High Risk of Recurrence of Malignancy Noted in Four-day rATG Regimen After Allogeneic PBSCT From Matched Sibling Donors

Hitherto, the optimal timing of rabbit anti-thymocyte globulin (rATG) in matched sibling donor peripheral blood stem cell transplantation (MSD-PBSCT) remains to be elucidated. We wanted to evaluate the effect of a new timing strategy of rATG in MSD-PBSCT patients on transplantation outcomes. In this prospective single-arm phase 2 clinical trial, 45 consecutive MSD-PBSCT patients were enrolled from February 1, 2019, to January 31, 2021. The rATG was administered intravenously at a total dose of 5 mg/kg from day -5 to day -2 before graft infusion (4d-ATG group). Thirty-seven MSD-PBSCT patients receiving rATG at the same total dose of 5 mg/kg from day -5 to day -4 before graft infusion from December 1, 2014, to January 31, 2019 served as historical control (2d-ATG group). No graft failure occurred in either group. In the 4d-ATG group, median timing to neutrophil and platelet engraftment was 12 days. The cumulative incidences (CI) of grade 2-4 and grade 3-4 acute graft-versus-host disease (GVHD) at day 100 were 37.8% and 4.4%. The 2-year CIs of severe chronic GVHD and extensive chronic GVHD were 2.2% and 9.6%. The rates of cytomegalovirus (CMV) and Epstein-Barr virus (EBV) reactivation at day 180 were 24.4% and 37.8%, respectively. No patients died of non-relapse causes. Twenty-one patients relapsed at a median of 203 days after transplantation, and the 2-year cumulative incidence of relapse (CIR) was 51.4%. The 2-year probabilities of overall survival (OS), disease-free survival (DFS), and GVHD-free and relapse-free survival (GRFS) were 72.4%, 48.6%, and 40.8%, respectively. There were no significant differences between the 4d-ATG group and 2d-ATG group with regard to timing of neutrophil and platelet engraftment, incidences of CMV reactivation, EBV reactivation, acute GVHD, chronic GVHD, probabilities of OS, and GRFS. The 2-year CIR was significantly increased, and the 2-year DFS was significantly reduced in 4d-ATG group compared with the control group (CIR: 51.4% versus 13.5%, P <.001; DFS: 48.6% versus 75.7%, P =.014). High CIR and worse DFS were noted in MSD-PBSCT receiving 4d-ATG regimen compared with historical control (2d-ATG regimen). Inappropriate rATG timing may increase the risk of relapse after MSD-PBSCT in patients with hematologic malignancies. (C) 2023 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved. (c) 2022 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.

Automated summary

The optimal timing of rabbit anti-thymocyte globulin (rATG) in matched sibling donor peripheral blood stem cell transplantation (MSD-PBSCT) remains unknown. This study aimed to evaluate the effect of a new timing strategy of rATG on transplantation outcomes in MSD-PBSCT patients. The results showed no significant differences in engraftment, GVHD, and viral reactivation between the 2-day and 4-day rATG groups. However, the 4-day rATG group had a significantly higher relapse rate and lower disease-free survival compared to the historical control group.