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Abstract Background: MM is an incurable disease with an anticipated overall survival ranging from months to decades. Novel therapies like bortezomib have activity in both the relapsed/refractory and up front settings. There are sparse data on whether novel therapies may overcome high risk features. Methods: Patients with newly diagnosed high-risk myeloma (beta-2 microglobulin [B2M] >= 5.5., plasma cell labeling index [PCLI] >= 1, or deletion 13q) were eligible. Patients were treated with bortezomib 1.3 mg/m2 day 1, 4, 8, and 11 every 21 days for 8 cycles as induction. After induction, patients received bortezomib 1.3 mg/m2 every other week indefinitely. Patients relapsing on maintenance schedule resumed full induction schedule. Responses were defined by the EBMT criteria. The primary end-point was the response rate (90% power to detect a response rate of >=50% ). Results: Between March 15, 2004 and March 10, 2005, 44 patients enrolled. Among the 43 eligible patients, median age was 63; 51% were male. All had high risk disease: deletion 13q (6/41); PCLI >=1% (17/33); t(4:14) (4/27) and B2M >= 5.5 (34/43). Response data are available for 37 of the 43 eligible patients. The overall response rate was 49% (95% CI: 0.32, 0.66) (0 patients with CR, 1 VGPR, 15 PR, 2 MR, and 11 inevaluable). The response rate allowing for use of serum monoclonal protein levels when a measurable urine monoclonal protein was unavailable at follow-up was 59.5% (1 patient with CR, 1 VGPR, 18 PR, 2 MR, and 6 inevaluable). The median progression free survival is 9.4 months. Thirty-three percent of patients completed the 8 cycles of planned induction therapy and moved to maintenance. Reasons for discontinuing therapy have included progression or death (n=18), adverse events (n=6), and other (n=14). Only 12% of patients remain on active therapy: 0% of deletion 13q patients; 25% of t(4:14) and 12% each of high B2M and high PCLI patients. Of the 14 patients who entered the maintenance phase of treatment, 3 have progressed. Of these 3, 2 took re-induction, and neither responded. Median time to progression for those entering maintenance was12.4 months from the time of starting maintenance. The most common adverse events of grade 3 or higher included neutropenia (33%), diarrhea (31%), hyponatremia (21%), anemia (19%), thrombocytopenia (16%), fatigue (14%). Grade 1–2 sensory peripheral neuropathy occurred in 53% of patients, with only 2% having grade 3 sensory neuropathy. One patient had grade 3 peripheral neuropathy. One patient died after receiving 2 doses of protocol treatment due to heart block and asystole. Updated results on the full study population will be presented at the meeting. Conclusions: In high risk patients, upfront bortezomib appears to result in comparable response rates to those reported for unselected cohorts of newly diagnosed myeloma patients. Continued follow-up of these patients will provide information about whether this will translate into better overall outcomes. Figure Figure

Abstract Background: Induction therapy with daunorubicin (Dauno) & cytarabine (Ara-C) [DA] has been the standard of care for eligible older adults (age ≥ 60 years) with newly diagnosed acute myeloid leukemia (AML) for over 2 decades. Single agent Clofarabine (CLO) induction & consolidation (Consol.) therapy has demonstrated important clinical activity in this age group in large phase II studies. Lower induction mortality (IM) & similar reported complete remission rate (CR) & overall survival (OS), as well as notable activity in those with higher risk disease features [including unfavorable cytogenetics, therapy-related AML (t-AML) & prior antecedent hematologic disorder (AHD)] raises the possibility that a non-Ara-C-based regimen could achieve similar or superior OS with lower toxicity. Methods: We performed a randomized United States Intergroup Phase III trial of single agent CLO [30mg/m2 x 5 days induction; 20 mg/m2 re-induction (if indicated) & 2 cycles Consol.] vs. standard DA therapy [Dauno 60mg/m2 