Abstract: The impact of pharmacologic prophylaxis for venous thromboembolism in patients undergoing neurosurgical intervention remains uncertain. We reviewed the efficacy and safety of pharmacologic compared with nonpharmacologic thromboprophylaxis in neurosurgical patients. Three databases were searched through April 2018, including those for randomized controlled trials (RCTs) and for nonrandomized controlled studies (NRSs). Independent reviewers assessed the certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Seven RCTs and 3 NRSs proved eligible. No studies reported on symptomatic proximal and distal deep vein thrombosis (DVT). Two RCTs reported on screening-detected proximal and distal DVTs. We used the findings of these 2 RCTs as the closest surrogate outcomes to inform the proximal and distal DVT outcomes. These 2 RCTs suggest that pharmacologic thromboprophylaxis may decrease the risk of developing asymptomatic proximal DVT (relative risk [RR], 0.50; 95% confidence interval [CI] , 0.30-0.84; low certainty). Findings were uncertain for mortality (RR, 1.27; 95% CI, 0.57-2.86; low certainty), symptomatic pulmonary embolism (PE) (RR, 0.84; 95% CI, 0.03-27.42; very low certainty), asymptomatic distal DVT (RR, 0.54; 95% CI, 0.27-1.08; very low certainty), and reoperation (RR, 0.43; 95% CI, 0.06-2.84; very low certainty) outcomes. NRSs also reported uncertain findings for whether pharmacologic prophylaxis affects mortality (RR, 0.72; 95% CI, 0.46-1.13; low certainty) and PE (RR, 0.18; 95% CI, 0.01-3.76). For risk of bleeding, findings were uncertain in both RCTs (RR, 1.57; 95% CI, 0.70-3.50; low certainty) and NRSs (RR, 1.45; 95% CI, 0.30-7.12; very low certainty). In patients undergoing neurosurgical procedures, low certainty of evidence suggests that pharmacologic thromboprophylaxis confers benefit for preventing asymptomatic (screening-detected) proximal DVT with very low certainty regarding its impact on patient-important outcomes.

Abstract: Recurrent somatic loss-of-function mutations in ASXL1 (Addition of sex combs-like 1) are common genetic events in a spectrum of myeloid malignancies and these alterations demarcate patients with poor outcome. ASXL1 forms a chromatin regulatory complex with the ubiquitin hydrolase BAP1 (BRCA1 associated protein-1), a protein that has been found to be transcriptionally repressed in MDS patients. These data are consistent with BAP1 having tumor suppressive activity in MDS; however, the mechanism by which disruption of the ASXL1-BAP1 axis leads to transformation is not well understood. We conditionally deleted Bap1 in the murine hematopoietic system utilizing Mx1-Cre (hereafter referred to as Bap1 KO). One hundred percent of mice with confirmed Bap1 deletion developed a fully penetrant MDS-like disease characterized by leukocytosis, anemia, and splenomegaly. Bap1 KO mice have an expansion of the granulocyte macrophage progenitor compartment (GMP; Lin- c-Kit+ Sca1- CD34+ Fcϒ+). Given the role of BAP1 in epigenetic regulation, we investigated the effect of Bap1 loss on chromatin state and transcriptional output. We first assessed epigenetic changes in Bap1 KO mice by performing histone mass spectometry in control and Bap1 KO hematopoietic stem and progenitor cells (HSPCs, c-Kit+ enriched). Bap1 loss increased H3K27me2/3 at the expense of H3K27me0/1. We confirmed that H3K27me3 was increased in Bap1 KO bone marrow cells by completing H3K27me3 ChIP-Sequencing in HSPCs. Enumeration of H3K27me3 peaks in Bap1 KO versus control cells indicated an increase in H3K27me3 domains (Figure A). We next overlaid RNA-Sequencing from GMP sorted Bap1 KO bone marrow cells with genes marked by H3K27me3, as indicated by ChIP-Sequencing. We found that Bap1 loss resulted in a global decrease in gene expression (68% downregulated, 657/968 genes, p-adj 〈 0.01) and that increased H3K27me3 identified genes with reduced expression after Bap1 loss (NES=-1.39, FDR 〈 0.001) (Figure A). Gene set enrichment analyses (GSEA) revealed that genes that were altered following depletion of Bap1 corresponded to differentiation, hematopoietic lineage specification, and proliferation pathways. Combined, these data suggest that Bap1 depletion results in increased H3K27me3 and represses gene targets implicated in normal and malignant hematopoiesis. Given the alterations in H3K27me3 in Bap1 KO mice, we investigated whether Bap1- deficient transformation could be rescued by abrogation of PRC2-mediated gene repression. We developed a genetic model with compound deletion of Bap1 and Ezh2, the catalytic component of the PRC2 complex. Co-deletion of Bap1 and Ezh2 resulted in a phenotypic