Mixed Phenotype Acute Leukemia Research Articles

Acute Leukemia

The acute leukemias are malignant clonal disorders characterized by aberrant differentiation and proliferation of transformed hematopoietic progenitor cells. These cells accumulate within the bone marrow and lead to suppression of the production of normal blood cells, with resulting symptoms from varying degrees of anemia, neutropenia, and thrombocytopenia or from infiltration into tissues. They are currently classified by their presumed cell of origin, although the field is moving rapidly to genetic subclassification. This review covers epidemiology; etiology; classification of leukemia by morphology, immunophenotyping, and cytogenetic/molecular abnormalities; cytogenetics of acute leukemia; general principles of therapy; acute myeloid leukemia; acute lymphoblastic leukemia; and future possibilities. The figure shows the incidence of acute leukemias in the United States. Tables list World Health Organization (WHO) classification of acute myeloid leukemia and related neoplasms, expression of cell surface and cytoplasmic markers for the diagnosis of acute myeloid leukemia and mixed-phenotype acute leukemia, WHO classification of acute lymphoblastic leukemia, WHO classification of acute leukemias of ambiguous lineage, WHO classification of myelodysplastic syndromes, European LeukemiaNet cytogenetic and molecular genetic subsets in acute myeloid leukemia with prognostic importance, cytogenetic and molecular subtypes of acute lymphoblastic leukemia, terminology used in leukemia treatment, and treatment outcome for adults with acute leukemia. This review contains 2 figures, 15 tables, and 119 references. Keywords: Acute leukemia, acute myeloid leukemia, acute lymphoblastic leukemia, cancer, cytogenetics, chromosomal abnormality

Acute Leukemia

The acute leukemias are malignant clonal disorders characterized by aberrant differentiation and proliferation of transformed hematopoietic progenitor cells. These cells accumulate within the bone marrow and lead to suppression of the production of normal blood cells, with resulting symptoms from varying degrees of anemia, neutropenia, and thrombocytopenia or from infiltration into tissues. They are currently classified by their presumed cell of origin, although the field is moving rapidly to genetic subclassification. This review covers epidemiology; etiology; classification of leukemia by morphology, immunophenotyping, and cytogenetic/molecular abnormalities; cytogenetics of acute leukemia; general principles of therapy; acute myeloid leukemia; acute lymphoblastic leukemia; and future possibilities. The figure shows the incidence of acute leukemias in the United States. Tables list World Health Organization (WHO) classification of acute myeloid leukemia and related neoplasms, expression of cell surface and cytoplasmic markers for the diagnosis of acute myeloid leukemia and mixed-phenotype acute leukemia, WHO classification of acute lymphoblastic leukemia, WHO classification of acute leukemias of ambiguous lineage, WHO classification of myelodysplastic syndromes, European LeukemiaNet cytogenetic and molecular genetic subsets in acute myeloid leukemia with prognostic importance, cytogenetic and molecular subtypes of acute lymphoblastic leukemia, terminology used in leukemia treatment, and treatment outcome for adults with acute leukemia. This review contains 2 figures, 15 tables, and 119 references. Keywords: Acute leukemia, acute myeloid leukemia, acute lymphoblastic leukemia, cancer, cytogenetics, chromosomal abnormality

Acute Leukemia

The acute leukemias are malignant clonal disorders characterized by aberrant differentiation and proliferation of transformed hematopoietic progenitor cells. These cells accumulate within the bone marrow and lead to suppression of the production of normal blood cells, with resulting symptoms from varying degrees of anemia, neutropenia, and thrombocytopenia or from infiltration into tissues. They are currently classified by their presumed cell of origin, although the field is moving rapidly to genetic subclassification. This review covers epidemiology; etiology; classification of leukemia by morphology, immunophenotyping, and cytogenetic/molecular abnormalities; cytogenetics of acute leukemia; general principles of therapy; acute myeloid leukemia; acute lymphoblastic leukemia; and future possibilities. The figure shows the incidence of acute leukemias in the United States. Tables list World Health Organization (WHO) classification of acute myeloid leukemia and related neoplasms, expression of cell surface and cytoplasmic markers for the diagnosis of acute myeloid leukemia and mixed-phenotype acute leukemia, WHO classification of acute lymphoblastic leukemia, WHO classification of acute leukemias of ambiguous lineage, WHO classification of myelodysplastic syndromes, European LeukemiaNet cytogenetic and molecular genetic subsets in acute myeloid leukemia with prognostic importance, cytogenetic and molecular subtypes of acute lymphoblastic leukemia, terminology used in leukemia treatment, and treatment outcome for adults with acute leukemia. This review contains 2 figures, 15 tables, and 119 references. Keywords: Acute leukemia, acute myeloid leukemia, acute lymphoblastic leukemia, cancer, cytogenetics, chromosomal abnormality

Venetoclax plus intensive chemotherapy with cladribine, idarubicin, and cytarabine in patients with newly diagnosed acute myeloid leukaemia or high-risk myelodysplastic syndrome: a cohort from a single-centre, single-arm, phase 2 trial

