Background: Graft-versus-host disease (GVHD) is one of the leading causes of non-relapse mortality and morbidity after allogeneic hematopoietic stem cell transplantation (allo-HCT).
Methods: We evaluated the outcomes of two well-established strategies used for GVHD prevention: in vivo T cell depletion using antithymocyte globulin (ATG) and ex vivo T cell depletion using a CD34-selected (CD34+) graft. A total of 525 adult patients (363 ATG, 162 CD34+) with intermediate or high-risk cytogenetics acute myeloid leukemia (AML) in first complete remission (CR1) were included. Patients underwent myeloablative allo-HCT using matched related or unrelated donors.
Results: Two-year overall survival estimate was 69.9% (95% CI, 58.5-69.4) in the ATG group and 67.6% (95% CI, 60.3-74.9) in the CD34+ group (p = 0.31). The cumulative incidence of grade II-IV acute GVHD and chronic GVHD was higher in the ATG cohort [HR 2.0 (95% CI 1.1-3.7), p = 0.02; HR 15.1 (95% CI 5.3-42.2), p < 0.0001]. Parameters associated with a lower GVHD-free relapse-free survival (GRFS) were ATG [HR 1.6 (95% CI 1.1-2.2), p = 0.006], adverse cytogenetic [HR 1.7 (95% CI 1.3-2.2), p = 0.0004], and the use of an unrelated donor [HR 1.4 (95% CI 1.0-1.9), p = 0.02]. There were no statistical differences between ATG and CD34+ in terms of relapse [HR 1.52 (95% CI 0.96-2.42), p = 0.07], non-relapse mortality [HR 0.96 (95% CI 0.54-1.74), p = 0.90], overall survival [HR 1.43 (95% CI 0.97-2.11), p = 0.07], and leukemia-free survival [HR 1.25 (95% CI 0.88-1.78), p = 0.21]. Significantly, more deaths related to infection occurred in the CD34+ group (16/52 vs. 19/112, p = 0.04).
Conclusions: These data suggest that both ex vivo CD34-selected and in vivo ATG T cell depletion are associated with a rather high OS and should be compared in a prospective randomized trial.
Keywords: Acute myeloid leukemia; Allogeneic hematopoietic cell transplantation; Antithymocyte globulin; CD34-selected graft; T cell depletion.