Japanese Pediatric Leukemia/Lymphoma Study Group Research Articles

TBI, etoposide, and cyclophosphamide conditioning for intermediate-risk relapsed childhood acute lymphoblastic leukemia.

In children with intermediate-risk relapsed acute lymphoblastic leukemia (ALL), allogeneic hematopoietic stem cell transplantation (allo-HSCT) has markedly improved the outcome of patients with an unsatisfactory minimal residual disease (MRD) response. Total body irradiation (TBI), etoposide (ETP), and cyclophosphamide (CY) have been shown to be equivalent to or better than TBI + ETP for conditioning, so we hypothesized that even greater survival could be achieved due to recent advances in HSCT and supportive care. We prospectively analyzed the efficacy and safety of allo-HSCT with a unified conditioning regimen of TBI + ETP + CY in children with intermediate-risk relapsed ALL, based on MRD in the bone marrow after induction, from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) ALL-R08-II nationwide cohort (UMIN000002025). Twenty patients with post-induction MRD ≥ 10-3 and two not evaluated for MRD underwent allo-HSCT. Engraftment was confirmed in all patients, and no transplantation-related mortality was observed. The 3-year event-free survival and overall survival rates after transplantation were 86.4% ± 7.3% and 95.5% ± 4.4%, respectively. Allo-HSCT based on post-induction MRD with TBI + ETP + CY conditioning was feasible in Japanese children with intermediate-risk relapsed ALL.

Experience with an international study on standard-risk relapsed childhood acute lymphoblastic leukemia (IntReALL SR 2010 study) in Japan

Many effective new agents for relapsed childhood acute lymphoblastic leukemia (ALL) are now becoming available, and international standard chemotherapy should be developed to optimize use of these agents. Randomized controlled trials (RCTs) are needed to establish a standard treatment, but few have been conducted for relapsed childhood ALL in Japan due to the small patient population. Participation in international RCTs is necessary to access sufficient patients for informative study results, but differences in approved drugs and healthcare systems between countries make this challenging. In 2014, the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) participated in an international study on standard-risk relapsed childhood ALL (IntReALL SR 2010) involving two RCTs and multiple drugs not approved in Japan, which was addressed by replacing the unapproved drugs with alternative approved drugs with the same or similar efficacy. This article discusses the historical background of treatment development for relapsed childhood ALL, our experience in participating in the IntReALL SR 2010 trial, and prospects for treating relapsed childhood ALL.

Integrated Analysis of KIT Exon 17 Mutations and Flow-MRD Refines Risk Stratification in Pediatric Acute Myeloid Leukemia with RUNX1:: RUNX1T1

INTRODUCTION: Pediatric acute myeloid leukemia (AML) with RUNX1:: RUNX1T1 is considered a favorable risk group, with a high probability of event-free survival (EFS) in recent clinical trials. However, 20-30% of patients still experience relapse within three years and some patients have poor outcome. Several prognostic factors, including secondary genetic abnormalities and treatment response, have been previously reported. Flow cytometry-based measurable residual disease (flow-MRD) has been suggested as a poor prognostic factor in AML with RUNX1:: RUNX1T1. Additionally, KIT mutations, particularly mutations of exon 17, have been associated with poor EFS in both adult and pediatric patients. However, the combined impact of KIT exon 17 mutations and flow-MRD on prognosis has not been thoroughly investigated. This study aims to evaluate the clinical and genetic features of pediatric patients with RUNX1:: RUNX1T1-positive AML enrolled in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-12 trial and determine if integrated analysis of flow-MRD and KIT exon 17 mutations can improve risk stratification. METHOD: A total of 101 pediatric AML patients with RUNX1:: RUNX1T1 were enrolled in the study. The patients were treated in the JPLSG AML-12 trial, and their clinical and genetic characteristics were analyzed. Targeted capture sequencing was performed on bone marrow samples obtained at diagnosis. The custom gene panel was designed for mutation profiling of pediatric AML, including 504 genes. Flow-MRD was centrally monitored at the end of induction 1 (EOI1) and the end of induction 2 but was not used to guide subsequent therapies. Leukemia-associated immunophenotypes were identified in diagnostic specimens and marker combinations that allowed detection of leukemia with a sensitivity of at least 0.1% were applied to subsequent samples. RESULTS: Patients with KIT exon 17 mutations had a higher white blood cell count at diagnosis and a significantly higher rate of MRD positivity (≥0.1%) at EOI1 compared to patients without KIT exon 17 mutations. Immunophenotypic analysis showed no significant differences in CD117 or CD33 expression between patients with and without KIT exon 17 mutations; whereas CD19 expression was observed less frequently and, although not significantly, CD56 expression was observed more frequently in the patients with KIT exon 17 mutations. The genetic landscape analysis revealed that KIT mutations were the most common and tended to coexist with ARID1B mutations, while NRAS mutations were mutually exclusive. The 5-year EFS and overall survival (OS) for the entire cohort were 67.3% and 82.7%, respectively. Negative MRD at EOI1 was associated with significantly superior 5-year EFS and OS (71.6% and 85.9%) compared to positive MRD (12.5% and 37.5%)(p<0.01). Patients with KIT exon 17 mutations had significantly inferior 5-year EFS and OS (46.9% and 62.2%) compared to those without KIT exon 17 mutations (76.8% and 92.4%) (p<0.01). Furthermore, we evaluated a prognostic impact of MRD within the KIT exon 17 mutated and non-mutated cases. As for the non-mutated cases, the 5-year OS in the patients with negative MRD was 92.2%. Among the KIT-mutated cases, the 5-year OS in the patients with negative and positive MRD was 68.0% and 33.3%, respectively. CONCLUSION: Patients with both non-mutated KIT exon 17 and negative MRD have the best prognosis, while positive MRD and KIT exon 17 mutations are associated with poorer outcomes. These findings indicated that integrated analysis of flow-MRD and KIT exon 17 status enables optimal risk assignment strategies in pediatric AML with RUNX1:: RUNX1T1.

Integrated Analysis Focusing on Genome-Wide DNA Methylation in Pediatric Acute Promyelocytic Leukemia: The Jccg Study, JPLSG AML-P05

Introduction: Pediatric acute promyelocytic leukemia (APL) represents approximately 5%-10% of all acute myeloid leukemia (AML). While the prognosis of APL patients has dramatically improved with the use of all-trans retinoic acid and arsenic trioxide, cases of relapse still exist. Moreover, the molecular biological basis of pediatric APL remains unknown. In adult and pediatric AML, to predict prognosis, DNA methylation patterns have been proposed as biomarkers. In this study, we aimed to investigate the molecular biological basis of pediatric APL and validate biomarkers associated with prognosis using an integrated analysis, including DNA methylation analysis, targeted deep sequencing, and RNA sequencing, in patients enrolled in the Japanese AML-P05 study conducted by the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG). Methods: Pediatric de novo APL patients (n = 38) who participated in the JPLSG AML-P05 trial from 2006 to 2009 were analyzed. Genome-wide DNA methylation analysis (n = 34), targeted deep sequencing (n = 35), RNA sequencing (n = 34), and motif analysis (n = 34) were performed. In the DNA methylation analysis, the Infinium MethylationEPIC v2.0 Kit (Illumina) was used. Results: Based on the most variable 1,000 DNA methylation values between patients, unsupervised hierarchical clustering classified APL patients into four clusters (cluster 1, 2a, 2b, and 3). Clusters 1 and 2a (n = 15) demonstrated a significantly higher DNA methylation levels at 87 CpG sites out of 1,000 compared to clusters 2b and 3 (n = 19). A part of the 87 CpG sites locate on the genes, such as CPM, GRB10 and BAALC, which have been reported to be associated with APL prognosis. A significant DNA methylation difference was found between the “high” (cluster 1 and 2a) and “low” (cluster 2b and 3) methylation groups at 2,372 CpG sites (Figure). Patients in the high methylation group presented with significantly worse outcomes compared to those in the low methylation group (3-year overall survival: 80% vs. 100%, p = 0.043; 3-year event-free survival: 73.3% vs. 94.7%, p = 0.049). Additionally, among the 2,372 CpG sites, motif analysis was performed for 783 CpG sites with an average methylation difference of 0.3 or higher. The binding domain of EBF1 was enriched among them. EBF1 is a critical transcriptional factor for B-cell differentiation. In the high methylation group, an aberrant B-cell differentiation was considered as a characteristic of APL. Gene expression analysis between the high and low methylation groups revealed significant differences in expression of 600 genes with more than twofold changes. Gene ontology analysis of the 600 genes revealed that their genes were enriched in T-cell and B-cell linage differentiation. In the targeted deep sequencing analysis, a total of 41 mutations in 21 genes in 25 patients were identified. The most frequent mutation was NRAS. Interestingly, previously unreported mutations in EP300 and BRCA2 were identified in APL, with EP300 mutations detected only in the high methylation group. Conclusions: DNA methylation analysis suggests that DNA methylation levels at specific CpG sites are effective biomarkers for the prognosis of pediatric APL. The presence of the EBF1 binding motif in the vicinity of these CpG sites suggests the involvement of EBF1 in prognosis.