D1-3 & Ara-C 100mg/m2 D1-7 induction x 1-2 cycles; 2 cycles Consol. with Ara-C (1.5g/m2 Q12hrs D1-6 age 60-69; once daily if age 70+)] in patients (pts) age ≥ 60 yrs with newly diagnosed AML. Patients with serum creatinine >1.0 (or GFR <60 mL/min) and those with AML-M3 and ECOG performance status >3 (PS>2 if age 70+ yrs) were excluded. Randomization was stratified by age (60-69 vs. 70+), t-AML, & AHD. Pts with HLA-matched donor were eligible for allogeneic transplantation (AlloHCT) after induction, and those completing Consol. were eligible for randomization #2 (R#2) to maintenance decitabine [20mg/m2 x 3D, monthly x 1 year] versus observation. With a target accrual of 747, E2906 was powered to determine non-inferiority [and possible superiority] of CLO vs. standard DA, and primary endpoint was OS. A weighted statistical analysis was performed to account for confounding impact of R#2. AlloHCT patients were censored at transplant in this analysis. Responses & cytogenetics were confirmed centrally and OS & CR rates were monitored by an independent Data Safety Monitoring Committee (DSMC) at pre-specified time points. Results: As of Feb 23, 2015, 727 pts were randomized. Median age was 68 years (range 60-86); 57% were male, and 38% were age ≥70 yrs. Treatment arms are well balanced for all baselineclinical & AML characteristics, & 30% had unfavorable cytogenetics. Of 659 with complete treatment information reported, 30.4% on DA vs. 40.1% on CLO received 2 cycles of induction (p=0.006). Median follow-up of surviving patients is 7.6 months. Table 1. shows early treatment results (CR, toxicity) for the 686 pts randomized as of Dec 23, 2014 (2 months prior to study end, & excluding 90 with ongoing response evaluation). DA CLO p-value CR/CRi 43.8% 42.8% p=0.87 30-day mortality 8.5% 7.9% p=0.89 60-day mortality 14.9% 13.1% p=0.58 Gr 4-5 Non-Heme Tox.Induction 27% 19% p=0.02 Gr 4-5 Non-Heme Tox.Consol. 20% 7% p=0.001 374 pts have died (174, DA; 200, CLO) & significantly inferior OS was observed for CLO vs. DA [Hazard Ratio (HR) 1.41 (95% CI 1.12-1.78)] (Fig. 1). Planned subgroup analyses were performed (Table 2) demonstrating significant differences in OS after CLO for patients age 60-69 yrs, without AHD, & with intermediate risk cytogenetics; but not for those with Unfav. Cytogen. (Fig. 2) or t-AML. Based on the primary weighted analysis, DSMC recommended suspension of new accrual to E2906 on Feb 23, 2015 & all active patients on CLO were transitioned to DA Arm. Table 2.NHR CLO/Standard (95% CI)*Weighted OS7271.41 (1.12-1.78)Unweighted OS7271.23 (1.00-1.50)Age 60-694491.48 (1.10-1.99)Age 70+2781.34 (0.93-1.93)Intermed. Risk Cytogen.3781.77 (1.27-2.47)Unfav. Risk Cytogen.2160.96 (0.65-1.43)No AHD6041.46 (1.13-1.89)AHD1231.22 (0.74-2.00)De novo AML6271.52 (1.18-1.96)Therapy-related AML1000.94 (0.54-1.61) Conclusions: Despite similar CR & IM, OS after single agent CLO is inferior to standard DA therapy for pts age ≥60 years with newly diagnosed AML who are fit for intensive therapy, and DA remains the standard of care. However no difference in OS was observed after CLO in some pre-specified high risk AML subgroups. R#2 & AlloHCT arms continue in E2906 for pts already enrolled. Embedded prospective minimal residual disease study at CR is being performed to identify pts at higher risk after CLO & DA. Figure 1. Weighted Kaplan-Meier Curves for OS Figure 1. Weighted Kaplan-Meier Curves for OS Figure 2. Unfavorable Cytogenetics OS by Therapy Figure 2. Unfavorable Cytogenetics OS by Therapy Disclosures Off Label Use: Use of clofarabine in AML, and maintenance therapy with decitabine in AML. Claxton:Medimmune: Research Funding; BMS: Consultancy; Astellas: Research Funding; Cyclacel: Research Funding; Merck: Research Funding; Ambit: Research Funding. Levine:Loxo Oncology: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Foundation Medicine: Consultancy. Altman:Seattle Genetics: Consultancy; BMS: Consultancy; Spectrum: Consultancy; Astellas: Consultancy; Ariad: Consultancy; Novartis: Consultancy. Al-Kali:Novartis: Research Funding.

