[Application of low-dose ATG for GVHD prophylaxis in patients undergoing PBSCT aged over forty years old]

Objective: To explore the effectiveness of a novel GVHD prophylaxis regimen containing low-dose anti-T lymphocyte globulin (ATG) in patients undergoing peripheral blood stem cell transplantation (PBSCT) from HLA-matched sibling donors (MSD) given both the patients and donors were aged over forty years old. Methods: From March 2013 to April 2017, 98 patients with hematologic malignancies were enrolled in the study. Standard GVHD prophylaxis consisted of the administration of cyclosporine A/tacrolimus and a short course of methotrexate. In ATG group, 43 patients received low-dose rabbit ATG (Sanofi, 1.5 mg/kg per day for 3 consecutive days) before PBSCT. A retrospective matched-pair analysis was performed and 55 matched controls were available. The therapeutic process and clinical outcome were retrospectively analyzed. Results: ①Neutrophil engraftment was achieved earlier in ATG group than the control one [13(11-17)d vs 14(12-24)d, P=0.001]. The time to platelet engraftment was similar between the two groups [14(11-43)d vs 15(11-42)d, P=0.071]. ②The cumulative incidence of aGVHD was significantly lower in ATG group [25.6% (95%CI 13.7%-39.3%) vs 49.1% (95%CI 35.2%-61.6%), P=0.018]. The incidences of grade Ⅱ-Ⅳ aGVHD [18.6% (95%CI 8.6%-31.5%) vs 23.6% (95%CI 13.4%-35.6%), P=0.509] and cGVHD [49.6% (95% CI 31.6%-65.3%) vs 56.4% (95% CI 41.4%-69.0%), P=0.221] were not significantly different between the two groups. ③The 1-year cumulative incidence of CMV viremia was similar between the two groups [21.1%(95%CI 10.3%-34.5%) vs 31.1% (95%CI 18.8%-44.2%), P=0.429]. ④The cumulative incidences of disease relapse [24.0%(95%CI 11.5%-38.9%) vs 24.0% (95% CI 12.1%-38.2%), P=0.608), non-relapse mortality [10.2% (95% CI 3.1%-22.1%) vs 21.6% (95% CI 9.4%-37.0%), P=0.411] and DFS [65.8% (95%CI 50.3%-81.3%) vs 54.4% (95%CI 37.7%-71.1%), P=0.955] were comparable between the two groups. 2-year overall survival (OS) was significantly better in ATG group than the control one [83.8% (95% CI 71.8%-90.0%) vs 58.0% (95% CI 42.2%-73.9%), P=0.019]. Conclusion: The addition of low-dose ATG decreased the incidence of aGVHD and improved OS. The incidences of viral infections and disease relapse remained to be similar between the two groups. These results suggested that elderly patients undergoing MSD-PBSCT may benefit from this low-dose ATG containing GVHD prophylaxis regimen.