Fludarabine, busulfan, and low-dose TBI conditioning versus cyclophosphamide and TBI in allogeneic hematopoietic cell transplantation for adult acute lymphoblastic leukemia.

The optimal conditioning regimen for adults undergoing transplantation for acute lymphoblastic leukemia (ALL) remains undetermined. Cyclophosphamide and total body irradiation (Cy/TBI) has emerged as a standard myeloablative regimen but is associated with significant toxicity. We compared outcomes between patients undergoing transplant for ALL at centers using Cy/TBI as standard of care and another center using fludarabine, busulfan, and low-dose TBI (400 cGy) in combination with anti-thymocyte globulin as its standard. Among 146 patients (74 Cy/TBI and 72 Flu/Bu/TBI) there were no significant differences in overall or progression-free survival between groups. Non-relapse mortality was similar (12% vs. 16.7% for Cy/TBI and Flu/Bu/TBI, respectively, p = .62) despite the Flu/Bu/TBI group having significantly worse performance status. Flu/Bu/TBI resulted in significantly lower cumulative incidence of relapse compared with Cy/TBI (2-year point estimate 18.5% vs. 31.5%, p = .05). These results demonstrate similar outcomes for patients receiving Flu/Bu/TBI versus Cy/TBI. Flu/Bu/TBI may allow the possibility of providing myeloablative conditioning to patients with poor performance status.