Clinical significance of the administration of cytarabine or thiotepa in addition to total body irradiation and cyclophosphamide for allogeneic hematopoietic cell transplantation in patients with acute leukemia

A multicenter retrospective study was performed to determine the significance of adding cytarabine (CA) or thiotepa (TT) in the context of total body irradiation (TBI) and cyclophosphamide (CY). A total of 322 patients who underwent allogeneic hematopoietic cell transplantation (HCT) were distributed to the following three groups: TBI/CY (n = 75), TBI/CY/CA (n = 77), and TBI/CY/TT (n = 170). In the TBI/CY/TT group, 164 of patients (96 %) received HCT during the previous year (2000–2005). Multivariate analysis revealed that the TBI/CY/TT group demonstrated a trend of poorer survival rate than the TBI/CY group, [hazard ratio (HR) = 1.49, 95 % confidence interval (CI) 0.99–2.24, P = 0.055] with a higher non-relapse mortality (NRM) (HR = 2.34, 95 % CI 1.35–4.06, P = 0.002) rates, while TBI/CY/CA group demonstrated similar outcomes. Even in the subgroup analyses of disease type or disease risk, the outcomes with intensified conditioning regimens were not superior to those with TBI/CY. In conclusion, although the significant bias has to be carefully considered, the clinical benefit of adding CA or TT to the TBI/CY regimen was not demonstrated.