Prolonged administration of granulocyte colony-stimulating factor (filgrastim) to patients with Fanconi anemia: A pilot study

This report examines the effect of filgrastim (granulocyte colony- stimulating factor, [G-CSF] in 12 patients with neutropenia [absolute neutrophil count [ANC] 3]) caused by Fanconi anemia (FA). Two of 14 patients who were evaluated for study entry were ineligible because of unsuspected cytogenetic abnormalities in their bone marrow (BM). G-CSF was started at 5 μg/kg/d. All patients had an increase in their ANC at week 8 (mean increase = 15,664/mm³). The median ANC during therapy was 5,030/mm³. Eight of 10 patients who completed 40 weeks on study maintained an ANC >1,500/mm³ on G-CSF given every-other-day. Four patients had an increase in their platelet count by week 8 without transfusion (maximum increase = 23,000 to 45,000/mm³); however, platelet counts fell toward baseline levels as the G-CSF dose was reduced. BM CFU-MK were increased at week 8 in three of four evaluable patients. Four patients who did not receive red blood cell transfusions had an increase in their hemoglobin level of at least 2.0 g/dL. A fifth patient had a red blood cell transfusion in week 2 and then had a similar increase in hemoglobin level without subsequent transfusion. Eight of 10 patients who completed 40 weeks of treatment showed increases in the percentage of BM CD34⁺ cells measured flow cytometry. The same proportion showed increases in peripheral blood CD34⁺ cells. Increased BM cellularity and myeloid hyperplasia were constant findings and were associated with increased expression of the proliferating cell nuclear antigen. Adverse experiences were mild fever (1 patient) and a new BM cytogenetic abnormality at week 40 (1 patient). This study shows that prolonged administration of G- CSF exerts a stimulatory effect on the BM of FA patients and may be used to maintain a clinically adequate ANC in these patients. G-CSF has beneficial effects on multiple hematopoietic lineages in some patients and may be a good candidate for use in combination cytokine protocols for FA patients with progressive aplastic anemia. G-CSF use results in an increase in circulating CD34⁺ cells, a finding with important implications for future gene transfer protocols.