Adverse effect on bone marrow protection of prechemotherapy granulocyte colony-stimulating factor support

Background: Increased proliferation of endogenous bone marrow progenitor cells in;response to the administration of hematopoietic growth factors, followed by reduced cell cycling or entrance of the cells into a quiescent state upon withdrawal of the growth factors, may have clinically relevant effects on the tolerance of the hematopoietic system to subsequent myelotoxic treatments. Purpose: We investigated the ability of granulocyte colony-stimulating factor (G-CSF) to protect progenitor cells in the bone marrow of cancer patients from the toxic effects of subsequent treatments with chemotherapeutic agents. Methods: Thirty-six patients with histologically documented, locally advanced or metastatic breast cancer were randomly assigned to receive doxorubicin once every 3 weeks at a dose of 75 mg/m(2) and cyclophosphamide at a dose of 1000 mg/m(2), with G-CSF administered either before and after chemotherapy (18 patients) or after chemotherapy only (18 patients). For prechemotherapy administration of G-CSF, recombinant human methionyl (r-met Hu) G-CSF was administered subcutaneously to patients twice per day for 5 days at a dose of 5 mu g/kg, with the last dose given 48 hours before the start of chemotherapy, For postchemotherapy administration of G-CSF, r-met Hu G-CSF was administered subcutaneously to patients once per day for 7 days at a dose of 5 mu g/kg, with the first dose given 24 hours after chemotherapy. Results: The incidence or the duration of grade 4 neutropenia was not reduced in all patients by the use of prechemotherapy G-CSF; the incidence over all cycles of chemotherapy was 74% for patients treated with prechemotherapy and postchemotherapy G-CSF and 66% for patients treated with postchemotherapy G-CSF only (two-sided P, adjusted for dose = .21) and the median duration in both treatment arms was 3 days (two-sided P =.19). Unexpectedly, the incidence of grades 3 and 4 thrombocytopenia was much greater in patients who received prechemotherapy G-CSF compared with those who did not (54% versus 6%, respectively, over all chemotherapy cycles; two-sided P, adjusted for dose <.001). No difference in the decrease in hemoglobin level (adjusted for red blood cell transfusions) between patients in the two treatment arms was observed, Conclusions and Implications: No beneficial effects were associated with the administration of G-CSF to cancer patients prior to chemotherapy. The observation of more severe thrombocytopenia in patients treated with prechemotherapy G-CSF led us to conclude that the proliferation of progenitor cells was still increased 48 hours after the last dose of G-CSF and that the administration of chemotherapy at or within this time period actually worsens the toxic effects on bone marrow. This result has important ramifications for the design of clinical cancer treatment protocols, especially those that involve shortened intervals between cycles of chemotherapeutic agent administration.