Effect of donor-recipient HLA matching at HLA A, B, C, and DRB1 on outcomes after umbilical-cord blood transplantation for leukaemia and myelodysplastic syndrome: a retrospective analysis

Umbilical cord blood stem cells: clinical trials in non-hematological disorders

BACKGROUND

Umbilical cord blood (UCB) has become the second most common source of stem cells for cell therapy. The recent boom in stem cell research and public fascination with promises of stem cell-based therapies, fueled by the media, have led researchers to explore the potential of UCB stem cells in therapy for non-hematological disorders.

SOURCES OF DATA

ClinicalTrials.gov database searched with key words 'cord blood stem cells' on December 28, 2011.

AREAS OF AGREEMENT

As a rich source of the most primitive hematopoietic stem cells, UCB has a strong regenerative potential in stem cell-based-therapy for hematological disorders.

AREAS OF CONTROVERSY

Potential of UCB stem cells in therapy for non-hematological disorders.

GROWING POINTS

Increasing number of clinical trials with UCB stem cell-based therapy for a variety of diseases.

AREAS TIMELY FOR DEVELOPING RESEARCH

A need for standardization of criteria for selection of UCB units for stem cell-based therapy, outcome measures and long-term follow-up.

Selection of optimal alternative graft source: mismatched unrelated donor, umbilical cord blood, or haploidentical transplant

Only 30% of patients who require an allogeneic hematopoietic cell transplant will have an HLA-matched sibling donor. A search for an unrelated donor will be undertaken for patients without a matched family donor. However, many patients, particularly patients of diverse racial and ethnic backgrounds, may not be able to rapidly identify a suitably matched unrelated donor. Three alternative graft sources, umbilical cord blood (UCB), haploidentical (haplo)-related donor, and mismatched unrelated donor (MMUD) are available. UCB is associated with decreased GVHD, but hematologic recovery and immune reconstitution are slow. Haplo-HCT is characterized by donor availability for transplantation and after transplantation adoptive cellular immunotherapy but may be complicated by a high risk of graft failure and relapse. A MMUD transplant may also be an option, but GVHD may be of greater concern. Phase 2 studies have documented advances in HLA typing, GVHD prophylaxis, and infection prevention, which have improved survival. The same patient evaluated in different transplant centers may be offered MMUD, UCB, or haplo-HCT depending on center preference. In this review, we discuss the rationale for donor choice and the need of phase 3 studies to help answer this important question.