Randomized Trial of Busulfan Vs Total Body Irradiation Containing Conditioning Regimens for Children with Acute Lymphoblastic Leukemia: a Pediatric Blood and Marrow Transplant Consortium Study

Conditioning regimens for children with ALL have generally included total body irradiation (TBI), which may result in significant sequelae. The primary aim of this study was to evaluate the outcome for children with ALL undergoing allogeneic stem cell transplant (SCT) with either busulfan (Bu) or TBI regimens. Patients <21 years with ALL undergoing allogeneic SCT were eligible. Conditioning included either Bu or TBI, with etoposide 40 mg/kg and cyclophosphamide 120 mg/kg. Randomization was stratified based upon duration of remission, remission status, and prior cranial irradiation. A total of 43 patients were enrolled; 21 received Bu and 22 TBI. Median patient age was 8 years (0.5-20 years). Remission status included 12 patients in CR1, 25 in CR2, and six in CR3. At a median follow-up of 43 months, event-free survival (EFS) is 45% at 3 years, with 29% EFS in the Bu arm and 58% in the TBI arm (P=0.03). There was no significant difference between Bu and TBI for patients who received stem cells from related donors (36 vs 58%, P=0.3). However, for URD, EFS was 20% for Bu and 57% for TBI (P=0.04). Relapses were similar in both arms. This randomized prospective study suggests that Bu is inferior to TBI for pediatric patients with ALL undergoing allogeneic SCT.