Devine, Steven M.

Abstract Allogeneic hematopoietic cell transplantation (allo‐HCT) is a potentially curative treatment for acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). While many factors influence the outcomes of allo‐HCT, the independent impact of donor–recipient ABO mismatching remains unclear. Using the Center for International Blood and Marrow Transplant Research (CIBMTR) database, we identified patients aged ≥18 years with AML or ALL who underwent allo‐HCT between 2008 and 2018. Our objectives were to analyze the outcomes of allo‐HCT based on the donor–recipient ABO status (match, minor mismatch, major mismatch, bidirectional mismatch). Among 4946 eligible patients, 2741 patients (55.4%) were ABO matched, 1030 patients (20.8%) had a minor ABO mismatch, 899 patients (18.1%) had a major ABO mismatch, and 276 patients (5.6%) had a bidirectional ABO mismatch. In multivariable analyses, compared to ABO matched allo‐HCT, the presence of a major ABO mismatch was associated with worse overall survival (HR 1.16, 95% CI 1.05–1.29; p = 0.005), inferior platelet engraftment (HR 0.83, 95% CI 0.77–0.90; p < 0.001), and higher primary graft failure (HR 1.60, 95% CI 1.12–2.30, p = 0.01). Relapse, acute graft versus host disease (GVHD) grades III‐IV and chronic GVHD were not significantly associated with ABO status. While donor age was not significantly associated with outcomes, older recipient age was associated with worse survival and non‐relapse mortality. Our study demonstrates that donor–recipient ABO status is independently associated with survival and other post‐transplantation outcomes in acute leukemia. This underscores the importance of considering the ABO status in donor selection algorithms and its impact in acute leukemia.

7006 Background: Measurable residual disease (MRD) prior to allogeneic hematopoietic cell transplantation (alloHCT) is associated with increased relapse and death in patients with acute myeloid leukemia (AML) in cytomorphological complete remission (CR). We recently demonstrated AML MRD detected in pre-alloHCT blood by DNA-sequencing was associated with increased relapse and decreased overall survival in patients randomized to reduced intensity conditioning (RIC) versus myeloablative conditioning (MAC). The clinical utility of such ultra-deep next-generation sequencing (NGS-MRD) had not yet been reported in a large multi-center cohort. Methods: Patients aged 18 or older who underwent first alloHCT between 2013-2017 for AML in first CR (CR1), reported to be FLT3, NPM1, IDH1, IDH2 and/or Kit mutated at diagnosis, with a pre-conditioning remission blood sample available in the CIBMTR biobank were eligible for this study. Ultra-deep anchored multiplex PCR-based NGS-MRD for the above mutations was performed on 500ng gDNA with error-corrected variant calling as previously described. The pre-specified statistical analysis plan was registered on OSF. Results: Of 457 patients with a sample available, 448 had sufficient clinical annotation and DNA for analysis. 147 of these 448 patients (33%) experienced relapse at a median of 5.6 months post-alloHCT. NGS-MRD was positive in 129 pre-alloHCT patient samples (29%), averaging 1.35 mutation(s)/patient (range: 1-4). 173 mutations were detected with a median VAF of 0.18% (range: 0.0054-62%), most frequently FLT3-ITD (n = 43 patients), NPM1 (n = 48), and IDH2 (n = 46). Testing positive by NGS-MRD prior to alloHCT was associated with a 3yr RFS of 36% (95% CI: 28-45%) compared with 56% (51-62%) in those testing negative (p < 0.001). Detection of NPM1 and/or FLT3-ITD mutations prior to alloHCT was associated with a 3yr relapse probability of 55% (43-67%) and RFS of 26% (16-37%). NGS-MRD impact was modified by conditioning intensity: positive patients receiving RIC/NMA had the highest relapse of 57% at 3yr, testing negative followed by RIC/NMA had the same relapse rate at 3yr (35%) as those who tested positive but received MAC (p < 0.001). At three years, those positive for FLT3-ITD and/or NPM1 mutations prior to RIC/NMA alloHCT had a relapse probability of 67% (50-83%) with a RFS of 19% (8-33%). HR for relapse if NGS-MRD positive pre-alloHCT in CR1 was 2.3 (p < 0.001, 95% CI 1.6-3.1) when adjusting for conditioning intensity and age group. Conclusions: In this largest cohort of NGS-MRD testing prior to alloHCT for AML reported to date, we confirm the ability to identify patients in CR1 but at high-risk of subsequent relapse. This evidence provides the foundation for future precision medicine approaches to reduce post-transplant AML relapse.

