CMV reactivation after allogeneic HCT is associated with a reduced risk of relapse in acute lymphoblastic leukemia.

Cytomegalovirus reactivation (CMVR) after allogeneic hematopoietic cell transplantation (HCT) is a frequent complication related to survival outcomes, but the impact of CMVR on relapse is still unclear, especially in acute lymphoblastic leukemia (ALL). In this nationwide retrospective study, we included patients with acute myeloid leukemia (AML) and ALL in first or second complete remission who underwent their first HCT using pre-emptive strategy for CMVR. Because ninety percent of cases with CMVR had occurred by day 64 and ninety percent of cases with grades II to IV acute GVHD had occurred by day 58, a landmark point was set at day 65. In the landmark analyses, 3793 patients with AML and 2213 patients with ALL who survived without relapse for at least 65 days were analyzed. In the multivariate analyses, CMVR was associated with a lower incidence of relapse in both AML (hazard ratio [HR], 0.81; 95% confidence interval [CI], 0.69-0.95; P = 0.009) and ALL (HR, 0.81; 95% CI, 0.66-0.99; P = 0.045). These findings were confirmed when we treated CMVR as a time-dependent covariate. Moreover, our study suggested that the protective effect of CMVR on relapse was independent of acute GVHD. A post-hoc subgroup analysis that combined AML and ALL showed that CMVR had a mild anti-leukemia effect without effect modification in contrast to the impact of CMVR on NRM. Our findings may provide important implications for the strategy used for CMV prophylaxis after HCT.