Reduced Risk of Chronic Graft-Versus-Host Disease (cGVHD) by Rabbit Anti-Thymocyte Globulin (ATG) in Patients Undergoing Matched Sibling Donor Transplantation in Hematological Malignancies.

BACKGROUND With the addition of anti-thymocyte globulin (ATG) to GVHD prophylaxis in patients undergoing transplantation of peripheral blood stem cells (PBSCT), the incidence of cGVHD decreases. However, the optimal dose and timing of ATG remain undetermined. MATERIAL AND METHODS In this historical controlled trial, data from 85 patients who had hematological malignancies and underwent matched sibling donor (MSD)-PBSCT were used to analyze the effectiveness of rabbit ATG (rATG) for prophylaxis of GVHD. Forty patients received 5 mg/kg rATG used for days -5 to -2, and 45 patients did not receive ATG. RESULTS All patients had successful engraftment except for 2 in the non-ATG group, who had platelet engraftment failure. The 2-year cumulative incidence of chronic GVHD (cGVHD) in the ATG group versus non-ATG group was 19.3% (95% CI, 8.4-33.6%) versus 61.4% (95% CI, 45.4-73.9%) (P<0.001), and in those with moderate to severe cGVHD it was 11.0% (95% CI, 3.4-23.6%) versus 31.8% (95% CI, 18.8-45.6%) (P=0.029), respectively. The 2-year cumulative incidence of non-relapse mortality and relapse (CIR) were 0% versus 15.5% (95% CI, 6.8-27.5%) (P=0.018), and 53.3% (95% CI, 35.6-68.1%) versus 26.7% (95% CI, 14.9-40.0%) (P=0.019), respectively. No differences were found in other survival outcomes. In the multivariate analysis, ATG was an independent protective factor for moderate to severe cGVHD (HR=0.314, 95% CI, 0.103-0.958, P=0.042), and was an independent poor risk factor for CIR (HR=2.337, 95% CI, 1.133-4.822, P=0.022). CONCLUSIONS ATG in our strategy was effective for prophylaxis of cGVHD, whereas the relapse rate was increased in patients with rATG.