PURPOSE Calcineurin inhibitors (CNI) are standard components of graft-versus-host disease (GVHD) prophylaxis after hematopoietic cell transplantation (HCT). Prior data suggested that CNI-free approaches using donor T-cell depletion, either by ex vivo CD34 selection or in vivo post-transplant cyclophosphamide (PTCy) as a single agent, are associated with lower rates of chronic GVHD (cGVHD). METHODS This multicenter phase III trial randomly assigned patients with acute leukemia or myelodysplasia and an HLA-matched donor to receive CD34-selected peripheral blood stem cell, PTCy after a bone marrow (BM) graft, or tacrolimus and methotrexate after BM graft (control). The primary end point was cGVHD (moderate or severe) or relapse-free survival (CRFS). RESULTS Among 346 patients enrolled, 327 received HCT, 300 per protocol. Intent-to-treat rates of 2-year CRFS were 50.6% for CD34 selection (hazard ratio [HR] compared with control, 0.80; 95% CI, 0.56 to 1.15; P = .24), 48.1% for PTCy (HR, 0.86; 0.61 to 1.23; P = .41), and 41.0% for control. Corresponding rates of overall survival were 60.1% (HR, 1.74; 1.09 to 2.80; P = .02), 76.2% (HR, 1.02; 0.60 to 1.72; P = .95), and 76.1%. CD34 selection was associated with lower moderate to severe cGVHD (HR, 0.25; 0.12 to 0.52; P = .02) but higher transplant-related mortality (HR, 2.76; 1.26 to 6.06; P = .01). PTCy was associated with comparable cGVHD and survival outcomes to control, and a trend toward lower disease relapse (HR, 0.52; 0.28 to 0.96; P = .037). CONCLUSION CNI-free interventions as performed herein did not result in superior CRFS compared with tacrolimus and methotrexate with BM. Lower rates of moderate and severe cGVHD did not translate into improved survival.

Abstract Background: Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment for acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). While many factors influence the outcomes of allo-HCT in these leukemias, the independent impact of ABO mismatching between the patient and donor remains unclear. Methods: Using the CIBMTR database, we identified adults aged ≥18 years with AML or ALL who underwent allo-HCT from HLA-matched sibling donor (MSD) or 8/8 matched unrelated donor (MUD) between 2008-2018. We excluded patients who underwent transplant from a mismatched donor source or who received an ex-vivo T-cell depleted graft. Patients were stratified into cohorts based on ABO status (match, minor mismatch, major mismatch, bidirectional mismatch). Outcomes such as overall survival (OS), disease free survival (DFS), non-relapse mortality (NRM), relapse, incidence of acute graft versus host disease (GVHD), chronic GVHD, neutrophil engraftment, platelet engraftment and graft failure were evaluated. Survival analysis was done using Kaplan-Meier method and significant predictors were evaluated using Cox-proportional hazard regression method. Multivariate regression model included main effect (ABO status) and covariates (patient age, gender match, disease type, disease status, HCT-CI, Karnofsky performance status, donor type, conditioning intensity/use of TBI, stem cell source, GVHD prophylaxis, ATG/alemtuzumab use, transplant year). Results: Of 4946 patients who met the study criteria, 2741 patients (55.4%) were ABO matched, 1030 patients (20.8%) had minor ABO mismatch, 899 patients (18.1%) had major ABO mismatch and 276 patients (5.6%) had bidirectional ABO mismatch. Graft manipulation for ABO incompatibility was performed in 900 patients (minor ABO mismatch=532; major ABO mismatch=226; bidirectional mismatch=142), however, the information on individual graft manipulation techniques was limited. In multivariable analysis (table 1), major ABO mismatch significantly affected the OS, platelet engraftment and primary graft failure. Compared to ABO matched allo-HCT, major ABO mismatched allo-HCT was associated with worse OS (major mismatch - HR 1.16, 95% CI 1.05-1.29; p=0.005), inferior platelet engraftment (HR 0.83, 95% CI 0.77-0.90; p=&lt;0.001), and higher risk of primary graft failure [4.5% (major mismatch) vs. 3.2% (ABO matched) - HR 