HLA-haploidentical peripheral blood stem cell transplantation following reduced-intensity conditioning with very low-dose antithymocyte globulin for relapsed/refractory acute leukemia in pediatric patients: a single-institution retrospective analysis

The prognosis of relapsed/refractory (R/R) pediatric acute leukemia is extremely poor. We retrospectively reviewed 20 consecutive pediatric patients with R/R acute leukemia who underwent a first HLA-haploidentical peripheral blood stem cell transplantation following reduced-intensity conditioning (haplo-RIC-PBSCT) with very low-dose antithymocyte globulin (ATG) between 2012 and 2019. Of these 20 patients, 7 patients had acute lymphoblastic leukemia, and 13 had acute myeloid leukemia. At the time of haplo-RIC-PBSCT, 15 patients had active disease. The median follow-up duration for survivors was 56 months (range 22–108 months). Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus, short-term methotrexate, methylprednisolone, and ATG 1.25 mg/kg on day-2. The 2-year cumulative incidence of transplant-related mortality and relapse were 5.0% [95% confidence interval (CI) 0.7–30.5%)] and 57.8% (95% CI 37.4–79.6%), respectively. Among the 20 patients, 16 (80.0%) developed grade III–IV acute GVHD, and 2 developed severe chronic GVHD. The 2-year event-free survival and overall survival rates were 40.0% (95% CI 19.3–60.0%) and 50.0% (95% CI 27.1–69.2%), respectively. Although the sample size is small, the survival outcomes of the present study are encouraging.