A marrow reaction associated with acute-graft-versus-host disease (a-GVHD) has been demonstrated in experimental models; its existence in human transplantation is controversial. The aim of the present study was to investigate whether clonogenic marrow precursors are an early marker for a-GVHD and transplant-related mortality (TRM). We prospectively studied 133 patients for colony-forming units-granulocyte-monocyte (CFU-GM) at day +18/+19 posttransplantation. CFU-GM frequency below the 25th percentile was predictive of an acute GVHD score I°-IV° when evaluated in multivariate logistic regression analysis (odds ratio = 13.551, 95% confidence interval [CI]: 1.583-116.031, p = 0.01). In the group with a clonogenic frequency below the 25th percentile, the cumulative incidence of GVHD grades II-IV was significantly more frequent with respect to the group with a frequency greater than the 25th percentile, 86% versus 54% (Gray test: p = 0.02). In multivariate Cox proportional analysis, a CFU-GM frequency below the 25th percentile at day +18 was associated with reduced overall survival (OS) (hazard ratio = 1.778, 95% CI: 1.022-3.093, p = 0.04). Patients with a frequency of CFU-GM greater than the 25th percentile had increased TRM with respect to patients with a clonogenic cell frequency greater than the 25th percentile (33.5% vs. 13.0%, p = 0.01). Patients were divided based on median content of viable CD34+ cells, and measurement of viable CD34+ cells was predictive for OS (p = 0.005) and TRM (p = 0.003). A weak correlation was observed between CFU-GM frequency in marrow at day +18 and levels of IL-2 receptor (IL-2R) in plasma (r = -0.226, p = 0.03). We conclude that marrow progenitor cell counts, on day +18 may be a useful marker for identifying patients at risk for severe a-GVHD, TRM, and inferior survival.
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