Background
Patients with severe combined immunodeficiency disease (SCID) who have matched sibling donors (MSD) can proceed to hematopoietic cell transplantation (HCT) without conditioning chemotherapy.
Objective
To determine whether the results of HCT without chemotherapy-based conditioning from matched unrelated donors (URD), either from volunteer adults or umbilical cord blood, are comparable to those from matched sibling donors (MSD).
Methods
A multicenter survey of SCID transplant centers in North America, Europe, and Australia to compile retrospective data on patients who have undergone unconditioned HCT, from either URDs (n = 37) or MSDs (n = 66).
Results
Most patients undergoing URD HCT (92%) achieved donor T-cell engraftment, compared to 97% for MSDs, however, estimated 5-year overall and event-free survival were worse for URD recipients (71% and 60%, respectively), compared to MSD recipients (92% and 89%, respectively; P <0.01 for both). URD recipients who received pre-HCT serotherapy had similar 5-year OS (100%) to MSD recipients. The incidences of Grade II-IV acute and chronic GVHD were higher in URD (50% and 39%, respectively), compared to MSD recipients (22% and 5%, respectively; P <0.01 for both). In the surviving patients, there was no difference in T-cell reconstitution at last follow-up between the URD recipients and MSD recipients, however MSD recipients were more likely to achieve B-cell reconstitution (72% vs. 17%; P <0.001).
Conclusion
Unconditioned URD HCT achieves excellent rates of donor T-cell engraftment similar to MSD recipients, and reconstitution rates are adequate. However, only a minority will develop myeloid and B cell reconstitution and attention must be paid to GVHD prophylaxis. This approach may be safer in children ineligible for intense regimens to spare potential complications of chemotherapy.
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