[Non-myeloablative or reduced intensity stem cell transplantation preparative regimens]

Allogeneic hematopoietic stem cell transplantation (HSCT) has been based on the use of myeloablative chemotherapy and radiotherapy conditioning regimens to eradicate malignancy and to eliminate host hematopoiesis and immune cells, but this approach is associated with a high risk of complications. A number of non-myeloablative or reduced-intensity preparative regimens for HSCT(NST or RIST) have been proposed to reduce regimen-related toxicities. Two general strategies have emerged, based on the use of (1) immunosuppressive chemotherapeutic drugs, usually a purine analog in combination with an alkylating agent, and (2) low-dose total body irradiation. NST/RIST have been feasible in elderly patients and in patients with organ dysfunction or other comorbidities precluding standard ablative conditioning, however the long-term impact is not yet established. The indication for NST/RIST and the optimal preparative regimen need to be defined for each malignancy in controlled clinical trials.