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Background: Though the outcome of patients with acute lymphoblastic leukemia (ALL) has been greatly improved, some high-risk patients still need hematopoietic stem cell transplantation (HSCT). In this study, we evaluated clinical characteristics of children with ALL who were treated according to Japan Association of Childhood Leukemia Study (JACLS) ALL-02 trial and received HSCT to determine prognostic factors for the outcome of HSCT. Methods: Between April 1, 2002 and March 31, 2008, 1,252 patients aged 1-18 years with newly diagnosed ALL were enrolled in JACLS ALL-02 trial. Ph+ALL, mature B-ALL, and NK-leukemia were excluded. Of all the 1,252 patients, 211 (16.8%) patients were reported to receive HSCT, of which 206 patients with adequate information of 1st HSCT were subjected to further analysis. In this study, HSCT in 1st complete remission (CR) in JACLS ALL-02 trial was indicated for the patients with extremely high risk (ER: BCP-ALL with PPR and/or evidence of t(4;11) (or KMT2A-AFF1 positive), hypodiploidy (≤ 44) and/or acute mixed lineage leukemia/ acute unclassified leukemia). As a precaution, in ER patients, the timing of HSCT differs depending on whether they have a matched related donor. Results: Of all the 206 patients, 83 patients received HSCT in first CR (CR1), 68 patients in CR2, 54 patients in non-CR and 1 patient in induction failure (IF). 5-year overall survival (5y-OS) for 206 patients was 50% (95% CI 42.7-56.8). In detail, 73.8% (95% CI 62.6-82.1) for CR1 patients, 49.4% (95% CI 35.9-61.5) for CR2 patients, and 14.8% (95% CI 6.9-25.5) for non-CR patients, respectively. In univariate analysis, JACLS risk classification, disease status at HSCT (CR or non-CR or IF), stem cell source were significant prognostic factors. In multivariate analysis, only disease status retained as prognostic factor (p Conclusion: The current study showed that the prognostic factors for HSCT varied according to the disease status or disease immunophenotype. Also, it is noteworthy that HHD patients may be rescued even in non-CR status by HSCT. Disclosures No relevant conflicts of interest to declare.

Introduction TP53 mutations in relapsed cases with pediatric acute lymphoblastic leukemia have been implicated in poor clinical outcomes. However, the prevalence and clinical significance of TP53 mutations at diagnosis have not been fully investigated. Such knowledge is essential for the care of patients, because treatment intensity is tailored to predictive prognosis, where increased attention has been directed toward de-escalation of treatment for the problem of long term effects and second malignancies in childhood cancer survivors. Methods Mutation status of TP53 was detected by targeted-capture sequencing of TP53 coding regions in 1,003 children with B-precursor ALL who had been treated in either of the two prospective clinical trials, JACLS (Japan Association of Childhood Leukemia Study) ALL-02 and TCCSG (Tokyo Children's Cancer Study Group) L04-16. Detection of common fusion genes, including BCR-ABL, ETV6-RUNX1, MLL-AF4, MLL-ENL, MLL-AF9, and TCF3-PBX1, were performed using qPCR assays. We designed SNP baits to analyze copy number status of chromosome 17, and also captured 662 probes tiling the entire IgH enhancer locus to identify IGH-DUX4 rearrangement. Result In total, 36 different non-silent coding TP53 mutations were identified in 30 (3%) patients, including 22 missense, 7 frameshift indel, 5 in-frame indel, and 2 nonsense mutations. All missense mutations were found in the core DNA-binding domain (n=21), except for one mutation, which affected the tetramerization motif. Variant allele frequencies (VAF) of TP53 mutations varied from 3% to 97% with 14 mutations showing < 10% VAFs. Showing a significant correlation with mutated TP53 (Odds ratio 20: 95%CI 6.4-61, P Conclusion TP53 mutations at diagnosis are common in Hypodiploid ALL and also found in a substantial fraction of MLL rearrangement and IGH-DUX4 ALL, where the mutations predict a poor prognosis. TP53 mutation is also found in NCI-SR cases but may not be associated with poor prognosis. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

Introduction The programmed death-1 (PD-1)-programmed death-ligand 1 (PD-L1) pathway is an inhibitory immune checkpoint that can suppress T-cell-mediated tumor cytotoxicity. Anti-PD-1 monoclonal antibodies have recently been recognized as promising therapy for adult patients with lymphoma, particularly in classical Hodgkin's lymphoma. However, little information is available regarding the expression patterns of PD-1 and PD-L1 in pediatric lymphoma. Therefore, this study aimed to investigate the expression patterns of PD-1 and PD-L1 in pediatric lymphoma. Methods Immunohistochemical analysis was performed on paraffin-embedded pretherapeutic tumor biopsies from 36 newly diagnosed pediatric patients (aged 0-15 years) with lymphoma or lymphoproliferative disorders treated at Kobe Children's Hospital (Kobe, Japan) from 2003 to 2018. Results Thirty-six samples comprising 11 of Burkitt lymphoma (BL), 7 of anaplastic large-cell lymphoma (ALCL), 6 of T-lymphoblastic lymphoma (T-LBL), 5 of diffuse large B-cell lymphoma (DLBCL), 3 of Hodgkin's lymphoma (HL), 2 of chronic active EBV-associated lymphoproliferative disorders (CAEBV-LPD), 1 of T cell/histiocyte rich B-cell lymphoma (T/HRBCL), and 1 of subcutaneous panniculitis-like T-cell lymphoma (SPTCL) were evaluated. PD-L1 and PD-1 staining results in each lymphoma type are explained below and in Table. Burkitt lymphoma None of the 11 samples stained for PD-L1 or PD-1 in BL cells. PD-1 was expressed in a small proportion of tumor-infiltrating lymphocytes (TIL) in 3 of the 11 samples. Anaplastic large-cell lymphoma PD-L1 was robustly expressed in ALCL cells in 5 of the 7 samples. However, PD-1 was not expressed in any ALCL cell samples but expressed in a small proportion of TIL in only 1 sample. T-lymphoblastic lymphoma None of the 6 samples stained for PD-L1 in T-LBL cells. PD-1 was stained in T-LBL cells in only 1 sample. Moreover, PD-1 was not stained in TIL in any samples. Diffuse large B-cell lymphoma None of the 3 samples with DLBCL-not otherwise specified (DLBCL-NOS) or 1 sample with DLBCL with IRF4 rearrangement expressed PD-L1 on tumor cells. Conversely, PD-L1 was overexpressed in tumor cells in 1 sample with DLBCL with an interfollicular pattern of proliferation (DLBCL-IF). However, PD-1 was not expressed in any DLBCL cell samples. PD-1 was expressed in a small proportion of TIL in 1 sample with DLBCL with IRF4 rearrangement. Hodgkin's lymphoma PD-L1 was overexpressed in HL cells in both nodular sclerosis classic HL (NScHL), whereas PD-L1 was not expressed in nodular lymphocyte predominant HL (NLPHL) cells. PD-1 was not expressed in HScHL or NLPHL cells but was expressed in a small proportion of TIL in 1 sample with NLPHL. Chronic active EBV-associated lymphoproliferative disorders PD-L1 was overexpressed in tumor cells in both samples with CAEBV-LPD. PD-1 was not expressed in tumor cells but was expressed in a small proportion of TIL in 1 sample. T cell/histiocyte-rich B-cell lymphoma PD-L1 was overexpressed on tumor cells in T/HRBCL. PD-1 was weakly expressed in a part of T/HRBCL cells but strongly expressed in TIL. Subcutaneous panniculitis-like T cell lymphoma PD-L1 was overexpressed in tumor cells in SPTCL. However, PD-1 was not expressed in SPTCL cells or TIL. Discussion In this pediatric cohort, PD-L1 was overexpressed in tumor cells in ALCL (5/7), DLBCL-IF (1/1), NScHL (2/2), CAEBV-LPD (2/2), T/HRBCL (1/1), and SPTCL (1/1), but not in BL, T-LBL, DLBCL-NOS, or NLPHL. While the PD-L1 expression in EBV-positive lymphoma cells has been reported before, this study demonstrated the PD-L1 overexpression in CAEBV-LPD. In addition, we demonstrated the PD-L1 overexpression on SPTCL and DLBCL-IF cells, whereas the PD-L1 overexpression in T/HRBCL cells was consistent with previous reports. This study demonstrated that the PD-1 expression in tumor cells was rare in pediatric lymphoma. In addition, PD-1 expressions in TIL tended to be low in pediatric lymphoma, except for NLPHL and T/HRBCL. Besides classic HL, PD-1 blockade might be a promising treatment strategy for ALCL, DLBCL-IF, CAEBV-LPD, T/HRBCL, and SPTCL in children. Indeed, anectodal reports showed promising efficacy in ALCL. Therefore, further investigations are required to assess the role of the PD-1-PD-L1 pathway in pediatric lymphoma. Disclosures No relevant conflicts of interest to declare.

Introduction: L-asparaginase (L-Asp) is one of the risk factor of thromboembolism during ALL chemotherapy. Although the pathogenesis has been still unclarified, L-Asp may have profound effects on hepatic synthesis of pro-, anti-coagulant and fibrinolytic factors. In addition, recent studies demonstrated that the age of over 10-years might be a risk factor for this L-Asp associated coagulopathy. In this study, we hypothesized that change of balance between coagulation and fibrinolysis contributes to hyper-coagulation condition during chemotherapy including L-Asp. In order to clarify our hypothesis, we investigated the global coagulation and fibrinolytic function during the ALL induction therapy with simultaneous thrombin and plasmin generation assay (T/P-GA). Patients: Seventy-two pediatric patients aged 1.0 to 15.2 years (43 males and 29 females) with newly diagnosed ALL were enrolled from Aug. 2014 to Mar. 2018 at four hospitals in Japan. All patients and their families had no thrombotic predisposition. Fifty-five cases (76.4%) (BCP-ALL; n=47, T-ALL; n=7, MPAL; n=1) received BFM-95 oriented protocol consisting of a total of 8 doses of E.coli L-Asp 5,000 U/m2, whilst the others (BCP-ALL; n=13, T-ALL; n=2, MPAL; n=1, Ph-ALL; n=1) received Japan Association of childhood Leukemia Study (JACLS)-ALL02-protcol consisting of a total of 6 doses of E.coli L-Asp 6,000 U/m2. Fifty-two cases (72.2%) were categorized to younger group (1-10 years; median, 4.3 years) and the other cases to older group (>10 years; median, 12.6 years). The percentage of patients of each category were similar in the two treatment protocols (p=0.764). Methods: The global functions of coagulation and fibrinolysis were evaluated using T/P-GA [Matsumoto et al. TH 2013]. This clotting was initiated by the mixture of recombinant human tissue factor (Innovin®, f.c. 1 pM), phospholipid vesicles (f.c. 4 μM) and tissue-type plasminogen activator (f.c. 3.2 nM). Thrombin and plasmin generation were monitored simultaneously using thrombin- and plasmin-specific fluorogenic substrate (Z-Gly-Gly-Arg-AMC and BOC-Glu-Lys-Lys-MAC, respectively) in separate microtiter wells. The first derivatives (velocity) of thrombin and plasmin generation were utilized to derive the parameters, lag time (LT), endogenous potential (EP), peak levels (peak), and time to peak (ttPeak). EP of thrombin generation (T-EP) and plasmin-peak (P-peak) were selected as parameters for evaluation in this study. A ratio of T-EP and P-peak of patients' plasmas to those of control normal plasma were calculated. The conventional laboratory markers of coagulation and fibrinolysis were also monitored by fibrinogen (Fbg), fibrin-Fbg degradation products (FDP), antithrombin (AT), thrombin-AT complex and plasmin-α2 plasmin inhibitor complex. Plasmas were collected at T0; pre-phase of L-Asp, T1; intermittent phase of L-Asp, T2; post-phase of L-Asp, and T3; post induction phase. Results: None of the cases developed L-Asp associated coagulopathy, and two cases (2.8%) developed induction failure. Thirteen cases (18.1%) received fresh frozen plasma transfusion for low Fbg level, whilst 52 (72.2%) cases received AT supplement for low AT level. Fbg showed a median of 165, 99.0, 97.0 and 316 mg/dl at T0, T1, T2 and T3, respectively, and AT showed a median of 143, 80.9, 80.0 and 105%, respectively, whilst the value of other conventional markers remained within reference value. T-EP revealed a median of 1,134, 1,135, 1,221, 1,277 and 1,102 nM, whilst P-peak showed a median of 5.33, 3.75, 3.63, 4.91 and 5.51 nM for T0, T1, T2, T3 and control plasma, respectively, indicating the elevated T-EP ratios and reduced P-peak ratios (Fig. 1). T-EP ratios showed significantly higher at T2 and T3 than at T0 and T1 (p Disclosures Nogami: Chugai Pharmaceutical Co., Ltd: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: Anti-FIXa/X bispecific antibodies , Research Funding, Speakers Bureau.

