Steep neutrophil recovery following unrelated bone marrow transplantation is a major risk factor for the development of acute graft-vs-host disease-a retrospective study.

The speed of neutrophil recovery following allogeneic hematopoietic cell transplantation (allo-HCT) varies widely among patients. We retrospectively evaluated the slope of neutrophil recovery (N slope) in 120 patients who underwent a first unrelated bone marrow transplantation with granulocyte-colony-stimulating factor support between 2009 and 2018. The median N slope was 205.5/µl/day. We classified patients into low (n = 59) and high (n = 61) N slope groups with a cutoff value of 200/µl/day. The high N slope group correlated with older patients, RIC regimen, high CD34+ cells, and recent transplantation. The cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was significantly higher in the high N slope group than in the low N slope group (44.3% vs. 16.9%, P < 0.001). In multivariate analysis, high N slope was identified as a significant independent risk factor for grade II-IV aGVHD, irrespective of the involved organs. There were no differences in relapse, nonrelapse mortality, or overall survival between the two groups. In conclusion, the difference in N slope after allo-HCT may predict the risk of aGVHD. Prevention and treatment of GVHD according to the changes in the neutrophil count may improve post-transplant complications.