Metabolic Reprogramming By PRDM16 Drives Cytarabine Resistance in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) patients with high PRDM16 expression frequently experience induction failure and have a poor prognosis. However, the underlying molecular mechanisms are poorly understood. Here, we show that AML cells with high PRDM16 expression acquire resistance to cytarabine (AraC) through the activation of oxidative phosphorylation (OxPHOS) via regulation of c-MYC. Initially, we established a murine model of AML with high Prdm16 expression. We transduced c-Kit + bone marrow cells from wild-type mice with a retrovirus vector encoding MLL-AF9 (MF9) and the oncogenic short form of Prdm16 (sPrdm16). Using MF9/sPrdm16 cells, we next investigated whether AML cells with high Prdm16 expression exhibited resistance to AraC and/or daunorubicin (DNR), chemotherapeutic agents commonly used for induction chemotherapy. In the cell viability assay, MF9/sPrdm16 cells showed significantly higher IC 50 against AraC, but not against DNR, compared to MF9/control (control) cells, suggesting that high sPrdm16 expression confers relative resistance to AraC on AML cells. Colony-forming assay also confirmed resistant to AraC in MF9/sPrdm16 cells compared to control. Moreover, MF9/sPrdm16 cells were also resistant to AraC in vivo as demonstrated by the shortened survival of mice receiving MF9/sPrdm16 cells. To elucidate the mechanism of AraC resistance, we first examined cell cycle status of MF9/sPrdm16 cells since AraC exerts cytotoxicity in cell cycle dependent manner. To our surprise, MF9/sPrdm16 cells were cycling more rapidly than control cells as demonstrated by decreased G 0 phase and increased S/G 2/M phase. Intriguingly, RNA-sequencing analysis revealed that MF9/sPrdm16 cells displayed a signature of high OxPHOS by gene set enrichment analysis (GSEA). Indeed, oxygen consumption rate, superoxide production from mitochondria, and mitochondrial membrane potential were significantly elevated in MF9/sPrdm16 cells compared to control cells. The inhibition of mitochondrial respiration with metformin, the electron transport chain complex I inhibitor, or tigecycline, the mitochondrial protein synthesis inhibitor, abrogated AraC resistance in MF9/sPrdm16 cells by inducing an energetic shift towards a lower OxPHOS status. These results clearly indicated that sPrdm16 overexpression conferred MF9 cells with AraC resistance byincreasing OxPHOS in mitochondria. Next, we explored the mechanism how sPrdm16 regulates OxPHOS. In addition to elevated OxPHOS signature, RNA-sequencing data also showed strong enrichment of Myc target-signature in MF9/sPrdm16 cells. Western blot analysis showed that sPrdm16 overexpression induced up-regulation of c-Myc and its transcriptional target, Slc1a5, a glutamine transporter. We went on to analyze metabolic changes induced by sPrdm16 overexpression by capillary electrophoresis and mass spectrometry-based metabolome analysis. We found that sPrdm16 induced the accumulation of glutamine, glutamate, α-ketoglutaric acid, succinate, fumarate, and malate in MF9 cells, possibly by activating glutaminolysis via the regulation of c-Myc and Slc1a5 expression, leading to the activation of tricarboxylic acid (TCA) cycle and OxPHOS. We also confirmed the contribution of c-Myc to AraC resistance by overexpressing c-Myc in MF9 cells. As expected, MF9/c-Myc cells mimicked the phenotype of MF9/sPrdm16 cells such as resistance to AraC and high OxPHOS status. Furthermore, 10058-F4, a c-Myc inhibitor, abrogated AraC resistance in MF9/sPrdm16 cells. Next, we asked if the observation in MF9/sPrdm16 cells could be translated into human AML cells. Human AML cell lines, MOLM-13 and THP-1, with sPRDM16 overexpression also showed significantly higher IC 50 against AraC compared to Mock expressed cells. Moreover, RNA-seq data from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 clinical trial showed that AML blasts with high PRDM16 expression demonstrated a gene expression signature associated with “OxPHOS” and “Myc Targets”. In conclusion, our findings demonstrate that PRDM16 overexpression activates mitochondrial respiration through metabolic reprogramming via c-MYC, thereby conferres AraC resistance on AML cells. These results suggest that targeting mitochondrial respiration might be a novel treatment strategy to overcome chemoresistance in AML patients with high PRDM16 expression.

Evaluation of High-Dose Cytarabine Induction Therapy and Flow Cytometric Measurable Residual Disease Monitoring for Children with De Novo Acute Myeloid Leukemia: A Report from the JPLSG-AML-12 Trial

Background: High-dose cytarabine (HDAC) in initial induction therapy has been tested in several clinical trials both in children and adults with acute myeloid leukemia (AML), however, the trial results are conflicting. In addition, there is growing evidence on significance of measurable residual disease (MRD) monitoring to predict subsequent relapse, but MRD in AML is still challenging in terms of methodology and quality control. In the nationwide clinical trial AML-12 by the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG), the hematological malignancy subgroup of the Japan Children's Cancer Group (JCCG), a role of HDAC in initial induction and feasibility and efficacy of central reference laboratory-based flow cytometric MRD (FCM-MRD) monitoring were evaluated in children with AML. Patients & Methods: JPLSG-AML-12 trial (registered as jRCTs041180128) was designed as a seamless phase II/III trial; because of a safety concern in HDAC induction, children (0-18 years old) with newly diagnosed de novo AML (excluding acute promyelocytic leukemia and AML in Down syndrome patients) registered in selected institutions were randomized to receive either standard ECM (etoposide, standard-dose cytarabine, and mitoxantrone) or experimental HD-ECM (etoposide, HDAC, and mitoxantrone) induction, while patients registered in non-selected institutions were non-randomly allocated to receive standard ECM; in the following phase III part, all the patients were randomized. FCM-MRD were measured at two time points [end of Induction-1 (EOI-1) and end of Induction-2 (EOI-2)] at either of the two central reference laboratories (Mie University or Kyoto University) but was not used to guide subsequent therapies. Following complete remission (CR) evaluation at EOI-2, patients achieving CR were allocated to either of the 3 risk groups and received post-remission chemotherapies; core-binding-factor standard risk (CBF SR), non-CBF SR, or high risk (HR) group. Only HR patients were allocated to receive allogeneic hematopoietic stem cell transplantation in first CR. Primary endpoints of the trial were 3-year EFS and positive FCM-MRD (≥0.1%) rate at EOI-1. Results: Total 359 eligible patients were registered at 102 institutions between 2014-2018. CR, 3-year EFS, and 3-year OS rates of all patients were 94.0%, 63.1% (95%CI, 57.9-67.9%), and 80.3% (95%CI, 75.8-84.1%), respectively. Among all, 324 patients were randomized (ECM, n=168; HD-ECM, n=156). Median follow-up period of these patients was 50.9 months (range, 0.2 - 84.7 months). No significant difference in outcomes were observed between the 2 arms; CR rates were 94.2% vs. 93.8% (p=0.998), 3-year EFS rates were 64.3% (95%CI, 56.5-71.0%) vs. 61.2% (53.1-68.4%) (p=0.551), 3-year OS rates were 84.4% (95%CI, 78.0-89.1%) vs. 75.3% (95%CI, 67.7-81.4%) (p=0.053), 3-year cumulative incidence of relapse were 28.6% (95%CI, 21.5-36.0%) vs. 30.9% (95%CI, 23.3-38.8%) (p=0.585), and 3-year non-relapse mortality rates were 0.9% (95%CI, 0.1-6.4%) vs. 1.8% (95%CI, 0.4-7.1%) (p=0.832). These outcome parameters were not different within each risk groups as well. FCM-MRD at EOI-1 was evaluated in 135 patients (80.4%) in the ECM arm and 127 patients (81.4%) in the HD-ECM arm; the positive FCM-MRD rates were 21.5% vs. 25.2% (p=0.575). Regarding grade 3 or higher adverse events (AEs) evaluated by CTCAE version 4 during Induction-1, disseminated intravascular coagulation was more frequent in the HD-ECM arm (1.8% vs. 6.4%, p=0.046), but no significant difference was observed for other AEs. Univariable Cox regression analysis for baseline characteristics revealed that the intermediate-risk cytogenetics and positive FLT3-ITD were significantly associated with decreased EFS rate. However, in multivariable analyses for EFS after EOI-1 and EOI-2, FCM-MRD was the sole poor prognostic factor; hazard ratios were 5.24 (95%CI, 3.19-8.63) (p<0.001) at EOI-1 and 5.56 (95%CI, 2.93-10.54) (p<0.001) at EOI-2. Conclusions: Although HDAC in initial induction did not improve the outcome of children with AML, overall outcomes were comparable to the recently completed pediatric AML trials worldwide. Central reference laboratory-based FCM-MRD measurement was feasible and MRD at both EOI-1 and EOI-2 were the most powerful prognostic factors to predict outcome of children with AML. Therefore, FCM-MRD should be included in future risk stratification for children with AML. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The treatment development for T cell acute lymphoblastic leukemia in children, adolescents, and young adults

