Effect of the Thiotepa dose in the TBF Conditioning regimen in Patients Undergoing Allogeneic Stem-Cell Transplantation for Acute Myeloid Leukemia in complete remission: A report from the EBMT Acute Leukemia Working Party

Abstract Background Allogeneic stem cell transplantation (allo-SCT) is a potentially curative therapy for patients with acute myeloid leukemia (AML) after achieving complete remission (CR). The aim of this study is to evaluate the optimal dose of thiotepa, administered as part of thiotepa-busulfan-fludarabine (TBF) conditioning regimen for allogeneic stem cell transplantation (allo-SCT) in adults with AML in CR. Methods In a retrospective multicenter analysis, we identified 240 patients allotransplanted from matched related or unrelated donors or T replete haplo-identical donors. We compared the transplantation outcomes of patients who received 5 mg/kg thiotepa and 2 days of iv busulfan at 6.4 mg/kg (T1B2F) versus those who received 10 mg/kg thiotepa with 2 days of iv busulfan at 6.4 mg/kg (T2B2F). The median follow-up was 20 months. Results On univariate analysis, the incidence of acute GVHD grade II-IV was significantly lower in the T1B2F group (19%) versus 32% in the T2B2F group (p=0.029). This result was confirmed on multivariate analysis; acute GvHD was higher for patients receiving T2B2F (p=0.024; HR 2.22). No significant change in NRM, PFS, or OS was observed between the 2 groups. Conclusion T2B2F is associated with a higher incidence of acute GVHD compared to T1B2F. These results suggest that a lower dose-intensity of thiotepa and busulfan in the TBF regimen may yield better results in AML patients in complete remission.