This study analyzed data on 35 infants with acute myeloid leukemia (AML) who were treated with intensive chemotherapy between 1995 and 1998 in Japan. The incidence of boys, younger age (< 6 months old), and hyperleukocytosis at onset was high in patients with the M4/M5 subtype (n = 23) in the French-American-British classification, compared with the non-M4/M5 subtype (n = 12). Thirteen (56%) and 16 (70%) patients with the M4/M5 subtype also showed 11q23 translocations and MLL gene rearrangements, respectively, whereas only one patient with the non-M4/M5 subtype had this rearrangement. All 35 patients were treated with the ANLL91 protocol consisting of etoposide, high-dose cytarabine, and anthracyclines. Overall survival and the event-free survival (EFS) rates at 3 years of all patients were 76% (95% confidence interval [CI], 61.3%-90.7%) and 72% (95% CI, 56.4%-87.9%), respectively. EFS showed no significant difference between 2 subgroups divided by age, gender, presence of the MLL gene rearrangements, and white blood cell count at onset; EFS in patients with the M4/M5 subtype tended to be better than those with the non-M4/M5 subtype. Although all 6 patients who underwent allogeneic stem cell transplantation (SCT) have been in complete remission, no benefit of SCT was confirmed. These findings suggest that the intensive chemotherapy with the ANLL91 protocol might have been responsible for the observed good outcome of infant AML, even without SCT. The presence of the MLL gene rearrangements or the age at onset had no impact on the outcome of infant AML.

Introduction B-progenitor acute lymphoblastic leukemia (B-ALLs) accounts for 85% of pediatric ALL and categorized into several molecular subgroups according to their ploidy and recurrent translocations, such as ETV6-RUNX1, TCF3-PBX1, BCR-ABL1, and MLL-rearrangements. In addition, recent genetic studies using high-throughput sequencing have disclosed landscapes of gene alterations in each subgroup, however, their clinical relevance have not fully been investigated in a large cohort of B-ALL patients who are uniformly treated and enrolled in an unbiased manner. Methods We enrolled a total of 515 pediatric B-ALL patients, who had been uniformly treated according to the Japan Association of Childhood Leukemia Study (JACLS) ALL-02 protocol between 2002 and 2008. These patients were categorized into three risk groups, including standard-, high-, and extremely high-risk. Infantile ALL as well as BCR-ABL1-positive and Down syndrome-associated cases were excluded. A total of 158 known or putative driver genes in pediatric ALL were analyzed for somatic mutations by targeted-capture sequencing. IgH rearrangements were captured using 662 baits tiling the entire IgH enhancer locus. Finally, an additional 1205 baits was also designed to enable sequencing-based genome-wide copy number detection. Results The median age at diagnosis and observation period were 5.2 (1-18.5) and 4.2 (1.8-9) years, respectively. Sixty-six of the 515 patients (13%) had relapsed diseases and 47 patients (9%) had been died. Real-time RT-PCR and conventional cytogenetic analyses revealed subgroup-defining genetic lesions in 368/515 (71%) patients: 117 (23%) cases with ETV6-RUNX1, 48 (9%) with TCF3-PBX1, 13 (3%) with MLL rearrangements, together with those with hyper- (169 [33%]), and hypo- (6 [1%]) diploid. Remaining 162 patients (31%) had none of these abnormalities. The mean depth of the targeted sequencing was 569× across the entire cohort. In total, 823 driver mutations (median 1 per patient, range 0-7) and 954 focal deletions (median 2 per patient, range 0-13) were detected in 483 patients (92%). Among these, most frequently detected were mutations/deletions in CDKN2A (24%), ETV6 (21%), NRAS (18%), KRAS (18%), and PAX5 (15%). IgH-rearrangements were detected in 51 patients, including IGH-DUX4 (26 [5.0%]), IGH-EPOR (3 [0.6%]) and IGH-CRLF2(2 [0.3%]). Genetic alterations were enriched in several functional pathways, of which most frequent was epigenetic regulation (53%), followed by B-cell development (47%), RAS signaling (46%) and cell cycle (40%). A number of novel recurrent genetic lesions were also identified, including those in DOT1L and PHF6. DOT1L encode an H3K79 methyltransferase and was inactivated by frameshift/nonsense mutations and/or deletions in 19 cases. Although frequently found in T-ALL, mutations of PHF6 had not previously been reported in B-ALL but were detected in 14 cases in the current cohort and strongly associated with TCF3-PBX1 translocation. Significant positive correlations were also demonstrated for an additional 10 combinations of common genetic lesions, suggesting functional links between these combinations. Thus, ERG deletions were highly associated with IGH-DUX4 rearrangement, while mutations in KRAS, NRAS, and CREBBP were significantly enriched in hyperdiploid cases. ETV6-RUNX1 fusion also showed positive correlations with alterations in ETV6, CDKN1B, ATF7IP, VPREB1, BTG1, and WHSC1. Furthermore, mutually exclusive relationship between ETV6-RUNX1 translocationsand FLT3mutations were also identified. Finally, we analyzed the prognostic impact of driver mutations. In multivariate analysis of the entire cohort, 4 genetic alterations were significantly associated with poor prognosis (HR [95%CI]): IKZF1 mutations/deletions (2.6 [1.5−4.8]), EBF1 deletions (3.0 [1.4−6.5]), KDM6A mutations/deletions (2.8 [1.2−6.5]), and TP53 mutations (2.7 [1.2−5.9]). Additional factors (q < 0.1) were identified in subgroup analyses, including alterations in ETV6 (5.4 [1.2−24]), CDKN1B (7.4 [1.6−33]) and CDKN2A (4.2 [1.4−12]) in ETV6-RUNX1 ALL, KMT2D (5.9 [1.3−26]) in TCF3-PBX1 ALLand TP53 (38 [4.1−364]) in IGH-DUX4ALL. Conclusions We revealed the landscape of genetic lesions in pediatric B-ALL including novel targets of recurrent mutations with clinical relevance of common genetic lesions. Our results should help in the better stratification of patients. Disclosures Ogawa: Kan research institute: Consultancy, Research Funding; Takeda Pharmaceuticals: Consultancy, Research Funding; Sumitomo Dainippon Pharma: Research Funding.

Background: It is important to establish proper intensity of chemotherapeutic regimen for low risk group of childhood B-precursor ALL (BCP-ALL) to avoid late effects. For this purpose, in Japan Association of Childhood Leukemia study (JACLS) ALL-02 clinical trial, we defined standard risk (SR) group as the patients ranged from 1 to 10 years showing white blood cell (WBC) count of less than 10,000/μL at the diagnosis without predonisolone poor responder, t(4;11), t(1;19) and CNS3 to treat with less intensive chemotherapy (JACLS ALL02 SR protocol). Herein, we report the outcome of JACLS ALL02 SR protocol and analyzed prognostic factors to identify super low risk group which is curable by less intensive chemotherapy. Patientss and treatment: JACLS ALL02 SR protocol consisted of early phase therapies for total 4 months including an induction therapy using vincristine (VCR), steroids, pirarubicin (THP-ADR), and L-asparaginase (L-asp) for 4 weeks, a consolidation therapy using cyclophosphamide and a combined administration of cytarabine and dexamethasone (DEX) or 6-mercaptopurine (6-MP), a sanctuary therapy with only two cycles of high-dose methotrexate (MTX) of 3g/m2, one course of 4 drugs re-induction therapy and maintenance phase with 6-MP and oral MTX combined with VCR and PSL every 5 weeks by the end of the second year. In addition, total of 12 times of triple intrathecal therapy were administered by the end of the first year. Estimation of event free survival (EFS) and overall survival (OS) was performed using the Kaplan-Meier method and the differences were compared using the log-rank test. Multivariate analysis was performed using a Cox regression model. Results: 1252 newly diagnosed ALL patients were enrolled from April 2002 to May 2008 in JACLS ALL02 clinical trial, which include 388 patients (192 males and 196 females) in SR group (31.0%). The median age at diagnosis was 4.2 years (range, 1.0 to 9.9 years) and the median WBC count was 3,700/μL (range, 370 to 9,984 /μL). The median follow-up time was 6 year and 5 months. 4y / 8y EFS and OS (±SE) of the SR group are 91.5±1.4% / 89.4±1.7% and 97.9±0.7% / 95.2±1.2%, respectively. 4y / 8y EFS of the patients of 1 to 5 years old (n=300) and 6 to 9 years old (n=88) are 93.5±1.4% / 93.0±1.5% and 84.9±3.9% / 75.8±5.8%, respectively (log rank p=0.0003). 4y / 8y EFS of the patients with day 15 M1 marrow (n=287 ) was 92.8±1.6% / 91.6±1.8%, while those of the patients with day 15 M2 marrow (n=101) was 88.0±3.3% / 83.7±3.9% (log rank p=0.0446). When 388 patients were further classified into 4 subgroups based on genetic abnormalities, such as ETV6-RUNX1 (n=89, 22.9%), high hyperdiploid (HHD) (n=97, 25%), normal karyotype (n=147, 37.9%), and others (n=55, 14.2%), 4y-EFS/OS of each group was 97.6±5.9 /100% (ETV6-RUNX1), 91.5±2.9 /100% (HHD), 89.6±2.5 /95.1±1.8% (normal karyotype), and 86.9±4.6 /98.2±1.8% (others), suggesting poor EFS of B-others group. When HHD subgroup was divided into two groups, such as triple trisomy (TT; n=35) (trisomy of chromosome 4,10,17) and non-TT (n=62), 4y-EFS of each sub-group was 100% and 84.5±4.5%, respectively (log rank p=0.0161). Interestingly, day 15 M2 marrow was associated with poor 4y/8y EFS only in the normal karyotype subgroup (day 15 M1 vs M2 92.0±2.6% / 90.2±3.1% vs, 81.3±6.9% / 77.2±7.7%, log rank p=0.0497). The rates for NCI-CTC grade 4 infection, allergy, increase of transaminase were 1.80%, 0.26%, and 22.9%, respectively. Multivariate analysis identifies the patients of 6 to 9 years old (HR=3.178, p= Discussion: Although JACLS ALL-02 SR protocol was less intensive chemotherapeutic regimen compared to the contemporary protocols used for NCI-SR patients, good outcome of the 4y EFS and OS (91.5±1.4 % and 97.9±0.7 %) was achieved with good feasibility. Because the specific genetic subgroups such as B-others and HHD without TT were associated with relatively poor outcome, those patients should be treated with more intensive chemotherapy, especially for the patients showing initial poor response (day 15 M2). On the other hand, ETV6-RNUX1 and TT subgroups showed excellent outcome. Thus, appropriate reduction of therapy should be explored for these subgroups. Disclosures No relevant conflicts of interest to declare.