Addition of the BCL2 inhibitor venetoclax to lower intensity therapy has been shown to improve overall survival in older (aged 75 years or older) and unfit patients with newly diagnosed acute myeloid leukaemia. The aim of this study was to investigate the activity of venetoclax combined with intensive chemotherapy in patients aged 65 years or younger with acute myeloid leukaemia. This cohort study was done at the MD Anderson Cancer Center in the USA, as part of the single-centre, single arm, phase 2, CLIA trial. Here we report on the independent cohort investigating the safety and activity of venetoclax added to intensive chemotherapy (the CLIA regimen [cladribine, high-dose cytarabine, idarubicin]). Eligible patients were aged 18-65 years with a new diagnosis of acute myeloid leukaemia, mixed phenotype acute leukaemia, or high-risk myelodysplastic syndrome (≥10% blasts or International Prognostic Scoring System ≥2 [intermediate]), who received no previous potentially curative therapy for leukaemia. Patients received cladribine (5 mg/m2) and cytarabine (1·5 g/m2 for patients aged <60 years, 1 g/m2 for patients aged ≥60 years) intravenously on days 1-5 and idarubicin (10 mg/m2) intravenously on days 1-3. Consolidation was cladribine (5 mg/m2) and cytarabine (1 g/m2 for patients aged <60 years and 0·75 g/m2 for patients aged ≥60 years) on days 1-3 and idarubicin (8 mg/m2) on days 1-2. Venetoclax (400 mg) was given on days 2-8 with each course. Patients with a known FLT3-ITD or FLT3-TKD mutation received midostaurin or gilteritinib. The primary outcome was composite complete response (complete response plus complete response with incomplete blood count recovery). Secondary outcomes were overall response, duration of response, event-free survival, overall survival, and safety. This trial was registered with ClinicalTrials.gov, NCT02115295. Between Feb 25, 2019, and March 23, 2021, 77 patients were assessed for eligibility, 50 of whom were enrolled. Median age was 48 years (IQR 37-56). 47 (94% [95% CI 83-98]) patients had composite complete response, with the same proportion also having an overall response; two (4% [1-14]) patients did not respond, and one (2% [0-11]) patient died during induction. 37 (82% [95% CI 68-92]) of 45 patients had undetectable measurable residual disease (MRD). At a median follow-up of 13·5 months (IQR 6·4-19·5), the median duration of response, event-free survival, and overall survival were not reached. At 12 months, the estimated duration of response was 74% (95% CI 60-92), event-free survival was 68% (54-85), and overall survival was 85% (75-97). The most common adverse events of grade 3 or worse were febrile neutropenia (42 [84%] patients), infection (six [12%]), and alanine aminotransferase elevations (six [12%]). There was one death during induction in a patient treated with CLIA-venetoclax plus a FLT3 inhibitor. Two patients died of infectious complications while in complete response in consolidation cycles, both of whom had FLT3-mutated acute myeloid leukaemia and were receiving combined therapy with a FLT3 inhibitor. No deaths were deemed to be treatment related. Venetoclax added to CLIA was safe and active in patients with newly diagnosed acute myeloid leukaemia or high-risk myelodysplastic syndrome, producing high rates of durable MRD-negative remissions and encouraging event-free survival and overall survival. MD Anderson Cancer Center.

PHF6 Mutations in Hematologic Malignancies.

Next generation sequencing has uncovered several genes with associated mutations in hematologic malignancies that can serve as potential biomarkers of disease. Keeping abreast of these genes is therefore of paramount importance in the field of hematology. This review focuses on PHF6, a highly conserved epigenetic transcriptional regulator that is important for neurodevelopment and hematopoiesis. PHF6 serves as a tumor suppressor protein, with PHF6 mutations and deletions often implicated in the development of T-lymphoblastic leukemia and less frequently in acute myeloid leukemia and other myeloid neoplasms. PHF6 inactivation appears to be an early event in T-lymphoblastic leukemogenesis, requiring cooperating events, including NOTCH1 mutations or overexpression of TLX1 and TLX3 for full disease development. In contrast, PHF6 mutations tend to occur later in myeloid malignancies, are frequently accompanied by RUNX1 mutations, and are often associated with disease progression. Moreover, PHF6 appears to play a role in lineage plasticity within hematopoietic malignancies, with PHF6 mutations commonly present in mixed phenotype acute leukemias with a predilection for T-lineage marker expression. Due to conflicting data, the prognostic significance of PHF6 mutations remains unclear, with a subset of studies showing no significant difference in outcomes compared to malignancies with wild-type PHF6, and other studies showing inferior outcomes in certain patients with mutated PHF6. Future studies are necessary to elucidate the role PHF6 plays in development of T-lymphoblastic leukemia, progression of myeloid malignancies, and its overall prognostic significance in hematopoietic neoplasms.

A Recurrent Cryptic MED14-HOXA9 Rearrangement in an Adult Patient With Mixed-Phenotype Acute Leukemia, T/myeloid, NOS.

To define the fusion genes in T/myeloid mixed-phenotype acute leukemia (T/M MPAL), we performed transcriptome sequencing of diagnostic bone marrow samples from 20 adult patients. Our analysis identified a second instance of a recurrent MED14-HOXA9 chimeric gene resulting from the in-frame fusion of exon 23 of MED14 and exon 1 of HOXA9, the first in an adult patient. The MED14-HOXA9 fusion gene was detected in both the diagnostic and relapsed blasts with reverse transcription-polymerase chain reaction and Sanger sequencing. The patient received combined conventional chemotherapy but suffered relapse at 11 months and died of disease progression one year after the initial diagnosis. Our data suggest that MED14-HOXA9 is a cryptic recurrent aberration in T/M MPAL, which might indicate an aggressive clinical course and inferior outcome after conventional chemotherapy. Further studies will be carried out to reveal the effects of the MED14-HOXA9 fusion on the differentiation and proliferation of leukemia stem cells, as well as suitable treatment strategies for this emerging entity.

Abstract 2349: Comparison of the blood, bone marrow, and cerebrospinal fluid metabolomes in children with acute leukemia

