Blood eosinophilia as a marker of favorable outcome after allogeneic stem cell transplantation.

Eosinophilia is observed in a variety of disorders including acute and chronic graft-versus-host disease (GVHD). The clinical records of 237 patients who underwent allogeneic stem cell transplantation (allo-SCT) were retrospectively reviewed. Eosinophilia, defined as a relative eosinophil count>4% within the first 100 days, was observed in 135 patients (57%). The incidence of grades II-IV acute GVHD was significantly higher in patients without eosinophilia than in those with eosinophilia (68% vs. 43%; P<0.001). The incidence of chronic GVHD was significantly higher in patients without eosinophilia than in those with eosinophilia (73% vs. 56%; P=0.011). Relapse rate was similar between patients with and without eosinophilia (33% vs. 27%; P=0.438). The probability of nonrelapse mortality was 10% in patients with eosinophilia, which was significantly lower than that in patients without eosinophilia (31%; P<0.001), and the overall survival (OS) at 3 years was 67% in patients with eosinophilia, which was significantly higher than that in patients without eosinophilia (51%; P=0.003). Multivariate analysis identified older age, high-risk disease, acute GVHD, sex disparity between patient and donor, and the absence of eosinophilia as significant factors for reduced OS. These data lead us to conclude that eosinophilia after allo-SCT may serve as a favorable prognostic marker.