ALBERT

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

Description: Introduction: Myeloid/Natural killer cell precursor acute leukemia (MNKPL) and myeloid/NK cell acute leukemia (MNKL) is a rare hematologic malignancy prevalent in East Asia. MNKPL is characterized by marked extramedullary involvement, immature lymphoblastoid morphology without myeloperoxidase (MPO) reactivity, a CD7+/CD33+/CD34+/CD16−/CD15−/+/HLA-DR+ phenotype, myeloid chemosensitivity, and a poor prognosis. By contrast, MNKL shows no extramedullary involvement, a HLA‐DR−/CD33+/CD16−/CD34−/+ phenotype, myeloid chemosensitivity, and a good prognosis. However, analysis of outcome and genetic alterations in these leukemias are limited. Here, we report outcome and genetic alterations in the patients with MNKPL and MNKL. Methods: The Leukemia and Lymphoma Committee of the Japanese Society of Pediatric Hematology and Oncology (JSPHO) sent out two questionnaires to 110 JSPHO affiliated hospitals. The first questionnaire requested details of the number of pediatric patients with MNKPL or MNKL had been diagnosed during the period 2000-2013. The second questionnaire requested more detailed information about clinical curses. Overall survival (OS) and event free survival (EFS) defined as relapse or death was analyzed. The protocol of this retrospective study was approved by the review boards of JSPHO and Ehime Prefectural Central Hospital. We also performed whole exome sequence (WES) using 7 children's samples (5 MNKPL, 2 MNKL) and target sequence using 2 adult's samples (2 MNKPL) from this and another independent cohort. The research protocol was approved by the review board of TMDU. Results: Thirteen children with MNKPL and 6 children with MNKL were identified. Median age of MNKPL was 8 year-old (range; 0.5-17) and median age of MNKL was 10 year-old (range; 2-13). There are 8 males and 5 females in MNKPL and 4 males and 2 females in MNKL. In MNKPL, central nervous system, mediastinum and lymph node involvement was observed in 1 case respectively. Nasal sinus involvement was observed in 1 case in MNKL. Eleven patients with MNKPL and 3 patients with MNKL were treated with acute myeloid leukemia style chemotherapy and 1 MNKPL patients and 3 MNKL patients were treated with acute lymphoblastic leukemia/non-Hodgkin lymphoma style chemotherapy. Complete remission after induction therapy was achieved in 8/13 MNKPL children and 4/6 MNKL children. Twelve out of 13 MNKPL children and all 6 MNKL children underwent hematopoietic cell transplantation (HCT) with myeloablative conditioning regimen. Median follow up period was 5.3 years in MNKPL and 3.8 years in MNKL patients. 5-year OS of MNKPL and MNKL was 67.3 % and 41.7 %, 5-year EFS of MNKPL and MNKL was 52.7 % and 41.7 % respectively. In genetic analysis, average 148 somatic mutations in MNKPL and 88 somatic mutations in MNKL were identified by WES. In combined analysis using adult cases, the recurrent mutations were observed in NOTCH1, NRAS (n=3, respectively), MAML2, MAP3K1, SIRPA (n=2, respectively) as activating signal genes, and CLTCL1 (n=2) as cell adhesion molecules, and RECQL4 (n=2) as cell cycle/DNA repair molecules, and PRDM2, CREBBP, SETBP1 (n=2, respectively) as epigenetic modifiers, and WT1, ZNF384, BCLAF1 (n=2, respectively) as transcription factors. Conclusions: Previously, it has been reported that outcome of MNKL is relatively good than MNKPL. MNKPL and MNKL children had a poor prognosis in our cohort even though most patients received HCT. We identified alteration of molecules involved in NOTCH signaling and RAS-MAPK pathways. In addition, mutations of several transcription factors such as WT1 were identified. The drugs targeting RAS pathway and epigenetic factors may have the potential to improve outcome. An international collaboration for clinical and cytogenetic research of MNKPL and MNKL is needed as they are complex and rare diseases. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: Myeloid/Natural killer (NK) cell precursor acute leukemia (MNKPL) is a rare hematologic malignancy prevalent in East Asia. MNKPL is characterized by extramedullary involvement, immature lymphoblastoid morphology without myeloperoxidase (MPO) reactivity, the CD7+/CD33+/CD34+/CD56+/HLA−DR+ phenotype. MNKPL is classified as mixed phenotype acute leukemia, and not otherwise specified rare types (MPAL NOS rare types) in WHO classification. However, its characteristic clinical feature and undetermined genetic feature suggests that MNPKL leaves open the possibility of a new independent disease concept. Here, we report clinical features and genetic alterations in patients with MNKPL. Methods: The Leukemia and Lymphoma Committee of the Japanese Society of Pediatric Hematology and Oncology (JSPHO) sent out questionnaires to 110 JSPHO affiliated hospitals and collected cases of MNPKL diagnosed during the period 2000-2013. Besides, the cases published as literature were recruited. The data of clinical features, cell surface antigen profiling, overall survival (OS), and event-free survival (EFS) defined as relapse or death were also collected as a secondary survey. The protocol of this retrospective study was approved by the review boards of JSPHO and Ehime Prefectural Central Hospital. Comprehensive genetic analysis including 13 whole-exome sequences (WES), 2 target sequence, 6 RNA sequence (RNA-seq), and 8 DNA methylation analysis was performed. We also performed single-cell RNA-seq using 1 sample of MNKPL patients and a normal bone marrow sample as the reference. The research protocol was approved by the review board of TMDU. Results: Sixteen children or young adults (〈 39 years old) and 2 older adults with MNKPL were identified. The median age of MNKPL patients was 11 (0.5-75) years old. There are 12 males and 6 females. The extramedullary involvement was observed in 7 patients. Complete remission after induction therapy was achieved in 8/14 (57%) patients treated with acute myeloid leukemia (AML) type chemotherapy and 2/4 (50%) patients treated with acute lymphoblastic leukemia (ALL)/non-Hodgkin lymphoma type chemotherapy, respectively. Fifteen patients underwent hematopoietic cell transplantation (HCT). The median follow-up period was 3.8 (0.1-16.0) years. 5-year OS and 5-year EFS was 49.5% and 40.7%, respectively. In genetic analysis, median 388 somatic mutations in MNKPL were identified by WES. The recurrent mutations were observed in NOTCH1 (n=5), MAML3 (n=4), NRAS, MAP3K4, RECQL4, CREBBP, ASXL2, and KMT2D (n=3, respectively), and MAML2, MAP3K1, FLT3, CARD11, MSH4, FANCI, WT1, ZNF384, and ERG (n=2, respectively). The distinct expression pattern, higher expression of RUNX3 and NOTCH1, and lower expression of BCL11B were identified in MNKPL samples which were compared to MPAL, AML, and T cell ALL in RNA-seq. The distinct methylation profile, hypomethylation of RUNX3 regulatory region, and hypermethylation of BCL11B regulatory region were identified in DNA methylation analysis. Single-cell RNA-seq analysis also showed distinct 4 subsets of MNKPL. Discussion and Conclusions: NK cells are the founding member of a family of innate lymphoid cells (ILC). Genetic abnormality of NOTCH1 pathway is a hallmark of MNPKL. RUNX3 is required for NK cell survival and proliferation in response to IL-15 signaling. RUNX3 high expression and hypomethylation of RUNX3 regulatory region also characterize MNKPL. Currently, MNKPL is classified as MPAL NOS, our genetic analysis revealed that MNKPL is a distinct group from MPAL. The prognosis of MNKPL was not satisfactory even though HCT was performed. The development of new therapeutic approaches based on these genetic analyses is highly expected. Disclosures Saito: Toshiba Corporation: Research Funding. Nakazawa:Toshiba Corporation: Research Funding.