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

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Highlights

  • Younger patients with acute lymphoblastic leukemia (ALL) are at increased risk for central bervous system (CNS) involvement.

  • Allogeneic hematopoietic stem cell transplantation (HSCT) using a non–total body irradiation (TBI) conditioning regimen led to similar early and long-term outcomes for pediatric ALL patients with and without CNS involvement.

  • Producing similar results as reported in other studies using TBI-based allogeneic HSCT in ALL patients with CNS involvement, a TBI-free allogeneic HSCT seems to be feasible and effective for CNS-involved ALL patients. This is especially important regarding the toxicity of TBI on CNS and the susceptibility of younger ALL patients to CNS involvement.

  • CNS relapse post-HSCT was associated with the poorest prognosis.

Abstract

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.

Key Words

Acute lymphoblastic leukemia
Central nervous system
Hematopoietic stem cell transplantation
Transplantation conditioning
Whole-body irradiation

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Financial disclosure: See Acknowledgments on page 2116.

A minor part of this study was presented at the 2015 BMT Tandem Meetings in San Diego, CA (11-15 February 2015).