Post-transplant cyclophosphamide versus anti-thymocyte globulin for graft-versus-host disease prevention in haploidentical transplantation for adult acute lymphoblastic leukemia

Abstract

Graft-versus-host disease (GVHD) prophylaxis for unmanipulated haploidentical hematopoietic cell transplantation (haplo-HCT) include post-transplant cyclophosphamide (PTCy) and anti-thymocyte globulin (ATG). Utilizing EBMT registry, we compared ATG versus PTCy based GVHD prophylaxis in adult acute lymphoblastic leukemia (ALL) patients undergoing haplo-HCT. Included were 434 patients; ATG (n=98) and PTCy (n=336). Median follow-up was ~2 years. Baseline characteristics were similar between the groups except that the ATG-group was more likely to have relapsed/refractory ALL (P=0.008), non-TBI conditioning (P<0.001), peripheral blood graft source (P=<0.001) and transplanted at an earlier time-period (median year of HCT 2011 vs. 2015). The 100-day grade II-IV and III-IV acute-GVHD was similar between ATG and PTCy, as was 2-year chronic-GVHD. On multivariate analysis (MVA), leukemia-free survival (LFS) and overall survival (OS) was better with PTCy compared to ATG prophylaxis. Relapse incidence (RI) was lower in the PTCy group (P=0.03), while non-relapse mortality (NRM) was not different. Advanced disease and lower performance score were associated with poorer LFS and OS and advanced disease with inferior GVHD-free/relapse-free survival (GRFS). Peripheral grafts were associated with higher GVHD compared to bone marrow grafts. In ALL patients undergoing unmanipulated haplo-HCT, PTCy for GVHD prevention resulted in lower RI and improved LFS and OS compared to ATG.

Figure 1.

Adjusted outcomes of patients with acute lymphoblastic leukemia undergoing haploidentical transplantation stratified by type of graft-versus-host disease prophylaxis. Data for recipients of anti-thymocyte globulin are shown in blue, those for recipients of post-transplant cyclophosphamide are shown in red. (A) Adjusted incidence of non-relapse mortality (NRM). (B) Adjusted relapse incidence (RI). (C) Adjusted estimates of leukemia-free survival (LFS), (D) Adjusted estimates of overall survival (OS).