Intravenous Busulfan and Melphalan, Tacrolimus, and Short-Course Methotrexate Followed by Unmodified HLA-Matched Related or Unrelated Hematopoietic Stem Cell Transplantation for the Treatment of Advanced Hematologic Malignancies

Results of allogeneic hematopoietic stem cell transplantation (HCT) to treat advanced leukemia or myelodysplastic syndrome (MDS) remain poor due to excessive relapse and transplant-related mortality. To improve transplant outcome in this patient population, 43 patients (median age, 46.1 years) with high-risk or advanced lymphoid (n = 5) or myeloid malignancy (n = 38) were prospectively enrolled on a pilot trial of cytoreduction with intravenous busulfan and melphalan followed by an unmodified HLA-A, -B, and –DRβ1–matched related (n = 18) or unrelated (n = 25) HCT. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus and methotrexate. Thirty-four patients had ≥ 5% blasts at the time of HCT; 12 of these had > 20% blasts. Seventeen patients had unfavorable cytogenetics, 8 patients underwent transplantation for secondary MDS or acute myelogenous leukemia, and 4 patients had relapsed after a previous allogeneic transplantation. Although mucositis was the most significant regimen-related toxicity, requiring the addition of folinic acid rescue and failure to receive all 4 doses of methotrexate in 23 patients, the nonrelapse mortality at 30 and 100 days was low at 0% and 16%, respectively. The cumulative incidence of grade II-IV acute GVHD was 24%, and that of extensive chronic GVHD was 7%. With a minimum follow-up of 18 months, the estimated 3-year overall survival is 37% and the estimated disease-free survival (DFS) is 33%. For 18 patients with MDS (≤ RAEB-2) or high-risk myeloproliferative disorder, the estimated 3 year DFS is 61%. These data demonstrate the curative potential of this regimen in patients with high-risk myeloid malignancies.