AbstractBackgroundThe extent to which obesity and genetics determine postoperative complications is incompletely understood.MethodsWe performed a retrospective study using two population cohorts with electronic health record (EHR) data. The first included 736,726 adults with body mass index (BMI) recorded between 1990 and 2017 at Vanderbilt University Medical Center. The second cohort consisted of 65,174 individuals from 12 institutions contributing EHR and genome‐wide genotyping data to the Electronic Medical Records and Genomics (eMERGE) Network. Pairwise logistic regression analyses were used to measure the association of BMI categories with postoperative complications derived from International Classification of Disease‐9 codes, including postoperative infection, incisional hernia, and intestinal obstruction. A genetic risk score was constructed from 97 obesity‐risk single‐nucleotide polymorphisms for a Mendelian randomization study to determine the association of genetic risk of obesity on postoperative complications. Logistic regression analyses were adjusted for sex, age, site, and race/principal components.ResultsIndividuals with overweight or obese BMI (≥25 kg/m2) had increased risk of incisional hernia (odds ratio [OR] 1.7–5.5, p < 3.1 × 10−20), and people with obesity (BMI ≥ 30 kg/m2) had increased risk of postoperative infection (OR 1.2–2.3, p < 2.5 × 10−5). In the eMERGE cohort, genetically predicted BMI was associated with incisional hernia (OR 2.1 [95% CI 1.8–2.5], p = 1.4 × 10−6) and postoperative infection (OR 1.6 [95% CI 1.4–1.9], p = 3.1 × 10−6). Association findings were similar after limitation of the cohorts to those who underwent abdominal procedures.ConclusionsClinical and Mendelian randomization studies suggest that obesity, as measured by BMI, is associated with the development of postoperative incisional hernia and infection.

Abstract We have previously shown that CD4+CD25+Foxp3+ regulatory T cells from NHL tumors suppress the function of infiltrating CD4+ T cells and cytolytic CD8+ T cells. Expression of Foxp3 has been demonstrated to be crucial to the development and function of CD4+CD25+ regulatory T cells. However, the mechanistic details that drive development of Foxp3 expression in T cells, in both the normal and malignant scenario, remains to be fully elucidated. Previous studies suggest that Foxp3 expression in CD4+CD25− T cells can be upregulated by tolerizing stimuli such as activation through TCR, corticosteroids, estrogen, and TGF-beta. Because lymphoma B cells have been shown to induce T-cell tolerance, we postulated that lymphoma B cells may play a role in the generation of regulatory T cells by inducing Foxp3 expression in CD4+CD25− T cells. FoxP3 expression was initially thought to be restricted to CD4+CD25+ regulatory T cell population. However, recent literature suggests that Foxp3 may also be expressed in CD4+CD25− T cells. Using biopsy specimens from patients with B-cell NHL, we found that a subset, 15%, of infiltrating CD4+CD25− T cells express Foxp3 and are capable of suppressing the proliferation and granule production of infiltrating cytotoxic CD8+ T cells. These initial studies suggest that CD4+CD25−Foxp3+ T cells have regulatory function. To explore the underlying mechanism by which Foxp3 expression is regulated, we determined the effect of costimulatory signals on Foxp3 expression in CD4+CD25−Foxp3− T cells. Activation with OKT3/anti-CD28 Ab as well as DC-mediated activation induced Foxp3 expression in a subset of CD4+CD25− T cells. We also found that the presence of lymphoma B cells during activation augmented the induction of Foxp3 expression in CD4+CD25− T cells and that NHL B cell-mediated Foxp3 expression was cell contact-dependent. To better understand the contribution of NHL B cells in Foxp3 expression, we explored the possibility that CD27-CD70 interaction may be involved in Foxp3 expression. Lymphoma B cells express CD70, but not B7-1 and B7-2, which have been shown to be important in protecting tumor cells from lysis and contributing to cancer pathogenesis. Ligation of CD27 by receptor cross-linking enhanced Foxp3 expression in infiltrating CD4+CD25− T cells in B-cell NHL. Taken together these studies reveal a novel role for NHL B cells in development of regulatory T cells. Our data show that lymphoma B cells induce expression of Foxp3 in infiltrating CD4+CD25− T cells and may result in development of T cells with regulatory function within the tumor microenvironment. Our results also suggest a potential role for CD27-CD70 interactions in this process. The ability of malignant B cells to drive development of regulatory T cells may be one mechanism by which lymphoma B cells protect themselves from anti-tumor immunity. (Supported in part by the Iowa/Mayo Lymphoma SPORE CA97274).

