Switzer, Galen E.

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.

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.

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.