Long-Term Outcomes of Hematopoietic Stem Cell Transplantation in Pediatric Patients with Acute Leukemia Based On Conditioning Regimen without Total Body Irradiation

Background: The current acceptable conditioning regimen used for hematopoietic stem cell transplantation (HSCT) in pediatric leukemia consists of total body irradiation (TBI) especially in acute lymphoblastic leukemia (ALL). Considering the complications and limitations of TBI-based conditioning regimens, some studies tried to uses non-TBI conditioning regimens.

Methods: From 1992 to 2012 in a retrospective study from our center pediatric patients (age <15) with acute myelobalstic leukemia (AML) and ALL candidate for HSCT included. The patients were prepared using a non-radiation-based conditioning regimen (busulfan/cyclophosphamide in allogenic and busulfan/etoposide in autologus). In the allogenic HSCT, Cyclosporine A and methotrexate were used as graft-versus-host disease (GvHD) prophylaxis regimen.

Results: Of 268 patients with AML (autologus=57, allogenic=104) and ALL (allogenic=107), 137(51%) of them were boys and 131(49%) were girls. The median age at transplantation were 11years (range: 1-15years) in AML patients and 12years (range: 0.8-15years) in ALL patients. With a median follow up of 31 months for AML patients, overall survival (OS), disease free survival (DFS)  for autologus and allogenic transplantations were 64%, 59.2% and 69%,61.5% respectively. In ALL patients with a median follow up of 14 months, OS and DFS were 80.3% and 70%. The most common cause of deaths in both AML and ALL patients was relapse (63% and 71%). Regarding GVHD occurrence, in AML and ALL patients 67 (41.6%) and 61 (57%) did experience acute GVHD. Considering chronic GVHD for AML and ALL patients, results were 20(12.4%) and 13(12.1%).

Conclusion: Regarding the adverse effects of using TBI-based conditioning regimen, it seems that in pediatric patients with AML and ALL using a non-TBI based conditioning regimen can be a good alternative in HSCT. However, large controlled well-designed studies are needed for further understanding of differences between TBI and non-TBI conditioning regimens.