Bone marrow transplantation using unrelated donors for haematological malignancies.

Bone marrow transplantation from unrelated donors is increasingly used to treat haematological malignancies. There are almost 4 million volunteer donors now available. Therefore, it is possible to find an HLA-A, -B and -DR-identical donor for around 70% of the patients. The major obstacles to unrelated bone marrow transplantations have been rejection, severe acute graft-versus-host disease (GVHD) and prolonged immune recovery leading to frequent infections and a high transplant-related mortality. However, with improved tissue typing using DNA techniques, immunosuppression using T-cell depletion in vitro or in vivo, the frequency of acute GVHD is acceptable and the results approach those obtained with HLA-identical siblings. For patients with chronic myeloid leukaemia, the worldwide 3-year survival is around 40%. Other indications for bone marrow transplantation with unrelated marrow include acute leukaemia and myelodysplastic syndromes with high-risk features. Unrelated cord blood cells and unrelated peripheral blood progenitor cells will be increasingly used as alternative haematopoietic stem cell sources to bone marrow. Improved immunosuppression, more accurate tissue typing, growth factors and better management of infections is expected to improve outcome using unrelated haematopoietic stem cells for transplantation in the near future.