Busulfan and cyclophosphamide as a conditioning regimen for pediatric acute lymphoblastic leukemia patients undergoing bone marrow transplantation.

Bone marrow transplantation (BMT) has become the standard therapy for children with relapsed acute lymphoblastic leukemia. The authors report their experience with histocompatible BMT for 52 children with acute lymphoblastic leukemia conditioned with a non-total body irradiation (TBI) regimen using busulfan and cyclophosphamide (Bu/Cy). The efficacy and long-term toxicity of the Bu/Cy regimen were determined. Overall survival was 35%. One-year, 3-year, and 7-year event-free survival rates were 54%, 33%, and 23%, respectively. Of the 52 BMT recipients, 26 relapsed. Thirteen of the relapsed patients received a second BMT and three were surviving as of this writing. The most frequent cause of death was leukemia relapse. An initial remission duration of less than 18 months was a factor in decreasing the event-free survival. The Bu/Cy regimen was well tolerated, with minimal transplant-related mortality. Neurocognitive function was tested before BMT and 1 year after BMT. When 1-year posttransplant neurocognitive test scores were compared with pretransplant scores, there was no decrease. However, there was a significant decrease in the pretransplant neurocognitive test scores in BMT recipients compared with their normal siblings. The use of Bu/Cy as a conditioning regimen for BMT does not appear to affect posttransplant neurocognitive function. Other long-term side effects, such as endocrinopathies and secondary malignancies, were also minimal. These data show that the Bu/Cy regimen is well tolerated, but the overall survival rate remains low.