1.60, 95% CI 1.12-2.30, p=0.01]. There was a significant interaction between the ABO status and graft type (peripheral blood vs. bone marrow) for the acute GVHD grades 2-4 model, and they are presented separately (table 1). Bidirectional ABO mismatch also significantly impacted the outcomes such as acute GVHD grades 2-4 (in bone marrow stem cell subgroup, HR 0.50, 95%CI 0.27-0.93, p=0.02) in addition to a trend towards inferior survival and NRM (p-value not significant). Other outcomes such as relapse (p=0.41), acute GVHD grades 3-4 (p=0.13), and chronic GVHD (p=0.30) were not significantly influenced by the ABO status. Conclusions: Our study demonstrates that pre-transplant ABO status is an independent predictor of survival and other post-transplant outcomes in a large cohort of patients with AML and ALL undergoing allo-HCT in the recent era. This demonstrates the importance of considering ABO status in the donor selection algorithms and potential strategies to mitigate its adverse impact. Due to the limited information available on graft manipulation strategies, the impact of graft manipulation techniques on the outcomes could not be evaluated and needs to be investigated in future studies. Figure 1 Figure 1. Disclosures Guru Murthy: Techspert: Consultancy; Guidepoint: Consultancy; Cancerexpertnow: Honoraria; Qessential: Consultancy; TG therapeutics: Other: Advisory board; Cardinal Health Inc.: Honoraria. Devine: Magenta Therapeutics: Current Employment, Research Funding; Tmunity: Current Employment, Research Funding; Sanofi: Consultancy, Research Funding; Johnsonand Johnson: Consultancy, Research Funding; Orca Bio: Consultancy, Research Funding; Be the Match: Current Employment; Vor Bio: Research Funding; Kiadis: Consultancy, Research Funding. Farhadfar: Incyte: Consultancy. Sharma: Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Novartis: Other: Salary support paid to institution; Spotlight Therapeutics: Consultancy; Medexus Inc: Consultancy; CRISPR Therapeutics: Other, Research Funding; Vindico Medical Education: Honoraria. Stefanski: Novartis: Honoraria. Pulsipher: Equillium: Membership on an entity's Board of Directors or advisory committees; Adaptive: Research Funding; Jasper Therapeutics: Honoraria. Shaw: mallinkrodt: Other: payments; Orca bio: Consultancy.

Abstract Post-remission strategies after dasatinib-corticosteroid induction in adult Philadelphia chromosome (Ph)–positive acute lymphoblastic leukemia (ALL) are not well studied. We evaluated dasatinib and dexamethasone induction then protocol-defined post-remission therapies, including hematopoietic cell transplantation (HCT). Adults (N = 65) with Ph-positive ALL received dasatinib-dexamethasone induction, methotrexate-based central nervous system (CNS) prophylaxis, reduced-intensity conditioning (RIC) allogeneic HCT, autologous HCT, or chemotherapy alone, and dasatinib-based maintenance. Key end points were disease-free survival (DFS) and overall survival (OS). The median age was 60 years (range, 22-87 years). The complete remission rate was 98.5%. With a median follow-up of 59 months, 5-year DFS and OS were 37% (median, 30 months) and 48% (median, 56 months), respectively. For patients receiving RIC allogeneic HCT, autologous HCT, or chemotherapy, 5-year DFS were 49%, 29%, and 34%, and 5-year OS were 62%, 57%, and 46%, respectively. Complete molecular response rate after CNS prophylaxis was 40%. Relative to the p190 isoform, p210 had shorter DFS (median 10 vs 34 months, P = .002) and OS (median 16 months vs not reached, P = .05). Relapse occurred in 25% of allogeneic HCT, 57% of autologous HCT, and 36% of chemotherapy patients. T315I mutation was detected in 6 of 8 marrow relapses. Dasatinib CNS concentrations were low. Dasatinib-dexamethasone followed by RIC allogeneic HCT, autologous HCT, or chemotherapy was feasible and efficacious, especially with RIC allogeneic HCT. Future studies should address the major causes of failure: T315I mutation, the p210 BCR-ABL1 isoform, and CNS relapse. This study was registered at www.clinicaltrials.gov as #NCT01256398.