Abstract Background: Children with acute leukemia (AL) are at risk for relapse, treatment toxicity, second neoplasms, and death. Understanding host and tumor response to therapy is necessary to achieve high survival rates and minimize adverse effects. Metabolomics, the characterization of small molecules in a biological system, may be useful for monitoring treatment response. In support of this, we previously identified metabolites in bone marrow (BM) plasma associated with end-induction minimal residual disease (MRD) and in cerebrospinal fluid (CSF) associated with fatigue. Because procedures for obtaining BM and CSF are invasive and subject patients to risk, we sought to determine whether the BM and CSF metabolomes of children undergoing therapy for AL were correlated with the blood metabolome. Methods: Blood plasma, BM, and CSF were collected at the end-induction from 11 patients with newly diagnosed AL treated at Texas Children's Hospital (Houston, TX). Global metabolomic profiling was performed by Metabolon (Durham, NC), using liquid chromatography-tandem mass spectrometry according to published methods. We assessed the number and type (e.g. lipid, amino acid) of metabolites in each sample. For each metabolite identified in ≥2 samples from ≥2 patients, we computed Spearman rank correlation coefficients to estimate the pairwise correlations between blood, BM, and CSF. Results: Patients were predominantly male (N=7) and Latino (N=9). Ten were diagnosed with B-cell acute lymphoblastic leukemia and one with mixed phenotype acute leukemia. Among 670 metabolites detected in ≥2 blood and BM plasma samples, 370 (58%) demonstrated moderate to strong correlations (Spearman's rho ≥0.5) and 317 (47%) were significant at p&amp;lt;0.05. Among 340 metabolites detected in ≥2 blood and CSF samples, 135 (40%) demonstrated moderate to strong correlations and 96 (28%) were significant at p&amp;lt;0.05. Among 318 metabolites detected in ≥2 BM plasma and CSF samples, 88 (28%) demonstrated moderate to strong correlations and 66 (21%) were significant at p&amp;lt;0.05. We observed generally moderate to strong correlations between BM and blood for 19 metabolites we previously reported were associated with MRD (median rho 0.51, interquartile range 0.24-0.69). We observed a strong positive correlation between CSF and blood for one of three metabolites we previously reported were associated with fatigue (dimethylglycine, rho=0.7, p=0.02), and a moderate inverse correlation for a second (gamma-glutamylglutamine, rho=-0.51, p=012). Conclusions: There is substantial correlation between the blood and BM plasma metabolomes at end-induction among children with ALL, including metabolites putatively associated with early treatment response. Correlations between CSF and blood or BM plasma are weaker, implying that the CSF metabolome is distinct. The blood plasma metabolome may approximate the BM but not CSF metabolome in children with ALL. Citation Format: Jeremy M. Schraw, J.P. Woodhouse, Melanie B. Bernhardt, Olga A. Taylor, Terzah M. Horton, Michael E. Scheurer, Mehmet F. Okcu, Karen R. Rabin, Philip J. Lupo, Austin L. Brown. Comparison of the blood, bone marrow, and cerebrospinal fluid metabolomes in children with acute leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2349.

Issue Highlights-July 2021.

Issue Highlights-July 2021.

Hemorrhagic stroke due to leukostasis in pediatric mixed-phenotype acute leukemia.

Hemorrhagic stroke due to leukostasis in pediatric mixed-phenotype acute leukemia.

Isolated Myeloperoxidase Expression in Pediatric B/Myeloid Mixed Phenotype Acute Leukemia Is Associated with Improved Survival Using ALL-Only Regimens

Background: Mixed phenotype acute leukemia (MPAL) represents a heterogeneous group of leukemias accounting for 2-5% of all newly diagnosed acute leukemias. Diagnostic criteria for mixed phenotype MPAL have evolved over time, with the World Health Organization (WHO) 2016 criteria now being recognized as the more definitive standard. According to WHO classification, isolated expression of myeloperoxidase (MPO) allows for myeloid lineage assignment in patients with an otherwise typical B-acute lymphoblastic leukemia (B-ALL) phenotype, thus meeting criteria for MPAL B/myeloid. Our goal was to determine if there were differences in treatment and survival between this group of patients, classified as MPAL B/myeloid isoMPO, and other MPAL patients.Methods: Data was obtained through a retrospective chart review of pediatric MPAL patients treated between 2001 and 2016 at Children's Healthcare of Atlanta. Cases were identified through our institutional tumor registry and pathology department flow cytometry database. Cases were eligible if the patients were between ages of 1 and 21 years at diagnosis and the leukemia met the WHO 2016 MPAL criteria. We excluded therapy related cases, non-myeloid cases (rare B/T subtype), and cases with a t(9;22) translocation. Data were extracted from clinical records for patient, disease and treatment related variables. All flow cytometry reports were reviewed by study hematopathologists. Cases were divided into two groups - MPAL B/Myeloid isoMPO and other MPAL cases. MPAL B/myeloid cases were classified as MPAL B/Myeloid isoMPO if there was a single B-lineage blast population expressing MPO as the only WHO MPAL myeloid marker. An event was defined as treatment failure requiring therapy change prior to end of induction (EOI), induction failure, induction death, remission death, or relapse. Event-free survival (EFS) and overall survival (OS) were calculated using Kaplan-Meier survival curves. Groups were compared using the log rank test. Chi-squared test was used for sampling distribution analyses.Results: Of the 35 MPAL cases included in our study, 21 (60%) met criteria for MPAL B/myeloid isoMPO. 20 of these patients were treated with ALL chemotherapy alone. One patient underwent bone marrow transplantation (BMT) due to a low DNA index. None of these patients were switched to myeloid therapy during their treatment course. The other 14 MPAL cases consisted of 5 MPAL B/myeloid (non-isolated MPO), 7 MPAL T/myeloid and 2 MPAL patients with t(v;11q23); MLL rearranged. Of these 14 cases, 10 were treated at least in part with myeloid chemotherapy and 7 proceeded to BMT. 6 of 10 patients in this group who started with ALL induction were switched over to AML therapy, with 3 being changed prior to EOI due to treatment failure. Despite these treatment differences, those with MPAL B/myeloid isoMPO had better outcomes. 3-year EFS was significantly higher at 84% for the MPAL B/myeloid isoMPO group compared to 57% in the other MPAL group (p=0.027 log rank test, Fig 1A). 3-year overall survival was 100% and 68%, respectively (p=0.083 log rank test, Fig 1B).Conclusion: There continues to be no consensus as to how to treat MPAL and the changing definition of MPAL has contributed to the difficulty in treating this rare and heterogeneous disease. While the WHO 2016 criteria have simplified the definition of MPAL, it has created a group of patients as shown here, that may be falsely categorized as MPAL. Our results suggest that MPAL B/myeloid isoMPO patients behave clinically like typical B-ALL patients, and should be treated as such. Consideration should be given to redefining the current MPAL WHO criteria to explicitly exclude these cases. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Comprehensive Analysis of Mixed Phenotype Acute Leukemia (MPAL) By Whole Genome Sequencing

