Impact of Early versus Delayed G-CSF Administration on Clinical Outcomes in Chemotherapy-induced Neutropenia: A Propensity Score-matching Cohort Study

Abstract Background: Chemotherapy-induced neutropenia is a significant complication in cancer treatment, increasing the risk of infection and treatment delay. Granulocyte-colony stimulating factor (G-CSF) is used to treat and prevent neutropenia; however, the optimal timing of administration remains uncertain. This study evaluates the impact of early (48–72 h postchemotherapy) versus delayed G-CSF administration on clinical outcomes. Materials and Methods: This retrospective cohort study was conducted at Koo Foundation Sun Yat-Sen Cancer Center and included patients with early-stage breast cancer who received adjuvant chemotherapy between 2013 and 2023. All patients received standardized adjuvant AC → T: doxorubicin 60 mg/m² plus cyclophosphamide 600 mg/m² (four 21-day cycles), followed by docetaxel 60 mg/m² over 60 min (four 21-day cycles). The patients were categorized according to the timing of first G-CSF administration in each chemotherapy cycle: early (48–72 h postchemotherapy; days 3–5) versus delayed (>72 h). Propensity score matching was applied to balance baseline characteristics, creating a matched cohort ( n = 236). The primary outcomes were febrile neutropenia and grade 2–3 neutropenia. Kaplan–Meier survival analysis and Cox proportional hazards models were used to assess differences in clinical outcomes. Results: Early G-CSF administration significantly improved event-free survival (hazard ratio [HR] = 0.46, 95% confidence interval [CI]: 0.31–0.67, P < 0.001), fever-free survival (HR = 0.36, 95% CI: 0.20–0.67, P = 0.001), and neutropenia-free survival (HR = 0.53, 95% CI: 0.35–0.81, P = 0.003). Sensitivity analyses confirmed the robustness of these findings. Conclusion: Early G-CSF administration significantly improved clinical outcomes in chemotherapy-induced neutropenia. Future prospective studies should refine patient selection for tailored G-CSF timing strategies.