Investigating the Relationship between CD34+and CD3+ Cell Doses, One-Year Graft-Versus-Relapse-Free-Survival, Graft-Versus-Host Disease, and Overall Survival in Haploidentical Hematopoietic Stem Cell Transplantation: A Single Center Experience

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.2051-2051
• Main Authors: Hsiao, Mindy, Martynova, Anastasia, Yaghmour, George, Foss, Chris
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-129647

Background: Haploidentical hematopoietic cell transplantation (haplo-HCT) has emerged as a popular alternative to traditional HLA-matched hematopoietic cell transplant. As the number of haplo-HCT's rises, investigating the factors that may affect outcomes is necessary in order to improve overall survival and reduce transplant-related mortality. The optimal dose of CD34+ cells used during haplo-HCT to ensure favorable outcomes using PTCy has not yet been reported though a range of 2 to 5.00x106 cells/kg is commonly used.Furthermore, the optimal dose of CD3+ cells is unknown however recent data has suggested less than 3.00x108 cells/kg may prevent the development of acute GVHD. The importance of studying the impact of CD34+/CD3+ cell dosing may help to improve outcomes in this setting. Methods: We retrospectively analyzed adult patients at USC Norris Cancer Hospital (age ≥ 21) who received haplo-HCT from 2014 to 2019. The primary end-point assessed was 1-year GVHD-free/relapse-free survival (GRFS) defined as grade 3-4 acute GVHD, systemic therapy-requiring chronic GVHD, relapse, or death in the first post-HCT year. Secondary end-points included 1-, 2-, and 3-year relapse-related mortality (RRM) and overall survival (OS) in addition to 1-year transplant related mortality (TRM) and incidence of both acute and chronic GVHD. Results: A total of 67 adult haplo-HCT recipients were reviewed. Of the patients evaluated, approximately 50% (n = 33) were male and 49% (n = 32) were female. The age range was 21-71 years old (median = 44), and the most common underlying hematologic disorders included AML (40%), ALL (38%), aplastic anemia (7.7%), and others (MDS, lymphoma, myelofibrosis, and HLH) (13.8%). 67% of patients received myeloablative conditioning regimens while 33% received reduced intensity regimens. 70% (n = 47) of patients received peripheral blood as a stem cell source with 30% (n = 20) receiving bone marrow. The mean CD34+ dose infused was 6.07x106 cells/kg and the mean CD3+ dose was 2.94x108 cells/kg. The mean time to recovery of platelets, neutrophils, and lymphocytes was 25, 18, and 37 days respectively. CD34+ stem cells ≥5.00x106 cells/kg was significantly associated with shorter time to lymphocyte recovery (p = 0.0265) though recovery less than 30 days was not significantly associated with OS (p = 0.5268). Incidence of 1-year GRFS was 71% (n= 46) and 1-, 2-, and 3-year RRM were 4.6%, 6%, and 7.7% respectively. 1-year TRM was 15.3% with 50% of deaths from