Allogeneic haematopoietic stem cell transplantation: current status and future outlook.

Allogeneic haematopoietic stem cell transplantation (allo-SCT) is an established treatment of haematological malignancies and other immunohaematopoietic disorders. The use of unrelated donors and cord blood (CB) grafts has increased the possibilities of finding a donor, and results are approaching those after sibling donor transplants. The use of peripheral blood stem cells (PBSCs), instead of bone marrow, results in faster engraftment and increased risk of chronic graft-versus-host disease (GVHD). High-dose myeloablative (MA) conditioning is recently challenged by reduced-intensity conditioning (RIC) for older patients and those with comorbidity. Better diagnostic tools and novel anti-microbial drugs have reduced morbidity and mortality from infections. A major problem is disease relapse. Early detection of minimal residual disease or recurrent recipient haematopoietic cells allows early intervention with immunotherapy. Donor lymphocyte infusions (DLIs) have not only an anti-leukaemic effect but also an anti-tumour effect against a variety of solid organ tumours. New indications such as metastatic solid tumours are investigated. Mesenchymal stem cells (MSC) may enhance engraftment and have immunomodulatory effects.