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.

<bold><italic>Introduction:</italic></bold> 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. <bold><italic>Methods:</italic></bold> We conducted a retrospective historical control study consisting of patients (<italic>n</italic> = 210) who underwent myeloablative allogeneic hematopoietic stem-cell transplantation (HSCT) from 2014 to 2020. <bold><italic>Results:</italic></bold> The incidence of acute GVHD was lower in the ATG group (51.4%) than the non-ATG group (control) (70.0%, <italic>p</italic> = 0.010). The incidence of chronic GVHD was also lower in the ATG group at 1-year (36.4% vs. 62.9%, <italic>p</italic> < 0.001) and 2-year (40.0% vs. 65.7%, <italic>p</italic> < 0.001) post-HSCT. The mortality due to GVHD was higher in the control (18.5%) than the ATG group (4.3%; <italic>p</italic> = 0.024). The severe GVHD-relapse-free survival was higher in the ATG group (36.4%) than the control (12.9%; <italic>p</italic> < 0.001). Nevertheless, the 2-year overall survival was similar. <bold><italic>Conclusion:</italic></bold> 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. [ABSTRACT FROM AUTHOR]