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

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.

Sixteen patients with hematologic malignancies underwent non-T-cell-depleted BMT following a low-intensity conditioning regimen consisting of fludarabine monophosphate 30 mg/m(2)/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-Hodgkin's lymphoma. Three of the patients had secondary leukemia and two were post-autologous BMT (ABMT). All patients were transplanted from fully matched unrelated donors.

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.

These results indicate that low-intensity conditioning is sufficient to ensure stable engraftment of bone marrow grafts in a matched unrelated setting.