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 cut‐off 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 to 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 to IV aGVHD, irrespective of the involved organs. There were no differences in relapse, non‐relapse 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.