RAS</i>^MT hierarchy (HR: 0.8; <i>P</i>=0.6). However, IDH2^MT (90% R140Q,10% R172K) and <i>RUNX1</i>^MT predicted worse OS in <i>RAS</i>^MT compared to <i>RAS</i>^WT (31 <i>vs.</i> 3 mo., <i>P</i>=0.007 and 30.7 <i>vs.</i> 9.7 mo.; <i>P</i>=0.04, respectively). <h3>Conclusions</h3> <i>RAS</i> ^MT account for one-third of CBF-AML and their prognostic relevance is still a matter of debate. Similar to previous studies, our analysis demonstrated no impact on OS for <i>RAS</i>^MT CBF-AML. However, the dissection of clonal succession and mutational ranking concluded that the acquisition of multiple hits in epigenetic regulators (<i>e.g., IDH2, RUNX1</i>) determined poorer OS in the <i>RAS</i>^MT CBF-AML.

The impact of KIT and other concomitant gene mutations on the prognoses of patients with core-binding factor acute myeloid leukemia

Objective: To study the impact of KIT and other concomitant gene mutations on the prognoses of patients with core-binding factor acute myeloid leukemia (CBF-AML). Methods: A total of 104 newly diagnosed patients with CBF-AML in Hebei Yanda Lu Daopei Hospital from January 2014 to February 2018 were analyzed, and high-throughput gene sequencing for the detection of mutations among 58 genes was executed. Also, the clinical features of KIT mutation-positive CBF-AML (KIT+CBF-AML) patients and the effects of other concomitant gene mutations on the prognoses of patients were also analyzed. Results: A total of 56 cases (53.85%) with KIT mutations were found in 104 CBF-AML patients. Among this, KIT D816 mutation was the most common (32 patients), followed by the N822 mutation (17 patients). Patients with KIT+CBF-AML have a higher proportion of bone marrow blasts at the time of diagnoses and are more likely to have sex chromosome loss. Among the 52 patients with KIT+CBF-AML who were followed up, the allogeneic hematopoietic stem cell transplantation (allo-HSCT) group had a higher overall survival rate (OS) than that of the chemotherapy group (88.9% vs 57.1%, χ(2)=6.076, P<0.05). The event-free survival (EFS) and OS of patients with KIT+CBF-AML with FLT3 mutation were both significantly lower than those of the FLT3 mutation-negative group (EFS: 40.0% vs 72.3%, χ(2)=6.557, P<0.05; OS: 60.0% vs 87.2%, χ(2)=8.305, P<0.05). The OS of the patient with TET2 mutation was lower than that of the TET2 mutation-negative group (50.0% vs 87.5%, χ(2)=4.130, P<0.05). Conclusion: Patients with KIT+CBF-AML with concomitant gene mutations, especially FLT3 and TET2, have poor prognoses, which can be improved by allo-HSCT.

Prospective evaluation of prognostic impact of KIT mutations on acute myeloid leukemia with RUNX1-RUNX1T1 and CBFB-MYH11

AbstractThe prognostic impact of KIT mutation on core-binding factor acute myeloid leukemia (CBF-AML) remains controversial. We registered 199 newly diagnosed de novo CBF-AML patients, aged 16 to 64 years, who achieved complete remission. They received 3 courses of high-dose cytarabine therapy and no further treatment until hematological relapse. Mutations in exons 8, 10-11, and 17 of the KIT gene were analyzed. Furthermore, we analyzed mutations in 56 genes that are frequently identified in myeloid malignancies and evaluated minimal residual disease (MRD). The primary end point was relapse-free survival (RFS) according to KIT mutations. The RFS in KIT-mutated patients was inferior to that in unmutated patients (hazard ratio, 1.92; 95% confidence interval, 1.23-3.00; P = .003). Based on subgroup analysis, KIT mutations had a prognostic impact in patients with RUNX1-RUNX1T1, but not in those with CBFB-MYH11, and only exon 17 mutation had a significant prognostic impact. Multivariate Cox regression analysis with stepwise selection revealed that the KIT exon 17 mutation and the presence of extramedullary tumors in patients with RUNX1-RUNX1T1, and loss of chromosome X or Y and NRAS mutation in patients with CBFB-MYH11 were poor prognostic factors for RFS. MRD was evaluated in 112 patients, and it was associated with a poorer RFS in the patients with CBFB-MYH11, but not in those with RUNX1-RUNX1T1. These results suggested that it is necessary to separately evaluate AML with RUNX1-RUNX1T1 or CBFB-MYH11 according to appropriate prognostic factors. This study was registered at www.umin.ac.jp/ctr/ as #UMIN000003434.