T-cell acute lymphoblastic leukemia (T-ALL) accounts for 10%-15% of pediatric ALL, and its frequency increases during the adolescent and young adult (AYA) periods. The improvements in pediatric T-ALL outcomes have been achieved through the treatment intensification strategies addressing the cranial radiotherapy omission issue. Furthermore, pediatric-inspired regimens have been adopted for AYA patients with T-ALL, improving outcomes. In Japan, the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) ALL-T11/JALSG T-ALL-211-U trial has been conducted for newly diagnosed patients with T-ALL aged <25 years and has been shown to have excellent outcomes. While early T cell precursor ALL is not an obvious poor prognostic factor in recent treatment strategies for pediatric T-ALL, the minimal residual disease (MRD) has been recognized as the most reliable prognostic indicator. Therefore, MRD is now widely used in T-ALL clinical trials for risk stratification and stem cell transplantation indications. Further progress in the novel therapeutic approaches can potentially improve the outcomes of pediatric and AYA patients with T-ALL.

Chemotherapy with the Use of TKIs Based on MRD Has the Potential to Avoid Hematopoietic Stem Cell Transplantation in Treatment for Children with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia (Ph+ALL). Results of the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) Study ALL-Ph13

Aims: Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) patients generally have a poor prognosis when treated with chemotherapy alone. In adults, allogeneic hematopoietic stem cell transplantation (HSCT) in first complete remission is still the standard strategy for Ph+ALL. However, in children, HSCT should be avoided as much as possible to eliminate late complications. There are some reports showing that the combination of tyrosine kinase inhibitors (TKIs) with chemotherapy may avoid HSCT in childhood Ph+ALL. Thus, we planned this clinical trial (JPLSG ALL-Ph13) with the aim of improving outcomes with as few HSCT by chemotherapy with TKIs based on Ig/TCR minimal residual disease (MRD).Methods: Patients aged 1 to 19 with Ph+ALL were enrolled in JPLSG ALL-Ph13 Study. The diagnosis of Ph+ALL was performed using reverse-transcription PCR for BCR-ABL1. Chemotherapy follows the BFM ALL high-risk regimen (IA, IB, HR3, HR2, HR1, III, IM, III, IM, III, and maintenance). Imatinib was started on day 15 of induction therapy and continued until the final day of maintenance therapy (Ima group). If Ig/TCR MRD was positive (≥10 -4) at the end of IB, imatinib was changed to dasatinib and chemotherapy was continued (Dasa group). If MRD was positive at the end of the HR blocks, HSCT was performed (HSCT group).Results: During the period 2013-17, 43 patients were registered in this study, and 2 patients were excluded by not meeting inclusion criteria. Thirty-three, 7, and 1 patient were stratified into Ima, Dasa, and HSCT groups, respectively. Induction rate was 52.6% at the end of IA and 89.2% at the end of IB. MRD-negative rate was 61.3% at the end of IB and 87% at the end of HR. Although 51.2% of patients eventually received HSCT, only 13.9% received HSCT at the first complete remission. In all patients, the 3-year event-free survival (EFS) rate was 65.1%, and the 3-year overall survival (OS) rate was 85.1%. Four patients died of serious infections during treatment (2 in IA, 2 in 1st III).Interpretation: In our previous study for children with Ph+ALL (the JPLSG Ph+ALL04 study), all patients underwent HSCT, with the 3-year EFS rate of 57% and the OS rate of 80%. In this ALL-Ph13 study, the EFS and OS are almost the same as those in the Ph+ALL04. These are also almost the same as those in the EsPhALL2010 study, which aimed at avoiding HSCT. However, as in the EsPhALL2010 study, the comparatively high incidence of fatal adverse events was a problem with this study.Conclusion: Chemotherapy with the use of TKIs based on MRD has the potential to avoid HSCT in treatment for children with Ph+ALL. Reducing the occurrence of fatal adverse events is a future challenge to overcome. DisclosuresNo relevant conflicts of interest to declare.

Intensification of Early-Phase Therapy to Diminish the Prognostic Effect of Myeloid Antigen Expression in Infants with KMT2A-Rearranged Acute Lymphoblastic Leukemia: A Report from the JPLSG MLL-10 Trial

Background KMT2A-rearranged acute lymphoblastic leukemia (KMT2A-r ALL) is a rare and dismal disease in infants. Despite restriction of the indication of allogeneic hematopoietic stem cell transplantation to the high-risk group (patients aged <180 days with KMT2A-r ALL or central nervous system involvement), adoption of an Interfant-06-based induction therapy with stricter age-related dosing followed by COG AALL0631-based post-remission chemotherapy with additional administration of high-dose cytarabine in the early intensification phase led to rapid clearance of minimal residual disease (MRD) in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) MLL-10 trial. The MLL-10 trial demonstrated an improved outcome of 66.2% in 3-year event-free survival (EFS) among infants with KMT2A-r ALL (Tomizawa D. Blood 2021). As the Interfant-06 study showed an association between the expression levels of myeloid markers (MM) and poor MRD clearance at end of induction (EOI) and a high relapse rate (Stutterheim J, J Clin Oncol.2021), we analyzed the significance of MM expression in the MLL-10 cohort and its association with prognosis.MethodsWe analyzed and compared the MM expression (defined as at least one positive marker [with a positive blast subset ≥ 10%] among CD117, CD13, CD33, and CD65/CD15) by using flow cytometry (FCM) in infants with KMT2A-r ALL who were registered in the JPLSG MLL-10 trial. We also compared the results of immunoglobulin/T-cell receptor (Ig/TCR) gene-based polymerase chain reaction (PCR)-MRD analyses or 4-color FCM-MRD assay between the MM-positive and MM-negative groups at EOI and end of early consolidation. The Ig/TCR-MRD results were classified as negative if <5 × 10 −4 and positive if ≥5 × 10 −4, while the FCM-MRD results were classified as negative if <0.01% and positive if ≥0.01%. We prioritized PCR-MRD and used FCM-MRD when we could not make a primer for PCR-MRD. The presence of MRD was not used as a basis for choosing the appropriate therapy.Results and DiscussionAmong the patients with KMT2A-rALL, 74 were included in this study, excluding one who was not evaluated with FCM at diagnosis. Of these patients, 42 were MM-positive and 32 were MM-negative. The 3-year EFS rates of the MM-positive and MM-negative patients were 62.3% (95% confidence interval [CI], 45.5-75.3) and 70.0% (95% CI, 50.3-83.1), respectively (p = 0.61). Their 3-year overall survival rates were 80.6% (95% CI, 65.0-89.8) and 87.5% (95% CI, 70.0-95.1), respectively (p = 0.74). The numbers of MM-positive and MM-negative patients according to age group are summarized in Table 1, and the difference in age distribution between the two groups was not significant. The MRD statuses of the patients at EOI in the two groups are also summarized in Table 1. No significant difference in MRD clearance was found between the MM-positive and MM-negative groups.ConclusionIn this study, we found no significant difference in survival rate between the MM-positive and MM-negative groups. The MM expression was not a prognostic marker in the infants with KMT2A-r ALL in the MLL-10 cohort. We believe that rapid MRD clearance in the early phase of treatment with enhanced chemotherapy would have the greatest contribution to the improvement of prognosis. In this study, the MM-positive patients from the MLL-10 cohort might have benefited from early-phase treatment intensification in terms of MRD clearance. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Effectiveness of Supportive Care Measurements to Reduce Infections during Induction for Children with Acute Myeloid Leukemia: A Report from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG)

