Primary Granulocyte Colony-Stimulating Factor Prophylaxis During the First Two Cycles Only or Throughout All Chemotherapy Cycles in Patients With Breast Cancer at Risk for Febrile Neutropenia

Abstract

Early breast cancer is commonly treated with anthracyclines and taxanes. However, combining these drugs increases the risk of myelotoxicity and may require granulocyte colony-stimulating factor (G-CSF) support. The highest incidence of febrile neutropenia (FN) and largest benefit of G-CSF during the first cycles of chemotherapy lead to questions about the effectiveness of continued use of G-CSF throughout later cycles of chemotherapy. In a multicenter study, patients with breast cancer who were considered fit enough to receive 3-weekly polychemotherapy, but also had > 20% risk for FN, were randomly assigned to primary G-CSF prophylaxis during the first two chemotherapy cycles only (experimental arm) or to primary G-CSF prophylaxis throughout all chemotherapy cycles (standard arm). The noninferiority hypothesis was that the incidence of FN would be maximally 7.5% higher in the experimental compared with the standard arm. After inclusion of 167 eligible patients, the independent data monitoring committee advised premature study closure. Of 84 patients randomly assigned to G-CSF throughout all chemotherapy cycles, eight (10%) experienced an episode of FN. In contrast, of 83 patients randomly assigned to G-CSF during the first two cycles only, 30 (36%) had an FN episode (95% CI, 0.13 to 0.54), with a peak incidence of 24% in the third cycle (ie, first cycle without G-CSF prophylaxis). In patients with early breast cancer at high risk for FN, continued use of primary G-CSF prophylaxis during all chemotherapy cycles is of clinical relevance and thus cannot be abandoned.