The use of ATG abrogates the antileukemic effect of cytomegalovirus reactivation in patients with acute myeloid leukemia receiving grafts from unrelated donors.

Several studies provided evidence of a consistent antileukemic effect induced by cytomegalovirus (CMV) replication in acute myeloid leukemia (AML) patients receiving allogeneic hematopoietic stem cell transplantation (HSCT), however the use of antithymocyte globulin (ATG) as graft-versus-host disease prophylaxis, may potentially abrogate the protective effect of CMV infection. To address this issue, we retrospectively analyzed the risk of relapse in a cohort of 101 patients with AML who received grafts from an unrelated donor after a conditioning regimen including ATG. The cumulative incidence of CMV reactivation, evaluated by RT qPCR, was 59% at 12 months, and 93% of CMV reactivations occurred within the first 100 days post HSCT. The 5-year cumulative incidence of relapse in patients with CMV reactivation was 29% compared with 37% for patients without CMV reactivation, and the only factor associated with a reduced 5-year cumulative incidence of relapse was the disease status at HSCT (P < 0.001). In the multivariable model adverse cytogenetics (HR 2.42, 95% CI 1.02-5.72; P = 0.044) and acute GVHD (HR 3.36, 95% CI 1.32-8.54; P =  0.011) were independent risk factors for reducing overall survival (OS), while the presence of chronic GVHD was associated with a better OS (HR 0.37, 95% CI 0.15-0.89; P = 0.027). CMV replication was not an independent risk factor for OS (HR 1.06, 95% CI 0.07-15.75; P = 0.965). In Conclusion, the results of present study suggest that relapse prevention in patients with AML receiving T-cell depleted HSCT using ATG do not benefit from CMV reactivation.