Abstract Background: Alzheimer’s disease (AD) is an epidemic with tremendous public health impacts because there are currently no disease-modifying therapeutics. Randomized controlled trials (RCTs) for prevention of AD dementia often use clinical endpoints that take years to manifest (e.g., cognition) or surrogate endpoints that are costly or invasive (e.g., magnetic resonance imaging [MRI]). Blood biomarkers represent a clinically applicable alternative surrogate endpoint for RCTs that would be both cost-effective and minimally invasive, but little is known about their value as surrogate endpoints for treatment responses in the prevention of AD dementia. Methods: The objective of this study is to investigate blood neuropathological, neurodegenerative, and neurotrophic biomarkers as surrogate endpoints for treatment responses to 3 interventions in older adults with amnestic mild cognitive impairment (aMCI, a prodromal stage of AD): aerobic exercise; cognitive training; and combined aerobic exercise and cognitive training (ACT). We chose these three sets of biomarkers for their unique mechanistic associations with AD pathology, neurodegeneration and neurogenesis. This study is built on the ACT Trial (1R01AG055469), a single-blinded, multi-site, 2×2 factorial Phase II RCT that examines the synergistic effects of a 6-month ACT intervention on cognition and MRI biomarkers (AD-signature cortical thickness and hippocampal volume) (n=128). In this ACT Trial Blood Biomarkers Study, we will enroll 120 ACT Trial aMCI participants and measure blood biomarkers at baseline, 3, 6, 12 and 18 months. The goals are to: (1) Determine the effect of interventions on blood biomarkers over 6 months; (2) Evaluate blood biomarkers as surrogate endpoints for predicting cognitive responses to interventions over 18 months; and (3; exploratory) Examine blood biomarkers as surrogate endpoints for predicting brain MRI biomarker responses to interventions over 18 months. Discussion: This study aims to identify new blood biomarkers that can track cognitive decline or AD-related brain atrophy among aMCI patients subjected to a regimen of aerobic exercise and cognitive training. Findings from this study will drive the further use of blood biomarkers in developing effective prevention and treatment strategies for AD dementia. Trial registration number: This study is an ancillary study of the ACT Trial which was registered with ClinicalTrials.gov, NCT03313895.

Abstract Abstract 2834 Background: Myelofibrosis (MF), Polycythemia Vera (PV) and Essential Thrombocythemia (ET) are 3 classic BCR ABL negative myeloproliferative neoplasms. MF is comprised of both primary myelofibrosis (PMF) and those with an antecedent PV or ET (Post PV and Post ET MF, respectively). The term secondary MF (SMF) when used sometimes includes those with histologic myelofibrosis without an MPN (i.e. secondary to another myeloid neoplasm or autoimmune conditions) as well as MPN associated MF (PMF and Post PV/ET MF). Limited published epidemiology data is available on these disorders. Literature reports MF incidence in the range of 0.4–1.4 per 100000. The objective of this study was to estimate prevalence and incidence using 2 real world US health insurance claims databases. Method: The US IMPACT® (∼30M enrollees/year) and US MARKETSCAN (∼40M enrollees/year) were used to retrospectively identify unique patients with PMF, SMF, PV and ET between 1/1/08 and 12/31/10. These databases can track patients longitudinally over multiple years, are linked at the patient level by a unique identifier that is consistent across services, health plans, and time and shown to be representative of the US population. ICD9 CM codes were used to identify PMF, SMF, PV and ET. Any MF was defined as having a diagnosis of either PMF or SMF. Incident cohort was constructed by selecting patients who had their first MF (or PV or ET) in 2010 confirmed by absence of diagnosis 3 years prior. Prevalent cohort was constructed by identifying patients who had MF (or PV or ET) in a given year. From the MF cohort, post ET and post PV patients were identified as those who had any ET or PV diagnosis in the calendar year prior. Primary MF was defined as PMF diagnosis alone without prior PV or ET. Annual prevalence rates were calculated for each calendar year from 2008–10. Continuous enrollment was required during the time period being evaluated. Estimates were adjusted for age distribution from census data. Result: About 8.5M enrollees from IMPACT and 17M from MARKETSCAN each year were included in prevalence estimates. Mean age of MF patients was 61 years in IMPACT and 67 in MARKETSCAN. Age adjusted incidence estimates of MF were about 2.4 per 100000 per year using IMPACT database, 1.7 per 100000 per year from MARKETSCAN. There is a slight increase in MF prevalence over time: from 4.9 to 5.6 in IMPACT, 3.6 to 4.2 in MARKETSCAN. Among MF patients, about 35–40% had PMF, 10% were post-PV patients, 15% were post-ET patients and the remaining had MF arising from myelodysplastic syndrome (∼30%), lupus (∼2%) and other heme and