Hemopoietic stem cell transplantation for myelodysplastic syndrome

The term myelodysplastic syndrome (MDS) describes a spectrum of disorders that are characterized by dysplastic marrow cell morphology, the development of peripheral blood cytopenias, and a tendency to evolve into acute myeloid leukemia. MDS has been recognized as a stem-cell disease, and hemopoietic stem-cell transplantation is currently the only potentially curative therapy. In patients with less advanced MDS (<5% blasts in the marrow), 3-year survival rates of 70% and 65% can be achieved with HLA-identical related and HLA-matched unrelated donors, respectively. The overall probability of disease recurrence in these patients is less than 5%. Of patients with advanced disease (5% marrow blasts or more), about 40% to 45% and 25% to 30% are surviving in remission after transplantation from a related or an unrelated donor, respectively. This inferior outcome is largely due to a higher incidence of post-transplantation relapse (20% to 30%). Inclusion of the International Prognostic Scoring System criteria into outcome analyses shows an inverse correlation between overall risk category and relapse-free survival after transplantation. Future trials should explore the usefulness of different transplantation regimens for different risk categories. Among patients with less advanced disease, use of a conditioning regimen that combines cyclophosphamide and busulfan, dose adjusted to reach target plasma levels, has been associated with improved survival in recipients of transplants from related and unrelated donors. It has also permitted successful hemopoietic stem-cell transplantation in patients as old as 66 years of age. Improved survival with transplants from unrelated volunteer donors has been achieved with selection of donors based on high-resolution HLA typing. Autologous stem-cell transplantation may provide excellent consolidation for selected patients who have obtained complete remission with conventional chemotherapy. High treatment-related morbidity and mortality rates, particularly after allogeneic transplantation, remain challenges that must be addressed with innovative approaches.