Peripheral blood eosinophilia has a favorable prognostic impact on transplant outcomes after allogeneic peripheral blood stem cell transplantation.

Peripheral eosinophilia after allogeneic stem cell transplant (ASCT) may reflect the activation of the Th2 cytokine pathway. A retrospective analysis was performed to evaluate the impact of early- (before day 100: EEo) or late-onset (beyond day 100: LEo) eosinophilia (> or =0.5 x 10(9)/L in peripheral blood) on transplant outcomes after peripheral blood SCT (PBSCT) in 237 patients. The incidence of EEo and LEo was 43% at day 100 and 62% at 2 years, respectively. Compared with patients without LEo, improved transplant outcomes were observed in patients with LEo: better overall survival (OS; 86% versus 41%, P = 5 x 10(-11)), lower nonrelapse mortality (NRM; 10% versus 37%, P = 3 x 10(-6)), lower relapse incidence (11% versus 31%, P = 3 x 10(-5)), and higher GVHD-specific survival (GSS; 90% versus 64%, P = 1 x 10(-6)) were observed. In addition, similar finding was observed when transplant outcomes were analyzed according to the occurrence of eosinophilia at the onset of cGVHD. The multivariate analyses confirmed a favorable implication of LEo on OS, NRM, and GSS. LEo was associated with: (1) less severe chronic GVHD (cGVHD), (2) higher prevalence of autoantibodies, and (3) rapid lymphocyte count recovery after ASCT. In summary, the development of eosinophila after allogeneic PBSCT seemed to be a prognostic marker for improving transplant outcome.