rescue of Bap1 KO associated splenomegaly (spleen weights, Bap1 KO avg. 541.6 mg, Bap1/Ezh2 KO avg. 157.0 mg, p 〈 0.005) (Figure B), leukocytosis (white blood cells counts, Bap1 KO avg. 51 K/uL, Bap1/Ezh2 KO avg. 8 K/uL, p 〈 0.005), anemia (hematocrit, Bap1 KO avg. 28.2%, Bap1/Ezh2 KO avg. 46.0%, p 〈 0.005). Importantly, the increased H3K27me3 levels in Bap1 KO mice were reduced in Bap1/Ezh2 KO mice (Figure B), suggesting that loss of Bap1 leads to Ezh2-dependent malignant transformation. EZH2 small molecule inhibitors have proven effective in EZH2-dependent models of B cell lymphoma. To determine if Ezh2 inhibition was efficacious in the setting of Bap1 loss, we treated a cohort of Bap1 KO mice with either vehicle (NaCMC) or 500 mg/kg EPZ011989, an EZH2 inhibitor with in vivo activity. Treatment of Bap1 KO mice for 16 days resulted in significant reduction of splenomegaly (spleen weights, vehicle avg. 522.0, EPZ011989 treated avg. 216.2, p 〈 0.005) (Figure C) and anemia (white blood cell counts, vehicle avg. 61.7 K/uL, EPZ011989 treated avg. 14.5 K/uL, p 〈 0.005), consistent with the phenotype of our genetic Bap1/Ezh2 compound deletion model. These data suggest that decreased BAP1 expression could serve as a biomarker for sensitivity to EZH2 inhibition. Figure 1. Figure 1. Disclosures Knutson: Epizyme, Inc: Employment. Campbell:Epizyme, Inc: Employment. Keilhack:Epizyme: Employment, Equity Ownership. Melnick:Janssen: Other: Research; ROCHE: Other: Research; Genentech: Speakers Bureau; Celgene: Consultancy; Eli Lilly: Consultancy; Epizyme: Consultancy. Armstrong:Epizyme, Inc: Consultancy. Levine:Foundation Medicine: Consultancy; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Loxo Oncology: Membership on an entity's Board of Directors or advisory committees.

Abstract: Background Stably acquired mutations in hematopoietic cells represent substrates of selection that may lead to clonal hematopoiesis (CH), a common state in cancer patients that is associated with a heightened risk of leukemia development. Owing to technical and sample size limitations most CH studies have characterized gene mutations or mosaic chromosomal alterations (mCAs) individually. The relationship between acquired gene mutations and mCAs in CH and their joint roles in leukemia development have not been systematically investigated. Methods We developed a method to reliably map mCAs at low cell fractions from deep targeted sequencing data. We applied this method in a cohort of 32,442 solid tumor patients who have undergone prospective clinical sequencing (MSK-IMPACT). We characterized gene mutations in our patient cohort using an established variant calling procedure from our previous studies. Results We jointly characterized 383 mCA events (median aberrant cell fraction 32%, range 10%-90%) and 14,789 mutations across 457 genes. mCA was significantly associated with age (OR=1.8, P & lt;0.001), male gender (OR=1.4, P=0.012), white race (OR=1.5, P=0.033) and prior receipt of external beam radiation therapy (OR=1.7, P=0.022). 217 (63%) mCAs co-occurred with at least one gene mutation, while 129 (37%) did not (OR=3.9, P & lt;0.001). mCA was especially enriched in CH cases with high mutation number and VAF, detectable in 5.8% of subjects with ≥3 gene mutations and 4.8% of those with mutations at & gt;20% VAF, compared to 1% of the general cohort. We identify co-mutational patterns characteristic of diverse mechanisms of clonal selection. We observe that mutations in DNMT3A, TET2, JAK2, MPL, EZH2, TP53 and ATM form recurrent double-hits with deletions or CNLOHs, resulting in either oncogene mutant dosage adjustment or inactivation of tumor suppressors. Notably, certain mCA events were highly directed events acting on previously acquired gene mutations in the corresponding loci. Of six events of 7qCNLOH, all six co-localized with an EZH2 (7q36.1) mutation (q & lt;0.001). Of 12 cases with 9pCNLOH, 11 (92%, q & lt;0.001) co-localized with a JAK2 V617F mutation. 