Treatment of relapsed acute leukemia by Ara C plus donor lymphocyte infusion using CD34＋ cells reserved at the time of allogeneic transplantation

Currently, there is no standard therapy available for relapsed acute leukemia after allogeneic hematopoietic cell transplantation (allo-HCT). In this study, we evaluated the efficacy of cytoreduction with cytarabine followed by granulocyte colony-stimulating factor (G-CSF)-primed donor lymphocyte infusion (DLI) for patients with acute leukemia who relapsed after allo-HCT. We retrospectively reviewed 255 patients who had received allo-HCT for acute leukemia/myelodysplastic syndrome. Patients were divided into two groups based on the CD34＋ cell dose they received during the initial transplantation; patients in the lower CD34＋ group received a dose lower than 6×10(6) cells/kg and those in the higher CD34＋ group received a dose higher than 6×10(6) cells/kg. No significant differences were noted between two groups with respect to overall survival, relapse-free survival, or graft-versus-host disease (GVHD)-free/relapse-free survival. Patients who relapsed after allo-HCT (n＝93) were assigned into early or late relapse groups using the median time to relapse as the threshold. Among the 93 patients with relapse, 39 received G-CSF-primed DLI. The median dose of CD3＋ cells was 2.82×10(7) cells/kg (range: 0.05-10.1). In the late relapse group, one-year overall survival was significantly higher in patients receiving DLI than that in patients not receiving DLI (53.4% ±7.4% vs. 26.7% ±7.4%; P＝0.039), whereas no DLI effect was detected within the early relapse group. In addition, the incidence of DLI-induced GVHD did not differ between the two groups. In conclusion, treatment with G-CSF-primed DLI after allo-HCT with a limited CD34＋ cell dose constitutes a feasible and effective option, which could replace second HCT in treatment of late-relapse patients.