solid tumors (∼3%). Mean age of PV patients was 55 and 36% were female in IMPACT database. In MARKETSCAN, mean age was 58 with 35% being female. Using IMPACT, annual age adjusted prevalence for PV was 57 cases per 100000. Estimates using MARKETSCAN varied from 45 to 48 cases per 100000. Age adjusted incidence of PV ranges from 22 to 27 cases per 100000 patients per year. Mean age of ET patients was 53 and 57 years in each database. In both, 67% of patients were female. Using US IMPACT, annual age adjusted prevalence for ET was 54 to 56 cases per 100000. Estimates using MARKETSCAN varied from 39 to 44 cases per 100000. Age adjusted incidence of ET ranges from 22 to 31 cases per 100000 patients per year. Conclusion: This is the first study utilizing two large national US claims databases to estimate prevalence of MPN disorders. In the US, MF prevalence ranges from 3.6–5.7 per 100,000 patients. Incidence estimates of MF range from 1.7–2.4 per 100,000 patients. PV prevalence estimates range from 45–57 cases and ET prevalence ranges from 39–57 cases per 100,000 patients. PV tends to affect more males while ET affects more female. These data provide compelling evidence to suggest that prevalence and burden of MPN associated MF is higher than has been reported in the past. Additional research using other national databases and/or study designs is needed to substantiate these findings. Disclosures: Mesa: Incyte: Research Funding; Lilly: Research Funding; Sanofi: Research Funding; NS Pharma: Research Funding; YM Bioscience: Research Funding. Mehta:Sanofi: Employment. Wang:Sanofi: Employment, Equity Ownership. Iqbal:Sanofi: Employment, Equity Ownership. Neumann:Sanofi-aventis: Employment. Zhang:Sanofi-aventis: Employment.

Abstract Abstract 1731 Background: Symptom burden in primary, post-ET and post-PV myelofibrosis (MF) is frequently severe and correlates with a poor prognosis. However, symptom manifestations are heterogeneous with variable presence of specific symptoms, splenomegaly and cytopenias. We sought to identify the spectrum and features of MF symptomatic phenotypes by cluster analysis of prospectively gathered information on MF symptoms and disease features. Methods: Data was collected among an international cohort of subjects with MF. Data included demographics, disease features and completion of the Brief Fatigue Inventory (BFI) and Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (MPN-SAF TSS) (Blood 2011; 118:401–408). Surveyed symptoms addressed key disease features on a 0 (absent) to 10 (worst-imaginable) scale. Cluster development was based on consideration of r-squared in hierarchical clustering using Ward's linkage. Final cluster assignment was based on the nonhierarchical k-means method. Comparisons between symptom clusters were based on ANOVA and chi-squared tests. Results: Subject Demographic and Disease Characteristics: Data from 329 prospectively enrolled persons with MF was collected (Chinese 102, French 54, German 19, Italian 22, Dutch 45, English 51, Spanish 29, Swedish 7) including 223 PMF, 67 post-ET MF and 39 post-PV MF patients. Participants were of typical age (mean 59) and gender (47% F). Among all participants, four natural symptom clusters were identified (Figure 1). Among clusters, disease features including leukopenia, thrombocytopenia, and enlarged spleen varied significantly between clusters (P<0.05). Cluster 1: The “Fatigue Dominant with Few Lab Abnormalities” Profile (n=150 (46%; 69% PMF, 20% post-ET MF, 11% post-PV MF)). Cluster 1, the largest, is characterized by fatigue-dominant complaints in the setting of the lowest overall MPN-SAF TSS and highest proportion of males (59%). Individuals among this group have the lowest prevalence of laboratory abnormalities (65% total; anemia, 67%; thrombocytopenia, 20%) or clinical deficiencies including enlarged spleen (average 6.0 cm below costal margin), prior thrombosis (9%), prior hemorrhage (5%) or prior RBC-transfusions (20.4%). Interestingly, individuals in this group are most likely to have had prior splenectomy (5.8%). Cluster 2: The “Cognitive Complaints with Enlarged Spleen” Cluster (n=105 (32%; 65% PMF, 20% post-ET MF, 15% post-PV MF)). Cluster 2 is the 2nd largest cluster. Subjects have relatively few abnormal lab values (67% vs 65%–77%) but have high severity of fatigue, sexual difficulties, insomnia, inactivity and reduced QOL. These individuals have the largest spleen size (8.7cm below costal margin). Cluster 3: The “Nighttime and Cognitive Complaints” Group (n=53 (16%; 64% PMF, 25% post-ET MF, 11% post-PV MF)). Cluster 3 is the smallest cluster. Subjects have many cognitive and nighttime-related complaints including sexual difficulties, night sweats, insomnia, and concentration problems. Subjects with post-ET MF are predominant. This cluster also has the 2ndsmallest spleen size (7 cm) or history of prior thrombosis (9.6%), hemorrhage (7.8%) or requirement for transfusions (21.2%). Cluster 4: The “Severe Fatigue with Few End-organ Complaints” Cluster (n=21 (6%; 81% PMF, 14% post-ET MF, 5% post-PV MF)). Cluster 4 is the most symptomatic