Curative potential of fludarabine, melphalan, and non-myeloablative dosage of busulfan in elderly patients with myeloid malignancy

Although the combination of fludarabine and high-dose melphalan (FLU/MEL) has been widely used in allogeneic stem cell transplantation, high-dose MEL causes life-threatening adverse events, especially in elderly patients. To reduce the toxicity of MEL without losing its antileukemic effect, we formulated a regimen comprising FLU (125 mg/m2), MEL (100 mg/m2), and a non-myeloablative busulfan dosage [4 mg/kg orally (oral) or 3.2 mg/kg intravenously (iv); FLU/MEL/BU]. We retrospectively analyzed 32 patients with myeloid malignancies who received FLU/MEL/BU at our institute. Median age was 59 years and the median observation period after allo-SCT was 8.2 years. The disease status of most of the patients (97%) at transplantation was controlled. The rate of neutrophil engraftment was 93.3%. The 5-year overall survival (OS), disease-free survival (DFS), non-relapse mortality (NRM), and relapse rate (RR) were 68.5%, 62.1%, 22.0%, and 15.9%, respectively, in all patients. Notably, the outcome of FLU/MEL/iv BU was excellent, with the 5-year OS and DFS being 75.6% and 70.8%, respectively, accompanied by a reduced 5-year NRM and RR of 19.3% and 9.8%, respectively. In conclusion, FLU/MEL/BU, particularly FLU/MEL/iv BU, has curative potential for controlled myeloid malignancies.