BACKGROUNDCurrent intensive chemotherapy for pediatric acute myeloid leukemia (AML) in conjunction with supportive care has increased survival rate up to 70%, and yet infections are still responsible for considerable morbidity and most treatment-related deaths. These factors have led to much interest in supportive care measurements to reduce infections and infectious mortality. The Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) trial AML-05 was a phase 2 study that included children with de novo AML treated with intensive chemotherapy. We surveyed participating JPLSG sites to assess the effect of each supportive care measurements on Induction I infection risk and non-relapse mortality for children in AML-05 study. METHODSBetween November 2006 and December 2010, JPLSG AML-05, registered at http://www.umin.ac.jp/ctr/ as UMIN000000511, recruited 447 eligible children (age <18 years) with de novo AML. AML-05 used 5 courses of intensive chemotherapy with Induction I consisting of etoposide 150mg/m2/dose intravenous (IV) every 24 h on day 1-5; cytarabine 200 mg/m2/dose intravenous (IV) every 12 h on days 6-12; mitoxantrone 5 mg/m2/dose IV on days 6-10; triple intrathecal treatment (methotrexate/ cytarabine/ hydrocortisone) (ECM 5+7+5). Data of Infectious complications were collected prospectively and monitored in real-time to optimize reporting accuracy. In this analysis, infectious events were limited to Induction I. Non-relapse mortality was defined as any induction death within 40 days of being taken off study due to non-disease related causes. The survey included questions on implementations in each patient participated in AML-05 study for antibacterial prophylaxis, antifungal prophylaxis, intestinal sterilization, use of HEPA-filter, surveillance culture, and use of G-CSF until count recovery. RESULTSThe survey response rate from the JPLSG sites was 359/447 (80.3%). In multiple regression, anti-bacterial prophylaxis reduced the development of febrile neutropenia during induction chemotherapy (Odds ratio [OR] 0.56, 95% confidence interval [CI] 0.39-0.88; p = 0.013). Sterile site bacterial infections increased in younger age group (OR 2.0, 95% CI, 1.09-3.66; p = 0.025) but decreased in patients who were routinely carried out surveillance culture (OR 0.5, 95% CI, 0.27-0.96; p = 0.038). Fungal infection during induction chemotherapy was associated with intestinal sterilization (OR 0.21, 95% CI, 0.61-0.70; p = 0.011) and the use of G-CSF (OR 3.83, 95% CI, 1.10-13.32; p = 0.035). Prophylactic antifungal agent had a tendency to reduce the frequency and duration of pyrexia, and the peak value of CRP. Nonetheless, routine prophylaxis with these agents did not impact non-relapse mortality. CONCLUSIONSProphylactic use of antibiotics was associated with less development of febrile neutropenia. Routine prophylaxis with these agents may be associated with incidence and severity of infectious complications, but did not impact non-relapse mortality during induction chemotherapy in childhood AML. DisclosuresNo relevant conflicts of interest to declare.

Biology and Prognostic Markers in Young Children with Acute Myeloid Leukemia -the Jccg Study, JPLSG AML-05-

[Introduction] Acute myeloid leukemia (AML) in children aged < 12 months of age was conventionally defined as infant AML. On cytogenetic and molecular analysis, 11q23/ KMT2A rearrangement (KMT2A -R) was found to be the most frequent (approximately 50%) cause of infant AML. On prognostic analysis, infant AML was reported to have favorable outcome compared with AML in older children, and only KMT2A -R and RBM15-MKL1 were known to be intermediate-risk prognostic factors in infants. Although infants have been treated in the same regimens as older children, in some clinical trials, drug dosage for infants has been reduced to avoid severe toxicities. However, new findings in young children with AML have been recently accumulated. A recent report by an international expert panel of pediatric AML has proposed AML in children aged < 24 months of age as a distinct age-subgroup because their morphologic and cytogenetic/molecular characteristics were considered to be similar to those of infants (Creutzig et al, 2012). Moreover, recent studies have identified novel inv(16)(p13.3q24.3)/ CBFA2T3-GLIS2 and t(11;12)(p15;p13)/ NUP98-KDM5A fusion genes in AMKL. In this study, we investigated biology and prognosis of children aged < 5 years, to identify unique characteristics of young children with AML and propose a novel risk-stratification for them.[Patients and Methods] A total of 369 children with AML were enrolled in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 trial. In this study, we analyzed 133 children aged < 5 years (36%). We screened fusion genes of CBFA2T3-GLIS2, NUP98-KDM5A, RBM15-MKL1, KMT2A -Rs, NUP98-NSD1, FUS-ERG, DEK-NUP214, RUNX1-RUNX1T1, and CBFB-MYH11, and gene mutations of KIT, NRAS, KRAS, WT1, NPM1, KMT2A -PTD, FLT3 -ITD, CEBPA, ASXL1, ASXL2, and CSF3R .[Results] In clinical characteristics, no change was observed in the sex ratio with age. The WBC count at diagnosis was the highest in children aged 2 years (24-35months), and a trend of lower WBC in children aged > 2 years (> 35 months). On FAB classification, the proportion of M5 and M7 was observed to be decline with age. Among fusion genes, KMT2A -R was the most frequently identified fusion gene (23%), followed by RUNX1-RUNX1T1, CBFB-MYH11, and CBFA2T3-GLIS2 (13.5%, 9.8%, and 8.3%, respectively). Conversely, neither NUP98-NSD1 nor DEK-NUP214 was found. Although the frequencies of KMT2A -R and CBFA2T3-GLIS2 tended to decrease with age, the frequency of RUNX1-RUNX1T1 significantly increased with age. Among gene mutations, KIT and NRAS were the most frequent, and gene mutations other than ASXL1 and KMT2A -PTD were recurrently identified. When correlation of fusion genes with gene mutation was analyzed, 21 (68%) of 31 children with CBF-AML had gene mutations, whereas only 8 (16%) of 51 children with non-CBF-AML had gene mutations (p < 0.001). For fusion genes, 28 (90%) of 31 KMT2A -R-positive children were aged < 3 years (< 36 months) (90%), and 17 (94%) of 18 RUNX1-RUNX1T1 -positive children were aged > 2 years. Thus, according to these molecular characteristics of young children with AML, we defined children aged < 3 years as the youngest subgroup with distinct biology (n = 99). We further performed prognostic analyses of the youngest subgroup. According to recent previous studies that reported poor prognosis of CBFA2T3-GLIS2 and NUP98-KDM5A in AMKL, these fusions were combined to the same group. The Kaplan-Meier analyses revealed that CBFA2T3-GLIS2 / NUP98-KDM5A -positive children had the poorest outcome in OS, EFS, and CIR (38%, 13%, and 88%, respectively). Surprisingly, children with CBF-AML had the second poorest outcome in EFS and CIR (45% and 55%, respectively), although this subgroup had an excellent OS (100%), indicating that children with CBF-AML in the youngest subgroup have a high-risk of relapse and might need more intensified therapy as an initial treatment.[Conclusions] The youngest subgroup of pediatric AML had a unique biology. Children with CBFA2T3-GLIS2 and NUP98-KDM5A had the poorest outcome, and children with CBF-AML also had a high relapse rate. Because this subgroup is known to have a high incidence of severe side effects and late effects, a novel risk-stratified therapy restricted to young children is required. DisclosuresNo relevant conflicts of interest to declare.

