Megadose CD34+ Hemopoietic Stem Cell Transplantation for Patients with High Risk Acute Myeloid Leukemia Who Have No HLA Matched Donor: A Pilot Study of a Full Haplotype Mismatch Transplantation

BACKGROUND : Haploidentical transplantation has become a popular modality of treatment for acute myeloid leukemia (AML) patients lacking donors with matching HLA. We attempted to assess the success rate and ramifications of full haplotype mismatch transplantation. METHODS : Four patients received stem cell transplantation from their full haplotype mismatched family donors. The conditioning regimen included total-body irradiation, intravenous busulfan, antithymocyte globulin, and fludarabine. Megadose CD34+ stem cell transplants were performed, in a dosage range between 10.9×10(6)/kg and 20.6×10(6)/kg. Neither GvHD prophylaxis nor post-transplant G-CSF were administered. We monitored patients’ bone marrow cellularity and peripheral blood chimerism using real-time PCR. RESULTS : All patients evidenced stable engraftment. The most frequent side effect was severe mucositis, but all patients recovered successfully, without early death. No patients exhibited acute GvHD. Two refractory patients relapsed soon after transplantation. The other 2 patients have remained in good clinical condition, with a follow-up duration of 1–4 months. CONCLUSION : Using a newly-developed conditioning regimen, we were able to circumvent GvHD and graft failure, which are the main limitations associated with full haplotype mismatch transplantation. According to our analysis of the relevant literature, it appears that this is the first report of such a conditioning regimen.