Effects of the in vivo Administration of Recombinant Human Granulocyte Colony‐stimulating Factor Following Cytotoxic Chemotherapy on Granulocytic Precursors in Patients with Malignant Lymphoma

We examined the effects of the in vivo administration of recombinant granulocytc colony‐stimulating factor (rhG‐CSF) on granulocytic precursors in the bone marrow of 4 patients with malignant lymphoma who received chemotherapy. Patients were treated with rhG‐CSF at doses of 100–800 μg/ m²/day intravenously for 14 days only in the first course of chemotherapy (G‐CSF course) followed by the second course of chemotherapy without rhG‐CSF which was used as a control course. In the G‐CSF course, white blood cell counts (WBCs) demonstrated a biphasic response consisting of a first peak observed within a few days after the initiation of rhG‐CSF administration, and a second peak observed on the last day of rhG‐CSF injection or the day after. In the second peak, the incidence of granulocyte‐macrophage colony‐forming units (CFU‐GM) in mononucleated bone marrow cells did not change significantly after treatment with rhG‐CSF as compared with a control. However, since the number of nucleated cells in the bone marrow increased, the absolute number of CFU‐GM in the bone marrow increased. The number of mature and immature granulocytes in the bone marrow increased. These findings suggest that G‐CSF stimulates the proliferation and differentiation of granulocytic precursors in the bone marrow in granulocytopenic patients who received cytotoxic drugs and causes mature granulocytes to be released from the bone marrow.