Comprehensive Immunophenotyping Panel in Japan Enables to Detect Rare Subtypes in Childhood Leukemia

[Background] Although the development of genome wide screening for risk stratification in childhood leukemia, immunophenotyping is still essential to decide initial treatment because of quick duration to make diagnosis. Immunophenotyping is also very useful to detect rare subtypes in leukemia. From 2011, Japanese pediatric leukemia/lymphoma study group (JPLSG) started nation-wide immunophenotyping with comprehensive panel including more than 50 antigens for childhood hematological malignancy. This panel led easier diagnosis not only for typical leukemia subtypes such as acute lymphoblastic leukemia (ALL) or acute myelogenous leukemia (AML), but for rare subtypes including mixed phenotype acute leukemia (MPAL), acute undifferentiated leukemia (AUL), and blastic plasmacytoid dendritic cell neoplasms (BPDCN). We report here the significance of comprehensive immunophenotyping panel, then clinical manifestations and immunophenotypic peculiarity of rare subtypes in childhood leukemia.[Methods] Immunophenotyping was done with comprehensive panel (Table 1) and diagnosis was done according to WHO 2008 classification. Briefly, determination of lineage was usually decided by major lineage specific markers such as myeloperoxidase (MPO), CD19, and cytoplasmic CD3. Then, more detailed categorization was done by analysis with other lineage, differentiation, or activation markers.[Result] In 4,033 case from January 2012 to December 2016, major immunophenotypes were as follows; B-precursor/pre-B (BCP-) ALL was 2,141, T cell (T-) ALL 348, AML 842, B-ALL 74, Lymphomas 171, transient myeloproliferative disorder (TAM) 244, chornic myelogenous leukemia (CML) 72. Out of other 141 cases, we also found 32 MPAL, 16 AUL, and 7 BPDCN. According to detailed immunophenotyping, MPAL cases could be divided into 3 distinct clusters, T-ALL/ AML-M1 biphenotypic subtype (8 cases), BCP-ALL/AML-M5 bilineal subtype (11), and BCP-ALL with MPO expression subtype (13). Furthermore, distinct cluster, ‘early T cell progenitor ALL (ETP)-like subtype’ was also distinguished from AUL.[Discussion] Acute leukemia of ambiguous lineage and BPDCN are both rare subtypes of acute leukemia. According to WHO 2008 classification, acute leukemia of ambiguous lineage is further classified as MPAL, AUL and natural killer lymphoblastic leukemia. In this study, we evaluate 32 MPAL, 16 AUL and 7 BPDCN. It is of note that we could not identify no natural killer lymphoblastic leukemia in this childhood leukemia cohort. We also evaluate 32 MPAL cases, which showed 3 distinct subgroups. T-ALL oriented cases indicate only one subtype ‘T-ALL/AML-M1 biphenotypic’, which indicated relatively older age, usually diagnosed as AML-M1 with morphologic FAB classification, and received mostly myeloid oriented therapy. BCP-ALL related cases were also divided into two groups, BCP-ALL/AML-M5 bilineal, and BCP-ALL with MPO expression. Bilineal leukemia often found in infantile ALL with MLL gene rearrangement (4 out of 11 cases), but still found 7 older cases without MLL gene rearrangemnt. Bilineal leukemia occasionally cause lineage-switch relapse, so diagnosis of bilineal leukemia seems to be very significant. Recent studies showed leukemia with ZNF384 fusion indicate CD10 negative or low BCP-ALL, and tended to express MPO. Our cases also tended to indicate negative or low CD10 expression. In addition, ETP-ALL like cases were positive for T cell antigens such as CD2 and/or CD7 and also some myeloid antigens but lacked cytoplasmic CD3 expression.In conclusion, we identified a spectrum of rare subtypes in childhood leukemia, including MPAL, AUL, and BPDCN by adoption of comprehensive immunophnotyping panel. In most of childhood MPAL cases were divided into 3 distinct clusters. It must be useful information for detection of genetic abnormality. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Etoposide, Cytarabine and Mitoxantrone- or Fludarabine, Cytarabine and Granulocyte Colony-Stimulating Factor-Based Intensive Reinduction Chemotherapy Is Recommended for Children with Relapsed Acute Myeloid Leukemia: The Results from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05R Study

Background:The current event-free survival rates of children with acute myeloid leukemia (AML) approach 60%, with hematopoietic cell transplantation (HCT) as an effective second-line therapy and improvements in supportive care; however, the overall survival rates of children with relapsed AML still remains 70%, which is an unsatisfactory situation that urgently needs to be solved. Patients &amp; Methods:In order to identify prognostic factors and improve their prognosis, we analyzed 111 patients with relapsed disease after treatment with the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 protocol, who were registered in the retrospective JPLSG AML-05R study. We collected the following data: age at relapse, time from the diagnosis to relapse, site of relapse, FAB classification, chromosomal analysis results, reinduction chemotherapy regimen, rate of achieving a second complete remission (CR2) after initial reinduction therapy, detailed information on HCT, outcome and cause of death. Moreover, ninety-three leukemic samples obtained from 111 patients at the time of their diagnosis were available for a genetic analysis. Mutational analyses ofFLT3-ITD,KIT, N-andK-RAS, NPM1,WT1,andKMT2A-partial tandem duplication were performed. Screening ofNUP98-NSD1was also performed. The high or low expression ofMECOMandPRDM16were determined based on theABL1ratio. Results:The 5-year overall survival rate was 36.1%. t(8;21) was found in 27 patients and inv(16) was found in 5 patients.KMT2Arearrangement was found in 23 patients (24.7%).KITmutations were found in 17 patients (17.5%). The following mutations were also detected:FLT3-ITD (n=10),N-RAS(n=10),WT1(n=7),K-RAS(n=4),NUP98-NSD1(n=2),KMT2A-PTD (n=2), andNPM1(n=2). The high expression ofMECOMandPRDM16was found in 24 (25.8%) and 32 (34.4%) patients, respectively. A genetic analysis revealed the prognostic significance ofFLT3-ITD as a poor prognostic marker (p=0.04) and core binding factor-AML, t(8;21) and inv(16), as a good prognostic marker (p&amp;lt;0.01). The five-year overall survival rate in the AML-05 risk groups were as follows: high risk, 14.7%; intermediate risk, 32.3%; and low risk 61.7% (p&amp;lt;0.01). The major determinant of survival was duration from the diagnosis to relapse. The mean duration in the non-surviving group (10.1±4.1 months) was shorter than that in the surviving group (16.3±8.3 months) (p&amp;lt;0.01). Moreover, achieving CR2 prior to HCT was associated with a good prognosis (p&amp;lt;0.01). "Etoposide, cytarabine and mitoxantrone" (ECM)- or "fludarabine, cytarabine and granulocyte colony-stimulating factor" (FLAG)-based regimens were therefore recommended for reinduction therapy (p&amp;lt;0.01). Conclusions:Achieving CR2 prior to HCT by intensive reinduction chemotherapy, ECM, or FLAG, is important for improving the prognosis of patients with relapsed pediatric AML. Liposomal daunorubicin or 3 fractionated doses of gemtuzumab ozogamicin is an attractive option which is under consideration for addition to FLAG. Moreover, recent molecular targeted therapeutics, such as FLT3 inhibitors, may contribute to improving the prognosis of these patients. Larger prospective investigations are needed in order to establish individualized treatment strategies for patients with relapsed childhood AML. Disclosures No relevant conflicts of interest to declare.