Introduction: Cryopreservation of peripheral blood stem cell (PBSC) or bone marrow (BM) grafts is rarely performed, thus information about the effect of cryopreservation on graft characteristics and HCT outcomes is limited. Given the global pandemic leading to changing practices for donor graft collection and increasing utilization of cryopreservation, we evaluated the outcomes of HCT recipients who received either fresh or cryopreserved allogeneic BM or PBSC grafts. The primary endpoint was engraftment. Secondary endpoints were incidence of acute graft-vs.-host disease (aGVHD), relapse, transplant related mortality (TRM), disease free survival (DFS), and overall survival (OS). Methods: We included 7397 patients transplanted between 2013 and 2018. 1883 cryopreserved graft recipients were divided into three cohorts based on graft source and donor type: matched related (MRD) PBSC (n=1,051), matched unrelated (MUD) PBSC (n=678), and matched related or unrelated bone marrow donors (n=154). All patients received conventional calcineurin-based GVHD prophylaxis strategies. Patients who received cryopreserved grafts were matched with 5514 patients who received fresh adjusting for graft type (BM vs. PB), donor source (MRD vs. 8/8 MUD), Disease Risk Index (DRI, low risk vs. intermediate risk vs. high risk), recipient age (within 5-years) and propensity score (within 1 standard deviation from pooled sample). The propensity score was based on age, Karnofsky score, diagnosis, disease risk index, HCT-comorbidity index, and conditioning intensity. The level of statistical significance for the main analyses was p&lt;0.01 due to multiple comparisons. The reason for cryopreservation was available on a subset of URD product recipients. Results: Baseline characteristics for all cohorts are shown in Table 1. CD34+ doses reflect enumeration at infusion. In univariate analyses, rates of graft failure and neutrophil recovery at day 28 were similar for cryopreserved and fresh grafts for BM or related PBSC recipients but differed in cryopreserved vs. fresh MUD PBSC (5% vs 2%, p&lt;0.001 and 87 vs 94%, p&lt;0.001, respectively). Rates of platelet recovery within 28 days were similar in marrow cohorts, but lower with cryopreserved related (92% vs 96%, p&lt;0.001) and MUD PBSC (87 vs 94%, p&lt;0.001) grafts. In matched pair multivariable analyses, there were no significant differences in any outcomes with cryopreserved vs fresh BM grafts, irrespective of donor type. With related donor PBSC, cryopreservation was associated with decreased platelet recovery (HR=0.73, CI=0.68-0.78, p&lt;0.001) and an increased risk of both grade II-IV (HR=1.27, CI=1.09-1.48, p=0.002) and grade III-IV (HR=1.48, CI=1.19-1.84, p&lt;0.001) aGVHD, but had no impact on other outcomes. In contrast, with MUD PBSC grafts, cryopreservation was associated with delayed engraftment of neutrophils (HR=0.77, CI=0.71-0.84, p&lt;0.001) and platelets (HR=0.61, CI=0.56-0.66, p&lt;0.001), an increased risk of TRM (HR=1.4, CI=1.18-1.66, p&lt;0.001) and relapse (HR=1.32, CI=1.11-1.58, p=0.002), and decreased DFS (HR=1.36, CI=1.20-1.55, p&lt;0.001) and OS (HR=1.38, CI=1.22-1.58, p&lt;0.001) but did not affect the incidence of aGVHD. In a subset analysis of 299 URD recipients, the most common reason for cryopreservation was delays due to patient-related events, eg., additional chemotherapy, infection. These recipients had decreased OS compared to products cryopreserved for non-patient reasons (HR=0.65, CI=0.44-0.96, p=0.029). Conclusions: The retrospective nature of this analysis, and the fact that cryopreservation is likely to have been performed in recipients with a different (higher) risk profile compared to those receiving fresh products limits our ability to draw firm confusions. Despite these limitations, we conclude that cryopreservation in some patient populations may have a negative impact on engraftment and transplant outcomes. The decision to cryopreserve donor grafts, particularly PBSC grafts, should be carefully considered and highlights the need for further investigation of the effect of cryopreservation of allogeneic grafts where patient factors can be controlled for. Disclosures Farhadfar: CSL Behring: Research Funding; Incyte pharmaceutical: Other: Member of GVHD advisory forum. Frey:Kite Pharma: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Syntax: Consultancy, Honoraria. Devine:Magenta Therapeutics: Consultancy. Shaw:Orca Bio: Consultancy. Wingard:Shire: Other: Personal Fees - serve on data monitoring committee for clinical trial; Ansun: Other: Personal Fees - serve on data monitoring committee for clinical trial; Merck: Other: Personal Fees - serve on data monitoring committee for clinical trial; Cidara: Other: Personal Fees - serve on data monitoring committee for clinical trial; ReViral: Other: Personal Fees - serve on data monitoring committee for clinical trial.

