Allogeneic hematopoietic stem cell transplantation (HSCT) after reduced intensity conditioning

Allogeneic hematopoietic stem cell transplantation (HSCT) following myeloablative (conventional) conditioning regimen is associated with a high incidence of transplant-related morbidity and mortality, limiting its use to younger patients without medical co-morbidities. Over the past few years, it has become more evident that the alloreactivity of transplanted donor immunocompetent cells against host tumor cells (graft-versus-tumor effects, GVT effects) plays a major role in eradicating malignancies after allogeneic HSCT. Based on these observations, several groups of investigators have developed reduced intensity conditioning (RIC) regimens allowing patients who are ineligible for conventional HSCT to benefit from the potentially curative GVT effects of allogeneic transplantation. Retrospective studies have suggested that, in comparison with myeloablative allogeneic HSCT, in patients aged 40-60 years, RIC HSCT was associated with a higher risk of relapse but a lower incidence of transplant-related mortality leading to similar progression-free and overall survivals. Prospective studies are ongoing to define which patients might most benefit from RIC HSCT, and to increase the anti-tumoral activity of the procedure while reducing the incidence and the severity of acute graft-versus-host disease (GVHD). In this article, we review the current status and perspectives of RIC HSCT.