Poster Session I: Stem cell transplantation - Clinical
Antithymocyte globulin (ATG), an important in vivo T-cell depletion strategy, has been used for graft-versus-host disease (GVHD) prophylaxis and shown significant clinical benefit. However, the optimal ATG dose remains unclear.
To assess the effectiveness of ATG at a total dose of 10.0 mg/kg and 7.5 mg/kg for haploidentical peripheral blood stem cell transplantation (PBSCT).
We retrospectively analyzed patients who underwent haploidentical PBSCT, receiving myeloablative conditioning and standard GVHD prophylaxis. ATG (rabbit thymoglobulin) at a total dose of 10.0 mg/kg (2.5 mg/kg on days −5 to −2) and 7.5 mg/kg (2.5 mg/kg on days −4 to −2) were used in the two groups.
40 and 35 patients were enrolled in the ATG-10 and ATG-7.5 groups, respectively. No significant difference was observed regarding the cumulative incidence of 100-day grade II-IV acute GVHD (20.0% vs 14.3%; p = 0.53) and 3-year chronic GVHD (13.7% vs 15.7%; p = 0.83). The 3-year probability of overall survival (OS) was 72.6% vs 74.4% (p = 0.81) and the 3-year probability of GVHD-free/relapse-free survival (GRFS) was 69.0% vs 53.0% (p = 0.16). The incidence of relapse in the ATG-7.5 group (30.9%) was higher compared with the ATG-10.0 group (17.1%), but this difference was not statistically significant (p = 0.20). In multivariate analysis, the ATG dose was not associated with relapse, while no further respond to therapy (NR) before PBSCT predicted relapse (HR 1.19, p = 0.04). There were 5 patients (12.5%) and 8 patients (22.9%) in NR in the ATG-10 and ATG-7.5 groups, respectively (p = 0.19). Additionally, the ATG-7.5 group had a trend for lower 300-day incidence of EBV reactivation (92.5% vs 80.0%; p = 0.14) and CMV reactivation (90.5% vs 80.0%; p = 0.16), and lower 100-day incidence of hemorrhagic cystitis (42.5% vs 28.6%; p = 0.15).
7.5 mg/kg ATG led to lower incidence of EBV reactivation, CMV reactivation and hemorrhagic cystitis without compromising control of grade II-IV acute GVHD, chronic GVHD and OS when compared with 10.0 mg/kg ATG. Therefore, ATG at a dose of 7.5 mg/kg could be considered for further study.