INTRODUCTION: Congenital pure erythroid leukemia (M6b) is exceedingly rare with only a few reported cases to date. Because of the extreme rarity, almost nothing is known about the pathogenesis, appropriate therapy and prognosis. Diagnosis of erythroid leukemia is usually based on the positivity for Glycophorin A, Glycophorin C or PAS staining. We report a first case of congenital pure erythroid leukemia expressing E-cadherin in the absence of Glycophorin A, Glycophorin C and PAS staining. We analyzed the cytogenetic abnormalities of this extremely rare disease. RESULTS: The patient was the first daughter of healthy and non-consanguineous Japanese parents, born at 40 weeks of gestation by emergency cesarean section in non-reassuring fetal state after uncomplicated pregnancy. Apgar score was 8/9. Characteristic facial appearance was not recognized. At birth, she presented with marked hepatomegaly, purpura and disseminated intravascular coagulation. White blood cell (WBC) count was 63.5x109/L with blastic cells with vacuoles. Although congenital leukemia was suspected, flow cytometric analyses using CD45 blast gating failed to demonstrate leukemic cells. Karyotype was 46, XX. Fluorescence in situ hybridization (FISH) for trisomy 21 and MLL split signal were negative. GATA1 mutation was not detected. WBC count has gradually decreased within 3-4 weeks with supportive care.However, liver failure, hemophagocytic lymphohistiocytosis and schistocytosis developed. Although treatment with dexamethasone and etoposide has started, multiple nodules appeared in the liver 11 weeks after birth. Liver biopsy demonstrated small round cell tumor with high N/C ratio and vacuoles infiltrating the liver. The tumor cells were immunohistochemically positive for CD43, CD71, E-cadherin, beta-catenin, Ki-67 and c-Myc and negative for CD45, CD20, CD10, PAX5, CD3, CD4, CD8, TdT, CD1a, CD34, CD56, cyMPO, c-kit, CD42b, CD61, Glycophorin A, Glycophorin C, tyrosine hydroxylase, PGP9.5, myogenin, glypican3, NKX2.2, CAM5.2 and Periodic Acid Schiff (PAS) staining etc. Flow cytometric analysis revealed CD43+ CD71+ CD36+ CD58+ cells within large CD45 negative cell population. These cells expressed almost no other hematopoietic cell markers used to screen for leukemia. These cells were indistinguishable from normal erythroblast based on surface markers only. However, flow cytometric cell sorting revealed these cells are blasts with vacuoles. Karyotype of tumor cells has changed to 50, XX, +7, +8, add(15)(q22), +19, add(19)(q13.1-13.3)×2, +21. Based on these results, she was diagnosed with pure erythroid leukemia. Low dose Cytosine Arabinoside improved her clinical symptoms. She is alive at 5 months of age. DISCUSSION: E-cadherin is a selective marker of immature erythroblast. In our case, E-cadherin was key in erythroid lineage assignment. To our knowledge, this is the first reported case of infantile pure erythroid leukemia expressing E-cadherin in the absence of Glycophorin A, Glycophorin C and PAS staining. These results suggest that the tumor cells originated from undifferentiated erythroblast. This disease entity should be recognized. Immunohistochemical staining of c-Myc showed strong positivity. The c-Myc gene is located on chromosome 8. FISH for c-Myc split signal was negative. G-banding and FISH revealed trisomy 8. Overexpression of c-Myc may be involved in the pathogenesis of this undifferentiated pure erythroid leukemia. At birth, karyotype was 46, XX and blasts in peripheral blood decreased with supportive care only. However, we observed changes in karyotype of blasts. We assume that second hit was added during clinical course. Whole exome sequencing analysis is in progress to reveal somatic and germline mutations underlying this unrecognized disease. Disclosures No relevant conflicts of interest to declare.

BACKGROUND: The trial JACLS ALL-02 for treatment of childhood acute lymphoblastic leukemia (ALL) was designed to reduce acute and long-term toxicity in selected patient groups with favorable prognosis and to improve outcome in unfavorable-risk groups by treatment intensification. These aims were pursued through a refined stratification strategy using white blood cell count, age, immunophenotype, unfavorable genetic aberrations, and treatment response providing an excellent discrimination of risk groups. PATIENTS AND METHODS: Between April 2002 and March 2008, 1252 children with newly diagnosed de novo ALL with 1-18 years of age were enrolled to JACLS ALL-02 trial. Ph+ALL, mature B-ALL, and NK-leukemia were excluded. Patients with BCP-ALL were stratified into 3 groups: standard-risk (SR), high-risk (HR), extremely high-risk (ER), based on initial prednisolone (PSL) response and the modified National Cancer Institute(NCI) workshop criteria. Prednisolone poor response (PPR) was determined after 7 days of monotherapy with prednisone and one intrathecal dose of methotrexate. PSL good responders (PGR; < 1,000 blasts/microL) were divided into SR and HR according to the modified NCI workshop criteria by WBC 10K and age 10, and received conventional therapy. BCP-ALL with PPR (≥ 1,000 blasts/microL) or t(4;11), and acute mixed lineage leukemia/ acute unclassified leukemia were assigned to ER and received intensified post-induction therapy . Patients with T-ALL were treated by a specific protocol that was different from the protocol used for BCP-ALL. Bone marrow response was also evaluated in aspiration smears on day 15 and 33 of induction treatment, and those who had slow early bone marrow response, defined as an M3 marrow on day 15 or M2/3 marrow on day33, shifted to the higher risk and received augmented post-induction therapy. Cranial irradiation was restricted to patients with initial central nerve system involvement or T-ALL with high WBC (≥10K) at diagnosis. Alternatively, protracted TIT was given during induction, intensification and maintenance depending on the risk group (12 doses in SR/T and 15 in HR/ER). Slow early responders who had an M3 marrow on day 15 in ER/T or M2/3 marrow on day33 in any risk, underwent to stem cell transplantation (SCT). PPRs without slow early bone marrow response underwent to SCT only if a matched sibling donor was available. The probability of event-free survival (EFS) and overall survival were constructed using the Kaplan-Meier method. Events in the analysis of EFS included induction failure, death, relapse and secondary malignant neoplasm. All statistical analyses were done according to intent-to treat methods. RESULTS: Estimated 4-year EFS and OS for all 1252 patients was 83.7% (SE=1.1) and 90.3% (SE=0.89), slightly better in EFS than the former study (ALL-97; 79.3%, SE=1.7, p=0.054). The SR group (N=457, 37%) achieved excellent 4-year EFS of 90.4% (95%CI: 87.2, 92.7) and 4-year OS 97.3% (95.3, 98.5); in SR without slow early bone marrow response, patients with hyperdiploid and triple trisomy showed excellent 4-year EFS/OS of 100%. In the HR group (N=542, 43%), the estimated 4-year EFS and 4-year OS were 84.9% (81.5, 87.7) and 89.3% (86.3, 91.6), respectively; older age (≥ 6 years) was predictive for inferior OS (hazard ratio=1.14, p CONCLUSIONS: Refined stratification and risk-adjusted therapy in the JACLS ALL-02 trial can bring about the abolition of prophylactic CRT in non-T ALL and the optimized indication of SCT without compromising the treatment results. Disclosures No relevant conflicts of interest to declare.

Since an excellent outcome was observed in a previous study (OCLSG-94) utilizing continuous cytarabine (CA) infusion in the consolidation phase for the treatment of pediatric B cell precursor acute lymphoblastic leukemia (BCP-ALL), a randomization trial was performed to test the superiority of continuous CA infusion to conventional repeated CA injection as consolidation therapy in Japan Association of Childhood Leukemia Study (JACLS) ALL02 clinical trial. Newly diagnosed children with standard-risk (SR) or high-risk (HR) BCP-ALL excluding patients with Ph+ ALL and infants were included in this study. Patients showing prednisolone good response (PGR) were assigned to SR or HR based on the age at onset and initial white blood cell (WBC) counts (SR: age 1 to 9 and WBC less than 10,000 /µL, HR: remaining patients). Patients achieving complete remission (CR) at the end of induction (day 33) proceeded to the randomization. HR patients with M3 marrow on day 15 were excluded. They were randomly assigned to Arm A (cyclophosphamide 750 mg/m(2) 1hr div: day 1 and 8, CA 75 mg/m(2) 1hr div: day 1-6, 8-13 and 6MP 50 mg/m(2) orally, day 1-14) or Arm B (cyclophosphamide 500 mg/m(2) 1hr div: day 1, 3 and 5, CA 100 mg/m(2) 24hr div: day 1-5 and DEX 5 mg/m(2) 1hr div twice a day, day 1-5). Intrathecal chemotherapy (MTX, HDC and CA) was administered twice in this phase in both arms. In the HR group two doses of pirarubicin (25 mg/m (2)) were added and this phase was repeated after re-induction therapy. Estimation of event free survival (EFS) and overall survival (OS) was performed using the Kaplan-Meier method and the differences were compared using the log-rank test. Between April 2002 and May 2008, 1252 children with newly diagnosed ALL were enrolled to JACLS ALL-02 study. Among these, the number of patients with SR and HR were 388 (arm A=200, arm B=188) and 513 (arm A=251, arm B=257, not assigned=5), respectively. The characteristics of eligible patients between arm A and B were not different statistically (Table). Among SR patients, the 4y-EFS were 89.7 +/- 5.2% and 93.4 +/- 4.7% in Arm A and B, respectively (p=0.70). Among HR patients, the 4y-EFS were 89.7 +/- 5.2% and 90.5 +/- 4.4% in Arm A and B, respectively (p=0.97). Although hematological toxicity was not different, in the next phase (sanctuary phase) following Arm A consolidation therapy the frequencies of hematological grade 3 and 4 adverse effects were higher in both SR and HR (SR: p Consolidation therapy with continuous infusion of CA (Arm B) was not superior to conventional CA regimen. Disclosures No relevant conflicts of interest to declare.