Background: Mixed phenotype acute leukemias (MPAL) comprise a rare subgroup of acute leukemias with significant expression of lineage-specific antigens of more than one cell lineage not allowing assignment to a single cell lineage. While two MPAL subgroups are genetically defined according to the WHO 2016 classification, i.e. MPAL with BCR-ABL1 and MPAL with KMT2A rearrangement, the majority of cases are grouped as MPAL, B/myeloid, NOS or MPAL, T/myeloid, NOS and lack any specific or characteristic genetics so far.Aims: Molecular characterization of MPAL by whole genome sequencing (WGS).Patient cohort and methods: Diagnostic peripheral blood or bone marrow samples of 12 MPAL patients (median age 64 years, range 38-96; 5 male, 7 female) were selected for WGS with 90x coverage. One had MPAL with BCR-ABL1, 5 had MPAL, B/myeloid, NOS and 6 had MPAL, T/myeloid, NOS. Library preparation was performed using Truseq DNA PCR-Free HT sample preparation kit (Illumina, San Diego, CA). Sequencing was performed on NovaSeq instruments (Illumina). Tumor-only data was aligned by BaseSpace (BS) WGS app with default parameters and (structural) variant calling was performed with the Tumor/Normal app using an unmatched reference DNA (Promega, Fitchburg, WI). Data was subsequently loaded into BS Variant Interpreter to filter and prioritize variants of interest. For the structural variants we looked at all high confidence variant calls passing filters with at least 5 paired reads and 3 split reads with a somatic QScore of >30. In addition, all calls were eliminated with a population frequency of >1% according to the DGV (Database of Genomic variants). We performed mutation signature analysis by looking at the distribution of base substitutions across the sample with a 3mer context (including the base before and after the substitution) to decompose somatic mutation patterns and compared the results to the COSMIC signature database. For mutation analysis variants with a read frequency of >0.2% and ExAC population frequency of <1% were considered. For the first set of analysis we filtered down the variant list to the coding region of 65 genes described mutated in hematologic malignancies. For the second set of analysis we considered also genes beyond these 65 genes but required that variants had an entry in the COSMIC database and were classified with a “damaging” score by PolyPhen-2 and SIFT data bases.Results: Regarding the first set of analysis we found a median of 6 (range 2-7) mutations per patient, 63 overall, involving 35 of the 65 investigated genes. The majority were missense mutations (n=31), frameshift mutations (n=14) and splice-site mutations (n=13). The genes listed in table 1 were found most frequently mutated. Except for RUNX1 none of the frequently encountered mutations affected the case with MPAL with BCR-ABL1 while there was no restriction of mutations to either of the two other MPAL subgroups. 11 of these 63 mutations had been previously analyzed by routine diagnostics applying next generation sequencing (NGS) yielding identical results.Regarding the second set of analysis without limitation on the above mentioned 65 genes we found a median of 83 (range 63-129) mutations per patient, 1079 overall, involving 736 genes. Specifically, four candidate genes were found mutated in at least five patients (table 2). NBPF1 has been described as tumor suppressor, PRAMEF2 belongs to the PRAME family of genes associated with various malignancies and as a prognostic factor in B-ALL, MUC12 is a highly polymorphous gene involved in a variety of cancer types and described to be epigenetically regulated and thus a marker for early cancer detection, ARSD has been described overexpressed and prognostic in CLL. Again, mutations were not restricted to one MPAL subgroup.We subsequently conducted a context-sensitive mutation signature analysis with the SNV data, using 96 substitution patterns rather than only 6 to increase the complexity. In all instances we found a highly similar pattern across all 12 samples with a strong bias towards C>T substitutions (figure 1).Conclusion: WGS is capable of reproducing routine NGS diagnostics and of identifying mutations not yet described for MPAL which might be used to better understand and categorize this disease. [Display omitted] DisclosuresKern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Nadarajah:MLL Munich Leukemia Laboratory: Employment. Meggendorfer:MLL Munich Leukemia Laboratory: Employment. Walter:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Integrative Genomic Analysis of Adult Mixed Phenotype Acute Leukemia (MPAL)

IntroductionMixed phenotype acute leukemia (MPAL) is a rare subgroup of acute leukemia characterized by blasts presenting both myeloid and lymphoid lineages. Standard of care for MPAL is not defined and prognosis of MPAL is poor. Genetic basis for mixed immunophynotype and distinct molecular characteristics from other leukemia is not well understood.MethodsWe studied 31 bone marrow samples from previously untreated MPAL patients (median age 53) meeting WHO criteria. Genomic DNA/RNA from bone marrow samples were analyzed by comprehensive genomic analysis including targeted capture sequencing of 295 genes (median 393x coverage), RNA sequencing, and Infinium methylation EPIC array (Illumina). Copy number alterations (CNA) were analyzed from methylation array data using ChAMP algorithm. Mutational landscape of MPAL was compared with194 AML, 71 B-ALL, and 14 T-ALL cases sequenced with the same platform. CpG methylation pattern of MPAL was also compared with 194 AML (TCGA), 505 B-ALL and 101 T-ALL cases (data shared by Nordlund et al. Genome Biology. 2013).ResultsOf the 31 MPAL cases, 18 (58%) had myeloid-T and 13 (42%) had myeloid-B phenotype. Four (13%) cases had Philadelphia chromosome, one (3%) had 11q23 rearrangement, and 8 (26%) had complex karyotypes. Eighteen patients (62%) were treated with ALL regimen, 8 (28%) received AML regimen, and 3 (10%) received other therapy.Targeted sequencing revealed 86 driver mutations (55 SNVs and 31 indels) in 35 genes in 29 samples (94%). MPAL carried median 2 (range 0-6) mutations per case that was similar to AML (P = 0.79) and T-ALL (P = 0.92) but was significantly higher than B-ALL(P < 0.001). The most frequently mutated genes were DNMT3A , IDH2 , NOTCH1 , and RUNX1 in 7 (23%) cases each (Figure 1). Myeloid-T and myeloid-B showed distinct patterns of mutations, in which mutations in NOTCH pathway genes had strong trend of enrichment in myeloid-T (P = 0.06), whereas RUNX1 mutations were significantly enriched in myeloid-B (P = 0.02). When mutation landscape was compared among AML, B-ALL, T-ALL and MPAL, TP53 , NRAS , and DNMT3A mutations were shared across all leukemia. In contrast, NPM1 mutation was specific to AML and mutations in NOTCH1 , FBXW7 , and IL7R were specific to myeloid-T MPAL and T-ALL. CNA analysis showed that CDKN2B as a significantly deleted gene in MPAL.Unsupervised hierarchical clustering of promoter methylation revelaed two distinct clusters. This methylation cluster had significant correlation with immunophenotype (73% of cluster 1 was myeloid-B and 88% of cluster 2 was myeloid-T, P < 0.001). Overall, myeloid-T had more hypermethylated CpG loci than myeloid-B (mean beta value 0.28 vs. 0.52 in myeloid-B vs. myeloid-T, P = 0.002). This difference in methylation was independent from IDH mutation. Molecular pathway analysis of differentially methylated probes (DMP) showed that T-cell receptor pathway, T cell differentiation, and activation pathway genes (CD3D , CD247 , LCK , PRF1 , RHOH , and PRKCQ ) were differentially methylated and were expressed between myeloid-B and myeloid-T. Furthermore, motif enrichment analysis of promoter DMP revealed that IRF8 and IRF4 binding motifs were significantly hyper-methylated in myeloid-T compared to myeloid-B. Consistent with this, RAG1 , RAG2 , CXCR4 and PAX5 , downstream targets of IRF4/IRF8 andessential genes in B-cell development, were differentially expressed between two phenotypes. RNA sequencing revealed two known translocations (NSD1-NUP98 , KMT2A-MLLT4 ) in addition to the novel translocations such as FOXP1-DNAJC15 , TNKS - LYZ , and NOP14 - PLEC in MPAL. We did not detect ZN384 fusions that have been reported in pediatric MPAL (Alexander et al. ASH 2016). Unsupervised hierarchical clustering of methylation pattern among MPAL, AML, B-ALL and T-ALL revealed that 41% and 59% of MPAL had AML-like and ALL-like methylation pattern, respectively (Figure 2). Patients who received therapy that matched with their methylation pattern had significantly better response to treatment than patients who received unmatched therapy (CR rate: 77% vs. 31%, P = 0.024).ConclusionMyeloid-T and myeloid-B MPAL showed distinct patterns of mutation, methylation and gene expressions. Methylation data could identify AML-like and ALL-like MPAL which corresponded to better response to therapy when matched therapy was given. These data suggest that molecularly guided therapy may be beneficial in the treatment of MPAL. [Display omitted] DisclosuresTakahashi:Symbio Pharmaceuticals: Consultancy. DiNardo:Agios: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Daiichi-Sankyo: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding. Jabbour:Bristol-Myers Squibb: Consultancy. Andreeff:Daiichi Sankyo: Consultancy. Kantarjian:Bristol-Meyers Squibb: Research Funding; Amgen: Research Funding; ARIAD: Research Funding; Pfizer: Research Funding; Delta-Fly Pharma: Research Funding; Novartis: Research Funding.