The outcomes of relapsed acute myeloid leukemia in children: Results from the Japanese Pediatric Leukemia/Lymphoma Study Group AML‐05R study

The prognosis of children with acute myeloid leukemia (AML) has improved with the efficacy of hematopoietic cell transplantation (HCT) as a second-line therapy and improvements in supportive care following anthracycline- and cytarabine-based chemotherapy; however, the outcomes of children with relapsed AML still remain unsatisfactory. In order to identify prognostic factors and improve their prognosis, we analyzed 111 patients who relapsed after treatment with the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 protocol and who were registered in the retrospective JPLSG AML-05R study. The 5-year overall survival rate was 36.1%. The major determinant of survival was duration from the diagnosis to relapse. The mean duration in the nonsurviving group (10.1 ± 4.1 months) was shorter than that in the surviving group (16.3 ± 8.3 months) (P<.01). Moreover, achieving a second complete remission (CR2) prior to HCT was associated with a good prognosis (P<.01). Etoposide, cytarabine, and mitoxantrone (ECM)- or fludarabine, cytarabine, and granulocyte colony-stimulating factor (FLAG)-based regimens were therefore recommended for reinduction therapy (P<.01). A genetic analysis also revealed the prognostic significance of FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication as a poor prognostic marker (P=.04) and core binding factor-AML, t(8;21), and inv(16) as good prognostic markers (P<.01). Achieving a CR2 prior to HCT is important in order to improve the prognosis of relapsed pediatric AML. Recent molecular targeted therapies, such as FLT3 inhibitors, may contribute to overcome their prognoses. Larger prospective investigations are necessary to establish individualized treatment strategies for patients with relapsed childhood AML.

Attempts to optimize postinduction treatment in childhood acute myeloid leukemia without core-binding factors: A report from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG).

We previously reported that risk-stratified therapy and intensive postremission chemotherapy (PRC) contributed to the improved survival of childhood acute myeloid leukemia (AML) in the AML99 study, which led us to consider a reduction in the number of PRC courses with more restrictive indications for stem cell transplantation (SCT) in the successor AML-05 study. We here report the outcome of AML patients without core-binding factor mutation (non-CBF AML) in the AML-05 study. Two-hundred eighty-nine children (age<18years old) with non-CBF AML were eligible. Patients with unfavorable cytogenetics and/or poor bone marrow response to the first induction course were candidates for SCT in the AML-05 study. After two courses of induction, a further three courses of PRC were given in AML-05, while four courses were given in the AML99 study. The 3-year event-free survival (EFS) rate in the AML-05 study (46.7%, 95% CI: 40.6-52.6%) was comparable to that of non-CBF AML in the AML99 study (51.5%, 95% CI: 42.7-59.6%) (P=.16). However, the 3-year overall survival (OS) rate in the AML-05 study (62.9%, 95% CI: 56.3-68.8%) was slightly lower than that in the AML99 study (71.6%, 95% CI: 63.2-78.5%) (P=.060), mainly due to decreased remission induction rate and increased nonrelapsed mortality. In conclusion, reductions in the number of PRC courses from four to three, together with repetitive cycles of high-dose cytarabine, were acceptable for non-CBF childhood AML.

The Detection of Minor Clones with Somatic KIT D816V Mutations Using Droplet Digital PCR in Pediatric De Novo AML: AML-05 Trial from the Japanese Pediatric Leukemia/Lymphoma Study Group

Introduction Recent medical advances and development of comprehensive genetic understanding dramatically improve the clinical outcome of whole pediatric cancers, particularly in pediatric acute lymphoblastic lymphoma. However, approximately 50% of patients have disease relapse, and overall survival (OS) of pediatric acute myeloid leukemia (AML) is less than 70% as of the major therapeutic challenges. AML is caused by various chromosomal aberrations, gene mutations/epigenetic modifications, and deregulated/overregulated gene expressions, leading to increased proliferation and decreased hematopoietic progenitor cell differentiation. AML with RUNX1-RUNX1T1 gene fusions are generally classified as a low-risk group and resulted in favorable prognosis. However approximately 30% of the patients relapsed within 3 years. Conversely, KIT mutations were found in approximately 30% of AML cases with RUNX1-RUNX1T1 and thought to be a risk factor for relapse, particularly when occurring in D816V within KIT exon 17. Recently, droplet digital PCR (ddPCR), a method for measuring target nucleic acid sequence quantity, has been used to determine low-prevalence somatic mutations that were not detectable using Sanger sequencing. It shows the possibility that there are some of Pediatric AML cases which were not detected minor clones with somatic KIT mutation by using ordinary PCR. In this study, we explored KIT D816V mutations including the cases which are not detected by Sanger sequencing and found the prognosis of them by using Japanese pediatric AML cases. Methods We reanalyzed somatic KIT mutations (p.D816V) in the DNA extracted from 335 pediatric AML patients with RUNX1-RUNX1T1 who participated in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 trial using ddPCR . In this trial, we conducted the tests as follows,: PCR mixture containing 10 μL 2x ddPCR Supermix for probes, 900 nM target-specific PCR primers, and 250 nM mutant-specific (FAM) and wild-type-specific (HEX) probes.20 µL of PCR mixture and 70 μL Droplet generation oil were mixed, and droplet generation was performed using a Bio-Rad QX100 Droplet Generator. The droplet emulsion was thermally cycled in the following conditions: denaturing at 95 °C for 10 min, 40 cycles of PCR at 94 °C for 30 s and at 57 °C for 2 min, and a final extension at 98 °C for 10 min. PCR amplification in the droplets was confirmed using Bio-Rad QX200 Droplet Reader. ThresholdThe threshold was determined by comparing the non-template ddPCR results. All the data were evaluated above the threshold. We also performed targeted gene mutation analysis of KIT in all patients using Sanger sequencing. Results We identified 24 KIT D816V mutations (7.2%) in the 335 pediatric AML. Variant allele frequency (VAF) was 0.1%-46.9%.It is noteworthy that 12 out of 24 KIT D816V mutations were undetected in our previous study using Sanger sequencing. Fourteen out of these 24 patients were AML with RUNX1-RUNX1T1, 5 cases with inv(16), and 5 cases with other alterations. Ten of the 14 RUNX1-RUNX1T1 (71%) patients were newly identified using ddPCR. Six of these 14 RUNX1-RUNX1T1 patients had relapsed, and D816V mutations were only detected using ddPCR in 4 of these 6 relapsed cases. The mean VAF of KIT D816V was 3.8% (0.1%-13.4%) in the 10 undetected patients with RUNX1-RUNX1T1. Two of the 5 patients with inv(16) were newly identified, and 1 had relapsed. All 5 cases with other alterations were already identified using Sanger sequencing. The mean VAF of KIT D816V in the 3 patients with inv(16) was 44.8% (42.7%-46.9%), detected using Sanger sequencing, whereas the mean VAF of KIT D816V was 8.6% (6.5% and 10.7%) in the undetected patients with inv(16). The mean VAF of KIT D816V with other alterations was 28.1% (16.2%-42.9%). Conclusion We identified 12 KIT D816V mutations using ddPCR that were undetected using Sanger sequencing. ddPCR may be useful for detecting accurate frequencies of mutations that were undetected using Sanger sequencing. Potential co-existing gene mutations may contribute different significance of leukemogenesis and relapse. Disclosures Ito: Asahi Kasei Pharma: Consultancy, Other: Grants; Astellas Pharma: Consultancy, Other: Grants; Teijin: Other: Grants; Novartis Pharma: Consultancy; Zenyaku Kogyo Co. Ltd: Consultancy; Chugai Pharma: Consultancy, Other: Grants; Japan Blood Products Organization: Other: Grants; Pfizer inc.: Other: Grants.