Introduction: Thromboembolism is a serious complication associated with ALL. The use of central venous catheter and treatment protocols involving corticosteroids and L-Asp is assumed as important thrombogenic factors at the induction phase. In particular, L-Asp has profound effects on hepatic synthesis of pro-, anti-coagulant and fibrinolytic factors. In this study, we hypothesized that change of coagulation and fibrinolytic function contributes to hyper-coagulation condition during the induction phase with L-Asp. In order to clarify this, we evaluated the dynamic change in coagulation and fibrinolysis by simultaneous measurement of both thrombin and plasmin generation assay (T/P-GA). Patients: Twenty-seven pediatric patients with newly diagnosed ALL were enrolled from Aug. 2014 to Oct. 2015 at 3 hospitals in Japan. All cases had no thrombotic predisposition. Eighteen cases (66.7%) (BCP-ALL; n=17, T-ALL; n=1) received Berlin-Frankfürt-Münster (BFM)-95 oriented induction therapy included prednisolone (and dexamethasone for T-ALL), vincristine, daunorubicin, and E.coli L-Asp (a total of 8 doses of 5,000 U/m2). The others (BCP-ALL; n=8, T-ALL; n=1) received Japan Association of childhood Leukemia Study (JACLS) ALL02 oriented induction therapy included prednisolone, dexamethasone, vincristine, daunorubicin, cyclophosphamide and E.coli L-Asp (a total of 6 doses of 6,000 U/m2). Methods: The individual hemostatic parameters were monitored by fibrinogen (Fbg), FDP, AT, TAT and PIC. Additionally, the global functions of coagulation and fibrinolysis were evaluated using T/P-GA established by our group [Matsumoto et al. TH 2013]. This assay was initiated by the addition of a mixture of optimized concentrations of tissue factor and tissue-type plasminogen activator. Thrombin and plasmin generation were monitored simultaneously using individual fluorescent substrates in separate microtiter wells. Standard curves were set using purified alpha-thrombin and plasmin. Patients' plasmas were collected at the following points, T0; pre-phase of L-Asp, T1; intermittent phase of L-Asp, T2; post-phase of L-Asp, and T3; post-induction phase. Endogenous potentials of thrombin generation (T-EP) for coagulant activity and plasmin peak levels (P-Peak) of plasmin generation for fibrinolytic activity were selected as parameters for evaluation in this study. A ratio of T-EP and P-Peak of patients' plasmas to those of control normal plasma were calculated. Results: All cases obtained first remission, and none of them developed coagulopathy. Six cases received FFP transfusion for low Fbg level, whilst 21 cases received AT supplement for low AT level. Fbg showed a median of 170, 99.0, 99.0 and 328 mg/dl at T0, T1, T2 and T3, respectively, whilst the other individual parameters showed relatively unchanged. T-EP revealed a median of 1,126, 1,059, 1,175, 1,343 and 1,132 nM, whilst P-Peak showed a median of 6.67, 4.54, 4.12, 5.50 and 5.77 nM for T0, T1, T2, T3 and control plasma, respectively, indicating the elevated T-EP ratios and reduced P-Peak ratios (Fig. 1). The most significant difference in both ratios demonstrated a median of 1.5-fold (range, 1.0 to 2.6) at T2, consistent with the lowest Fbg levels. The FFP transfusion group showed significantly lower T-EP ratios than non-transfusion group at T1 (a median of 0.87 vs. 1.01, P=0.041) and T2 (a median of 0.96 vs. 1.07, P=0.009), whilst P-Peak ratios revealed no significant changes. The AT supplement group showed no significant changes of both ratios. Conclusion: The results from decreased Fbg and unchanged FDP might reveal the hepatic synthesis disorder of Fbg, whilst the results from T/P-GA showed that their hemostatic dynamics appear likely to be thrombotic tendency, since their coagulation state was hyper-coagulation and anti-fibrinolysis at post-phase of L-Asp. These results suggest that the impaired balance of coagulation and fibrinolysis due to L-Asp therapy might play an important role of a thrombotic complication at induction phase. On the other hand both conventional FFP transfusion and AT supplement therapy might not dramatically repair this unbalance state. A further research would be required to examine the role of coagulant and fibrinolytic function using T/P-GA in the pathogenesis of coagulopathy associated with L-Asp therapy in order to establish the optimal supportive therapy. Figure 1 The Changes of Both T-EP and P-Peak Ratios Figure 1. The Changes of Both T-EP and P-Peak Ratios Disclosures Nogami: F. Hoffmann-La Roche Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sysmex Corporation: Patents & Royalties, Research Funding; Chugai Pharmaceutical Co., Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Matsumoto:Sysmex Corporation: Patents & Royalties, Research Funding; Chugai Pharmaceutical Co., Ltd.: Patents & Royalties, Research Funding. Shima:Chugai Pharmaceutical Co., Ltd.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; F. Hoffmann-La Roche Ltd.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sysmex Corporation: Patents & Royalties, Research Funding.

Twenty percent to 30% of transient abnormal myelopoiesis (TAM) observed in newborns with Down syndrome (DS) develop myeloid leukemia of DS (ML-DS). Most cases of TAM carry somatic GATA1 mutations resulting in the exclusive expression of a truncated protein (GATA1s). However, there are no reports on the expression levels of GATA1s in TAM blasts, and the risk factors for the progression to ML-DS are unidentified. To test whether the spectrum of transcripts derived from the mutant GATA1 genes affects the expression levels, we classified the mutations according to the types of transcripts, and investigated the modalities of expression by in vitro transfection experiments using GATA1 expression constructs harboring mutations. We show here that the mutations affected the amount of mutant protein. Based on our estimates of GATA1s protein expression, the mutations were classified into GATA1s high and low groups. Phenotypic analyses of 66 TAM patients with GATA1 mutations revealed that GATA1s low mutations were significantly associated with a risk of progression to ML-DS (P < .001) and lower white blood cell counts (P = .004). Our study indicates that quantitative differences in mutant protein levels have significant effects on the phenotype of TAM and warrants further investigation in a prospective study.

The mixed lineage leukemia (MLL) gene located at chromosome band 11q23 is frequently rearranged in patients with therapy-related acute monocytic leukemia who received topoisomerase II inhibitors. We have identified a novel fusion partner of MLL(FAB M5b) in a patient who developed t-AML 9 years after treatment for acute lymphoblastic leukemia (ALL). The leukemic cells had a sole karyotypic abnormality of t(3;11) (p21;q23). Screening of a genomic DNA library, prepared from leukemic cell DNA, identified rearranged clones composed of MLL and a novel gene on chromosome 3p21 (AF3p21). The AF3p21 gene encodes a protein of 722 amino acids, which contains an Src homology 3 (SH3) domain, a proline-rich domain, and a bipartite nuclear localizing signal (NLS). RNA analysis demonstrated that exon 6 of the MLLgene fused to exon 2 of the AF3p21 gene. The resulting chimeric protein consists of AT-hooks, methyltransferase, and transcription repressor domains of MLL in addition to the AF3p21 proline-rich domain and NLS but not the AF3p21 SH3 domain.

We conducted a prospective multicenter study to compare the efficacy of repeated immunosuppressive therapy (IST) with stem-cell transplantation (SCT) from an alternative donor in children with acquired aplastic anemia (AA) who failed to respond to an initial course of IST. Patients with severe (n = 86) and very severe disease (n = 119) received initial IST consisting of antithymocyte globulin (ATG) and cyclosporine. Sixty patients failed to respond to IST after 6 months from the initial IST and were eligible for second-line treatment. Among them, 21 patients lacking suitable donors received a second course of IST. Three patients developed an anaphylactoid reaction to ATG and could not complete the second IST. A trilineage response was seen in only 2 of 18 (11%) evaluable patients after 6 months. Thirty-one patients received SCT from an alternative donor. At 5 years from the initiation of second-line therapy, the estimated failure-free survival (FFS), defined as survival with response, was 83.9% (± 16.1%, SD) in the SCT group compared with 9.5% (± 9.0%) in the IST group (P = .001). These results suggest that SCT from an alternative donor offers a better chance of FFS than a second IST in patients not responding to an initial IST.

Introduction: Pediatric mature B-cell non-Hodgkin lymphoma (B-NHL) is mostly classified as Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL). It has a predominantly germinal center origin. In pediatric BL, some cases are difficult to distinguish from DLBCL, which has been referred to as atypical BL or Burkitt-like lymphoma (BLL). In the recent World Health Organization classification of 2008, B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and BL (IDB) was defined as a new but heterogeneous category. This group has morphological and genetic features of both DLBCL and BL. Therefore, IDB includes atypical BL or BLL in children. To the best of our knowledge, little is known about the exact difference between pediatric BL and IDB, and a distinction needs to be made between the clinical aspects of these two groups. In this study, we performed a clinicopathological study using the cohort from Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) B-NHL03 study, which was the nation-wide prospective study for pediatric B-NHL in Japan, to understand the meaning of the classification of BL in children. Methods: From November 2004 to January 2011, 346 cases of newly diagnosed pediatric B-NHL were enrolled in the B-NHL03 study. Of these, 208 cases were diagnosed in the central pathology review system with reference laboratory results. Seventy-eight cases were subclassified as BL (37.5%), 42 as IDB (20.2%), 57 as DLBCL (27.4%), and 31 as not subclassified (14.9%). Finally, 120 cases of BL or IDB were included in our study cohort. The pathological features and diagnostic and prognostic factors of those cases were analyzed. Results: The median age was 9.0 years (range, 1.9–15.5) in BL patients and 9.1 years (3.0–15.8) in IDB patients. Male (M) predominance was observed in both groups and the M/female (F) sex ratio was 5.5 (M/F 66/12) in BL and 9.5 (38/4) in IDB cases. According to the Murphy staging system, 7.7%/24.4%/39.7%/28.2% of BL patients and 14.3%/40.5%/26.2%/19.0% IDB patients were at stage I/II/III/IV, respectively. The frequency of the cases with central nervous system diseases and cerebrospinal fluid (CSF) blasts were 10.3% and 5.1% in BL and 7.1% and 2.4% in IDB, respectively. In addition, the number of the cases with elevated lactate dehydrogenase (LDH) levels (more than twice the institutional upper limit) was 43.6% for BL and 33.3% for IBD. 4-year overall survival and event-free survival (EFS) were 93.6% and 91.0% for BL and 95.2% and 85.7% for IBD, respectively. In general, there is little statistical difference in clinical presentation between both groups. Pathological examination showed that BL has a significantly high frequency of C-myc translocation (57.1% vs. 33.3%, p = 0.03). Immunohistochemistry demonstrated that most cases in both groups were CD10 positive (BL 97.4%, IBD 95.1%), Bcl-6 positive (both groups 100%), and overexpressed Ki67 (≥90%; BL 93.6%, IBD 92.9%). Moreover, 11.1% of BL and 5.7% of IBD patients were Bcl-2 positive. Because a large difference was not observed in the clinicopathological presentation of the two patient groups, we combined both to analyze prognostic factors. To determine the effects of various risk factors of EFS, log-rank testing with stratification for age (≥10 or Conclusions: We conclude that in our cohort, the distinction between BL and IDB does not have much meaning in B-NHL in children. Furthermore, our study shows that the prognostic factors in childhood B-NHL identified in clinical trials in Western countries are identified in patients with the broad BL in Japan. Disclosures No relevant conflicts of interest to declare.

BACKGROUND: Recently, several studies have demonstrated that absolute lymphocyte counts (ALC) after induction therapy predicted treatment outcome. To address this issue, we here assessed the impact of the ALC at the end of induction therapy on outcomes in childhood ALL. METHODS: We reviewed 141 cases of pediatric ALL with 1-21 years of age treated on the Japan Association Childhood Leukemia Study group ALL-02 series of treatment trials between 2002 and 2013. Patients with Philadelphia chromosome-positive ALL were excluded. Variables retrospectively analyzed included ALC at several time points during remission induction, age at diagnosis, gender, initial white blood cell count (WBC), cytogenetics, immunological phenotype, stratified risk, treatment response for bone marrow (the percentage of blasts at day 15), and outcome. Events in the analysis of event-free survival (EFS) included induction failure, death, relapse and secondary malignant neoplasm. The comparison of categorical variables between groups was performed by chi-square test. The probability of EFS and overall survival (OS) were analyzed with the use of the Kaplan–Meier method and a stratified log-rank test. A multivariate analysis of survival was performed with the use of a Cox proportional-hazard model to evaluate the treatment effect with adjustment for stratification factors. RESULTS: The subjects included 121 of B-precursor ALL, 10 of T cell ALL, and 4 of acute mixed lineage leukemia/ acute unclassified leukemia. We found high WBC count at diagnosis (>100K/microL) and slow early responder for bone marrow at day 15 to be an unfavorable prognostic indicator, and also the ALC at the end of induction (day29) to be a statistically significant predictor of improved OS and EFS in our cohort. Patients with ALC ≥ 800/microL had a superior 5-year overall survival (100 ± 1.7% vs 88.1 ± 4.3 %, p=0.0001) and EFS (98.3 ± 1.7% vs 81.8 ± 5.0 %, p=0.0001). Multivariate analysis demonstrated that ALC at day29 was an independent, clinically significant predictor of improved EFS and OS after controlling WBC at diagnosis, gender, age at diagnosis, and cytogenetics. Multiple regression analysis adjusting for initial WBC count, peripheral blast counts at day8, and cytogenetics, also revealed an independent relationship (p=0.005) between treatment response (the percentage of blasts at day 15) and ALC at day29. CONCLUSIONS: ALC is a simple, statistically significant prognostic factor in childhood ALL that may refine current risk stratification algorithms. Disclosures No relevant conflicts of interest to declare.