4 out of 9 (44%, q & lt;0.001) 1pCNLOH events co-localized with a MPL (1p34.2) mutation. In addition, we observe recurrent composite genotypes (4q24-/SRSF2, 7qCNLOH/ASXL1, 20q-/U2AF1) indicative of co-operating or epistatic interactions as well as loss of gatekeeper function (i.e. TP53) presenting with multiple chromosomal aneuploidies (5-, 7-, 3+). In total, these recurrent composite genotypes resembling known genetic interactions in leukemia genomes underlie 23% of all detected autosomal mCAs. During patient follow-up, the 3-year cumulative incidence of leukemias was significantly higher in patients with composite CH genotypes (14.6%, CI: 7-22%) as compared to patients with either mCA, gene mutation alone or no CH, of which all had a 3-year cumulative incidence of & lt;1% (Figure 1). We performed a multivariable cause-specific Cox regression model and showed that mCA was independently predictive of subsequent leukemia diagnosis (HR=14, 95% CI: 6-33, P=1.2e-09) after adjusting for number of gene mutations and VAF in putative drivers. Conclusions Our joint characterization of gene mutations and mCAs in a large prospective sequencing cohort reveals a previously unrecognized layer of complexity in the evolutionary dynamics of clonal hematopoiesis that converges towards characteristic genotypes associated with distinct leukemia subtypes. This puts mCAs in the context of the continuous evolutionary process of oncogenesis that can often span years and sheds new lights on its patterns of acquisition and progression. We demonstrate that the integration of chromosomal aberrations provides additional resolution to risk stratification as well as interpretation of clinical phenotypes and that mCAs should be screened in conjunction with gene mutations to improve existing CH surveillance programs in cancer patients. Disclosures Bolton: GRAIL: Research Funding. Medina:Isabl: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Mantha:MJH Associates: Honoraria; Physicians Education Resource: Honoraria. Solit:Pfizer: Honoraria; Loxo Oncology: Honoraria; Lilly Oncology: Honoraria; Illumina: Honoraria; Vivideon Therapeutics: Honoraria. Diaz:Neophore: Consultancy, Current equity holder in private company; Merck: Consultancy; Johns Hopkins University: Patents & Royalties; Jounce Therapeutics: Current equity holder in private company; Thrive Earlier Detection: Current equity holder in private company; Personal Genome Diagnostics: Consultancy, Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Berger:Illumina: Research Funding; Roche: Consultancy; Grail: Research Funding. Levine:Lilly: Consultancy, Honoraria; Janssen: Consultancy; Roche: Consultancy, Honoraria, Research Funding; Loxo: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Imago: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; C4 Therapeutics: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Isoplexis: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Research Funding; Prelude Therapeutics: Research Funding; Gilead: Honoraria; Amgen: Honoraria; Morphosys: Consultancy; Novartis: Consultancy; Astellas: Consultancy; Qiagen: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Zehir:Memorial Sloan Kettering Cancer Center: Current Employment; Illumina: Honoraria. Papaemmanuil:Celgene: Consultancy, Honoraria, Research Funding; Prime Oncology: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Illumina: Consultancy, Honoraria; Kyowa Hakko Kirin: Consultancy, Honoraria; Isabl: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; MSKCC: Patents & Royalties.

Abstract: The occurrence of clonal T cells in multiple myeloma (MM), as defined by the presence of rearrangements in the T-cell receptor (TCR)–β chains detected on Southern blotting, is associated with an improved prognosis. Recently, with the use of specific anti–TCR-variable-β (anti–TCRVβ) antibodies, the presence in MM patients of expanded populations of T cells expressing particular Vβ regions was reported. The majority of these T-cell expansions have the phenotype of cytotoxic T cells (CD8+CD57+ and perforin positive). Since Vβ expansions can result from either a true clonal population or a polyclonal response, the clonality of CD8+TCRVβ+ T cells was tested by TCRVβ complementarity-determining region 3 length analysis and DNA sequencing of the variable region of the TCR. In this report, the CD57+ and CD57− subpopulations within expanded TCRVβ+CD8+ cell populations are compared, and it is demonstrated that the CD57+ subpopulations are generally monoclonal or biclonal, whereas the corresponding CD57− cells are frequently polyclonal. The oligoclonality of CD57+ expanded CD8+ T cells but not their CD57− counterparts was also observed in age-matched controls, in which the T-cell expansions were mainly CD8−. The CD8+CD57+ clonal T cells had a low rate of turnover and expressed relatively lower levels of the apoptotic marker CD95 than their CD57− counterparts. Taken together, these findings demonstrate that MM is associated with CD57+CD8+ T-cell clones, raising the possibility that the expansion and accumulation of activated clonal CD8+ T cells in MM may be the result of persistent stimulation by tumor-associated antigens, combined with a reduced cellular death rate secondary to reduced expression of the apoptosis-related molecule CD95.

