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.