PURPOSEDocetaxel-based chemotherapy regimens (DBRs) are commonly used in the treatment of early-stage breast cancer (EBC). The prophylactic use of pegylated recombinant human granulocyte colony-stimulating factor (PEG-rhG-CSF) has been shown to reduce the incidence of neutropenia induced by DBRs. However, the clinical usage of PEG-rhG-CSF in EBC patients undergoing DBRs in China remains unclear.METHODSThis retrospective study was conducted in 137 EBC patients receiving DBRs from September 2022 to February 2024. We compared the incidence of chemotherapy-induced neutropenia (CIN) between patients who was treated with prophylactic PEG-rhG-CSF or not by complete blood counts, evaluating the effectiveness of PEG-rhG-CSF in preventing CIN. Prophylactic PEG-rhG-CSF was given at 100 μg/kg body weight (maximum total dosage of 6 mg) once 24-48 h following chemotherapy. Meanwhile, we also collected basic patient information, the area under time-concentration curve of docetaxel, and liver and kidney function indicators. Multivariate logistic regression and Receiver operating characteristic (ROC) curve analysis were employed to explore independent factors influencing neutropenia.FINDINGSIn this study, 87 of 137 EBC patients were administrated with prophylactic PEG-rhG-CSF, while 50 were not. Compared to patients who did not receive PEG-rhG-CSF, those who received prophylactic injections had a significantly lower incidence of grade 3-4 CIN (20% vs. 4.6%, P < 0.05). Higher body surface area (BSA), lower body mass index (BMI), elevated alanine aminotransferase (ALT), and nonprophylactic use of PEG-rhG-CSF were found to be positively correlated with CIN occurrence. ROC curve analysis indicated an area under the curve of 0.756 for predicting CIN in EBC patients when BSA was 1.66 m², BMI was 24.8 kg/m², and ALT was 41 U/L, with a sensitivity of 73.08% and specificity of 73.87%.IMPLICATIONSProphylactic use of PEG-rhG-CSF significantly reduces the incidence of CIN, particularly grades 3 and 4. BSA, BMI, ALT, and PEG-rhG-CSF prophylaxis are independent influencing factors for the occurrence of neutropenia.