Introduction. Our previous flow cytometry-based comparison of HIV(+) and HIV(-) autologous hematopoietic stem cell transplant (auto-HSCT) recipient immunomes at 56, 180 and 365 days post-transplant to each other and to healthy controls (HCs) showed that both sets of auto-HSCT recipient immunomes approached HCs over time, but retained significant differences. HIV(+), but not HIV(-), auto-AHCT recipients retained pro-inflammatory features consistent with chronic HIV infection. Here, we report the results of a quantitative and functional analysis of immune reconstitution in HIV(+) patients treated with allogeneic hematopoietic stem cell transplant (allo-HSCT), in comparison with HIV(+) auto-HSCT recipients and HCs. Methods. Blood samples were collected for analysis at days 56, 180 and 365 post-transplant from HIV(+) transplant recipients and at 1 time point from HCs. Whole blood analysis was performed by five-color flow cytometry across 100 immune marker combinations. Comparisons were made between HIV(+) allo-HSCT recipients (n=17, acute myeloid leukemia, acute lymphocytic leukemia, myelodysplastic syndrome, Hodgkin and non-Hodgkin lymphoma that received myeloablative or reduced intensity conditioning on the BMT-CTN-0903/AMC-080 trial), HIV(+) auto-HSCT recipients (n=36, aggressive B cell non-Hodgkin lymphoma or Hodgkin lymphoma that received myeloablative conditioning on the BMT-CTN-0803/AMC-071 trial) and 71 HCs. Unsupervised principal component analysis (PCA) examined differences in immune cell proportions, identified by flow cytometry across 100 cell subsets at each time point. Wilcoxon rank-sum tests compared median absolute counts and median proportions of cell subsets. An independent feature importance score analysis (FIS) identified contributions of immune cell populations expressing specific immune marker combinations to the differences between HIV(+) auto-HSCT recipients, HIV(+) allo-HSCT recipients and HCs. Functional responsiveness of HIV(+) allo-HSCT recipients' T cells to stimulation with CD3- and CD28-directed antibodies, NK cells to stimulation with IL-12 and IL-18 and monocytes to stimulation with lipopolysaccharide (LPS) was assessed in a preliminary mass cytometry on peripheral blood mononuclear cells isolated at the same time points (n=2) and compared to HCs (n=2). Results. PCA showed that immunomes of HIV(+) allo-HSCT recipients and HIV(+) auto-HSCT recipients clustered together with each other, but away from HCs at all time points throughout the post-transplant year. FIS identified: 1) 13 cell subsets that defined the difference between HIV(+) allo-HSCT recipients (all visits) and HCs, and 2) 11 immune cell subsets that defined the difference between HIV(+) auto-HSCT recipients (all visits) and HCs; in both of these comparisons, activated CD3+/HLA-DR+ T cells had the greatest impact on the difference between HIV(+) and HC immunomes. At 1 year, both HIV(+) transplant recipient cohorts had higher absolute numbers of activated T cells, effector T cells and CD8+ T cells than HCs (Wilcoxon rank-sum test, p<0.0031). HIV(+) autologous and allogeneic HSCT recipients also had lower numbers of CD4+ T cells, naïve T cells and activated NK cells compared to HCs (p<0.0031). FIS also identified 20 immune cell subsets that defined the difference between HIV(+) autologous and allogeneic HSCT recipients immunomes at 1 year, with CD8+/CD27- effector T cell subset exerting the highest impact on the difference. Preliminary functional mass cytometry analysis of 2 HIV(+) allo-HSCT recipients and 2 HCs showed that: 1) IFNʏ production by CD8+ T cells was increased above that of HCs at all time points. 2) Expanded populations of CD4+/T-bet+ cytotoxic cells expressing granzyme B and perforin, and CD8+ cytotoxic T cells expressing granzyme B and perforin, persisted in HIV(+) allo-HSCT recipients at all time points, but not in HCs. 3) NK cells retained an ability to produce IFNʏ in response to stimulation with IL-12 and IL-18 in HIV(+) allo-SCT recipients. 4) Monocytes showed an enhanced production of TNFα in response to stimulation with LPS in HIV(+) allo-HSCT recipients compared to HCs at 1 year post-HSCT. Conclusion. Chronic HIV infection confers the pro-inflammatory immune features on the phenotypic and functional profiling of the T lymphocyte immunome of stem cell transplant recipients, irrespective of allogeneic or autologous stem cell donor source. Disclosures Devine: Bristol Myers: Other: Grant for monitoring support & travel support; Kiadis Pharma: Other: Protocol development (via institution); Magenta Therapeutics: Other: Travel support for advisory board; My employer (National Marrow Donor Program) has equity interest in Magenta. Noy:Janssen: Consultancy; Medscape: Honoraria; Prime Oncology: Honoraria; NIH: Research Funding; Pharamcyclics: Research Funding; Raphael Pharma: Research Funding. Popat:Bayer: Research Funding; Incyte: Research Funding; Jazz: Consultancy. Hofmeister:Celgene: Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees; Nektar: Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Imbrium: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees. Navarro:Atara Biotherapeutics: Employment, Equity Ownership. Behbehani:Fluidigm corporation: Other: Travel funding. Lozanski:Boehringer Ingelheim: Research Funding; Beckman Coulter: Research Funding; Stemline Therapeutics Inc.: Research Funding; Genentec: Research Funding. Baiocchi:Prelude: Consultancy.

