The Total Body Irradiation Schedule Affects Acute Leukemia Relapse After Matched T Cell–Depleted Hematopoietic Stem Cell Transplantation

Abstract

We sought to determine whether the total body irradiation (TBI) schedule affected outcome in patients with acute leukemia in complete remission who received Tcell-depleted allogeneic hematopoietic stem cell transplantation from HLA identical siblings. The study recruited 55 patients (median age, 48years; age range, 20-66years; 30 men and 25 women; 34 with acute myeloid leukemia and 21 with acute lymphoid leukemia). Hyperfractionated TBI (HTBI) (1.2Gy thrice daily for 4days [for a total dose of 14.4Gy] from day -12 to day -9) was administered to 29 patients. Single-dose TBI (STBI) (8Gy, at a median dose rate of 10.7cGy/min on day -9) was given to 26 patients. All patients achieved primary, sustained engraftment with full donor-type chimerism. At 10years, the overall cumulative incidence of transplant-related mortality was 11% (SE, ±0.1%). It was 7% (SE, ±0.2%) after HTBI and 15% (SE, ±0.5%) after STBI (P=.3). The overall cumulative incidence of relapse was 33% (SE, ±0.5). It was 13% (SE, ±0.5%) after HTBI and 46% (SE, ±1%) after STBI (P=.02). The overall probability of disease-free survival (DFS) was 59% (SE, ±7%). It was 67% (SE, ±0.84%) after HTBI and 37% (SE, ±1.4%) after STBI (P=.01). Multivariate analyses showed the TBI schedule was the only risk factor that significantly affected relapse and DFS (P=.01 and P=.03, respectively). In patients with acute leukemia, HTBI is more efficacious than STBI in eradicating minimal residual disease after HLA-matched Tcell-depleted hematopoietic stem cell transplantation, thus affecting DFS.