Outcome Analysis of Pediatric Patients with Acute Lymphoblastic Leukemia Treated with Total Body Irradiation-Free Allogeneic Hematopoietic Stem Cell Transplantation: Comparison of Patients with and Without Central Nervous System Involvement

Hematopoietic stem cell transplantation (HSCT) with a non-total body irradiation (TBI) conditioning regimen has proven feasible for treating patients with acute lymphoblastic leukemia (ALL). However, it is commonly believed that for extramedullary involvement of ALL in sanctuary sites, such as the central nervous system (CNS), TBI shall not be abandoned. In this study, the outcomes of pediatric ALL patients with CNS involvement (CNS+) and without CNS involvement (CNS−) treated with TBI-free allogeneic HSCT were retrospectively compared. The patients received a TBI-free busulfan plus cyclophosphamide conditioning regimen. Comparing CNS+ (n = 27) and CNS− (n = 134) patients, the 5-year probabilities of relapse (44.4% versus 41.8%; P = .799), disease-free survival (DFS; 48.1% versus 43.3%; P = .642) and overall survival (OS; 51.9% versus 47.0%; P = .646) were not significantly different. Although transplantation-related mortality (TRM) was higher in the CNS− patients, the difference between the 2 groups was not significant (3.7% versus 12.7%; P = .177). In multivariate analysis, there were no significant between-group differences in OS (P = .502), DFS (P = .424), relapse rate (P = .226), or TRM (P = .117). These findings suggest that HSCT using a non-TBI-containing conditioning regimen can lead to similar outcomes in pediatric ALL patients with and without CNS involvement. TBI-free allogeneic HSCT might be feasible and effective for CNS+ ALL patients.