Abstract History of prior cancer is a widespread exclusion criterion in cancer trials. Up to 80% of NCI-sponsored and 80% of industry-sponsored lung cancer trials exclude patients with a prior cancer. We suspect this exclusion is commonly applied in other cancer trials, although no definitive data exist. Prior cancer is especially common among older patients and those with certain cancer types. Among patients >65 years, 15.1% overall have prior cancer. In Multiple Myeloma, the most common plasma cell disorder (PCD), prevalence of prior cancer is as high as 17.4%. Examining the prior cancer exclusion criterion is important because the number of US cancer survivors is large and rapidly growing. Arbitrarily excluding cancer survivors from trials is not evidence-based and exclusion presumably arises from assumptions that higher mortality of patients with prior cancer could hinder study conduct and bias trial outcomes. However, few data exist to support this assumption of higher mortality. In fact, we demonstrated that lung cancer patients with a prior cancer have similar or lower mortality risk, compared to those without prior cancer. In this abstract, we reviewed prior cancer related eligibility criteria in three of the most common PCD (Multiple Myeloma, Amyloidosis and Waldenström Macroglobulinemia) clinical trials sponsored or endorsed by 5 major Co-Operative groups in North America (Table 1). We use descriptive statistics (n, %) and Fisher's exact tests to describe characteristics of trials with and without exclusion criteria. Of 33 trials, 26 (79%) excluded patients with prior cancer as follows - active cancer (12%), within 2-3 years of PCD diagnosis (9%), or within 5 years of PCD diagnosis (55%). Many trials had exceptions to prior cancer exclusion. Specifically, 67% of trials allowed non-melanoma skin cancer, 58% allowed in-situ cervical cancer, 12% allowed early stage prostate cancer. Table 2 shows the association between clinical trial characteristics and prior cancer exclusion. There was no association between prior cancer exclusion and phase of study, transplant studies, or survival end point. Exclusion criteria varied across year of activation (p=0.01); for example, 75% of studies activated 1990-1999 excluded prior cancer, compared to 100% of studies activated after 2010. Type of PCD was marginally associated with exclusion criteria (p=0.08); 74% of Multiple Myeloma trials excluded patients with prior cancer compared to 100% of the Amyloidosis and Waldenström Macroglobulinemia trials. Conclusion: A substantial proportion of potential participants may be excluded from PCD clinical trials because of a history of prior cancer. This practice impacts accrual, generalizability, and fair access to cutting-edge treatments and the highest level of clinical care. As treatment outcomes for other cancers continue to improve, it is likely that the prevalence of multiple primary cancers will increase. This exclusion criterion is applied widely across studies, including more than two-thirds of those with non-survival endpoints. Our study is the first to examine the prevalence and potential impact of prior cancer exclusion in PCD clinical trials. Using population-based cancer registry data, we plan to undertake further research to understand the appropriateness and ramifications of this standard exclusion policy in PCD cancer trials. Disclosures Collins: Agios: Research Funding; Bristol Myers Squibb: Research Funding; Celgene Corporation: Research Funding; Arog Pharmaceuticals: Research Funding. Devine:Kiadis Pharma: Consultancy. Usmani:Amgen, BMS, Celgene, Janssen, Merck, Pharmacyclics,Sanofi, Seattle Genetics, Takeda: Research Funding; Abbvie, Amgen, Celgene, Genmab, Merck, MundiPharma, Janssen, Seattle Genetics: Consultancy. Anderson:Amgen: Speakers Bureau; Takeda: Speakers Bureau; Celgene: Speakers Bureau. Kumar:Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Roche: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Abstract Dasatinib with corticosteroid yields high complete remission (CR) rates in Ph+ ALL with minimal induction death. Optimal post-remission therapy is not known. We report a prospective study evaluating dasatinib/dexamethasone induction then consolidation with reduced-intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (alloHCT), autologous HCT (autoHCT), or chemotherapy alone (chemo), followed by dasatinib-based maintenance. Methods: We conducted a phase II, 3-arm, non-randomized trial (NCT01256398, Support: U10CA180821, U10CA180882, U10CA180861, U24CA196171) at 17 US centers with primary objectives to determine 3-year overall survival (OS) and disease-free