Background: In pediatric B cell precursor acute lymphoblastic leukemia (BCP-ALL), aberrant JAK-STAT signaling is one of the key leukemogenic mechanisms. Although activating mutations of JAK2 are found in high-risk BCP-ALL patients in western countries, such mutations are rare in Japanese cohorts, led to speculation of other factors contributing abnormal activation of JAK-STAT pathway. The adaptor protein LNK (SH2B3) is one of the negative regulator of JAK-STAT signaling, and its loss of function mutations have been identified in myeloproliferative neoplasms and high-risk BCP-ALL. In addition, the loss of function of LNK has been demonstrated to increase proliferation of B cells in vivo. Based on these findings, we conducted genetic analysis to determine the prognostic impact of LNKin BCP-ALL, and functional analysis to investigate its possible mechanisms. Methods: For genetic analysis, we evaluated diagnostic bone marrow or peripheral blood samples of 164 pediatric BCP-ALL patients treated with the Japan Association of Childhood Leukemia Study (JACLS) ALL02 protocol along with peripheral blood samples from 9 healthy volunteers. The LNK expression level was determined by qRT-PCR. Deletion of IKZF1 was determined by MLPA, and direct sequencing was employed to detect LNK mutations in patients with IKZF1 deletion. For functional analysis, thrombopoietin (TPO)-dependent BaF3-MPL cells expressing LNK (BaF3-MPL-LNK) was established by retroviral transduction to investigate if LNKexpression levels impact on drug sensitivity for prednisolone (PSL), doxorubicin (DOX) or vincristine (VCR). For growth assay, BaF3-MPL cells with or without LNK were cultured for four days in the presence of TPO and the viable cell number was counted. For drug sensitivity test, BaF3-MPL cells with or without LNK were treated with each drug for 48 hours in the presence of TPO, then the IC50 was calculated. Phospho-specific flow cytometory (Phos-Flow) was performed to measure JAK-STAT activation. Results: The LNK expression levels in pediatric BCP-ALL patients’ samples were significantly lower than in samples from healthy donors (P < 0.01). When analyzing all 164 cases, the expression level of LNK was decreased in relapsed patients but there was no statistical significance (P = 0.067). IKZF1 deletion was found in 25 (15% of all) patients, and in these patients, LNK expression level dose not relate to relapse (P = 0.39). Intriguingly, when patients with known high-risk factor (i.e., IKZF1 deletion or poor response to PSL) were excluded, the expression level of LNK was significantly higher in non-relapsed patients (P < 0.05). In functional assay, we observed inhibition of TPO dependent growth of BaF3-MPL cells by expression of LNK (P < 0.01), consistent with previous reports. Phos-Flow analysis revealed that LNK expression suppressed TPO–induced phosphorylation of STAT5 in BaF3-MPL cells. In drug sensitivity test, we found that IC50 of PSL and DOX were substantially lower in BaF3-MPL-LNK cells from in BaF3-MPL-mock cells (0.70 vs 3.93 nM, P < 0.01 and 0.61 vs 1.14 nM, P < 0.05, respectively). Decline in IC50 of VCR by LNK expression was not statistically significant (1.38 vs 2.45 nM, P = 0.056). We next compared the impact of LNK with Ruxolitinib (RUX), a potent synthesized JAK2 inhibitor. The diminution in IC50 of PSL in BaF3-MPL-mock cells treated with RUX (50 nM) was comparable of that in BaF3-MPL-LNK cells (0.31 nM, combination index (CI) = 0.39), consistent with our hypothesis that LNK is working as a JAK2 inhibitor. Since we identified two amino-acid substitutions in N-terminal proline-rich dimerization domain (R139H) and PH domain (P242S), we also examined their function. Transductions of these genes in BaF3-MPL cells, however, did not alter cell growth, suggesting they are single nucleotide variants. Discussions: Our findings that high LNK expression is associated with low relapse rate in intermediate risk (IKZF1 intact, good PSL response) patients indicate potential of LNK to restrain relapse in such patients, presumably by suppressing JAK-STAT signaling. Since we proved the impact of LNK expression to improve sensitivity of PSL in vitro which was comparable to RUX, RUX could compensate lack of internal LNK expression to induce cell death of BCP-ALL cells. Collectively, targeting JAK-STAT pathway will be promising therapeutic option for intermediate risk BCP-ALL patients with low expression level of LNK. Disclosures No relevant conflicts of interest to declare.

Introduction: Anthracyclines (Atc) are the key drugs in the treatment of acute promyelocytic leukemia (APL) combined with all-trans retinoic acid (ATRA), however, dose-dependent risk of long-term cardiac toxicity is sometimes problematic especially in pediatric patients. To evaluate efficacy of the treatment with reduced cumulative doses of Atc in childhood APL, we conducted a nationwide non-randomized prospective study, AML-P05, in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG). Patients & Methods: Between April 2006 and March 2011, forty-six children with newly diagnosed APL were enrolled in this study. All patients received at least 3-day precedence of ATRA monotherapy (45mg/m2/d for 35 days in total), followed by chemotherapeutic agents consisted of cytarabine (200mg/m2/d for 7 days) and daunorubicin (DNR, 45mg/m2/d for 3 days) as the first induction therapy. The second induction therapy and subsequent 3 courses of consolidation therapy consisted of ATRA, either high- or intermediate-dose of cytarabine, triple intrathecal injection, and single dose of Atc; 10mg/m2 of mitoxantrone (MIT) in the first 2 courses and 45mg/m2 of pirarubicin (THP) in the last 2 courses. Finally, patients received one-year maintenance therapy with ATRA for 15 days every 3 months. Results: Among the 46 patients registered in this study, 3 were excluded because of PML/RARA negativity, and the remaining 43 patients including 2 with molecular variants were evaluated. The median age at diagnosis was 9 years (range, 11 months to 15 years old). The median follow up period was 4.47 years (0.00-7.45 years). FLT3-ITD was positive in 6 out of 40 patients examined. Two patients died during induction therapies; one of coagulopathy in first course and the other of infection in second course. Two patients developed differentiation syndrome but resolved with temporary cessation of ATRA and supportive therapies. Three patients did not achieve complete remission (CR) after 2 courses of induction therapy, and overall CR rate was 85.7% (36/42, 95%CI: 71.5-94.6%). Neither cardiac adverse events nor treatment-related death were observed during consolidation and maintenance therapies. Three patients exhibited relapse during or after maintenance therapy, and another one developed secondary acute myeloid leukemia. Consequently, the 3-year event-free (EFS) and overall survival rate were 83.6% (95%CI: 68.6-91.8%) and 90.7% (95%CI: 77.1-96.4%), respectively. Age less than 4 years old at diagnosis and non-M1 marrow after first induction therapy were associated with lower EFS. High WBC count (>10,000/μL), low platelet count ( Conclusions: According to the JPLSG criteria of Atc equivalents, cumulative Atc dose in this study was converted to 246mg/m2 of doxorubicin (for 1:0.83 for DNR, 1:4 for MIT, and 1:0.6 for THP). The dose was much lower than that in recent US or European protocols, especially in those designed primarily for adult APL patients where more than 600mg/m2 of Atc were used. Comparing with these studies, we have achieved equivalent good results with minimum does of Atc. Therefore, single administration of Atc in each consolidation phases seems sufficient in the treatment of childhood APL. This trial is registered with UMIN Clinical Trials Registry (UMIN-CTR, URL: http://www.umin.ac.jp/ctr/index.htm), number UMIN000000645 Disclosures No relevant conflicts of interest to declare.

Forty-four infants with acute lymphoblastic leukemia (ALL) characterized by MLL gene rearrangements were treated on a protocol of intensive chemotherapy followed by hematopoietic stem cell transplantation (HSCT) between November 1998 and June 2002. The remission induction rate was 91.0%, and the 3-year overall survival and event-free survival (EFS) rates, with 95% confidence intervals, were 58.2% (43.5%-72.9%) and 43.6% (28.5%-58.7%), respectively. Univariate analysis of EFS by presenting features indicated a poorer outcome in patients younger than 6 months of age with high white blood cell counts (/= 100 x 10(9)/L; EFS rate, 9.4% versus 55.1% for all others, P = .0036) and in those with central nervous system invasion (EFS rate, 10.0% versus 56.9% for all others, P = .0073). The 3-year posttransplantation EFS rate for the 29 patients who underwent HSCT in first remission was 64.4% (46.4%-82.4%). In this subgroup, only the timing of HSCT (first remission versus others) was a significant risk factor by multivariate analysis (P.0001). These results suggest that early introduction of HSCT, possibly with a less toxic conditioning regimen, may improve the prognosis for infants with MLL(+) ALL. Identification of subgroups or patients who respond well to intensified chemotherapy alone should have a high priority in future investigations.

Background Acute myeloid leukemia harboring internal tandem duplication of fms-like tyrosine kinase 3 (AMLFLT3-ITD) is associated with poor prognosis, but the previous studies have reported that the inferior outcome is only confined to those with high allelic ratio (AR) of ITD/wild type (WT). In our previous AML99 study (2000-2002), AMLFLT3-ITD showed a poor outcome compared to the WT cases (5-year OS; 35% vs. 84%, P Patients & Methods AML-05 study, registered at http://www.umin.ac.jp/ctr/ as UMIN000000511, is a Japanese nation-wide multi-institutional study for children (age0.4 as high and AR ≤ 0.4 as low as previously reported (Meshinchi S. Blood2006). Results We found 47 patients (10.6%) with AMLFLT3-ITD in this study (30 males, 17 females, and median age of 11 years at diagnosis). The median WBC count was 65,300/ml (3,690 - 522,050/mL). FAB classification included M1 (n=10), M2 (n=9), M4 (n=9), and M5 (n=11), and AML with normal karyotype was dominant (19/47, 40.4%). Of the 29 patients (61.7%) who achieved CR, twenty-seven received HSCT in 1CR and 19 patients survived (19/27, 70.4%). On the other hand, 14/16 non-CR patients received HSCT, but only 4 survived. The only demographic difference between the 29 CR and 16 non-CR cases was the median WBC count at diagnosis (19,000 vs. 124,000/μL, P AR was analyzed in 44 patients with median ratio of 0.68 (range, 0.11 to 4.47). Median AR was not different between CR vs. non-CR cases (0.53 vs. 0.72). There were no difference in 5-year OS (52.8% vs. 42.5%, P=0.302), DFS (54.5% vs. 64.5%, P=0.524), and EFS (50.0% vs. 34.4%, P=0.283) between patients with low (n=12) and high AR (n=32), however, induction rate was significantly higher in the low AR patients (91.7% vs. 53.1%, P=0.018). It was rather surprising that all FLT3-ITDs were found only in JM domain and not in TKI domain in the current trial. In addition, six of 47 (12.8%) AMLFLT3-ITD patients had NPM1mutation simultaneously, and all received HSCT at 1CR and survived. Discussion and Conclusion We observed a different induction rate between AMLFLT3-ITD patients with low and high AR, but poor final outcomes in both. Regardless of the level of AR, patients with AMLFLT3-ITD, especially who fail to achieve remission, have dismal outcome and effective therapy combined with novel FLT3 inhibitor is urgently needed to overcome the disease. Disclosures: No relevant conflicts of interest to declare.

Background Previous studies have reported that IKZF1 deletion was an adverse prognostic factor in pediatric B-cell-precursor ALL (BCP-ALL). However, the prognostic significance of CRLF2 over-expression (OE) is controversial. In order to assess the prognostic value of CRLF2 OE and genetic alterations involving CRLF2, we conducted genetic analysis of CRLF2 in pediatric BCP-ALL treated according to Japan Association of Childhood Leukemia Study (JACLS) ALL02 cohort. Methods We examined diagnostic bone marrow or peripheral blood samples of 167 pediatric BCP-ALL patients treated on the JACLS ALL02 protocol. The analyzed cohort included 68 patients classified in NCI-SR and 99 patients in NCI-HR. The deletion of IKZF1 and gain of CRLF2 were determined by MLPA. CRLF2 expression level was determined by quantitative RT-PCR and OE was defined as 10 times more than mean expression level of 167 cases. The P2RY8-CRLF2 fusion was detected by RT-PCR. To identify fusion transcript related to CRLF2 OE, we performed messenger RNA sequencing (mRNA-seq) on six of 17 patients with CRLF2 OE without CRLF2 gain and P2RY8-CRLF2 fusion. Results CRLF2 OE was identified in 30 (18%) of 167 patients, which was similar to that reported previously. IKZF1 deletion was found in 25(15%) of 167 patients, which was found more in CRLF2 OE patients than non-CRLF2 OE patients (30% vs 11%, p Discussions The current analysis revealed that CRLF2 OE was caused by several different mechanisms, such as CRLF2 gain, P2RY8-CRLF2 fusion and rare fusion transcript related to CRLF2. However, regardless of type of genetic alterations of CRLF2, concomitant IKZF1 deletion holds the major impact on poor prognosis in CRLF2 OE patients. Especially, CRLF2 gain and IKZF1 deletion were mutually exclusive. Thus, CRLF2 OE caused by CRLF2 gain was not poor prognostic factor for high risk BCP-ALL. The prognostic significance of CRLF2 should be evaluated in consideration of IKZF1 status. Disclosures: No relevant conflicts of interest to declare.