PHF6 Mutations Defines a Subgroup of Mixed Phenotype of Acute Leukemia with Aberrant T-Cell Differentiation

Mixed phenotype acute leukemia (MPAL) is a rare form of acute leukemia, and comprises 2% of all acute leukemia diagnoses. With the exception of a small subset harboring BCR/ABL1 or MLL translocations (around 15% in combination), the genetic aberrations of MPAL are largely unknown. PHF6 gene is located at Xq26-27 and encodes plant homeodomain finger 6, a zinc finger containing protein. Recurrent somatic PHF6 mutations are frequent in T-ALL (up to 30%) and rarely in AML (~3%). Here we report recurrent PHF6 mutations in approximately 20% of MPAL patients, making PHF6 the most common genetic aberrations identified in MPAL.From 2013 to 2016, a total of 1329 patients with myeloid neoplasms were sequenced at the MSKCC with a targeted next generation sequencing panel containing 30 genes that are frequently mutated in acute leukemia. We identified 38 PHF6 mutations with predicted pathologic significance in 33 patients (2.5%) spanning the whole coding sequence: 10 frameshift, 11 nonsense, 1 splicing site, and 16 missense (Figure 1). The most common co-mutant gene observed in cases with PHF6 mutations was RUNX1 (30%, 11/37). No TP53 mutations are detected within the PHF6-mutant cohort(Figure 2). The 33 patients with PHF6 mutations included patients with a diagnosis of MPAL (n=5), AML (n=19), MDS (n=5), and MPN (n=4).The disproportional distribution of PHF6 mutations in MPAL prompted us to further analyze these patients. During the same period of time, 24 MPAL patients were identified and confirmed based on WHO 2016 classification (excluding AML-MRC and t-AML). Within this cohort, 3 (12%) had BCR-ABL1 (p190) fusion, and 1 (4%) had MLL translocation, two distinct genetically defined subgroups. Importantly, 5 (21%) harbored PHF6 mutations, these mutations were mutually exclusive with BCR-ABL1 or MLL. Four of the 5 patients showed T-cell lineage differentiation, in contrast to MPAL with BCR-ABL1 or MLL translocations which were characterized by B/myeloid differentiation. The 2-year overall survival for the PHF6 mutation positive MPAL was markedly reduced compared to non-mutated cases (40% vs. 100% in PHF6 unmutated cases (p=0.005)).In the larger subset of AML cases, PHF6 mutations were nearly exclusively present in secondary AML (11 AML-MRC, 6 t-AML and only 1 de novo AML). In contrast to their rarity in de novo AML, PHF6 mutations were identified in 11% (11/88) of AML-MRC and 7.1% (6/84) of t-AML. Interestingly, T-cell markers (cytoplasmic CD3, CD2, CD5, CD7) were often expressed on the blasts of secondary AML cases regardless of PHF6 mutational status (56%, 9/16 vs. unmutated 51%, 36/70). In comparison to unmutated cases, the blasts were often negative for CD33 (69%, 11/16, vs 28%, 20/70, p=0.004 by Fisher's exact test) and CD38 (44%, 7/16, vs. 17%, 12/70, p=0.04 by Fisher's exact test) in PHF6 mutated AML, suggestive of a stemness phenotype with aberrant T-cell differentiation.In conclusion, PHF6 mutations are the most common somatic alteration identified in MPAL and define a subgroup of MPAL with altered T-cell differentiation and inferior outcome. Amongst AML, PHF6 mutations are almost exclusively seen in secondary AML and are also associated with T-cell antigen expression and a more primitive stem/progenitor immunophenotype. PHF6 mutations co-exist with RUNX1 mutations but are mutually exclusive to TP53 mutations. Notably, PHF6 mutations may provide a genetic and functional link between MPALs with poor outcome and secondary AML and provide insights into shared mechanisms of transformation. RNA sequencing studies on the sorted blast population are ongoing and will be presented at the ASH meeting. [Display omitted] DisclosuresArcila:Invivoscribe: Honoraria; Archer: Honoraria; Raindance Tecnologies: Honoraria. Levine:Celgene: Research Funding; Roche: Research Funding; Qiagen: Equity Ownership; Roche: Research Funding; Celgene: Research Funding; Qiagen: Equity Ownership.