survival (DFS) of adults ≥18 years (yrs) old with untreated Ph+ ALL treated with dasatinib/dexamethasone induction, CNS prophylaxis with systemic and intrathecal methotrexate, consolidation with alloHCT, autoHCT, or chemo, then dasatinib maintenance. Induction (Course I) used dasatinib 140 mg orally daily and dexamethasone 10 mg/m2/day orally or IV days 1-7. If ≤20% lymphoblasts in marrow at Day 15, Course II continued dasatinib with 7 days of dexamethasone. If >20% lymphoblasts, patients (pts) also received vincristine and daunorubicin. Pts not in CR/CRi received a second induction (Course III) with dasatinib, cyclophosphamide, vincristine, daunorubicin, and dexamethasone. CNS prophylaxis (Course IV) used dasatinib, IV vincristine and IV, oral, and intrathecal methotrexate. Course V consisted of HCT or chemo. Pts 18-70 yrs old underwent RIC alloHCT if they had a HLA-matched donor; otherwise they underwent autoHCT. AlloHCT conditioning used fludarabine 30 mg/m2/day IV day -7 through -3, alemtuzumab 20 mg/day IV day -7 through -3, and melphalan 140 mg/m2 IV once on day -2. GVHD prophylaxis with tacrolimus began day -2. Pts undergoing autoHCT received etoposide 10 mg/kg/day (age >65, 5 mg/kg/day) CIV for 4 days and cytarabine 2 g/m2 (age >65, 1 g/m2) IV every 12 hours for 8 doses then G-CSF for mobilization. AutoHCT conditioning was melphalan 100 mg/m2/day IV on days -2 and -1. Pts >70 yrs old or unable to undergo HCT received etoposide/cytarabine alone. Dasatinib maintenance (Course VI) began day 30 of Course V and continued for 12 months and until 2 consecutive negative BCR-ABL1 RT-PCR assays 3 months apart or relapse. BCR-ABL1 isoform and ABL1 kinase domain (KD) mutation determination were done locally. Results: From 12/15/2010 to 11/14/2014, 64 eligible pts enrolled. Median age was 60 yrs (22-87); median WBC 23.2 x 103/μl (0.3-454). The dominant BCR-ABL1 isoform was p190 in 59%, p210 in 17%, and not reported in 23%. The CR rate was 97% with no induction deaths. Fifty-five pts completed CNS prophylaxis (Course IV). Twenty pts underwent protocol-specified alloHCT, 7 autoHCT, and 9 chemo. Nine pts underwent off-study alloHCT and 5 skipped Course V. Dasatinib maintenance was tolerable with 72%, 80%, and 80% receiving >50% of planned maintenance doses in alloHCT, autoHCT, and chemo arms, respectively. With a median follow up of 48 months (37-78) for survivors, 3-yr OS and DFS were 55% (median OS 45 months) and 43% (median DFS 30 months), respectively. For pts undergoing consolidation with protocol-specified alloHCT, autoHCT, or chemo, 3-yr OS was 75%, 71%, and 55% respectively with median OS not reached (NR) for all groups. DFS at 3-yrs was 55%, 43%, and 46% respectively. Median DFS for alloHCT was 42 months vs 15 months for autoHCT and 34 months for chemo (Log-Rank P=0.4). Outcomes were similar with inclusion of off-study alloHCT and chemo patients skipping Course V. Relative to p190 BCR-ABL1 isoform, p210 was associated with shorter median OS (NR vs 16 months, P=0.04) and median DFS (35 months vs 10 months, P<0.0001). Three-year DFS was 9% with p210. Relapse occurred in 23 pts with 5 CNS relapses reported, one isolated. Relapse occurred in 25% of alloHCT, 43% of autoHCT, and 37% of chemo pts. T315I mutation in ABL1 KD was detected in 6 of 8 marrow relapses (75%). One isolated CNS relapse had no ABL1 KD mutations. Conclusions: Dasatinib and dexamethasone followed by alloHCT, autoHCT, or chemo yield similar 3-yr survival comparable to approaches using intensive induction chemotherapy. Pts with the p210 BCR-ABL1 isoform had dismal outcomes and may benefit from alternate approaches. T315I mutation was the major cause of relapse and should be addressed in future studies. Disclosures Wieduwilt: Amgen: Research Funding; Reata Pharmaceuticals: Equity Ownership; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Leadiant: Research Funding; Shire: Research Funding; Merck: Research Funding. Uy:GlycoMimetics: Consultancy; Curis: Consultancy. Powell:Rafael Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Kolitz:Magellan Health: Consultancy, Honoraria. Liedtke:Caelum: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen/Onyx: Consultancy, Honoraria, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; celgene: Research Funding; Genentech/Roche: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Prothena: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BlueBirdBio: Research Funding. Stock:Jazz Pharmaceuticals: Consultancy. Devine:Kiadis Pharma: Consultancy. Larson:BristolMyers Squibb: Consultancy, Research Funding; Ariad/Takeda: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding.

