UCSF

Limited clinical data are available to assess whether the sequencing of cyclophosphamide (Cy) and total body irradiation (TBI) changes outcomes. We evaluated the sequence in 1769 (CyTBI, n = 948; TBICy, n = 821) recipients of related or unrelated hematopoietic cell transplantation who received TBI (1200 to 1500 cGY) for acute leukemia from 2003 to 2010. The 2 cohorts were comparable for median age, performance score, type of leukemia, first complete remission, Philadelphia chromosome-positive acute lymphoblastic leukemia, HLA-matched siblings, stem cell source, antithymocyte globulin use, TBI dose, and type of graft-versus-host disease (GVHD) prophylaxis. The sequence of TBI did not significantly affect transplantation-related mortality (24% versus 23% at 3 years, P = .67; relative risk, 1.01; P = .91), leukemia relapse (27% versus 29% at 3 years, P = .34; relative risk, .89, P = .18), leukemia-free survival (49% versus 48% at 3 years, P = .27; relative risk, .93; P = .29), chronic GVHD (45% versus 47% at 1 year, P = .39; relative risk, .9; P = .11), or overall survival (53% versus 52% at 3 years, P = .62; relative risk, .96; P = .57) for CyTBI and TBICy, respectively. Corresponding cumulative incidences of sinusoidal obstruction syndrome were 4% and 6% at 100 days (P = .08), respectively. This study demonstrates that the sequence of Cy and TBI does not impact transplantation outcomes and complications in patients with acute leukemia undergoing hematopoietic cell transplantation with myeloablative conditioning.