Novel preparative regimens in hematopoietic stem cell transplantation.

Hematopoietic stem cell transplantation is an established treatment modality for malignant and non-malignant diseases. Prior to the infusion of allogeneic or autologous cells, patients usually receive radiation or chemotherapy. This "preparative" or 'conditioning' regimen provides treatment for the underlying disease and is expected to impair the recipient's immune system and allow engraftment. The last decade witnessed a significant reduction in treatment-related mortality, in great part a result of less toxic preparative regimens and improvements in supportive care. Another important trend has been the incorporation of newer drugs to 'classic' conditioning regimens, as illustrated by the addition of rituximab to BEAM and other combinations. It is expected that this trend will continue leading to increased cure rates by incorporation of targeted therapies to hematopoietic transplant. The next decade will likely witness further integration of new preparative regimens with graft engineering, and pharmacologic, cellular and immunologic post transplant interventions. The design of creative clinical trials that will allow the critical evaluation of the role of these new approaches in transplantation will also be a major challenge to the transplant community in the years to come. In this article, we review newer transplant conditioning regimens and discuss their indications and future directions in this rapidly changing landscape.