Haploidentical- versus identical-sibling transplant for high-risk pediatric AML: A multi-center study

Background: Human leukocyte antigen-identical sibling donor (ISD)-hematopoietic stem cell transplantation (SCT) is a potentially curative treatment for high-risk pediatric acute myeloid leukemia (AML). A haploidentical donor (HID) is readily available to almost all children. Previous studies have demonstrated that patients with HID-SCT had similar outcomes compared to ISD-SCT for pediatric and adult AML. However, the role of HID-SCT in high-risk pediatric AML is unclear.

Methods: To compare the overall survival of high-risk AML children who underwent either HID-SCT or ISD-SCT, we analyzed 179 cases of high-risk AML patients under 18 years of age treated with either ISD-SCT (n = 23) or HID-SCT (n = 156). Granulocyte colony-stimulating factor plus anti-thymocyte globulin-based regimens were used for HID-SCT. We also analyzed the subgroup data of AML patients at first complete remission (CR1) before SCT with known cytogenetic risk.

Results: The numbers of adverse cytogenetic risk recipients were 8 (34.8%) and 13 (18.8%) in the ISD-SCT group and the HID-SCT group, and the number of patients with disease status beyond CR1 were 6 (26.1%) and 14 (20.3%) in the two groups. The cumulative rates of grades II-IV acute graft-versus-host disease (GVHD) were 13.0% in the ISD-SCT group and 34.8% in the HID-SCT group (P = 0.062), with a three-year cumulative rates of chronic GVHD at 14.1% and 34.9%, respectively (P = 0.091). The relapse rate in the ISD-SCT group was significantly higher than that in the HID-SCT group (39.1% vs. 16.4%, P = 0.027); with non-relapse mortality at 0.0% and 10.6% (P = 0.113), respectively. The three-year overall survival rates were 73.0% for the ISD-SCT group and 74.6% for the HID-SCT group (P = 0.689). In subgroup analysis, the three-year relapse rate in the ISD-SCT group was higher than that in the HID-SCT group (50.0% vs. 9.2%, P = 0.001) and the three-year DFS in the ISD-SCT group (50.0%) was lower than that in the HID-SCT group (81.2%) (P = 0.021).

Conclusions: Unmanipulated HID-SCT achieved DFS and OS outcomes comparable to those of ISD-SCT for high-risk pediatric AML patients with potentially higher rate but manageable GVHD.