Post-Induction Minimal Residual Disease Measured By Flow Cytometry and Deep Sequencing of Mutant GATA1 Are Both Significant Prognostic Factors for Children with Myeloid Leukemia and Down Syndrome: A Nationwide Prospective Study of the Japanese Pediatric Leukemia/Lymphoma Study Group

Background: Myeloid leukemia in Down syndrome (ML-DS) is associated with good response to chemotherapy thus results in a favorable outcome. However, relapsed and refractory cases are rarely salvageable, regardless of receiving hematopoietic stem cell transplantation. Several factors such as certain chromosomal abnormalities and age at diagnosis are somewhat prognostic, but no universal prognostic factor has been found to date. In order to identify a subgroup with high risk of treatment failure, the role of minimal residual disease (MRD) with three methods were explored in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) trial AML-D11. Procedure: AML-D11 is a nationwide single-arm clinical trial for children (4 months to 17 years old) with ML-DS. All patients received an identical chemotherapy to the previous AML-D05 study (Taga T. Pediatr Blood Cancer 2016). MRD was evaluated at two time points, one after the induction therapy and another at the end of whole chemotherapy, using 3 different methods; flow cytometric MRD (FCM-MRD), deep sequencing MRD of mutant GATA1 (GATA1-MRD) and PCR MRD of WT1 mRNA expression (WT1-MRD). WT1-MRD was measured in both bone marrow (BM) and peripheral blood (PB) samples, while FCM- and GATA1-MRD were measured only in BM samples. Results: A total of 78 patients were eligible and followed-up with a median of 47.6 months (range, 8 to 68.8 months). Seventy-six patients were stratified to the standard risk (SR) and one patient to the high risk (HR) group by morphological response. One patient died of sepsis during initial induction therapy. Three-year event-free survival (EFS) and overall survival (OS) rates were 87.2% (95%CI, 77.5 to 92.9%) and 89.7% (95%CI, 80.5 to 94.7%), respectively. FCM-MRD and GATA1-MRD after initial induction therapy were positive in 5/65 and 7/59 patients, respectively, which were both significantly prognostic (Fig.1). Prognostic significance of WT1-MRD could not be evaluated due to a limited number of collected samples. Conclusions: MRD detections by FCM and targeted deep sequencing of GATA1 after initial induction therapy are both significant prognostic factors for predicting relapse. Risk stratification using FCM-MRD is currently incorporated in the on-going Japan Children's Cancer Group ML-DS trial (AML-D16; jrct.niph.go.jp, jRCTs041190047). Figure 1 Disclosures No relevant conflicts of interest to declare.

Late Effects in Survivors of Infant Acute Lymphoblastic Leukemia from the 3 Consecutive Japanese Nationwide Clinical Trials

Background Very few studies have reported the incidence of and risk factor for late effects of infant leukemia. In addition, the long-term impact of a preparative regimen for very young children undergoing allogeneic stem cell transplantation (SCT) is not evident. Method To examine the late effects in survivors of infant acute lymphoblastic leukemia (ALL) treated on the Japanese Infant Leukemia Study Group (JILSG) trials MLL96, MLL98 and the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) trial MLL03, we performed a cross-sectional survey using questionnaires by the attending pediatricians from 2015 to 2017. In all 3 studies, infants with KMT2A gene rearranged (MLL-R) ALL were allocated to receive SCT in their first remission. Choice of preparative regimen was left to the physician's choice in the MLL96/98 studies, while use of non-total body irradiation (TBI) regimen with busulfan (BU) was mandatory in the MLL03 study. Results Seventy out of 102 (69%) eligible subjects were evaluated: 33 were males and 37 were females. 62 patients had an MLL-R ALL. The median age of diagnosis was 5.5 months (range, 0-12m) and 35 (50%) were &lt;6 months of age. At the time of analysis, the median age of the 70 patients was 13.5 years (range, 7-21y) and the median follow-up duration from diagnosis was 12.5 years (range, 7-20y). Fifty-seven (81%) of the 70 patients underwent SCT. Eight patients received the TBI-based regimen, while 35 received BU regimen and one received non-TBI, non-BU regimen. Thirteen patients had SCT twice and twelve patients received both TBI and BU regimen. Relapses occurred in seventeen patients (24%). Only two patients received cranial radiation therapy in 13 patients with central nervous system involved. At least one late effect was observed in 62 of the 68 patients (91%). Identified abnormalities included: underweight (body mass index [BMI]&lt;18.5) (69%), hypogonadism (56%), teeth mal-development (52%), short stature (52%), bone abnormalities (28%), thyroid dysfunctions (27%), skin abnormalities (24%), ophthalmic dysfunctions (24%), pulmonary dysfunctions(22%), neurocognitive dysfunctions (22%), and cardiovascular dysfunctions (14%), gastrointestinal dysfunctions (5%), renal dysfunctions (4%), second malignancy (3%), and overweight (3%). The mean standard deviation (SD) heights at last follow up with TBI regimen were -4.2 and those with multiple SCT (BU+TBI) were -3.8. Both were significantly lower than those with single SCT by BU regimen (-1.4) (TBI vs BU, P=0.014; BU+TBI vs BU, P&lt;0.001). The mean BMI at last follow up was lower in the TBI group (16.8) compared with that in the BU group (17.8) without statistical significance (TBI vs BU, P=0.342), whereas the mean BMI in the BU+TBI group (15.1) was significantly lower than that in the BU group (BU+TBI vs BU, P=0.020). Univariable analysis revealed that the risk of both thyroid dysfunctions (odds ratio [OR]=14.0, P=0.005) and the need of growth hormone (GH) treatment (OR=10.7, P=0.011) were significantly lower in the BU group than those in the TBI group. Hypothyroidism (OR=5.8, P=0.012), teeth mal-development (OR=2.8, P=0.066) and the need of GH treatment (OR=3.5, P=0.084) were more frequently observed in children who were diagnosed at less than 6 months of age. In addition, short stature (OR=23.3, P=0.003), thyroid dysfunctions (OR=4.1, P=0.023), cataract (OR=6.9, P=0.038) and alopecia (OR=6.8, P=0.038) were more frequently observed in relapsed patients. Overall, SCT significantly increased the incidence of short stature (OR=15.5, P=0.012) and underweight (OR=5.3, P=0.018). Conclusion In this study, survivors of infant leukemia had prolonged and various types of late effects. We observed serious growth failure in height and weight in patients treated with SCT and it was further pronounced in the TBI group and in the multiple SCT (BU+TBI) group. More than half of the patients had dental late effects and a third of all the patients had thyroid dysfunctions, which were more frequent in children diagnosed earlier. The number of patients over 20 years was limited in our study, more complications may increase in additional follow-up. Continuous long-term follow up and optimal intervention are crucial for survivors of infant leukemia who are transplanted. Disclosures Kada: Bayer Yakuhin: Other: personal fees for a member of independent data monitoring committee of clinical trials, outside of the submitted work..

Coexistence and Prognostic Significance of EVI1 Expression and Driver Mutations in KMT2A-Rearranged Acute Myeloid Leukemia

