Low-intensity conditioning is sufficient to ensure engraftment in matched unrelated bone marrow transplantation

Objective Matched unrelated bone marrow transplantation (BMT) for patients with hematological malignancies is associated with a high incidence of transplant-related complications due to high doses of chemoradiotherapy administered pre-BMT to ensure engraftment. The aim of this study was to investigate the feasibility of low-intensity conditioning for BMT from matched unrelated donors. Patients and Methods Sixteen patients with hematologic malignancies underwent non–T-cell–depleted BMT following a low-intensity conditioning regimen consisting of fludarabine monophosphate 30 mg/m2/day for 6 days, busulfan 4 mg/kg/day for 2 days, anti–T lymphocyte globulin 10 mg/kg/day for 4 days. Seven of the patients suffered from chronic myelogenous leukemia, four from acute lymphoblastic leukemia, four from acute myelogenous leukemia, and one from Ki-1 non-Hodgkinʹs lymphoma. Three of the patients had secondary leukemia and two were post–autologous BMT (ABMT). All patients were transplanted from fully matched unrelated donors. Results Fifteen of the 16 patients had 100% donor chimerism; no graft rejection was observed. None of the patients developed >Grade II veno-occlusive disease, sepsis, multiorgan failure, or renal or pulmonary toxicity. Four patients died posttransplant; one of thrombocytopenia and severe hemorrhagic cystitis, one of central nervous system toxicity, one of Grade IV graft-vs-host disease, and one following relapse (9 months post-BMT). Survival and disease-free survival at 36 months are 75% (95% confidence interval 46–90%) and 60% (95% confidence interval 30–80%), respectively. Conclusion These results indicate that low-intensity conditioning is sufficient to ensure stable engraftment of bone marrow grafts in a matched unrelated setting.