Irradiation free conditioning regimen is associated with high relapse rate in Egyptian patients with acute lymphoblastic leukemia following allogeneic hematopoietic stem cell transplantation

Abstract

Abstract Background Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is a curative treatment for adult patients with acute lymphoblastic leukemia (ALL). Cyclophosphamide plus total body irradiation (TBI/Cy) or plus busulfan (Bu/Cy) is a widely used pre-transplant conditioning regimen for ALL. We retrospectively compared the overall survival (OS), disease-free survival (DFS), and other transplant outcomes of allo-HSCT in 119 adult patients with ALL who received an HLA-matched sibling allo-HSCT using TBI-based versus non-TBI-based conditioning regimens. Patients were divided into two groups by their conditioning regimen: TBI/Cy or Bu/Cy. Results Median OS was 11 months in the TBI/Cy group and 6.2 months in the Bu/Cy group. Median DFS was 11.1 months in the TBI group versus 6.8 months in the Bu group, without a statistically significant difference. A higher risk of relapse was observed with the Bu/Cy regimen (HR 2.709, CI 95% 1.106 to 6.638, p = 0.029). Patients who received a transplant in ≥ CR2 were associated with poor DFS. Conclusion Despite the high relapse rate in the non-TBI regimen (Bu/Cy), both regimens had no statistically significant differences in OS, DFS, and NRM. Additional prospective studies are indeed warranted to evaluate the long-term outcomes of radiation-free regimens, including oral and intravenous busulfan, and compare these regimens with TBI-based ones.