cohort with the highest proportion of subjects with PM. There is a lower frequency of end-organ complaints including abdominal pain, cough, and headaches. Symptoms including sexual difficulties, sad mood and insomnia are predominant. No subjects had prior splenectomy. Subjects also have the highest prevalence of prior thrombosis (29%), hemorrhage (14%), and transfusions (43%). Additionally, this cohort has the largest prevalence of lab abnormalities (77%) with thrombocytopenia (71%), leukopenia (41%) and anemia (41%). Conclusion: This analysis will allow us to examine a new framework for evaluating persons with MF using symptom profiles and is the 1st cluster evaluation of MF. Lab and physical findings contrast significantly between symptom clusters indicating these phenotypic symptoms likely result from etiological factors present in specific disease phenotypes. Future studies should evaluate whether there is a correlation between cluster profiles, prognosis and genotype. Disclosures: Kiladjian: Celgene: Research Funding; Novartis: Honoraria, Research Funding; Shire: Honoraria. Roy:Novartis, BMS: Speakers Bureau. Harrison:Novartis: Honoraria, Research Funding, Speakers Bureau; YM Bioscience: Consultancy, Honoraria; Sanofi Aventis: Honoraria; Shire: Honoraria, Research Funding. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees. Passamonti:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees. Mesa:Incyte: Research Funding; Lilly: Research Funding; Sanofi: Research Funding; NS Pharma: Research Funding; YM Bioscience: Research Funding.

Abstract Abstract 1739 BACKGROUND: Differences in symptom burden characteristics between persons of European and non-European descent with BCR-ABL negative MPNs including essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (MF) are not studied. We reported significant clinical and laboratory differences between these populations age at diagnosis and survivals (Blood 2011;119: 2469–73) which could affect symptom burden. Given China represents one-fifth of the global population, we aimed to evaluate MPN symptom burden among a cohort of Chinese MPN patients. METHODS: Data were collected from Chinese with MPNs and their physicians and compared these to a previously collected data from a cohort of subjects of predominately European descent (N=1488). Subject data included MPN-SAF (Blood 2011;118:401-8) and BFI score (Cancer 1999;85: 1186–96), demographics, and disease-related features. Statistical methods included ANOVA, chi-squared tests, and multiple regressions. RESULTS: Demographic and Disease Characteristics: 397 Chinese subjects were prospectively enrolled with a distribution of 172 (43%) ET, 102 (26%) PV, and 123 (31%) MF (of which 103 [84%] were PMF, 14 [11%] were post-ET MF, and 6 [5%] were post-PV MF). Median age (56.0 y) was younger in Chinese than in the European-descent cohort (63.0 y, p<0.001) despite relative gender equality. Laboratory abnormalities including anemia (76%, p<0.001) and disease features including bleeding (1%, p<0.001), were more common and present at a significantly higher incidences in the European-descent cohort than amongst Chinese. Chinese Symptom Severity and Incidence by MPN type: When comparing across MPN types, symptoms of worst fatigue, early satiety, abdominal discomfort, inactivity, concentration, depression, cough, night sweats, weight loss, and total MPN-SAF TSS score varied significantly (p<0.05) with MF being most severe for each symptom. Chinese versus European-descent Symptom Severity: After adjusting for age and MPN type, Chinese subjects had significantly higher mean severity for fever, sexual difficulties, and quality of life (Table 1). Symptoms of worst fatigue, early satiety, abdominal discomfort and overall BFI score had a significantly higher mean severity in the European descent cohort. Chinese versus European-descent Symptom Incidence: The European-descent cohort had significantly greater incidence of worst fatigue (90% vs 81%, p<0.001), abdominal pain (47% vs 35%, p<0.001), early satiety (65% vs 57%, p=0.005), concentration problems (64% vs 58%, p=0.04), numbness (63% vs 56%, p=0.02), insomnia (68% vs 58%, p<0.001), and depression (62% vs 56%, p=0.02) compared to Chinese subjects. In contrast, symptoms of dizziness (63% vs 57%, p=0.04), sexual difficulties (72% vs 61%, p<0.001), and fever (23% vs. 18%, p=0.03) were significantly worse amongst Chinese. CONCLUSION: We found a significant divergence in severity and incidence of key symptom burdens including QOL, fever, sexuality, dizziness, abdominal pain, early satiety, and fatigue between Chinese and persons of European descent with MPNs. Biological and cultural factors likely account for these differences and should be considered when interpreting outcomes of clinical trials of diverse populations. When the target of therapy is reversing symptoms, the best strategy may require revision for different populations. Disclosures: Mesa: Incyte: Research Funding; Lilly: Research Funding; Sanofi: Research Funding; NS Pharma: Research Funding; YM Bioscience: Research Funding.