Long-term survivors of acquired aplastic anemia (AA) have an increased risk of developing clonal evolution after immunosuppressive therapy (IST). We previously reported that the duration of granulocyte colony-stimulating factor (G-CSF) treatment and non-response to IST at 6 months were risk factors for clonal evolution. In 2008, the revised World Health Organization (WHO) classification proposed a new entity, “refractory cytopenia of childhood” (RCC), which is often difficult to differentiate from aplastic anemia (AA). The spectrum of patients with RCC is wide, ranging from patients with severe hypocellular bone marrow (BM) with mild dysplasia to those with normocellular BM with distinct dysplasia meeting the criteria for refractory cytopenia with multilineage dysplasia (RCMD) in adults. Few studies have investigated the correlation between morphological classifications of bone marrow failure (BMF) and clonal evolution. Before introducing the criteria of RCC, we conducted a prospective study with antithymocyte globulin (ATG) and cyclosporine for patients with acquired BMF (AA 97 study), which provided a unique opportunity both to compare the long-term outcome of patients with RCC and AA and to analyze risk factors for clonal evolution. We retrospectively reviewed BM morphology in 186 children (median age, 8 years;range, 1–16 years) who were enrolled in the AA 97 study between July 1999 and November 2008. The median follow-up period was 87 months (range, 1–146 months). Fifty patients had non-severe, 54 had severe, and 82 had very severe disease. RCC criteria were defined as persistent cytopenia with 2 cell lineages or >10% within 1 cell lineage. RCMD criteria were defined as persistent cytopenia with 10% dysplastic changes in >2 cell lineages. Morphologically, 62 patients (33%) were classified as AA, 94 (49%) as RCC, and 34 (18%) as RCMD. Disease severity differed among the three groups as follows: 76% of the AA patients had very severe disease, while 41% of the RCMD patients had non-severe disease (p40 days was a significant risk factor for the development of monosomy 7 (p=0.016). Death, relapse, development of myelodysplastic syndrome or acute myeloid leukemia (AML), or disease progression requiring clinical intervention was considered to represent treatment failure. A second therapeutic intervention was required in some children. A second IST was therefore performed in 20 children, including five with AA, 11 with RCC, and four with RCMD. Hematopoietic stem cell transplantation was performed in 64 children, including 25 with AA, 29 with RCC, and 10 with RCMD. The rate of failure-free survival at 10 years was not significantly different among the three groups. On the other hand, the rate of overall survival at 10 years was significantly lower in the AA group (85±5.1%) than in the RCC (97±1.9%) and RCMD (100%) groups (p=0.01). Two patients died due to AML, and five patients died due to transplantation-related complications in the AA group. To confirm these results, we are currently conducting a prospective study involving IST in patients with acquired BMF classified according to WHO classification before treatment. Disclosures: No relevant conflicts of interest to declare.

Abstract 2615 Background: Infants (age Patients & Methods: JPLSG AML-05 study, registered at http://www.umin.ac.jp/ctr/as UMIN000000511, is a nation-wide multi-institutional study and recruited 447 eligible children (age Results: The median follow-up period for living patients was 3.06 years (range, 0.84 – 5.36 years). Although, there was no difference in 3-year probability of event-free survival (pEFS) between infants and patients ≥1 year old [56.0% (95%CI, 38.7 – 70.1%) vs. 55.2% (49.8 – 60.2%) (p = 0.63)], 3-year probability of overall survival (pOS) in infants was inferior; 56.0% (95%CI, 37.9 – 70.7%) vs. 75.0% (70.0 – 79.4%) (p = 0.011). When the outcome of infants were compared with patients 1 - The inferiority of pOS in infants compared to the patients 1 - Conclusions: Our experience suggests that appropriate chemotherapeutic dose modification in induction therapy to avoid early deaths is essential in treating infants with de novo AML. As dose intensification approach is difficult to apply for this age subgroup, incorporation of less toxic targeted agents based on biological features is needed to attain better outcome for infants with AML. Disclosures: No relevant conflicts of interest to declare.

Abstract 3545 Background: With intensive chemotherapy and optimal risk stratification, 80–90 % of children with acute myeloid leukemia (AML) achieve complete remission (CR) which translates into a long-term disease-free survival in as many as 50–60% of patients. We have previously reported that risk stratified therapy and intensive use of cytarabine improved the outcome of childhood AML in AML99 study with 5-year event free survival (EFS) of 61.6% and 5-year overall survival (OS) of 75.6% (Tsukimoto I. J Clin Oncol 2009;27:4007–13), which gave us an additional impetus to reduce the number of consolidation courses with more restrictive indication for stem cell transplantation (SCT). We here report the outcome of successor nation-wide multi-institutional study AML-05, focusing on the AML patients without core binding factor (CBF). Patients & Methods: 47 eligible children (age Results: Three-year EFS and 3y-OS of all 444 patients was 55.3% (95%CI, 50.2 – 60.1%) and 73.2% (68.3 – 77.5%), respectively. The median follow-up period for living patients was 3.1 years (range, 0.8 – 5.4 years). Two hundred eighty-nine non-CBF-AML patients [t(9;11), N=39 (13.5%); 11q23, N=27 (9.3%); Normal, N=81 (28.0%); Others, N=137 (47.4%)] in the AML-05 and 151 patients [t(9;11), N=15 (9.9%); 11q23, N=26 (17.2%); Normal, N=53 (35.1%); Others, N=55 (36.4%)] in AML99 were compared. There were no significant differences in basic characteristics such as sex and age/WBC at diagnosis. Incidence of FLT3-ITD in AML-05 cohort were identical to that in AML99 [AML-05 cohort, N= 42/289 (14.5%); AML99, N= 15/82 (18.2%), p=0.41]. CR rate in AML-05 was inferior to that in AML99 (81.0% vs. 90.7%, p = 0.008). There was no significant differences in 3y-EFS of non-CBF AML among 2 cohort [47.5% in AML-05 (95%CI, 41.2– 53.6%) vs. 49.7% in AML99 (41.5 – 57.3%), p= 0.43], however, there was a tendency of lower 3y-OS among them [62.8% in AML-05 (95%CI, 56.2– 68.7%) vs. 70.9% in AML99 (62.9 – 77.4%), p = 0.083]. The early death within 42 days in AML-05 (2.1%) were equivalent to that of AML99 (2.0%), whereas non-relapsed mortality were significantly increased in AML-05 compared with that of AML99 [44/289 (15.2%) in AML-05; 11/151 (7.3%) in AML99, p=0.022], which was due to increased mortality among infants. SCT rate in the 1stCR was lower in the non-CBF AML-05 compared with that in AML99 [47/289 (16.3%) in AML-05; 40/151 (26.4%) in AML99, p=0.011]. Conclusions: Reduction on consolidation chemotherapy courses from four to three, together with incorporation of repetitive cycles of high-dose cytarabine were adequate for non-CBF childhood AML, and did not compromise the treatment results in AML-05 despite of adaptation of more restrictive indication for SCT in 1st CR. Non-CBF-AML is a cytogenetically heterogeneous disease, hence the mechanism underlying these prognostic differences should be studied. Disclosures: No relevant conflicts of interest to declare.

Abstract 1455 Introduction: Despite the progress of the current therapy, approximately 20 % of pediatric patients with B-cell-presursor (BCP)-ALL experience relapse who had no conventional adverse prognostic factor. Recently, alteration of the IKZF1 gene has been reported to be associated with a poor outcome in pediatric BCP-ALL without BCR-ABL. In addition, it is also reported that a significant proportion of these cases with the alteration of IKZF1 shared the point mutation of JAK2 and over-expression of cytokine receptor-like factor 2 (CRLF2). Herein, in order to assess the prognostic value of these genetic abnormalities in Japanese cohort, we conducted genetic analysis of IKZF1, JAK2 and CRLF2 in pediatric BCP-ALL. Materials and Methods: Diagnostic bone marrow or peripheral blood samples of 215 pediatric BCP-ALL patients treated according to Japan Association of Childhood Leukemia Study (JACLS) ALL02 protocol from April, 2002 to May, 2008 were examined in this study. All patients were categorized into high risk (HR) group defined as follows;(1) initial white blood cell counts more than 10,000 /μl, (2) age at diagnosis is > 10 years and (3) good response to initial predonisolone (PSL) treatment ( blast counts in peripheral blood is less than 1,000 /μl after one week PSL treatment). Ph+ALL and infantile ALL patients were excluded in this protocol. The patients with Down syndrome were also excluded in this genetic analysis. The deletion of IKZF1 was determined using multiplex ligation-dependent probe amplification (MLPA) in 212 patients whose diagnostic DNA samples were available. The expression of isoform of IKZF1 was determined by RT-PCR in 113 patients whose diagnostic RNA samples were available. The expression level of CRLF2 was also determined by real time RT-PCR in 112 patients and over-expression was defined as over ten times more than median expression value. The presence of P2RY8-CRLF2 fusion was examined by RT-PCR or MLPA in the patients with CRLF2 over-expression or IKZF1 deletion. JAK2 mutations were also determined by direct sequencing of the exon 16, 20 and 21 in the patients with IKZF1 deletion. Results: The deletion of IKZF1 gene was present in 19 of 212 (9.0 %) patients. In detail, the mono-allelic deletion of entire IKZF1 gene was present in 10 of 19 patients. On the other hand, the expression of dominant-negative IK6 isoform was present in 9 of 112 (8.0%) patients including 12 patients with IKZF1 deletion. The expression of IK6 was present in 4 of 12 (33.3%) IKZF1 deleted patients. Interestingly, 5 of 9 patients with IK6 expression had no alteration of IKZF1 gene. In terms of CRLF2, over-expression was detected in 16 of 112 patients (14.3 %). However, P2RY8-CRLF2 fusion was not detected in these 16 patients with altered CRLF2 expression. Strikingly, none of the patients with IKZF1 deletion (n=19) had either P2RY8-CRLF2 fusion or JAK2 exon 16, 20 and 21 mutation. Patients with IKZF1 gene deletion had significantly worse relapse rate than those without IKZF1 deletion (7/19 vs 22/193, p Discussions: This study confirmed that the presence of IKZF1 deletion was strongly correlated with risk of relapse in intermediate risk group in JACLS ALL02 cohort. Thus, we expect that IKZF1 deletion is an independent predictor of treatment outcome and represents a candidate of prognostic marker to be integrated in future algorithms for early risk stratification in pediatric BCP-ALL. Strikingly, point mutation of JAK2 exon 16, 20 and 21 or P2RY8 -CRLF2 fusion was rarely present even in BCP-ALL patients with IKZF1 deletion. There might be unrevealed class I mutation cooperating with IKZF1 alteration in Japanese BCP-ALL cohort. Disclosures: No relevant conflicts of interest to declare.

