Myeloablative Conditioning Regimen in Haploidentical Stem Cell Transplantation With Posttransplant Cyclophosphamide in Children With High-risk Hematologic Malignancies

Limited information is available on outcomes of haploidentical stem cell transplantation (haploSCT) with posttransplant cyclophosphamide using myeloablative conditioning regimens in children and adolescents. We report the results of a single-institution retrospective study of myeloablative haploSCT in 36 children and adolescents (median age, 8 y; range, 9 mo to 22 y) with high-risk hematologic malignancies. Donor engraftment occurred in 31 of 33 evaluable patients (94%). Recovery of neutrophils and platelets occurred at a median of 15 and 20 days. Cumulative incidence of acute graft-versus-host-disease (GVHD) grades II to IV and grades III to IV at 100 days was 36 +/- 8.7% and 10 +/- 5.4% and of chronic GVHD at 1 year was 55 +/- 9.2%, with 31 +/- 8.6% moderate to severe. Nonrelapse mortality was 16 +/- 6.1% and 22 +/- 6.9% at 100 days and 1 year. The cumulative incidence of relapse at 4 years was 32 +/- 8.8%. With a median follow-up of 57 months (range, 8 to 89 mo), the overall survival and event-free survival at 4 years was 55.6 +/- 8.7% and 44.8 +/- 8.5%. Myeloablative conditioning T-replete haploSCT with posttransplant cyclophosphamide is a viable alternative to matched unrelated transplantation for children and adolescents with high-risk hematologic malignancies. The high rates of nonrelapse mortality and chronic GVHD is a concern and deserves careful consideration.