Total Body Irradiation and Cyclophosphamide Plus Antithymocyte Globulin Regimen Is Well Tolerated and Promotes Stable Engraftment as a Preparative Regimen before T Cell–Replete Haploidentical Transplantation for Acute Leukemia

Abstract

We compared total body irradiation (TBI, 700 cGy)/cyclophosphamide (Cy, 3.6 g/m2)/simustine (250 mg/m2) plus antithymocyte globulin (ATG) (TBI/Cy plus ATG) with cytarabine (8 g/m2)/i.v. busulfan (Bu, 9.6 mg/kg)/Cy (3.6 g/m2)/simustine (250 mg/m2) plus ATG (modified Bu/Cy plus ATG) as preparative therapy in T cell–replete haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for acute leukemia. From August 2009 to August 2013, 38 consecutive patients using TBI/Cy plus ATG regimen for T cell–replete haplo-HSCT (TBI group) at our center were eligible, which contained 28 high-risk and 10 standard-risk patients. A nested case-control study was designed. Seventy-seven patients using modified Bu/Cy plus ATG regimen (Bu group) were randomly selected in a 1 to 3:1 ratio matching for age, disease and status, year of HSCT (±2 years), and length of follow-up. Only 1 graft failure occurred in the TBI group. The incidence and time of neutrophil and platelet engraftment were comparable between the 2 groups. Severe grades III/IV graft-versus-host disease was observed in 13.4% of Bu group and only 2.6% of TBI group (P = .083). More toxicity of the liver (37.7% versus 10.5%; P = .002) and more hemorrhagic cystitis occurred in the Bu group (49.3% versus 23.7%, P = .008). Diarrhea was more common in the TBI group (44.7% versus 22.1%; P = .031). No significant differences were found in the 2-year incidences of relapse (26.5% for TBI group versus 32.3% for Bu group, P = .742), 1-year transplant-related mortality (12.6% versus 16.2%, P = .862), 2-year overall survival (60.2% versus 57.0%, P = .937), and 2-year incidence of disease-free survival (57.9% versus 56.6%, P = .845) between the 2 groups. We conclude that the TBI/Cy plus ATG regimen seems to be feasible in T cell–replete haplo-HSCT, which promotes stable engraftment and a lower incidence of liver toxicity and hemorrhagic cystitis. However, longer follow-up is necessary to determine the late relapse rate and late toxicity.