Haematopoietic stem cell transplantation: current status.

Haematopoietic stem cell transplantation (HSCT) is now an established treatment fora number of non-malignant and malignant conditions. Bone marrow- or peripheral blood-derived allogeneic SCT from an HLA-identical sibling or matched unrelated donor cures more than half the patients with severe aplastic anaemia, thalassaemia major, congenital immunodeficiency diseases and genetic metabolic disorders. Among the malignant conditions, acute and chronic leukaemia, multiple myeloma, Hodgkin and non-Hodgkin lymphoma, and high risk neuroblastoma are important conditions that can be treated by HSCT. The major morbidities associated with HSCT are regimen-related toxicities, development of acute or chronic graft-versus-host disease (GVHD), failure of engraftment of the bone marrow and complications related to the immunodeficiency that occurs in the post-transplant period. Peripheral blood stem cells are now being used as an alternative to bone marrow stem cells for allogeneic HSCT and exclusively for autologous HSCT. Reduced intensity conditioning for allogeneic HSCT has resulted in a lower frequency and severity of GVHD and risk of infections. This has resulted in allogeneic HSCT being done in older patients and for those with co-morbid conditions. Patients with low grade Hodgkin and non-Hodgkin lymphoma, chronic lymphocytic leukaemia and multiple myeloma appear to benefit more with this approach. Prevention of acute GVHD while maintainingthe graft-versus-tumour effect and close monitoring of the kinetics of chimerism hold promise for improving the outcome of those receiving reduced intensity allogeneic HSCT. In recipients ofautologous HSCT, identification of patients at increased risk for relapse and use of agents (interferon, interleukin-2) post-transplant to augment the graft-versus-tumour effect are possible areas of further research.