Impact of Cytomegalovirus Reactivation and Natural Killer Reconstitution on Outcomes after Allogeneic Hematopoietic Stem Cell Transplantation: A Single-Center Analysis.

Cytomegalovirus (CMV) reactivation and natural killer (NK) cell reconstitution are well-recognized immunologic events occurring after allogeneic stem cell transplantation (allo-SCT). We aimed to study the outcome of CMV reactivation (CMVR) and NK cell reconstitution in patients with hematologic malignancies after allo-SCT. We retrospectively studied 246 adult patients (152 men, 94 women; median age, 51 years [range, 18 to 69]) who underwent allo-SCT for hematologic malignancies at the Kanagawa Cancer Center. CMVR was defined as initiation of preemptive CMV therapy after pp65 antigenemia surveillance. All patients' lymphocyte subsets were monitored by flow cytometry at 180, 365, and 730 days post-transplant. The median follow-up period was 3.2 years (range, .8 to 9.6 years). CMVR occurred in 141 patients (57%) at a median of 45 days (range, 15 to 93). In patients without CMVR (CMVR-) versus those with CMVR (CMVR+), 5-year overall survival (OS), nonrelapse mortality (NRM), and cumulative incidence of relapse (CIR) were 79% versus 55% (P < .001), 3% versus 16% (P = .012), and 28% versus 38% (P = .09), respectively. CD8+ T cell and CD3-CD56+ NK cell subset were higher in CMVR+ patients at day 100 post-transplant. Multivariate analysis showed that adverse factors for OS were represented by no remission, CMVR, and lower CD16+CD57-NK cell counts. Overall, a higher NK cell subset significantly contributed to a lower CIR. Among subgroups of CMVR+ patients, CD16+CD57-NK cells represented a favorable factor for OS, NRM, and CIR. CMVR was an adverse event after allo-SCT. NK cell reconstitution may contribute to improved outcomes, especially in CMVR+ subgroups.