Granulocyte colony-stimulating factor (rh G-CSF) as an adjunct to interferon alpha therapy of neutropenic patients with hairy cell leukemia

Summary Six patients with hairy cell leukemia (HCL) and neutropenia (median neutrophil count 563/l, range 30–1200) were treated with recombinant human granulocyte colony-stimulating factor (G-CSF) at a dose of 5g/kg by daily subcutaneous injection as an adjunct to interferon-alpha (IFN-a) therapy, in order to ameliorate neutropenia. Five of six patients responded to G-CSF with normalization of neutrophil counts (>1800/l) within 2–11 days and a median neutrophil count of 5211/l (range 4312–10160) at the end of G-CSF therapy. In three of these patients, infections resolved when neutropoiesis recovered. In one patient with very severe neutropenia (30/l), in whom myeloid progenitors were not detectable, G-CSF therapy failed to restore granulopoiesis. Cessation or interruption of G-CSF after 2–5 weeks of therapy resulted in a rapid decline of neutrophil counts to lower or subnormal levels (median value 1478/l, range 770–2739) within 1 week, suggesting that the improvement of granulopoiesis was dependent on G-CSF and not due to IFN-a therapy. G-CSF may be a useful adjunct to IFN-a therapy in patients with HCL in order to manage or prevent neutropenic complications in the early phase of treatment.