Impact and Outcomes of RAS gene Mutations in Core Binding Factor Acute Myeloid Leukemia

Acute myeloid leukemia (AML) with t(8;21) or inv(16) chromosomal rearrangements are distinct heterogeneous disease entities within AML that are classified together as core binding factor AML (CBF-AML). Given the nature of the chromosomes involved, these rearrangements lead to the production of leukemogenic chimeric transcripts (RUNX1-RUNX1T1 and CBFB-MYH11) which disrupt the physiologic activity of the heterodimeric transcription factor CBF complex. Although CBF-AML patients have a favorable prognosis and good response to treatment compared to other AML subtypes, survival outcomes are not uniform. Indeed, 30-50% of patients with CBF-AML eventually relapse, and the 5-10 yr survival ranges between 55-61% for patients &lt; 60 yr in MRC/NCRI AML trials. Studies have analyzed the clonal architecture of CBF-AML patients and identified cooperating mutations independently of receptor tyrosine kinases (FLT3, KIT) mutations while others have found a 30% occurrence of KIT mutations. Studies of murine models of Runx1 and Cbfb have demonstrated that inactivation of both genes does not lead to leukemia, suggesting that other factors are necessary to recapitulate the leukemia phenotype fully. Although mutations in RAS family of genes (NRAS/KRAS) are among the most frequently observed mutations described in CBF-AML [54% in inv(16) and 30% in t(8;21)], no associations between those mutations and survival outcomes have been found. Because of the lack of association between RASMT and clinical outcomes, their role in CBF-AML is still unknown. Here, we focused on dissecting the impact of RAS mutations (NRAS/KRAS; RASMT) on the clinical characteristics, survival outcomes, and the molecular associations among CBF-AML patients by evaluating the clonal succession of RASMT. In total, 284 CBF-AML patients were identified, in whom inv(16) and t(8;21) represent 61% (n=173) and 39% (n=111) of the cases, respectively. Thirty-five % (99/284) of the patients carried RAS mutations (NRAS=78; KRAS=21) with 8 patients harboring 2 mutations comprising NRAS, KRAS, or both NRAS/KRAS genes. RAS mutations were point mutations affecting known hotspots in NRAS and KRAS. Both RASMT and RASWT had a median age &lt; 60 years (55 (14-83) vs. 49 (7-83) years, P=0.9) and sex was equally distributed among the two groups. Leukopenia, defined as white blood cell count &lt;3.5 x 109/L, was the only significant different hematological parameter between RASMT and RASWT. Fewer RASMT patients had leukopenia (3 vs. 12%; P=0.02). Compared to RASWT patients, RASMT patients had more often +8 (14 vs. 6%; P=0.02) and less -Y (7 vs. 16%; P=0.04) abnormalities. The analysis of 30 genes frequently mutated in myeloid malignancies revealed that RASMT patients had a significantly lower number of additional mutations compared to RASWT patients (n=59 vs. 197; P=0.03). Focusing on molecular associations, there were no differences in the frequency of FLT3 (TKD or ITD) mutations between RASMT and RASWT (15 vs. 18%). Although RASWT were more enriched with ASXL1, DNMT3A, IDH1/2, TET2, and WT1 mutations, no significant difference in frequencies was found when compared to RASMT. KIT mutations have been associated with poor outcomes in CBF-AML. In our cohort, KIT mutations (small deletions, points mutations), were significantly less associated with RASMT than RASWT (8 vs. 59%; P&lt;.0001). RASMT were ancestral events in 58% of the cases (with FLT3 mutations the most common secondary lesions), secondary in 38% (with TET2,ASXL1, RUNX1 and IDH2 mutations represented the most common dominant hits), and codominant in 11% (with KIT mutations). RASMT in CBF-AML was associated with worse OS (HR: 1.520; P=0.04) compared to RASWT. Clonal hierarchy and succession analysis showedno change in OS when RASMT were secondary vs. dominant hits in CBF-AML (HR: 0.8; P=0.5). In sum, our study of the frequency, clonal architecture and impact on survival of RASMT in CBF-AML patients points out the unique characteristics of this specific disease subgroup in which sole RASMT might represent, in addition to KITMT, a mutational lesion cooperating with inv(16) and t(8;21) rearrangements in driving leukemic evolution. Disclosures Meggendorfer: MLL Munich Leukemia Laboratory: Employment. Advani:Glycomimetics: Consultancy, Research Funding; Macrogenics: Research Funding; Abbvie: Research Funding; Amgen: Research Funding; Pfizer: Honoraria, Research Funding; Kite Pharmaceuticals: Consultancy. Nazha:Abbvie: Consultancy; Incyte: Speakers Bureau; Jazz Pharmacutical: Research Funding; Tolero, Karyopharma: Honoraria; MEI: Other: Data monitoring Committee; Novartis: Speakers Bureau; Daiichi Sankyo: Consultancy. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Sekeres:Millenium: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Maciejewski:Alexion: Consultancy; Novartis: Consultancy.

