Effect of peripheral-blood progenitor cells mobilised by filgrastim (G-CSF) on platelet recovery after high-dose chemotherapy

The haemopoietic growth factor granulocyte colony-stimulating factor (G-CSF; filgrastim) substantially shortens the period of severe neutropenia that follows high-dose chemotherapy and autologous bone-marrow infusion by stimulating granulopoiesis. Filgrastim also increases numbers of circulating progenitor cells. We have studied the ability of filgrastim to mobilise peripheral-blood progenitor cells and assessed their efficacy when infused after chemotherapy on recovery of neutrophil and platelet counts. 17 patients with non-myeloid malignant disorders received filgrastim (12 μg/kg daily for 6 days) by continuous subcutaneous infusion. Numbers of granulocyte-macrophage progenitors in peripheral blood increased a median of 58-fold over pretreatment values, and numbers of erythroid progenitors increased a median of 24-fold. Three leucapheresis procedures collected a mean total of 33 (SEM 5·7) × 10 4 granulocyte-macrophage progenitors per kg body weight. After high-dose chemotherapy in 14 of the patients (busulphan and cyclophosphamide), these cells were used to augment autologous bone-marrow rescue and post-transplant filgrastim treatment. Platelet recovery was significantly faster in these patients than in controls who received the same treatment apart from the infusion of peripheral-blood progenitors; the platelet count reached 50 × 10 9/l a median of 15 days after infusion of haemopoietic cells in the study patients compared with 39 days in controls (p = 0·0006). The accelerated neutrophil recovery associated with filgrastim treatment after chemotherapy was maintained. This method may be widely applicable to aid both neutrophil and platelet recovery after high-dose chemotherapy; it will allow investigation of peripheral-blood progenitor-cell allotransplantation.