Abstract Abstract 1554 T cells in the tumor microenvironment influence the biology of malignant cells in many hematologic malignancies, often through cytokine-mediated interactions. Recent studies involving healthy B cells and CD4+T cells identified an interplay between IL-6 and IL-21, whereby IL-6 increased IL-21 production by T cells, driving the differentiation and IL-6 secretion of nearby B cells. In addition to their known effects on healthy B cell function, IL-6 and IL-21 have also been implicated in the pathology of various lymphomas. In Waldenstrom's macroglobulinemia (WM), IL-6 is elevated in the bone marrow and is associated with increased IgM production. However, the function of IL-21 in the WM tumor microenvironment and its relationship to IL-6 is poorly understood. Our objective in this study was to characterize IL-21 production and function in WM and to examine the role of IL-6 and IL-21 in regulating interactions between malignant B cells and T cells in the tumor microenvironment. Immunohistochemistry revealed significant IL-21 staining in bone marrows of patients with WM (n=5), but the areas of infiltration by WM in the bone marrow sections appeared negative for IL-21 staining. To better understand the origin of IL-21 in in the tumor microenvironment, IL-21 expression was assessed by PCR in the CD19−CD138− fraction of cells remaining in patient bone marrow aspirates after positive selection for malignant B cells (n=5). IL-21 transcript was detected in 4/5 samples. CD19−CD138− cells activated with anti-CD3 and anti-CD28 antibodies expressed higher levels of IL-21 transcript and secreted significantly higher levels of IL-21 protein compared to unstimulated cells, suggesting that IL-21 in the WM bone marrow is derived from activated T cells. Intracellular expression of IL-21 protein was confirmed in CD4+ and CD8+ cells within the CD19−CD138− population using flow cytometry. Furthermore, dual staining of WM bone marrow sections with antibodies against IL-21 and CD3 or CD20 revealed co-staining of IL-21 with CD3+ T cells but not with CD20+ B cells. The response of WM B cells to T-cell derived IL-21 was then assessed in positively selected CD19+CD138+ WM B cells (n=5) and in the MWCL-1 cell line. Using flow cytometry, both the IL-21 receptor and the required common gamma chain subunit were detected on all patient samples as well as on MWCL-1 cells. Treatment of MWCL-1 cells with IL-21 (100 ng/mL) for 72 h increased proliferation by 35% (p<0.05) and IgM secretion by 80% (p<0.005). Similarly, in primary CD19+CD138+ WM cells (n=5), proliferation increased on average by 38% and IgM secretion by 71%. No apoptotic effects were associated with IL-21 in WM. Characterization of STAT activation in response to IL-21 revealed significant phosphorylation of STAT3 in both CD19+CD138+ WM cells and MWCL-1 cells and was associated with increases in BLIMP-1 and XBP-1 protein and decreases in PAX5. As STAT3 activation is known to regulate IL-6, we assessed the effect of IL-21 on B cell-mediated IL-6 secretion using ELISA. IL-21 significantly increased IL-6 secretion by both primary CD19+CD138+ WM cells (n=4) and MWCL-1 cells (87.9 +/− 10.9 ng/mL vs. 297.8 +/− 129.2 ng/mL, p<0.05). Treatment with IL-6 and IL-21 together had no additional effect over IL-21 alone on proliferation or IgM secretion in MWCL-1 cells, but culturing anti-CD3/anti-CD28-activated CD19−CD138−cells from WM bone marrows with IL-6 significantly increased IL-21 secretion (n=3). Overall, these data indicate that T-cell derived IL-21 significantly promotes growth and immunoglobulin production by malignant WM B cells and that subsequent IL-6 secretion by malignant B cells may enhance the secretion of IL-21 by T cells within the bone marrow microenvironment. Disclosures: No relevant conflicts of interest to declare.

