TITLE Improved Survival after Unrelated Donor Bone Marrow Transplant in Children with Primary Immunodeficiency using a Reduced Intensity Conditioning Regimen. SHORT TITLE Improved survival after PID transplants using RIC. AUTHORS

The optimal approach to stem cell transplantation in children with immunodeficiency who lack a matched family donor is controversial. Unrelated donor stem cell transplant gives equivalent outcome to mismatched family donor stem cell transplant in Severe combined immunodeficiency whereas unrelated donors may be preferable in nonSevere combined immunodeficiency children. However, unrelated donor stem cell transplant with conventional conditioning regimens has been associated with significant treatment related toxicity, particularly in non-severe combined immunodeficiency patients with pre-existing organ dysfunction. We report the outcome of a series of 33 consecutive unrelated donor transplants performed at our centre in children with primary immunodeficiency using a reduced intensity conditioning regimen between 1998 and 2001. We have compared these outcomes with a retrospective control cohort of 19 patients transplanted with myeloablative conditioning between 1994 and 1998. All children in both groups had primary engraftment. There was no statistical difference in the speed of immune reconstitution or incidence of graft versus host disease between the 2 groups. Overall survival was significantly better in the reduced intensity conditioning group-31/33 (94%) compared with 10/19 (53%) in the myeloablative conditioning group (p = 0.014). We conclude that the reduced intensity conditioning regimen results in improved survival and reduced transplant related mortality compared to myeloablative conditioning in high risk patients undergoing unrelated donor transplant. For personal use only. on August 30, 2017. by guest www.bloodjournal.org From