Abstract 1451 Children with Down syndrome (DS) have a 10- to 20-fold increased risk of developing acute lymphoblastic leukemia (ALL). In DS-associated ALL (DS-ALL), the chromosome aberrations which are generally common in childhood ALL, such as hyperdiploidy and t(12;21), are less frequent. Recent studies have shown that activating JAK2 mutations and overexpression of cytokine receptor-like factor 2 (CRLF2) gene are identified in approximately 20% and 50–60% of DS-ALL in Western countries, respectively. Most of the patients with CRLF2 overexpression have been reported to be associated with interstitial deletions of the pseudoautosomal region 1 (PAR1) of the sex chromosomes and the P2RY8-CRLF2 fusion gene. In addition, one report showed that the activating CRLF2 F232C mutation was identified in about 10% of DS-ALL. However, there have been no studies to determine the incidence of these genetic aberrations in Asian patients with DS-ALL. In this study, 23 patients with DS-ALL in Japan were screened for mutations in the pseudokinase domain of the JAK2 gene, the P2RY8-CRLF2 fusion gene, and the CRLF2 F232C mutation by PCR/RT-PCR and direct sequencing. Fourteen patients, whose bone marrow RNAs were available, were also screened for CRLF2 overexpression by real-time quantitative RT-PCR. We identified the JAK2 R683G mutation in 2 patients (9%) and the P2RY8-CRLF2 fusion gene in 4 patients (17%). The CRLF2 F232C mutation was not detected in any patient. CRLF2 overexpression was observed in 2 of 14 patients examined (14%). Although bone marrow RNA was available in only 1 of 4 patients positive for P2RY8-CRLF2, high-level expression of CRLF2 was confirmed in this patient. The other patient with CRLF2 overexpression was negative for P2RY8-CRLF2, indicating the involvement of the other type of CRLF2 rearrangement, IGH@-CRLF2 in this patient. We also performed a preliminary study on JAK1, JAK3, and Interleukin-7 receptor-α (IL7R) mutations, and 14, 11, and 12 patients were screened for mutations in the pseudokinase domain of JAK1, JAK3, and exon 5 and 6 of IL7R, respectively. However, no mutations were identified in any patient. Our results show the lower incidence of CRLF2 rearrangements in DS-ALL patients in Japan than that in Western countries. Gene alterations other than CRLF2 rearrangements may contribute to leukemogenesis in Japanese patients with DS-ALL. To clarify if the incidences of the mutations in JAK1-3, CRLF2, and IL7R are also lower in DS-ALL patients in Japan than those in Western counties, more patients need to be studied. Disclosures: No relevant conflicts of interest to declare.

Abstract 3421 Bone marrow transplantation (BMT) from an HLA-matched family donor (MFD) is the treatment of choice for severe aplastic anemia (SAA) in children. For children without an MFD, immunosuppressive therapy (IST) with a combination of antithymocyte globulin and cyclosporine has been successful. However, this treatment approach is based on the results of comparative studies between these therapies conducted in the 1980s, and the outcomes of both BMT and IST have improved markedly over the past three decades. Therefore, updated evidence for treatment decisions in pediatric SAA is required. In the present study, we compared the outcomes of children with SAA who received IST (subjects enrolled in the prospective multicenter trials of IST conducted by the Japan Childhood Aplastic Anemia Study Group) or BMT from an MFD (subjects registered in the Transplant Registry Unified Management Program conducted by the Japan Society for Hematopoietic Cell Transplantation). The influence of potential risk factors on overall survival (OS) and failure-free survival (FFS) was assessed according to first-line treatment, time period of treatment (1992–1999 and 2000–2009), age and other variables related to each treatment. FFS was defined as survival with treatment response. Death, primary or secondary graft failure, relapse and secondary malignancy were considered treatment failures in patients who received BMT. Death, relapse, disease progression requiring stem cell transplantation from an alternative donor or 2nd IST, clonal evolution and evolution to paroxysmal nocturnal hemoglobinuria were considered treatment failures in patients who received IST. Between 1992 and 2009, 599 children with SAA younger than 17 years received BMT from an MFD (n=213) or IST (n=386) as first-line treatment. While the OS did not differ between patients receiving IST and BMT (88±2% vs. 90±2% at 15 years), FFS was significantly inferior in patients receiving IST as compared to those receiving BMT (54±3% vs. 84±3% at 15 years, P Disclosures: No relevant conflicts of interest to declare.

Abstract 2400 Introduction: Immunosuppressive therapy (IST) with antithymocyte globulin (ATG) plus cyclosporine A (CyA) has been the standard therapy for aplastic anemia (AA) patients. Recently, telomerase shortening was observed in constitutional marrow failure and some acquired AA patients. In addition, constitutional marrow failure syndrome of variable severity may be present in otherwise phenotypically normal individuals and can masquerade as acquired AA. Calado et al. reported that androgens increased telomerase activity in vitro. The addition of androgens to immunosuppressive therapy may increase the response rate by the effect for these hidden patients. Because all patients in the AA-92 study received danazol and patients in AA 97 study did not receive danazol, we have a unique chance to evaluate the effects of androgen. In this report we present results comparing AA-92 (ATG+CyA+danazol) with AA-97 (ATG+CyA) protocol for children with AA using a matched-pair analysis. Patients and Methods: We conducted two prospective multicenter studies: the AA-92 and AA-97, which began in November 1992 and October 1997, respectively. From 1992 to 2009, 530 children with AA were treated with IST. IST consisted of horse ATG (15 mg/kg/day, days 1 to 5), CyA (6 mg/kg/day, days 1 to 180) and methylprednisolone. All patients in the AA-92 study received danazol at a dose of 5 mg/kg/day for 6 months. We selected pairs of patients treated with either AA-92 or AA-97 by matching the variables of disease severity, age, sex, and duration from diagnosis to IST. We assessed hematologic response at 3 and 6 months after initiation of therapy as well as overall survival and failure-free survival. Definition of treatment failure was death, relapse, disease progression requiring stem cell transplantation or second IST, and clonal evolution. Results: Among 530 patients, 104 pairs were matched and their disease severity was very severe (VSAA) (n=43), severe (SAA) (n=34), and non-severe (NSAA) (n=27). Median age was 8 years (1–15) and 53 (51.0%) were male. In the AA-92 study, the response rates at 3 and 6 months were 48/104 (46.2%) and 71/104 (68.3%), respectively. In the AA-97 study, the response rates at 3 and 6 months were 49/103 (47.6%) and 59/104 (56.7%), respectively. The overall 10-year survival rates in AA-92 and AA-97 were 82.7% and 93.6%, respectively. In VSAA patients, the response rate at 6 months in AA-92 was significantly higher than in AA-97 (69.8% vs 46.5%, p=0.029). However, the overall 10-year survival rates for patients with VSAA in AA-92 and AA-97 were 81.4% and 90.4%, respectively. The failure-free 7-year survival rates for patients with VSAA in AA-92 and AA-97 were 55.5% and 61.5%, respectively. The cumulative incidence of clonal evolution between studies did not differ. Conclusions: Our results showed that the response rate of VSAA patients at 6 months in the danazol group was significantly higher than in those not receiving danazol, but overall survival and failure-free survival were not different. There is a possibility that a number of cases with androgen-responsive congenital bone marrow failure syndrome, such as dyskeratosis congenita, were hidden in our series of AA patients, which may explain the higher response rate with danazol in AA-92. Disclosures: No relevant conflicts of interest to declare.

Abstract 3204 Poster Board III-141 Diamond-Blackfan anemia (DBA) is an inherited congenital bone marrow failure syndrome, characterized by red blood cell aplasia, macrocytic anemia, and increased risk of malignancy. Although anemia is the most prominent feature of DBA, the disease is also characterized by growth retardation and congenital malformations, which occur in about 40% of patients. Approximately 90% of patients present during the first year of life or in early childhood. Recent studies have shown that the disease is associated with heterozygous mutations in the ribosomal protein (RP) genes RPS19, RPS24, and RPS17, encoding small ribosomal subunit proteins, and in RPL5, RPL11 and RPL35a, encoding large ribosomal subunit proteins, in about 50% of patients with DBA in Western countries. There have been no studies to determine the incidence of these mutations in Asian patients with DBA. In this study, 44 probands (46 patients) with DBA in Japan were screened for mutations of the 6 known DBA genes RPS19, RPS24, RPS17, RPL5, RPL11, and RPL35a, in addition to RPS14, which is implicated in the 5q- syndrome, a subtype of myelodysplastic syndrome characterized by a defect in erythroid differentiation. Mutations in RPS19, which have been found in 25% of patients in Western countries, were detected in 6 probands (13.6%). Missense mutations were noted in 5 of these probands, and a frameshift mutation caused by a single-nucleotide insertion was found in 1 case. Three of 7 patients had multiple malformations. Novel mutations in RPL5 were identified in 3 probands (6.8%). Insertion of 2 nucleotides was found in 1 case, affecting the reading frame. Two cases had point mutations, which resulted in a loss of the first initiation codon. All 3 patients with RPL5 mutations had multiple physical anomalies. Remarkably, 2 of 3 patients with RPL5 mutations had cleft palate, whereas no other DBA patients presented with cleft palate. Mutations in RPL11 were identified in 2 patients (4.5%). Deletion of 1 or 2 nucleotides was found in each case, leading to a shift in the reading frame. In contrast to previous reports on patients with RPL11 mutations, thumb anomalies were not seen. Deletion of 1 nucleotide in RPS17 was identified in 1 patient (2.3%), resulting in introduction of a premature stop codon. RPS17 mutations are rare and have been only reported in 2 patients with DBA. Anomalies were not seen in our patient. In summary, RP gene mutations were identified in 27.3% of DBA index cases in Japan. No mutations were detected in RPS14, RPS24 and RPL35a. In Japan, the frequency of mutations in the RP genes appears to be lower than in Western countries. Mutations in RPL5 are associated with multiple physical abnormalities, including cleft palate. Disclosures No relevant conflicts of interest to declare.

Although the therapeutic outcome for acquired aplastic anemia (AA) has improved markedly with the introduction of immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporine A (CyA), a significant portion of patients treated with IST subsequently relapse and require second-line therapy. However, detailed analysis of the relapse cases has not been reported. In this study, we assessed the relapse rate, response to second-line treatment after relapse and prognosis. From November 1992 to July 2007, 473 newly diagnosed AA children (213 female, 260 male) entered two consecutive prospective studies (AA-92 and AA-97). The median age was 8 years, ranging from 1 to 18 years. Patients with very severe (n = 210), severe (n = 149) and non-severe disease (n = 114) received initial IST consisting of ATG and/or CyA. At six months after the initial IST, 280 patients (59.2%) achieved CR (n = 94) or PR (n=186). Relapse is defined by conversion to no response (NR) from partial or complete response (PR/CR). Among the 280 patients who responded to IST, 49 (17.5%) relapsed. The cumulative incidence of relapse was 19.6% at 10 years and the median time to relapse was 18 months, ranging 7 to 138 months. Among the 49 patients who relapsed, 22 received a second round of IST with ATG and CyA. Fourteen patients (63.6%) responded to the second round. However, three relapsed, and two developed paroxysmal nocturnal hemoglobinuria. Eight patients received CyA after relapse. Four patients responded to CyA, but two relapsed subsequently. Hematopoietic stem cell transplantation (HSCT) was attempted in 26 patients who relapsed after initial responses. Before HSCT, nine received a second course of IST with ATG and CyA and two received CyA. Fifteen patients progressed directly to HSCT. Bone marrow transplantation (BMT) from an HLA-matched sibling (n =7), HLA-matched family member (n = 1), or HLA-mismatched family member (n = 2) was performed in 10 patients, and all are presently alive. BMT from an unrelated donor was attempted in 13 patients, and four died of complications related to BMT. Cord blood transplantation from an unrelated donor was attempted in two patients and two patients are alive. Of the 26 patients who received HSCT, 21 are alive and well, 22 to 137 months (median 72 months) following transplantation. There were seven deaths out of total 49 who initially relapsed. The causes of death were HSCT-related complications (n = 5), MDS/acute myelogenous leukemia (n = 1), bacteremia (n = 1). Eight of 9 patients who received HSCT following a second round of IST are alive and well. The present study suggests that a second round of IST should be offered to the patients who relapse, and HSCT should be considered for the patients who fail to respond to the second round of IST.

