PF753 IMPACT OF ANTI‐THYMOCYTE GLOBULIN DOSES IN UNRELATED HEMATOPOIETIC STEM CELL TRANSPLANTATION FOR PATIENTS WITH MYELOID NEOPLASM

Abstract

Background:Anti‐thymocyte globulin (ATG) is widely used for the prophylaxis of graft‐versus‐host disease (GVHD) in hematopoietic stem cell transplantation (HSCT). However, there is still controversy regarding the optimal dose of ATG.Aims:We analyzed the impact of ATG doses in unrelated HSCT for patients with myeloid neoplasm.Methods:This was a retrospective multi‐center study that assessed the impact of ATG doses on clinical outcomes in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) undergoing an unrelated HSCT. The patients who received peripheral blood stem cells (PBSC) transplantation after conditioning regimens containing i.v. busulfan (BU), fludarabine and rabbit ATG between 2010 and 2017 were included in this study.Results:A total of 96 patents, median age 45 years, with AML (n = 74) or MDS (n = 22) were included in our analyses. 66 patients (69%) received a myeloablative regimen (i.v. BU>6.4 mg/kg). High‐ATG (ATG 9 mg/kg), intermediate‐ATG (ATG 4.5–5 mg/kg) and low‐ATG (ATG 3 mg/kg) were given in 11, 49 and 36 patients, respectively. After a median follow‐up of 23 months, the cumulative incidence of extensive chronic GVHD was 9.1% in the high‐ATG group, 13.8% in the intermediate‐ATG group and 29.7% in the low‐ATG group (p = 0.31). The rate of 2‐year relapse‐free survival was significantly higher in the intermediate‐ATG group than other groups (30% in the high‐ATG group vs. 73.2% in the intermediate‐ATG group vs. 53.8% in the low‐ATG group, p = 0.048). The rate of 2‐year overall survival was similar (45.5%, 68.5% and 44.8%, respectively; p = 0.09). The rate of chronic GVHD–free and relapse‐free survival at 2 years was significantly higher in the intermediate‐ATG group (18.2% in the high‐ATG group vs. 53.8% in the intermediate‐ATG group vs. 18.8% in the low‐ATG group, p = 0.0086).Summary/Conclusion:Our study shows that the incidence of extensive chronic GVHD was similar regardless of the doses of ATG after transplantation of PBSC from unrelated donor for patients with AML or MDS. However, the rate of relapse‐free survival and the rate of a composite end point chronic GVHD–free and relapse‐free survival were significantly higher in the intermediate dose (4.5–5 mg/kg) of ATG group.