Abstract Systemic mastocytosis (SM) is a rare hematologic neoplasm characterized by abnormal growth and accumulation of tissue mast cells (MC) in various organ systems, including bone marrow (BM). Indolent and advanced forms of SM have been described. Whereas patients with ISM have a normal or near normal life-expectancy, patients with advanced SM, including those suffering from mast cell leukemia (MCL) have a poor prognosis. In these patients, neoplastic MC are usually resistant against conventional drugs and various targeted drugs. In rapidly progressive aggressive SM (ASM) and MCL, polychemotherapy followed by allogeneic hematopoietic stem cell transplantation (alloHCT) has been proposed. However, outcome of alloHCT in advanced SM is unknown, and it also remains uncertain whether clinically relevant graft-versus-SM (GVSM) effects may occur in these patients, as only sporadic case reports have been published. We performed a retrospective multi-center analysis to evaluate the outcome of alloHCT in patients with advanced SM. Fifty-four advanced SM patients receiving SCT in 32 transplantation centers in Europe and America were identified between 1990 and 2013. The median patient age was 45 years. Donors were: HLA identical siblings (31), unrelated donors (URD) (15), umbilical cord blood donors (UCB) (2), and haploidentical donors (1). In 5 patients, stem cell source was not defined (5). Thirty-four patients received myeloablative conditioning (MAC) and 18 received reduced intensity conditioning regimens (RIC). In 2 patients, conditioning regimen was not specified. Indications for alloHCT were SM with an associated clonal hematologic non-mast cell lineage disease (SM-AHNMD) (n=32), MCL (n=13, including one with MCL-AHNMD), 8 with ASM and 1 with myelomastocytic leukemia (MML). The most prevalent AHNMD was acute myeloid leukemia (AML, n=16). With follow-up of 35-6180 (median 365) days, SM responses (defined as ≥50% decrease in BM mast cells ± decrease in serum tryptase ± regression of other organ manifestations) were observed in 39 patients (72%), including complete responses (CR) documented in 12 patients (22%). Eleven patients had stable disease, whereas 4 patients (7%) progressed immediately after alloHCT (primary resistance). In addition, 10 patients progressed (5 of them within 100 days) after an initial response. Progression was most frequently seen in MCL patients (n=6, 50%). In the AHNMD group, only 8 patients relapsed/progressed (25%). The overall survival (OS) and SM progression-free survival (PFS) at 1 year were 63% and 50% for all patients, 77% and 68% for SM-AHNMD, 63% and 50% for ASM, and 25% and 17% for MCL, respectively. The strongest predictive variable associated with inferior survival was a diagnosis of MCL. Other factors associated with poor outcome were: Karnofsky performance status ≤70%, ≥2 SM regimens given before alloHCT (e.g., steroids, cladribine, chemotherapy, tyrosine kinase inhibitor), donor source (alternative donors-UCB and haploidentical compared to sibling or URD), SM progression within the first 100 days, normal cytogenetics (compared to t(8;21) (q22;q22), and RIC (compared to MAC). The following variables were not associated with poor outcome: patient and donor age, recipient-donor sex match status, graft source (BM vs. peripheral stem cells), BM mast cell percentage at time of alloHCT, and CR status of AML or SM response at time of alloHCT. This largest multi-center analysis of results in advanced SM provides evidence for clinical efficacy of alloHCT, presumably because of a GVSM effect of alloHCT (achieving CR, and response to donor-lymphocyte infusions and RIC alloHCT). However, responses varied among different SM categories: while patients with SM-AHNMD enjoyed excellent outcomes, the OS for MCL patients in general, was poor. Nevertheless it is remarkable that 3 of 13 patients with MCL – an otherwise fatal disease with a median survival of &lt;12 months – became long-term survivors after alloHCT. In summary, our results support development of a prospective alloHCT study, with the aim to optimize therapy and to improve overall outcome in advanced SM. Based on our pilot study, alloHCT should also be considered in practice for eligible and fit patients with SM-AHNMD (if treatment of AHNMD component needs alloHCT or SM component is aggressive), rapidly progressing ASM, MCL and MML when a suitable HLA-matched sibling donor or URD is available. Disclosures: Vercellotti: Sangart Inc.: Research Funding; Seattle Genetics: Research Funding. Akin:Novartis: Consultancy. Valent:Novartis: Consultancy, Honoraria, Research Funding.