title: Impact of ABO mismatching on the outcomes of allogeneic related and unrelated blood and marrow stem cell transplantations for hematologic malignancies: IPD-based meta-analysis of cohort studies.
abstract: BACKGROUND
  The impact of donor-recipient ABO matching on outcomes after allogeneic stem cell transplantation has been a matter of controversy.
  
  
  METHODS
  Individual patient data-based meta-analysis was conducted with a pooled data set provided through six published and one unpublished cohorts. Outcomes in recipients of peripheral blood or bone marrow transplantation for hematologic malignancies were evaluated. A multivariate Cox model was used to adjust differences in outcomes of patients receiving ABO-matched grafts with those receiving major, minor, or bidirectional mismatched grafts. Considering multiple testing, p values of less than 0.05 and 0.001 were considered significant for the primary and secondary endpoints, respectively.
  
  
  RESULTS
  In all, 1208 cases, including 697 ABO-matched and 202 major, 228 minor, and 81 bidirectional mismatched transplants, were analyzed. Overall, adverse impact of ABO matching on overall survival (OS), as a primary endpoint, was not observed (adjusted hazard ratios [95% confidence intervals]: major, 1.03 [0.82-1.30], p = 0.81; minor, 1.19 [0.97-1.47], p = 0.10; bidirectional, 1.25 [0.91-1.72], p = 0.17). Among related stem cell recipients, ABO matching had no significant influence on OS, while the minor and bidirectional mismatched groups among unrelated stem cell recipients exhibited lower OS with marginal significance, especially in patients with acute leukemia, patients who received transplants after 1998, and patients who underwent transplants at Asian centers.
  
  
  CONCLUSIONS
  Our meta-analysis demonstrates no adverse association between any ABO mismatching and survival. However, marginally lower OS found in recipients of minor or bidirectional mismatched grafts from unrelated donors suggested the need for larger studies focusing on unrelated transplants.
authors.affiliation: Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, Japan. jkanda16@kuhp.kyoto-u.ac.jp
authors.forename: Junya
authors.initials: J
authors.lastname: Kanda
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Ichinohe
authors.forename: Keitaro
authors.initials: K
authors.lastname: Matsuo
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Benjamin
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Klumpp
authors.forename: Primoz
authors.initials: P
authors.lastname: Rozman
authors.forename: Neil
authors.initials: N
authors.lastname: Blumberg
authors.forename: Jayesh
authors.initials: J
authors.lastname: Mehta
authors.forename: Sang-Kyun
authors.initials: SK
authors.lastname: Sohn
authors.forename: Takashi
authors.initials: T
authors.lastname: Uchiyama
mesh_terms: D000017:ABO Blood-Group System / Q000276:immunology*; D000465:Algorithms; D001773:Blood Cells / Q000276:immunology / Q000502:physiology; D001782:Blood Donors; D001788:Blood Grouping and Crossmatching / Q000009:adverse effects* / Q000379:methods / Q000401:mortality; D001854:Bone Marrow Cells / Q000276:immunology / Q000502:physiology; D002423:Cause of Death; D015331:Cohort Studies; D016208:Databases, Factual; D005190:Family; D006086:Graft vs Host Disease / Q000453:epidemiology / Q000401:mortality; D019337:Hematologic Neoplasms / Q000276:immunology / Q000628:therapy*; D018380:Hematopoietic Stem Cell Transplantation / Q000009:adverse effects / Q000379:methods* / Q000401:mortality; D006801:Humans; D014184:Transplantation, Homologous
chemical_list: D000017:ABO Blood-Group System