Abstract: Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), occurs in ∼1 to 2 individuals per 1000 each year, corresponding to ∼300 000 to 600 000 events in the United States annually. Objective: These evidence-based guidelines from the American Society of Hematology (ASH) intend to support patients, clinicians, and others in decisions about treatment of VTE. Methods: ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and adult patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment. Results: The panel agreed on 28 recommendations for the initial management of VTE, primary treatment, secondary prevention, and treatment of recurrent VTE events. Conclusions: Strong recommendations include the use of thrombolytic therapy for patients with PE and hemodynamic compromise, use of an international normalized ratio (INR) range of 2.0 to 3.0 over a lower INR range for patients with VTE who use a vitamin K antagonist (VKA) for secondary prevention, and use of indefinite anticoagulation for patients with recurrent unprovoked VTE. Conditional recommendations include the preference for home treatment over hospital-based treatment for uncomplicated DVT and PE at low risk for complications and a preference for direct oral anticoagulants over VKA for primary treatment of VTE.

Abstract: Acute Myeloid Leukemia (AML) is a biologically diverse disease with subtypes that can be identified through integrated cytogenetic, mutational, and epigenetic characterization. Mutations in epigenetic regulators such as IDH1, IDH2, and DNMT3A are among the most common gene mutations found in AML (Cancer Genome Atlas Research et al. 2013; Papaemmanuil et al. 2016). Targeted inhibitors of IDH1 and IDH2 have recently been approved by the FDA for the treatment of AML (DiNardo et al. 2018; Stein et al. 2015). In addition, IDH/DNMT3A dual mutant AMLs exhibit a distinct epigenetic signature and are characterized by increased in vitro sensitivity to MEK inhibition (Glass et al. 2017). Here we explore the clinical course of AML patients with IDH1, IDH2, and DNMT3A mutations treated at Memorial Sloan Kettering Cancer Center (MSKCC) between 2012 and 2018. Treatment regimens included standard chemotherapy, as well as investigational therapies such as IDH1, IDH2, and pan-IDH inhibitors (Table 1). Using overall survival as our endpoint, we assessed contributions of WHO risk, age, treatment regimen, and gene mutations using multivariate Cox Proportional Hazards modeling. Among intermediate risk patients, we found that the presence of concurrent IDH1/DNMT3A mutations (n=16) conferred the highest mortality risk compared to DNMT3A mutation alone (HR=2.31; p=0.046). In contrast, IDH2/DNMT3A mutated AML conferred similar mortality risk compared to DNMT3A mutation alone (HR=1.07; p=0.85). When compared to intermediate risk IDH1/DNMT3A mutated AML, intermediate risk IDH2/DNMT3A mutated AML had a lower risk of mortality (HR=0.345; p=0.038), (Fig. 1). This adverse risk of IDH1/DNMT3A mutations persists after adjusting for IDH inhibitor therapy (HR=2.42; p=0.05). In multivariate analysis, IDH1 mutation and use of low intensity therapeutic regimens conferred an increased risk of mortality after adjusting for WHO risk (HR=2.25; p=0.016 and HR=1.71; p=0.036, respectively). Induction chemotherapy provided an overall survival benefit after adjusting for WHO Risk and the presence of IDH1, IDH2, DNMT3A, or dual IDH/DNMT3A mutations (HR=0.50; p 〈 0.01). The increased risk associated with IDH1/DNMT3A dual mutations approached statistical significance after adjustment for WHO Risk and therapeutic modality (HR=2.00; p=0.08). Overall, our findings suggest that AML with dual IDH1/DNMT3A mutations constitutes a higher risk disease entity. Further study of targeted treatment modalities such as dual IDH1/MEK inhibition or combined chemotherapy/IDH1 inhibition may be helpful in the treatment of these higher risk AML patients. Disclosures Levine: Isoplexis: Equity Ownership; Qiagen: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Imago: Equity Ownership; Gilead: Honoraria; Janssen: Consultancy, Honoraria; C4 Therapeutics: Equity Ownership; Novartis: Consultancy; Epizyme: Patents & Royalties; Loxo: Consultancy, Equity Ownership; Prelude: Research Funding; Roche: Consultancy, Research Funding; Celgene: Consultancy, Research Funding. Tallman:AbbVie: Research Funding; Cellerant: Research Funding; Orsenix: Other: Advisory board; BioSight: Other: Advisory board; AROG: Research Funding; Daiichi-Sankyo: Other: Advisory board; ADC Therapeutics: Research Funding. Goldberg:Abbvie: Research Funding; AROG: Research Funding; Pfizer: Research Funding; Celgene: Research Funding. Stein:Pfizer: Consultancy; Celgene: Consultancy; Bayer: Consultancy; Daiichi Sankyo: Consultancy; Agios: Consultancy; Novartis: Consultancy.