Background: KMT2A(MLL)-rearrangements are among the most frequent chromosomal abnormalities in acute myeloid leukemia (AML) and high EVI1 expression is known as an adverse prognostic factor in this subgroup. A recent study showed driver mutations are associated with poor prognosis in pediatric KMT2A-rearranged AML, however, the relationship between EVI1 expression and driver mutations is unclear. In this study, we examined coexistence and prognostic significance of these genetic abnormalities in pediatric and adult KMT2A-rearranged AML. Patients and Methods: Forty-four pediatric KMT2A-rearranged AML samples collected in the AML-05 study, conducted by the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG), were analyzed for 338 genes by targeted sequencing. In addition, 85 adult KMT2A-rearranged AML samples in MLL Munich Leukemia Laboratory were analyzed for 16 genes (ASXL1, BRAF, CBL, CEBPA, FLT3-ITD, FLT3-TKD, IDH1, IDH2, KIT, KRAS, NPM1, NRAS, PTPN11, RUNX1, TP53 and WT1) by amplicon deep-sequencing, direct Sanger sequencing, or melting curve analysis. In both studies, EVI1 expression was measured using quantitative RT-PCR. Results and Discussion: In pediatric KMT2A-rearranged AML (n=44), among 28 patients with low EVI1 expression, 13 patients (EVI1-WT, 46.4%) had no driver mutations and 15 patients (EVI1-MT, 53.6%) had one or more driver mutations. Among 16 patients with high EVI1 expression, 2 patients (EVI1+WT, 12.5%) had no driver mutations and 14 patients (EVI1+MT, 87.5%) had one or more driver mutations. Mutations in activated signaling pathway genes (FLT3, NRAS, KRAS, PTPN11, CBL, and BRAF) were detected in most patients with EVI1-MT (12/15, 80.0%) and EVI1+MT (13/14, 93.3%). The frequency of mutations in epigenetic regulator genes (SETD2, ASXL1, ASXL2, BCOR, KDM6A, and CREBBP) was significantly higher in EVI1-MT patients (7/15, 46.7%), compared with EVI1+MT patients (1/14, 7.1%) (P=0.04). By contrast, the frequency of mutations in cohesion complex genes (STAG2 and SMC3) was significantly lower in patients with EVI1-MT patients (0/15, 0.0%), compared with EVI1+MT patients (4/14, 28.6%) (P=0.04). The frequency of mutations in transcription factor genes (WT1, MECOM, SPI1, GATA2, and RUNX1) was also lower in EVI1-MT patients (2/15, 13.3%), compared with EVI1+MT patients (5/14, 35.7%) (P=0.21). In adult patients, the frequency of ASXL1 mutations was higher in EVI1-MT patients (3/18, 18.8%), compared with EVI1+MT patients (1/29, 3.4%) (P=0.15) and those of WT1 and RUNX1 mutations were lower in EVI1-MT patients (0/18, 0.0%), compared with EVI1+MT patients (4/29, 13.8%) (P=0.28), which were compatible with the tendency in pediatric KMT2A-rearranged AML. Next, we examined the prognostic significance of EVI1 expression and driver mutations. Compared with EVI1-WT patients, EVI1-MT patients had lower event-free survival (EFS) (3-years EFS: 84.6% vs. 65.2%, P=0.24). EFS of EVI1+MT patients (3-years EFS: 30.8%) was significantly lower than that of EVI1-WT patients (P=0.001) and EVI1-MT patients (P=0.04). EFS of EVI1+WT patients (3-years EFS: 0.0%) was also lower than that of EVI1-WT patients (P=0.003) and EVI1-MT patients (P=0.09). There was no significant difference in EFS between EVI1+WT and EVI1+MT patients (P=0.88). The results of overall survival (OS) were similar except for EVI1+WT patients (n=2) (3-years OS: EVI1-WT 92.3%, EVI1-MT 70.6%, EVI1+WT 100.0%, EVI1+MT 46.6%). Multivariate analysis including EVI1 expression, driver mutations, age, white blood cell count, and KMT2A-MLLT4 fusion showed EVI1+ is an independent prognostic factor for EFS (hazard ratio (HR): 3.02, 95% confidence interval (CI): 1.08-9.48, P=0.04). There was no prognostic significance in driver mutations (HR:1.24, 95%CI: 0.39-4.74, P=0.73). As a whole, adult patients' survival data were lower, however, the tendency was similar to that of pediatric data (3-years EFS: EVI1-WT 41.7%, EVI1-MT 24.5%, EVI1+WT 9.1%, EVI1+MT 13.5%; 3-years OS: EVI1-WT 55.6%, EVI1-MT 30.7%, EVI1+WT 18.2%, EVI1+MT 36.2%). These data showed that there is an association between EVI1 expression and the pathway of driver mutations, suggesting these abnormalities may have some cooperative mechanisms in leukemogenesis. Compared with driver mutations, high EVI1 expression may have a stronger impact on poor prognosis in KMT2A-rearranged AML, however, the results should be confirmed in the larger cohort. Disclosures Ogawa: RegCell Corporation: Equity Ownership; Kan Research Laboratory, Inc.: Consultancy; ChordiaTherapeutics, Inc.: Consultancy, Equity Ownership; Dainippon-Sumitomo Pharmaceutical, Inc.: Research Funding; Asahi Genomics: Equity Ownership; Qiagen Corporation: Patents &amp; Royalties. Meggendorfer:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Intensive Chemotherapy Along with Aggressive Supportive Care Can Spare Stem Cell Transplantation in a Subset of Patients without Compromising an Outcome in Infants with Acute Lymphoblastic Leukemia; A Report from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) Trial MLL-10

BACKGROUND: Outcome of infants with acute lymphoblastic leukemia (ALL), especially those with rearrangement of MLL (KMT2A) gene (MLL-r), is extremely poor. A strategy to perform allogeneic hematopoietic stem cell transplantation (HSCT) for all the infants with MLL-r ALL in first remission (1CR) have been tested in the previous Japanese trials MLL96/98/03, however, the improvement was modest. Given the recent evidence of a limited role of HSCT especially in infants lacking poor prognostic factors, efficacy and safety of an intensive chemotherapy and risk stratification to limit HSCT for only infants with high-risk of relapse were evaluated in the JPLSG MLL-10 trial (UMIN000004801). PATIENTS &amp; METHODS: Infants age less than 365 days with ALL were registered in the MLL-10 study and were stratified by their MLL gene status, age at diagnosis, and presence of CNS disease; low-risk (LR), if the patients had germline MLL gene (MLL-g); intermediate-risk (IR), if the patients with MLL-r ALL were age 180 days or older and lack CNS disease; high-risk (HR), if the patients with MLL-r ALL were age &lt;180 days or having CNS disease. All the infants with MLL-r ALL received Interfant induction followed by COG AALL0631 post-remission chemotherapy with modification of adding high-dose cytarabine in early intensification phase. All the HR cases were allocated to HSCT in 1CR. LR cases were treated based on the Japanese MLL96/98 MLL-g chemotherapy. Minimal residual disease (MRD) was evaluated in 3 methods, flowcytometry, PCR of MLL fusion transcripts, and PCR targeting IgH/TCR rearrangements, but were not used to guide therapies. RESULTS: A total of 90 eligible infants with ALL were registered in the MLL-10 study between Jan/2011 and Dec/2014; 15 cases were stratified as LR, 19 as IR, and 56 as HR. Remission status was evaluated after 2 chemotherapy courses; 82 (91.1%) achieved 1CR, 3 failed to achieve 1CR, and 5 discontinued the trial before CR evaluation. No early death was observed. With median follow-up period of 1954 days (range, 534-2835 days) in the live patients, 3-year probability of event-free survival (pEFS) and overall survival (pOS) were 70.9% (95% CI, 60.0-79.3%) and 86.6% (77.6-92.2%), respectively. Among the MLL-r cases, 3-year pEFS and pOS were 66.2% (53.9-75.9%) and 83.9% (73.4-90.5%), respectively. According to the risk groups, 3-year pEFS were 93.3% (61.2-99.0%) for LR, 94.4% (66.6-99.2%) for IR, and 56.6% (42.4-68.6%) for HR cases. Regarding the MRD studies, correlation of MRD results in 3 methodologies seemed reasonable, but while flow-MRD could be evaluated in 85 cases, MLL-fusion PCR-MRD (MLL-r cases only) and IgH/TCR PCR-MRD could only be evaluated in 55 and 50 cases, respectively. In the univariable analysis for MLL-r cases, female sex (P=0.04), younger age at diagnosis (P=0.01), and 0.01%&lt; flow-MRD after 2 courses of chemotherapy (P&lt;0.01) had negative impact on pEFS. In multivariable analysis, female sex (P=0.01) and positive flow-MRD (P&lt;0.01) were poor prognostic. Among the 38 HR cases who received HSCT in 1CR per protocol, 3-year probability of disease-free survival was 65.7% (48.3-78.4%) and only one non-relapse death was observed. CONCLUSIONS: Introduction of intensive chemotherapy enabled us to spare allogeneic HSCT in 1CR at least in a subset of infants with MLL-r ALL without compromising their outcome. This was accomplished also because of the aggressive supportive care provided to the study cases, such as full hospitalization during and after the intensive treatment phases, intensive use of rasburicase to prevent tumor lysis syndromes, and aggressive infection prophylaxis. However, outcome of HR MLL-r cases is still unsatisfactory, and introduction of novel agents is mandatory for further improvement in the outcome of infants with ALL. Figure Disclosures No relevant conflicts of interest to declare.