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

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

Therapy for Children and Adults with EGIL- or WHO2008-Defined Mixed Phenotype Acute Leukemia: A Systematic Review and Meta-Analysis

The rarity of Mixed-Phenotype Acute Leukemia (MPAL) and competing definitions has resulted in diffuse literature reporting small case series and precluded a consensus treatment approach. We therefore conducted a meta-analysis and systematic review to investigate the association of treatment type (acute lymphoblastic leukemia [ALL], acute myeloid leukemia [AML], or “hybrid” regimens) and disease response. We searched seven databases from inception through 2017 without age or language restriction. Included studies reported sufficient treatment detail for de novo MPAL classified according to the European Group for Immunological Characterization of Acute Leukemias (EGIL) or World Health Organization (WHO2008). Meta-analyses were performed for the endpoints of complete remission (CR) and overall survival (OS). A compiled case series for multivariable analysis was established from patients with data from time of diagnosis.We identified 92 reports meeting criteria, resulting in 1,265 unique patients included in at least one quantitative analysis. Using either definition of MPAL, meta-analyses revealed that AML Induction was less likely to achieve a CR as compared to ALL regimens, (WHO2008 Odds Ratio [OR] = 0.34, 95% Confidence interval [95%CI] 0.18-0.65; EGIL, OR=0.22, 95%CI 0.09-0.53). Multivariable analysis of the compiled case-series supported poorer efficacy for AML Induction (Table 1). Meta-analyses found better OS with ALL therapy (WHO2008 OR=0.48, 95%CI 026-0.89; EGIL, OR=0.45, 95%CI 0.22-0.93) but multivariable analysis of the compiled case series showed only adult age as predictive of lower survival (Table 1). MPAL definition did not impact trends within each endpoint. Examination of presenting features of MPAL revealed hyperleukocytosis and central nervous system involvement to be uncommon (<25%). For either classification system of MPAL, ALL-directed therapy is associated with higher initial remission rates and is at least equivalent to more intensive AML therapy for long-term survival. Prospective trials are urgently needed to establish a uniform approach to this heterogeneous disease. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Impact of Donor Type on Long-Term Outcomes of Hematopoietic Cell Transplantation for Adult Acute Lymphoblastic Leukemia during First Remission

Background: Standard therapy for adult patients with high-risk acute lymphoblastic leukemia (ALL) consists of hematopoietic cell transplantation (HCT) including autologous-HCT (AUTO) and allogeneic-HCT from a matched-sibling donor (MSD) or matched unrelated donor (MUD). When a conventional donor is not available, HCT from a partially-mismatched unrelated donor (MMUD), cord blood transplantation (CBT) or a familial haploidentical donor (HID) is considered.Aim: Although HCT outcomes of those alternative strategies are advancing with optimization of pre-conditioning regimens with immunosuppressive agents, there are still subjects to debate. We tried to analyze the long-term HCT outcomes according to the donor types including MMUD, double CBT (DCBT) and AUTO as an alternative choice compared to the conventional donors.Methods: We enrolled 661 adult ALL patients who underwent transplantation from 1995 to 2015 in their first remission (CR1). Patients with acute undifferentiated leukemia (AUL, n=5) and mixed phenotype acute leukemia (MPAL, n=52) in the same department were also enrolled and median age was 33 years old (range, 15-65). Before 2010, our treatment strategy for ALL patients in CR1 was to offer allogeneic or autologous HCT according to the donor availability and the presence of high-risk features. After 2010, DCBT was mainly used for patients who were not available with conventional donors. For myeloablative regimen, we administered cyclophosphamide (120 mg/kg) combined with TBI (1320 cGy), and reduced intensity regimen was applied for elderly or patients with comorbid conditions which consisted of fludarabine (150 mg/m2 in total) and melphalan (140 mg/m2 in total). Conditioning regimen for AUTO was TBI (1200 cGy), ARA-C (9g/m2 in total) and melphalan (100mg/m2 in total), and fludarabine (150mg/m2 in total) was used for DCBT instead of melphalan. Graft-versus-host disease (GVHD) prophylaxis was attempted by administering calcineurin inhibitors (cyclosporine for MSD, tacrolimus for others) plus methotrexate or mycophnolate mofetil (for DCBT). Antithymocyte globulin (ATG) was administered to the patients who received grafts from MMUD.Results: Engraftment was successful in all donor types, but neutrophil and platelet recovery was significantly delayed only after DCBT (median recovery for neutrophil and platelet was 25 and 33.5 days respectively). After median follow-up of 80.4 months (range, 6.5-259.1), 7-year OS for the entire 661 patients was 57.0%. In detail, 7-year OS for MSD, MUD, MMUD, DCBT, and AUTO was 56.9%, 56.8%, 62.6%, 65.1% and 48.6% (p=0.423). MSD, MUD and MMUD showed similar relapse rate (27.5%) and non-relapse mortality (NRM) rate (20.6%), but DCBT showed significantly higher NRM rate (29.6%) and AUTO showed significantly higher relapse rate (41.6%). In contrast, DCBT showed lower relapse rate (7.2%) and AUTO showed lower NRM rate (9.7%). Interestingly, 7-year GVHD and relapse-free survival (GRFS) for MSD, MUD, MMUD, and DCBT was 34.1%, 15.0%, 40.9%, and 50.3%, respectively, which was related with higher incidence of severe chronic GVHD in MUD (27.6%) and MSD (14.1%) compared to DCBT (4.2%, p < 0.001). In high-risk subgroup (n=517) including 233 Philadelphia chromosome (Ph)-positive ALL, 7-year OS for MSD, MUD, MMUD, DCBT, and AUTO was 54.9%, 58.1%, 57.8%, 60.7%, and 33.3%, respectively. But the 7-year GRFS for MSD, MUD, MMUD, and DCBT was 30.7%, 14.5%, 35.3%, and 47.7%, respectively, which revealed lower relapse rate (8.7%) and low severe chronic GVHD (2.6%) of DCBT. Multivariate analysis showed that old age and AUTO was related with poor OS in high-risk ALL patients group, and old age and poor-risk karyotype and MUD transplant without ATG were related with poor GRFS.Conclusion: Our data showed similar transplant outcomes of alternative donors such as DCBT and ATG-applied MMUD compared to conventional donor transplants in ALL patients in CR1. In addition, GRFS was rather superior in patients treated with DCBT. Our long-term transplantation outcome results revealed that DCBT might be a good alternative choice for patients who are not available with conventional allogeneic donors, and AUTO may be considered for selected standard-risk patients with low NRM rate without a risk of GVHD. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Semi-Quantitative Analysis of CD19 and CD22 Expression in B-Lymphoblastic Leukemia and Implications for Targerted Immunotherapy

