Unrelated versus related allogeneic stem cell transplantation after reduced intensity conditioning

Background. The use of reduced intensity conditioning (RIC) regimens in allogeneic hematopoietic stem cell transplantation (HSCT) has increased over the past five years. Patients. In this study, involving 137 patients, we compared the outcome after RIC in patients receiving grafts from matched unrelated donors (MUD; n=74) and sibling donors (n=63). The MUD and sibling groups were comparable regarding diagnosis, including solid tumors and hematological malignancies, and conditioning regimens. Results. Engraftment was successful in most patients (88%), with no significant difference between MUD and sibling transplants. Cytomegalovirus (CMV) infection was more common in the MUD group (65%) than in the sibling group (46%) (P=0.04). No difference in severe acute graft-versus-host disease (GVHD) was found between the groups. However, the incidence of chronic GVHD was higher after sibling transplants. This was probably due to higher donor age in this group, since this was the only significant risk factor for chronic GVHD in multivariate analysis. The incidence of transplant related mortality (TRM) was significantly higher after MUD transplantation (40%) than after sibling transplantation (16%) (P < 0.01). Because relapse/disease progression was more common after sibling transplantation, there was no significant difference in overall survival between the two groups. Conclusion. Using unrelated donors after RIC is feasible, but it resulted in more CMV infection and increased transplant-related mortality. Survival was comparable to that of sibling transplants.