Prospective, Randomized, Comparative Study of Myeloablative Fludarabine/Busulfan and Fludarabine/Busulfan/Total Body Irradiation Conditioning in Myeloid Diseases

<b>Background/Objectives</b>: Allogeneic hematopoietic stem cell transplantation (alloSCT) is a curative treatment for myeloid diseases, yet relapse remains the major cause of post-transplant mortality. To reduce the risk of recurrence, we evaluated the addition of 400 cGy total body irradiation (TBI) to conditioning with fludarabine-busulfan (Flu/Bu4). <b>Methods</b>: In this prospective study, 46 patients with myeloid diseases were randomized to Flu/Bu4 or Flu/Bu4/TBI conditioning group. The Flu/Bu4 conditioning regimen consisted of fludarabine 40 mg/m² on days -6 to -3 followed by busulfan 130 mg/m² on days -6 to -3. Flu/Bu4/TBI conditioning regimen added 400 cGy TBI on day -1 to the FluBu4 regimen. <b>Results</b>: Among 34 acute myeloid leukemia (AML) patients, relapse was numerically lower in those who received Flu/Bu4/TBI (25%) versus Flu/Bu4 (44.4%) at three years (HR = 0.58, 95% CI 0.19 to 1.81, <i>p</i> = 0.35). Flu/Bu4/TBI appeared to increase the risk of non-relapse mortality (NRM) vs. Flu/Bu4 in AML patients at three years (25.0% versus 11.1%; HR = 2.11, 95% CI 0.51 to 8.83, <i>p</i> = 0.65). Overall survival (OS) was similar in AML patients undergoing conditioning with Flu/Bu4 (72.2%) versus Flu/Bu4/TBI (62.5%) at one year (<i>p</i> = 0.4). <b>Conclusions</b>: In conclusion, the addition of 400 cGy TBI to Flu/Bu4 reduced the risk of relapse but did not improve OS as a consequence of higher regimen-related mortality. Clinicaltrials.gov identifier: NCT01366612.