IntroductionAcute lymphoblastic leukemia (ALL) is the most common childhood cancer, accounting for 30% of pediatric cancers and 75% of pediatric leukemias. While overall survival in children with ALL exceeds 85%, survival rates for children who relapse are low. In recent years, targeted immunotherapy has shown significant responses in refractory ALL. CAR-modified T-cells and Blinatumomab are two immunotherapy treatments targeting the CD19 antigen that have shown to be effective in treating patients with relapse refractory ALL. Moxetumomab and Inotuzumab are agents that target CD22 on lymphoblasts. However, some patients do not respond and others relapse with antigen-negative disease after targeted therapy. Expression levels of CD19 and CD22 may predict response to therapy. Hence, it is important to quantify expression levels of CD19 and CD22 in B lymphoblastic leukemias and correlate with response to immunotherapy.MethodsThe flow cytometry archives at the Children's Hospital of Philadelphia from 2002 - 2017 were reviewed. The majority of cases reviewed were de-novo ALL and prior to any targeted immunotherapy. The flow cytometry panels included CD45-PC7, CD19-PE, CD10-PC5, CD9-FITC, CD20-ECD, CD38-FITC, CD34-ECD, and CD22-PE antibodies (all from BD Biosciences). During this time period, the flow cytometry panels were similar, run on similar instruments and analyzed the same way. To quantify the expression of CD19, a 4-point logarithmic scale was used. The scale ranged from 0-3 with 0 representing no expression, 1 representing dim expression, 2 representing normal expression in circulating B cells, and 3 representing bright expression of the surface antigen. CD19 vs CD10 dot plots of CD45dim gated pure populations of blasts were used to accurately quantify the number of CD19-negative events. Other antigens expressed on blasts such as CD34, CD24, CD9, CD38, and HLA-Dr were used if the blasts were CD10-negative. Surface CD22 expression was determined using a 3 point scale since CD22 expression is universally weak compared to CD19. Proportion of CD22 negative cells could not be determined as there was no other blast marker along with CD22 in our panel. Cytogenetics, FISH, and whole genome SNP array (2008-2017) data were obtained on all cases. All cases showed strong expression of CD79a, terminal deoxy transferase (TdT) and lacked strong myeloperoxidase (MPO) or CD3 expression ruling out AML or a mixed phenotype acute leukemia per the current WHO criteria. In parallel, RNA expression data from the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) study for Pediatric ALL was analyzed to identify cases with dim CD19 and CD22 expression.Results348 cases of B -ALL were identified, of which 304 were de novo and 45 were relapsed cases. 18% of all B-ALL specimens showed significant (>1%) populations of CD19-negative blasts. 7% of B-ALL specimens were negative for surface CD22. 5% of cases showed downregulation of both CD19 and CD22 antigens suggesting a correlation between various B cell antigens. Of the specimens that showed downregulation of CD19, 3% had the ETV6-RUNX1 translocation, 29% showed hyperdiploidy, and 19% showed rearrangement of the MLL gene. Of the specimens that showed downregulation of CD22, 17% showed the ETV6-RUNX1 translocation, 13% showed hyperdiploidy, and 13% showed rearrangement of the MLL gene. Cases with bright expression of CD19 or CD22 antigen were also determined. 12% of B-ALL showed overexpression of CD19 antigen when compared to normal mature B cells. 11% of B-ALL showed an overexpression of CD22 antigen when compared to normal mature B cells. Of the 157 cases analyzed from the TARGET study, 18% showed dim CD19 RNA expression and 11% showed dim CD22 RNA expression similar to the immunophenotypic findings.ConclusionWe have comprehensively analyzed CD19 and CD22 expression in a large number of B-ALL cases from a single institution. We conclude that a significant number of B-ALL cases have dim CD19 and CD22 that may correlate with response to immunotherapy. Many cases also showed significant populations of CD19-negative cells that may be responsible for antigen negative relapses. We also identified cases with bright CD19 and CD22 that may predict good response to immunotherapy. Future directions include correlation of antigen expression with response to immunotherapy. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Post-Transplant Maintenance Therapy with Azacitidine and Gemtuzumab Ozogamicin for High-Risk Hematologic Malignancies

