Non-myeloablative allogeneic stem cell transplant: Achievements and perspectives

In the past concept, conditioning regimens for allogeneic hematopoietic ste m cell transplantation (HSCT) were assumed to have two roles: myeloablation and immunosuppression. Recent clinical and experimental data have shown th at intense immunosuppression, rather than myeloablation, is the primary req uirement for stable engraftment and that the main therapeutic component of allogeneic HSCT is attributed to graft-versus-leukemia/tumor (GVL/T) effect mediated by donor-derived T cells. Based on these findings, a new strategy of non-myeloablative stem cell transplantation (NST) has been developed fo r patients who are ineligible for conventional stem cell transplantation (C ST) because of the old age or organ dysfunction. Recent reports from many t ransplant centers have shown that application of NST decreased regimen-rela ted toxicities (RRT), while associated with consistent stable engraftment. In this review we overview the clinical development (background, clinical e xperience), remaining problems and future directions of NST.