Impact of Early Cytomegalovirus Reactivation after Allogeneic Hematopoietic Stem Cell Transplantation on Relapse in Patients with Myelodysplastic Syndrome: A Nationwide Retrospective Study from Adult Myelodysplastic Syndrome Working Group of the JSTCT

Cytomegalovirus (CMV) reactivation is a prominent complication associated with adverse outcomes in allogeneic hematopoietic stem cell transplantation (HSCT). However, CMV reactivation after allogeneic HSCT may be associated with a lower incidence of relapse in some hematological malignancies. This study analyzed the Japanese registry data from 1,082 patients with myelodysplastic syndrome (MDS) who underwent their first allogeneic HSCT and survived for 100 days after transplantation without graft failure or disease relapse to investigate this association. Patients who received cord blood transplants, demonstrated in vivo T cell depletion, underwent prophylactic anti-CMV treatment, or diagnosed with secondary MDS were excluded. CMV reactivation measured by pp65 antigenemia within 100 days after allogeneic HSCT was observed in 57.5% of patients, with a median time of 46 days from transplant. The 5-year overall survival and cumulative incidence of relapse (CIR) in the cohort were 60.5% and 15.6%, respectively. The 5-year CIR showed no significant difference between patients with and without CMV reactivation (14.4% vs. 17.2%; P = 0.185). Interestingly, CMV reactivation within 100 days was significantly associated with a lower 5-year CIR (7.6% vs. 16.4%; P = 0.002) in patients with <5% myeloblasts in the bone marrow (BM) just before HSCT. Furthermore, this relevancy comfirmed even when excluding patients with Grade II to IV acute GVHD (Hazard ratio: 0.38; 95% confidential intervals: 0.18–0.801; P = 0.011). Our findings indicate a correlation between early CMV reactivation and MDS relapse, based on the proportion of myeloblasts in the BM. These results may contribute to the development of effective CMV prophylaxis post-HSCT.