BACKGROUND: Post remission therapy is one of the most important issues in the treatment of acute myelocytic leukemia (AML). Recently, autologous peripheral blood stem cell transplantation (PBSCT) has become an accepted procedure to support high dose chemotherapy in children with AML. But collection of PBSC from small pediatric patients provides many challenges not faced when collecting from adult patients. Therefore, the efficient procedures and optimal timing to perform the leukapheresis should be
decided. The goal of the present study was to evaluate the practice of PBSC mobilization and collection and establish predictors of the leukapheresis in children with AML.
METHODS: From November 1995 to February 1998, PBSC mobilizations were performed in 15 patients with AML. PBSCs were mobilized by high dose of cytosine arabinoside and etoposide plus G-CSF. CBC and peripheral blood smear were performed daily after WBC nadir. Leukapheresis was started when the WBC count recovered to 1,000/㎕ from myelosuppression and monocytes appeared on the peripheral blood smear. Leukapheretic products were assayed for mononuclear cells, CD34+cells and CFU-GM colonies.
Correlations between the yields of leukapheresis and patients characteristics were evaluated by Wilcoxon rank sums test and Pearson correlation analysis.
RESULTS:Eighteen mobilizations were done in 15 patients. The duration of absolute neutrophil count <0.5×10 3/㎕ and platelet count <20×10 3/㎕ were 6 days (0∼10 days) and 8 days (5∼21 days) after mobilization chemotherapy, respectively. Duration of fever was 1 day, but documented septicemia was not occurred in any of the patients. A median 5 leukaphereses (range : 3∼6) were undergone per patient. The WBC on the first day of the leukapheresis was 1,640/㎕ (850∼16,840/㎕) and percentage of monocyte on the first day of the leukapheresis was 12% (4∼36%). A median 5 leukaphereses yielded median of 11.02×10 8(4.5∼26.42×10 8) MNCs/㎏, 7.63×10 6(0.33∼42.21×10 6) CD34+cells/㎏, and 8.46×10 4(0.27∼147.83×104) CFU-GM/㎏. The dose of 1×10 8 MNCs was harvested in 100% after 3 harvests and 1×10 6CD34+ cells in 87% after 3 harvests. No serious adverse effects occurred in all patients during the leukapheresis procedures. A rapid rise in WBC count (≥3,000/㎕/day) during recovery was independent variable correlated to the peak MNCs, average MNCs, peak CD34 +cells and average CD34+cells (P<0.01).
CONCLUSIONS: Mobilization procedures using high dose cytosine arabinoside and etoposide plus G-CSF are tolerable and the leukapheresis can be initiated when WBC count recovers to 1,000/㎕ from myelosuppression and monocytes appear on the peripheral blood smear. Sufficient numbers of PBSC can be obtained by three leukapheresis procedures without serious adverse effects in children with AML.

Keywords: Peripheral blood stem cell, Mobilization, Leukapheresis, Acute myelocytic leukemia, Children