The purpose of this observational study is to evaluate real-world safety and efficacy of pegfilgrastim (Neulasta) administered as secondary prophylaxis in Korean female patients with breast cancer receiving chemotherapy regimens recently covered under national health insurance. This is a prospective, observational, open-label trial with a target enrollment of 1400 subjects.

Primary endpoint The primary aim of this study is to determine the incidence of febrile neutropenia.

Secondary endpoint Major secondary endpoint include a) Incidence of bone pain, b) All adverse events, c) Percentage of patients with RDI (relative dose intensity) ≥ 85%

Inclusion Criteria:

• ≥ 19 years old, and ≤ 64 years old, and
• Female patients with breast cancer receiving chemotherapy recently covered under national health insurance (only chemotherapy regimens in the table below), and
• Patients with neutropenic events (febrile neutropenia or grade 4 neutropenia) in any previous cycle that did not use G-CSF for the prevention of neutropenia

Exclusion Criteria:

Patients with any of the followings are excluded.

• Patients with a history of allergic reactions to E-coli derived proteins, human granulocyte colony-stimulating factors such as pegfilgrastim or filgrastim
• Uses for off-label indications such as chronic myelogenous leukemia, myelodysplastic syndrome

Please refer to the inclusion criteria