Characterization of mutational pattern of patients with core-binding factor acute myeloid leukemia

To characterize the mutational profile of patients with core-binding factor acute myeloid leukemia (CBF-AML). A total of 81 acute myeloid leukemia patients were recruited, which included 36 cases of CBF-AML and 45 cases of cytogenetically normal acute myeloid leukemia (CN-AML) . Mutations of FLT3-ITD, FLT3-TKD, NPM1, c-KIT, NRAS, KRAS, TET2, IDH1/2, RUNX1, DNMT3A, GATA2, ASjXL1, TP53, PTPN11, JAK2V617F, SETBP1 and CEBPA genes were simultaneously detected by DNA-based PCR and Sanger sequencing. Over all, mutations were detected in 68 patients (83.9%), with the most common ones including double CEBPA mutations (n=17), followed by NPM1 (n=15), c-KIT (n=11), NRAS (n=10), TET2 (n=9), FLT3-TKD (n=9), FLT3-ITD (n=8), IDH1 (n=7), RUNX1 (n=7), KRAS (n=7), DNMT3A (n=6), IDH2 (n=4), and GATA2 (n=4) mutations. AML1-ETO and CBFβ-MYH11 fusions were present in 21 and 15 patients, respectively. Coexistence of ≥2 mutations was more common in CN-AML comparing with CBF-AML. The mutation rate of NPM1, FLT3-ITD, DNMT3A, IDH1 and CEBPA double mutations were higher in patients with CN-AML. NRAS, c-KIT and KRAS mutations were identified more frequently in patients with CBF-AML (P<0.05). Based on the function, aberration of genes involved in DNA methylation, NPM1 proteins and transcription predominated in CN-AML, while tyrosine kinase receptor signaling and RAS pathways have predominated in CBF-AML. The genomic landscape of CBF-AML patients has differed from that of CN-AML patients. Synergy of fusion genes with particular mutations may impact the clinical phenotype and prognosis of patients.

Prognostic significance of cellular and molecular genetic abnormalities in pediatric core binding factor-acute myeloid leukemia

Core binding factor-acute myeloid leukemia (CBF-AML) is a common cellular genetic subtype in children with acute myeloid leukemia (AML), accounting for 25%-30% of AML, and it has a good clinical prognosis. However, there are still 30%-40% of CBF-AML patients with recurrence, and the cellular molecular genetic abnormal events accompanying such patients may be related to their clinical prognosis. At present, dasatinib has been reported in the therapy of adult CBF-AML. Different molecular genetic backgrounds have become a new idea for precise targeted therapy, but there are still few related studies on pediatric CBF-AML. The author summarizes clinical prognostic impacts of cellular and molecular genetic abnormalities which are commonly seen in pediatric CBF-AML, aiming to provide new ideas for individualized treatment of pediatric CBF-AML. Key words: Core binding factors; Leukemia, myeloid, acute; Chromosome aberrations; Prognosis; Child