Abstract Introduction Acute panmyelosis with myelofibrosis (APMF) is classified under acute myeloid leukemia not otherwise specified by World Health organization (WHO). The clinical course of this entity is rapidly progressive and fatal, therefore, it is essential to make the accurate diagnosis and distinguish it from its mimickers, particularly acute megakaryoblastic leukemia; AML-M7 (AMKL). The main objective of this study is to identify clinical and pathologic features which could help distinguish APMF from AMKL. Methods We evaluated all patients treated at our institution between 1994 and 2013, with APMF and AMKL. We retrospectively reviewed their clinical data, laboratory results, and initial bone marrow morphologic evaluation. The lineage of blasts was evaluated using immunohistochemical staining with antibodies to CD34, anti-megakaryocyte antibodies CD41, CD61, and polyclonal factor VIII. Flow cytometry and cytogenetic studies were reviewed. Results i) Clinical characteristics 28 patients were studied which included 8 with APMF (median age 63 years) and 20 with AMKL (median age 65 years). Splenomegaly was commonly seen in AMKL (40%) as opposed to APMF (12.5%) (P=0.21). None of the APMF patients had an antecedent hematologic malignancy, compared to 50% of AMKL patients (p=0.02). Accordingly, APMF patients had a lower incidence of the JAK2V617F mutation compared to AMKL (14% vs. 78%, p=0.04). ii) Pathological features Patients with APMF had a hypercellular marrow with increased erythropoiesis (87% vs. 10%, p<0.01) and granulopoiesis (100% vs. 25%, p<0.01), with lower bone marrow blast percentage (14% vs. 33%, p<0.01), with all blasts staining positive for CD34 (p=0.23) compared with AMKL. In AMKL, the majority of blasts stain positive for anti-megakaryocytic antibodies CD61 (100% vs. 30%, p=0.02), CD41 (75% vs. 20%, p=0.10), and factor VIII (50% vs. 20%, p=0.02). On flow cytometry, all cases of APMF demonstrated multilineage proliferation with subsets of blasts positive for CD61, CD117, and MPO. In comparison, all cases of AMKL expressed megakaryocytic marker CD61. iii) Treatment Half of our patients received intensive induction chemotherapy in each group. Median survival was similar in APMF and AMKL of 8.6 and 7.6 months respectively (P=0.82). Of the 8 APMF patients, two are alive, with follow-up duration of 14 and 20 months, respectively. In the AMKL group, only one patient is alive, with follow-up duration of 55 months. All three patients have undergone allogeneic bone marrow transplant. Conclusion In summary, our study illustrated important clinical and pathologic differences between APMF and AMKL, two similar but distinct conditions. Allogenic stem cell transplant has shown promise in limited number of cases. Future trials evaluating the efficacy of novel therapies are warranted.Table 1Clinical and Laboratory features including treatment details of patients with APMF and AMKLAPMFN=8AMKLN=20P-valueAge in years (median)63650.11Gender, M:F5:310:100.69Splenomegaly at diagnosis, n (%)1 (12.5)8 (40)0.21Antecedent hematological malignancy08- myeloproliferative neoplasm 2- myelodysplastic syndromes0.02Hgb [median] g/dl9.68.70.73WBC [median] x 109/L1.14.40.15Platelets [median ] X 109/L28360.29Blast % [median]2130.47LDH [median]4227090.12JAK2V617F mutation, n (%)1/7 (14)7/9 (78)0.04Bone marrow Cellularity, n (%): - Hypercellular - Normocellular - Hypocellular8 (100) 13 (65) 4 (20) 3 (15)0.07 0.29 0.54↑erythropoiesis, n (%)7 (87)2 (10)<0.01Left shift, n (%)5 (62)6 (30)0.20↑granulopoiesis, n (%)8 (100)5 (25)<0.01Left shift, n (%)8 (100)9 (55)0.01↑megakaryopoiesis, n (%)7 (87)16 (80)1.00Micromegakaryocytes, n (%)7 (87)18 (90)1.00↓megakaryocyte nuclear lobulation, n(%)7 (87)12 (60)0.21Clustering of megakaryocytes, n (%)5 (62)13 (65)1.00BM blast % [median]3314<0.01% of blasts CD34 + [median]100300.23% of blasts + for megakaryocyte markers [median] - CD61+ - CD41+ - Factor VIII+30 20 20100 75 500.020.10 0.01Reticulin fibrosis ≥ 3+, n (%)5 (62)9 (45)0.67Complex karyotype, n (%)4(50)10(50)1.00Treatment, n (%) - Induction chemotherapy - Hypomethylating agent - Clinical trial - Supportive care4 (50) 0 0 4(50)10(50) 2(10) 2 (10) 6(30)Allogeneic bone marrow transplant, n (%)3 (38)3 (15)Overall survival in months (median)8.677.610.82 Disclosures No relevant conflicts of interest to declare.