321: Efficacy and Toxicity of a Conditioning Regimen with 8-Gy Total Body Irradiation, Fludarabine and Cyclophosphamide for Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Hematologic Malignancies

We examined the efficacy and toxicity of a conditioning regimen with fractionated 8-Gy total body irradiation, fludarabine, and cyclophosphamide in allogeneic hematopoietic stem cell transplantation (HSCT) for pediatric hematologic malignancies. Among a total of 22 children who received related or unrelated HSCT, nine were transplanted with refractory disease and/or from HLA 2 or more-loci mismatched family donors. The Seattle grading system revealed that 18 patients had no regimen-related toxicity, whereas the remaining patients had grade I gastrointestinal toxicity alone. According to the National Cancer Institute Common Toxicity Criteria, Grade II or higher toxicity in the liver, mucosa, and gastrointestinal tract among eight organs was documented in approximately 10–35% of patients, and was attributed to engraftment syndrome and/or acute graft-versus-host disease. None of the patients developed graft failure. The estimated overall survival and leukemia-free survival (LFS) at 2 years were 56.3% and 46.7%, respectively, in 10 patients with acute lymphoblastic leukemia; 91.7% and 81.5%, respectively, in 12 patients with myeloid leukemia. The incidence of treatment-related mortality was 5.3% at 2 years. It is possible that our preparative regimen confers successful engraftment combined with minimized regimen-related toxicity, and a favorable LFS rate for children with hematologic malignancies, especially for those with myeloid leukemia.