This study is to determine whether once-per-cycle DA-3031(PEG-G-CSF) is not inferior to daily G-CSF in chemotherapy-induced neutropenia.

Eligible subjects are randomly assigned to receive once-per-cycle DA-3031(PEG-G-CSF) or daily G-CSF(up to 10 days). This study is conducted for 6 cycles of chemotherapy, that each cycle is repeated every 21 days.

Inclusion Criteria:

1. Age : ≥18, ≤70
2. Diagnosis of stage II, III or IV breast cancer
3. ANC≥1,500/mm3, Platelet≥100,000/mm3, ECOG : 0 or 1
4. Creatinine < 1.5 x ULN
5. Total bilirubin/AST/ALT < 1.5 x ULN, ALP < 2.5 x ULN
6. Have given a written, informed consent

Exclusion Criteria:

1. Prior chemotherapy
2. Prior bone marrow or stem cell transplantation
3. Other malignancy history within 5 years
4. Prior exposure to pegfilgrastim or filgrastim or other colony-stimulating factors
5. Received any other investigational drugs within 30 days of informed consent date
6. Radiation therapy within 4 weeks of informed consent date
7. Infective symptom before chemotherapy into this study
8. Received systemic antibiotics within 72 hours of randomization into this study.
9. HIV positive
10. Pregnant or lactating women