Real-World Impact of Routine Addition of Antithymocyte Globulin to Standard GVHD Prophylaxis in Myeloablative Unrelated Donor Transplants: Important Gains in Graft-versus-Host Disease Prevention though No Difference in Overall Survival

Acta Haematol. 2024 Aug 28:1-11. doi: 10.1159/000541071. Online ahead of print.

Abstract

Introduction: Antithymocyte globulin (ATG) has been demonstrated to reduce the incidence of graft-versus-host disease (GVHD); however, it remains controversial whether these gains are offset by an increase in relapse.

Methods: We conducted a retrospective historical control study consisting of patients (n = 210) who underwent myeloablative allogeneic hematopoietic stem-cell transplantation (HSCT) from 2014 to 2020.

Results: The incidence of acute GVHD was lower in the ATG group (51.4%) than the non-ATG group (control) (70.0%, p = 0.010). The incidence of chronic GVHD was also lower in the ATG group at 1-year (36.4% vs. 62.9%, p < 0.001) and 2-year (40.0% vs. 65.7%, p < 0.001) post-HSCT. The mortality due to GVHD was higher in the control (18.5%) than the ATG group (4.3%; p = 0.024). The severe GVHD-relapse-free survival was higher in the ATG group (36.4%) than the control (12.9%; p < 0.001). Nevertheless, the 2-year overall survival was similar.

Conclusion: Our results confirm the effectiveness of ATG in prevention of GVHD in the real-world setting and enhanced GVHD-free survival. An important result is the equalization of overall survival between the ATG and control groups at 1- and 2-year post-HSCT and implies that earlier GVHD-associated mortality may be offset by later relapse mortality producing similar overall survival over time.

Keywords: Allogeneic hematopoietic stem-cell transplantation; Antithymocyte globulin; Graft-versus-host disease; Mortality; Relapse; Survival.