BackgroundDisease recurrence is the principal cause of treatment failure after allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematologic malignancies. New strategies for maintaining remission are urgently needed. The pilot study suggested that post-transplant therapy with low dose Azacitidine (AZA), a DNA methyltransferase inhibitor, was safe and promising for patients with high-risk hematologic malignancies although the long-term outcome remains to be seen (Cancer. 2010; 116: 5420-31). Gemtuzumab ozogamicin (GO) is a calicheamicin-conjugated antibody to CD33 which exerts anti-leukemic effect in a Syk expression dependent manner and AZA restores Syk expression of leukemic blasts. We previously conducted the pilot study to evaluate the safety and efficacy of post-transplant maintenance therapy with AZA and GO (AZA-GO) (Br J Haematol. 2015; 169: 756-9). Herein, we analyzed the outcome of patients with high-risk hematologic malignancies who received AZA-GO as post-transplant maintenance therapy at our institute.MethodsTwenty-three adult patients with high-risk hematologic malignancies (21 acute myeloid leukemia, 1 myelodysplastic syndromes excess blast-2, and 1 mixed-phenotype acute leukemia) harboring CD33 positive leukemic blasts were enrolled. AZA-GO was started after sufficient hematological recovery following allo-HSCT. AZA at 30 mg/m2 was administered for 7 days, followed by GO at 3 mg/m2 on day 8. Next cycle was given upon hematological recovery. The maximum number of cycles was 4. To evaluate the impact of AZA-GO on survival, overall survival (OS), disease-free survival (DFS), relapse and non-relapse mortality rates were compared with 69 matched-control patients, who survived more than 30 days after transplant and did not receive any post-transplant maintenance treatment. The matched-control patients were randomly selected from the patient database at our institution, matched for diagnosis, refined disease risk index (R-DRI), and number of transplants.ResultsUsing R-DRI, patients were stratified into intermediate (n=4), high (n=14), and very high (n=5) risk groups. Median age was 54 years (range, 17 to 67). At transplant, 17 patients did not achieve complete remission. Eight patients harbored adverse cytogenetics and 4 patients received AZA-GO after second HSCT. Eight patients received allo-HSCT from HLA haploidentical donor and 11 patients received reduced-intensity conditioning. Patients received a total of 52 cycles of AZA-GO, starting at a median of 78 days from transplant (range, 24 to 251). The median cycle of treatment was 2. Reasons for stop receiving AZA-GO were relapse (n=6), infections (n=4), thrombocytopenia (n=3), deterioration of GVHD (n=1), elevated creatinine (n=1), and refusal (n=1). The median follow-up of survivors was 526 days (range, 141 to 1627) from allo-HSCT. Grade 4 neutropenia and thrombocytopenia were experienced by 22 of 23 and all patients. Febrile neutropenia occurred in 10 patients. During observation, 13 patients had died and the causes of death included relapse (n=10), infection (n=2) and thrombotic microangiopathy (n=1). One patient developed fatal pneumocystis pneumonia. Of 13 patients suffered from disease recurrence following AZA-GO treatment, 7 patients underwent allo-HSCT as a salvage therapy and none of them developed sinusoidal obstructive disease. During AZA-GO treatment, 3 patients developed grade III acute GVHD. Compared to matched case-control group, the patients who received AZA-GO maintenance showed higher OS (68.8% vs 47.9% at 1 year, p=0.13), DFS (57.0% vs 36.5% at 1 year, p=0.24), lower relapse (32.7% vs 41.3% at 1 1year, p=0.67) and non-relapse mortality rate (10.4% vs 22.2% at 1 year, p=0.16), although the differences were not statistically significant.ConclusionAZA-GO maintenance therapy was tolerable in early post-transplant settings and showed acceptable OS and DFS considering nearly three quarters of patients were not in remission at transplant. However, half of the patients developed disease recurrence and there were no significant differences between AZA-GO and control group on their survival and relapse rates. Our current post-transplant strategy requires longer follow-up and further modifications to maintain long-term remission. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Fusion gene map of acute leukemia revealed by transcriptome sequencing of a consecutive cohort of 1000 cases in a single center

Fusion genes (FGs) are important genetic abnormalities in acute leukemias, but their variety and occurrence in acute leukemias remain to be systematically described. Whole transcriptome sequencing (WTS) provides a powerful tool for analyzing FGs. Here we report the FG map revealed by WTS in a consecutive cohort of 1000 acute leukemia cases in a single center, including 539 acute myeloid leukemia (AML), 437 acute lymphoblastic leukemia (ALL), and 24 mixed-phenotype acute leukemia (MPAL) patients. Bioinformatic analysis identified 792 high-confidence in-frame fusion events (296 distinct fusions) which were classified into four tiers. Tier A (pathogenic), B (likely pathogenic), and C (uncertain significance) FGs were identified in 61.8% cases of the total cohort (59.7% in AML, 64.5% in ALL, and 63.6% in MPAL). FGs involving protein kinase, transcription factor, and epigenetic genes were detected in 10.7%, 48.5%, and 15.1% cases, respectively. A considerable amount of novel FGs (82 in AML, 88 in B-ALL, 13 in T-ALL, and 9 in MPAL) was identified. This comprehensively described real map of FGs in acute leukemia revealed multiple FGs with clinical relevance that have not been previously recognized. WTS is a valuable tool and should be widely used in the routine diagnostic workup of acute leukemia.

Improving pneumococcal vaccination rates in pediatric acute lymphoblastic leukemia/lymphoblastic lymphoma.

e18666 Background: Pediatric Acute Lymphoblastic Leukemia/ Lymphoblastic Lymphoma (ALL/LLy) is the most common pediatric cancer. Invasive pneumococcal disease (IPD) is prevalent in this population and the Centers for Disease Control and Prevention recommends pneumococcal vaccination to decrease morbidity and mortality. Despite these recommendations, vaccination rates remain low and the incidence of IPD among children with hematologic malignancy is significantly higher compared to the average pediatric population. An interventional study was designed to improve the vaccination rate and reduce the incidence of IPD in our institution. Methods: A plan-do-study-act (PDSA) model of quality improvement (QI) was used. Chart review at our institute was done for the 6-month period of January 2020 - June 2020 and baseline rates for pneumococcal polysaccharide (PPSV23) vaccination were calculated. Patients were included if they were ≥ 2 years old, diagnosed with ALL/LLy, and undergoing maintenance. A multidisciplinary team performed the root cause analysis. Immunization records were obtained and reviewed and targeted interventions were implemented. The interventions used are outlined in Table. The percentage of pediatric ALL/LLy patients per month in maintenance who received age-appropriate pneumococcal vaccinations was monitored before and after the interventions. Results: Analysis of the 6-month retrospective cohort (n=36) showed a baseline vaccination rate of 5.5%. During the subsequent 6-month phase with interventions, 40 patients were prospectively enrolled. Demographics showed a mean age of 10.2 years (range, 2-21) and a predominantly male (66.7%) cohort. B-cell ALL/LLy comprised the majority (78.9%); the rest included T-cell ALL/LLy and mixed phenotype acute leukemia. As seen in Table, the percentage receiving at least 1 pneumococcal vaccine increased from 5.5% to 84.8% over the first 3 months, this plateaued around 81%. Completion of the series mirrored this and increased to 74.2%. Pre-visit planning and cues proved to be the most helpful interventions. Conclusions: Use of a PDSA model successfully improved pneumococcal vaccination rates in the pediatric ALL/LLy population. We suggest these results can be achieved with planning and implementation of the outlined interventions. [Table: see text]