Aplastic anemia (AA) is defined as a pancytopenia caused by bone marrow failure; its pathogenesis is thought to involve autoimmune processes. Immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporine (CyA) provides response rates of 50–70% for children with AA, but predictive markers of response to therapy have not been well defined. We previously investigated the clinical relevance of HLA, a minor population of paroxysmal nocturnal hemoglobinuria-type cells, and a specific auto-antibody associated with AA in pediatric patients and reported that there was no correlation between these markers and response to therapy (Yoshida N, et al. Br J Haematol, 2008). In the current study, we prospectively evaluated whether clinical and laboratory findings before treatment, including age, sex, interval between diagnosis and treatment, etiology, severity of disease, white blood cell (WBC) count, neutrophil count, hemoglobin level, reticulocyte count, and platelet count, could predict the IST response at 6 months. Subjects included a large population of pediatric AA patients enrolled in a multicenter AA-97 study conducted by the Japan Childhood Aplastic Anemia Study Group. Between October 1997 and September 2006, 312 children (186 boys and 126 girls) younger than 18 years who were newly diagnosed with AA were enrolled in the study and treated with a combination of ATG and CyA. The median age at diagnosis was 8 years (range, 1–17 years). Of the 312 patients, 261 had idiopathic AA, 44 had hepatitis-associated AA, and 7 had AA from other causes. In terms of severity, 156 patients had very severe disease, 107 had severe disease, and 49 had moderate disease. The median interval between diagnosis and treatment was 15 days (range, 1–180 days). The overall response rate was 56%. In multivariate analyses, lower WBC count, shorter interval between diagnosis and therapy, and male sex were predictive markers of better response. Patients with WBC

Background: Acute lymphoblastic leukemia (ALL) in infants represent 2.5% to 5% of all childhood ALL, and has an inferior therapeutic outcome compared to that of older children. Among several risk factors, rearrangement in MLL gene is most closely associated with this poor outcome. This is the first series of cooperative group trials stratifying ALL in infants with MLL gene status. Procedure: Infants with ALL, age less than 12 months, were registered on two consecutive multi-center trials designated MLL96 and MLL98. All the patients were tested for MLL gene rearrangements by Southern Blot analysis and/or fluorescence in situ hybridization. According to the MLL gene status, patients with rearranged MLL gene were allocated to intensive chemotherapy followed by hematopoietic stem cell transplantation (HSCT), and those with germline MLL were treated with standard chemotherapy alone (total treatment duration was 83–85 weeks). In MLL98 study, treatment intensification and early use of HSCT were introduced compared to MLL96 study. Results: A total of 101 infants were enrolled between December 1995 and December 2002. Seventy-nine had rearranged MLL and 22 had germline MLL. Event-free survival (EFS) of all 101 infants with ALL was 52.0% at 5 years; 5-year EFS for MLL rearranged cases was 39.7%, and for MLL germline cases was 95.5% (p Conclusions: Risk stratification with MLL gene status was successful for infants with ALL. Excellent results were obtained for the germline MLL group using chemotherapy alone, and early introduction of allogeneic HSCT in first remission seemed effective for the MLL rearranged group. However, use of HSCT with less toxic conditioning regimens or development of effective chemotherapy including molecular target therapy are needed for MLL rearranged patients in order to avoid severe late effects for infants.

Backgrounds/Aims: Hepatic veno-occlusive disease (VOD) is a life-threatening complication associated with allogenic stem cell transplantation (SCT). Although some risk factors including the intensified conditioning regimen, the second SCT, and liver dysfunction have been implicated on the pathogenesis of VOD, its etiology remains undetermined. Plasma von Willebrand factor (VWF) is produced in vascular endothelial cells (ECs) as unusually-large VWF multimers (UL-VWFMs) and released into circulation, where UL-VWFMs are cleaved into the small multimers with a specific metalloprotease ADAMTS13. Thus, the elevated level of plasma VWF, together with UL-VWFMs, has been thought in part to be a reflection of vascular EC injuries. Previously, we reported that plasma ADAMTS13 activity significantly decreased in patients with VOD during the first 4 weeks after SCT, compared with those without VOD (BMT2002, 29:789). Since ADAMTS13 down-sizes UL-VWFM by its proteolytic cleavage and reduces its thrombogenicity, we have here performed multicentric, prospective randomized study as to whether the infusion of fresh frozen plasma (FFP), a source of ADAMTS13, can prevent the occurrence of VOD in high-risk group patients with SCT. Methods: The study was conducted at 10 hospitals between April 2001 and March 2003. Patients for allogenic SCT were enrolled to participate in the study, if they were high-risk for VOD abovementioned. Forty-three patients enrolled in this study were randomly divided into two groups: 23 patients with FFP infusion and 20 patients without. FFP was infused twice a week during conditioning regimen and until day 28 after SCT. The amount of FFP infused depends on body weight as follows; 1 unit (=80 ml) for patients under 10 kg, 2 units for 10–20 kg, 3 units for 20–30 kg, 4 units for 30–40 kg, and 5 units for over 40 kg. Plasma ADAMTS13 activity was measured by a novel monoclonal antibody-based highly sensitive ELISA (Transfusion2006, 46:1444). Results: Three patients with hepatic VOD occurred within 20 patients who did not receive the FFP infusion, but none were observed in 23 patients who received the FFP infusion. We analyzed both the groups with special references to plasma levels of VWF and ADAMTS13. A significant difference was found in plasma levels of VWF:Ag, where the patients received FFP infusion had the lower values at day 0, day 7, and day 28, than those without receiving FFP infusion. However, no clear difference of plasma levels of ADAMTS13 activity was observed in both the groups. Most interestingly, however, a heightened degradation of VWFM (a total lack of the high ~ intermediate molecular size multimers) was found in patients with VOD who did not receive FFP infusion, but this finding was not seen in those without VOD who received FFP infusion. Conclusions: FFP infusion apparently reduces plasma levels of VWF:Ag, together with the disappearance of UL-VWFMs, and thereby prevents the occurrence of VOD. On the other hand, in the patients with hepatic VOD, prior to the disease progression the high~intermediate multimers including UL-VWFMs were already consumed, by which platelet aggregation/thrombi might occur, as evidenced by VWFM analysis.

BACGROUND: Acquired aplastic anemia (AA) is thought to be an immune-mediated disease. Immunosuppressive therapy (IST) has been the treatment of choice for patients who did not have suitable donors. Previously, we had published promising results of IST for children with acquired AA. In the study, overall survival rate (OS) at 4 years was 83% in patients with vSAA and 92% in those with SAA/nonSAA. OBJECTIVES: Here we report follow-up results focusing on pediatric patients with relapse and clonal diseases, MDS/AML and PNH. PATIENTS and TREATMENT: From 1992 to 1997, 119 newly diagnosed children with acquired AA (median age; 9) entered AA-92 study. 50 vSAA patients were treated with ATG+CyA+mPSL+danazole +G-CSF, 36 SAA and 28 nonSAA patients were treated with ATG+CyA+mPSL+danazole +/−G-CSF. Complete remission (CR) was defined as a neutrophil count >1.5x10^9/L, a platelet count >100xx10^9/L, and a hemoblobin level of >11 g/dl. Partial response (PR) was defined as a neutrophil count >0.5x10^9/L, a platelet count >20x10^9/L, and a hemoglobin level of >8.0 g/dl. Relapse was indicated by the return of the PB counts to levels meeting the definition of SAA and/or the requirement for blood transfusion. Response rate was 71% at 6 months in vSAA patients, 65% in SAA/nonSAA patients, respectively. There was no statistical difference in 6-month response rate between G-CSF +/− treatments. No patient responded after 6 months. Therefore, 75 responders and 29 non-responders at 6 months were analyzed their OS, relapse rate (RR), and treatment-failure-free survival (TFFS). The median observation time of surviving patients is 118 months, ranging from 75 to 168 months. RESULTS: Among 119 patients, 38 patients received BMT and 17 patients died during an observation period. The OS was 81.9+−3.8% at 10 years, but has not reached plateau. Of the 75 6mo-responders, 23 patients relapsed and the RR was 33.6+−6.0% at 10 years. TFFS of the 75 was 67.4+−5.5%. Fourteen patients received 2nd ATG therapy and 5 of them responded. Eleven of the 23 patients with relapse received alternative donor BMT and 8 are alive. 10y-OS of these relapsed patients was 73.4+−9.4%. Nineteen of the 29 6mo-non-responders received alternative donor BMT and 15 are alive. There is no statistically significant difference in 10y-OS between the responders and the non-responders (89.1+−3.7% vs. 75.0+−8.2%, p=0.09). New clonal abnormalities appeared in 9 of 119 patients (10.0+−3.2%KM probability): monosomy 7(3 patients), trisomy 8(3 patients), trisomy 9, trisomy11, del (13)(1 patient each). There is no statistically difference in 10y-OS, RR, and incidence of clonal abnormality between randomized G-CSF+/− treatments. Clinical PNH with symptomatic hemolysis developed in 3 of the responder patients, 96, 105 and 138 months after the AA diagnosis, respectively. Among 65 surviving responders, 33(51%) have CR and 26(40%) PR at last follow-up time. CONCLUSIONS: Our data demonstrate that IST is effective for children with acquired AA, but relapse are common. Effective 2nd line treatment should be developed. PNH developed even in pediatric AA patients during long-term observation.

Immunosuppressive therapy (IST) has been shown to be an effective therapy for aplastic anemia (AA) patients without HLA-matched family donors. However, a significant proportion of patients are refractory to IST. Although the efficacy of repeated IST and stem cell transplantation (SCT) from an alternative donor has been confirmed, a direct comparison between these two procedures has not yet been conducted. In this study, we prospectively compared the efficacy of these two treatments. Between Oct. 1997 and Apr. 2003, 231 patients (125 male, 106 female; median age, 9 y; range, 0 to 17 y) were enrolled in the AA-97 study. Analysis was performed in April 2004. A total of 103 very severe AA and 74 severe AA patients received first-line IST consisting of antithymocyte globulin (ATG; Lymphoglobulin), Cyclosporin (CyA) and methylprednisolone (Mepred), while 54 non-severe AA patients received IST consisting of ATG and Mepred with or without CyA. G-CSF was administered only to patients with very severe AA. Sixty patients (26%) were non-responders to first-line IST and were eligible for 2 nd -line therapies. Of these, 29 patients lacking suitable donors received 2 nd-line IST with ATG (Lymphoglobulin), CyA and Mepred. Four developed severe anaphylactoid reactions and could not complete the 2 nd-line treatment. Twenty-nine patients received SCT as follows: BMT from an unrelated donor (n=22), BMT from an HLA-mismatched family donor (n=4) and cord blood SCT from an unrelated donor (n=3). Two patients did not receive any 2 nd-line treatment. Median interval between 1 st -line IST and 2 nd-line treatment was 8 mo for the SCT group (range: 4–20 mo) and 7 mo for the IST group (range: 5–14 mo). One patient receiving 2 nd-line IST and 5 patients receiving SCT died of infections. The overall probability of survival at 5 y from the start of 2 nd-line treatment was 82 ± 10% in the SCT group and 97 ± 5% in the IST group (p:0.08 ). However, trilineage response to a 2 nd course of IST was seen in only 3 of 25 evaluable patients (12%), and 10 non-responders to 2 nd-line IST later received BMT from an unrelated donor as a 3 rd -line therapy. Blood counts normalized in all patients following SCT. Failure-free survival (FFS) was defined as survival with treatment response. The estimated FFS at 5 y was significantly better (p Conclusion: SCT from alternative donors offers a better chance of FFS than 2 nd-line IST in non-responders to 1 st -line IST. However, overall survival rate is not different between two approaches.