Background: There is compelling evidence that blood-borne tissue factor that is predominantly found on circulating microparticles (MPs) plays an important role in both, cancer biology and organ and stem-cell transplantation (SCT). Therefore, we hypothesized that numbers of tissue factor bearing MPs might be associated with complications and outcome in allogeneic SCT (allo-SCT).
Materials and methods: In a prospective study, we enumerated total, platelet, endothelial, and tissue factor bearing MPs in plasma samples obtained from up to 60 patients with hematologic diseases at different time-points during the course of allo-SCT by flow cytometry. Patient- and transplant-related risk factors were included in statistical analysis.
Results: Mean follow-up time was 968 days (0-1981 days). Thirty-four (56.7%) patients died, 17 due to transplant-related mortality (28.3%). High numbers of tissue factor positive MPs more than 500/μL before conditioning were predictive for shorter overall survival (P=0.017, hazard ratio=4.5) in multivariate analysis. This was mainly caused by an increase in transplant-related mortality (P=0.010, hazard ratio=11.0) with cumulative incidences at 1 year of 68.8% compared with patients with lower values (20.1%; P=0.002).
Conclusions: Tissue factor bearing MPs might be useful biomarkers for risk stratification in allo-SCT patients and further studies should investigate their origin, functional properties, and optimal cut-off values.