The effects of macrophage activation on the outcome of allogeneic hematopoietic SCT (allo-HSCT) have yet to be fully examined. A total of 70 adult patients who received a first allo-HSCT for hematological diseases were studied. We counted the number of hemophagocytic cells in BM clot sections on day +14±7, and analyzed its impact on subsequent outcome. In all, 23 patients were diagnosed as having increased numbers of hemophagocytic cells (HP group), whereas 47 were not (non-HP group). The HP group was not associated with an increased incidence of acute or chronic GVHD, but was associated with worse hematopoietic recovery than the non-HP group. The 2-year OS for the HP group and the non-HP group was 30 and 65% (P<0.01), respectively, and 2-year non-relapse mortality was 48% and 27% (P<0.01), respectively. Multivariate analysis confirmed that the HP group was associated with a lower OS (hazard ratio (HR)=2.3; 95% confidence interval (CI), 1.0-5.4; P=0.048) and higher non-relapse mortality (HR=4.0; 95% CI, 1.6-9.9; P<0.01). The HP group had higher incidences of death due to graft failure (P<0.01) and endothelial complications, such as sinusoidal obstruction syndrome and transplant-associated microangiopathy (P=0.01). Macrophage activation is a previously unrecognized complication with negative impact on outcome of allo-HSCT.
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