Early full donor myeloid chimerism after reduced-intensity stem cell transplantation using a combination of fludarabine and busulfan

Background and Objectives. The aim of this study was to evaluate lineage-sp ecific chimerism reconstitution after reduced-intensity allogeneic stem cel l transplantation (RIST) using a combination of fludarabine (30 mg/m(2) for 6 days) and busulfan (4 mg/kg for 2 days). Design and Methods. We prospectively enrolled 8 consecutive patients with h ematologic malignancies who were not candidates for conventional transplant ation because of either high age or organ dysfunction. Host-donor chimerism was evaluated using polymerase chain reaction-based amplification of a pol ymorphic short tandem repeat region. Results. All of our patients achieved engraftment within a median of 11 day s after transplantation. On day 30, full donor myeloid cell chimerism (> 90 %) was achieved in 7 patients whereas full donor T-cell chimerism was achie ved in only one patient. Thus, in contrast to other reported results, full donor chimerism was achieved earlier in the myeloid lineage than the T-cell lineage. On day 60, however, T-cell chimerism caught up with myeloid chime rism. Two patients developed grade II-IV acute graft-versus-host disease (G VHD) before the detection of full donor T-cell chimerism. Interpretation and Conclusions. Our findings suggest that the kinetics of l ineage-specific chimerism depend on the agents used in the conditioning reg imen, and may provide insight into the chimerism should be modified accordi ng to the type of conditioning regimen applied. (C) 2001, Ferrata Storti Fo undation.