title: Cord blood transplants: one, two or more units?
abstract: OBJECTIVE
  This review summarizes the current status of double-unit cord blood transplantation (CBT) to improve engraftment, reduce transplant-related mortality, and improve disease-free survival.
  
  
  RESULTS
  Transplantation of cord blood provides a potentially curative therapy for many patients without a suitably human leukocyte antigen-matched related or unrelated donor. Single-unit CBT outcomes have been compromised, however, in adults and larger children by limited cell dose. The introduction of double-unit CBT has improved engraftment and transplant-related mortality in adult patients transplanted for hematologic malignancies, with recent data also suggesting a protection against relapse. These improved outcomes are seen despite only a single unit being responsible for sustained donor hematopoiesis in nearly all patients. The study of double-unit CBT provides unique insights into transplant biology, with emerging data suggesting unit dominance is related to unit viability and unit-versus-unit immune interactions. Multiple unit CBT further serves as a platform to test novel graft manipulations.
  
  
  CONCLUSIONS
  The development of double-unit CBT now allows the majority of patients, regardless of size or racial/ethnic background, access to transplant therapy. Ongoing investigation will serve to further improve outcomes and expand the role of CBT in the future.
authors.affiliation: Department of Medicine, Allogeneic Bone Marrow Transplant Service, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Avery
authors.forename: Juliet N
authors.initials: JN
authors.lastname: Barker
mesh_terms: D000328:Adult; D036101:Cord Blood Stem Cell Transplantation / Q000379:methods*; D006085:Graft Survival; D006801:Humans