This is a prospective, single-center, single-arm clinical study, to evaluate the clinical efficacy, safety and tolerance of patients with early breast cancer receiving ddEC adjuvant chemotherapy, accepting PEG-rhG-CSF as primary prevention of neutropenia.

Inclusion Criteria:

• Breast cancer patients in need for adjuvant chemotherapy confirmed by histopathology, whom should accept ddEC regimen.
• ECOG<=1
• Expected survival is greater than 6 months
• Qualified for chemotherapy，WBC>=3*109/L, ANC>=1.5*109/L, Hb>=80g/L, PLT>=80*109/L. With no bleeding tendency or systemic hematology disorder symptoms.
• No obvious EKG abnormality, no obvious cardiac dysfunction, and normal left ventricular ejection fraction.
• Liver function, ALT and AST should less than 2.5 times of the upper limit.
• Renal function, Cr and BUN should less than 1.5 times of the upper limit.
• Subjects voluntarily participate in this study and sign informed consent.

Exclusion Criteria:

• Total amount of doxorubicin used in previous chemotherapy>240mg/m2, or epirubicin>360mg/m2
• Has received hematopoietic stem cell transplantation or bone marrow transplantation
• Other drugs are currently in clinical trials
• There are currently hard-to-control infections, body temperature is higher than 38 degrees.
• Received PEG-rhG-CSF treatment before enrollment
• Received chemotherapy in 4 weeks before enrollment
• Patients with any visceral metastasis
• Patients with severe heart, kidney, liver or any other important organs chronic diseases
• Patients with severe uncontrolled diabetes
• Patients with allergic diseases, or allergies to this product or other biological products derived from genetically engineered e. coli
• Suspected or real drug users, substance abusers, alcoholics
• Pregnant or lactating women
• Severe mental or neurological disorders that affect informed consent and adverse reactions described or observed