Supplementary Material for: Real-world impact of routine addition of anti-thymocyte globulin to standard GVHD prophylaxis in myeloablative unrelated donor transplants: important gains in graft vs host disease prevention though no difference in overall survival

Introduction: Anti-thymocyte 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 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.