This paper describes the successful mobilization of peripheral blood stem cells for autologous transplantation in three children with malignant diseases by using plerixafor (Mozobil™; Genzyme Corporation, Cambridge, MA) and granulocyte-colony stimulating factor (G-CSF) after failed previous mobilizations. A median sixfold increase in the number of circulating CD34+ cells after plerixafor treatment as compared with the baseline level was observed. An optimal CD34+ cell count for transplantation with one or two leukapheresis sessions was achieved. Mobilization using plerixafor was found to be safe with no adverse events. Therefore, the combination of G-CSF and plerixafor in children results in effective increases in peripheral CD34+ cell counts and reduces the risk of mobilization failure.

Background: During the last four decades the prognosis of childhood acute myeloid leukemia (AML) has been substantially improved due to an increase in complete remission (CR) rates, event-free survival (EFS) and reduced early mortality. The relapsed AML still remains a therapeutic challenge. Aim: To report the AML treatment results of the Bulgarian pediatric oncohematological centers. Materials and methods: Retrospective analysis of the treatment results of children and adolescents (age from 0 to 20 years) with primary AML. Unifi ed AML BFM-backbone type treatment protocol is used. Results: This study included 97 newly diagnosed patients (44 girls and 53 boys) with AML in Bulgaria between 2003 and 2016. The median age at diagnosis was 10.2 years. The most frequent FAB-morphologic subtype was М2 followed by М4. First complete remission (CR1) was achieved in 83 patients (85.6%). The 13-year EFS was 49%, while the overall survival (OS) was 54.6%. Twenty seven (27.8%) patients relapsed, with only 5 of them being still alive towards the end of the study period. Conclusion: The EFS and OS for the children with AML in Bulgaria are comparable with those reported by other European groups. The prognosis of relapsed AML remains still unfavorable for the past 13 years. BACKGROUND

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