Breast cancer patients scheduled to receive myelosuppressive chemotherapy (AC regimen) will be enrolled in this study. Eligible patients receive single SC injection of pegcyte or neulastim 24 hours after administration of chemotherapy (Doxorubicin and Cyclophosphamide) in the first cycle (14 days each cycle). Blood samples are collected to determine the serum concentration of investigational drugs at specific time points in the first cycle. Absolute neutrophil count, CD34+ count, Cmax (maximum serum concentration), AUC0-t (area under the curve of the plasma concentration time) and Tmax (time required to reach Cmax) will be calculated from the serum concentration profile

Inclusion Criteria:

• Female patients aged between 18 - 65 years.
• Patients with histological confirmed primary invasive breast cancer; stage I, II or III.
• Patients had no prior chemotherapy treatments.
• Patients scheduled to undergo myelosuppressive Doxorubicin and Cyclophosphamide chemotherapy for 04 cycles, and Paclitaxel chemotherapy for the next 04 cycles; patients were available for 14 days of each cycle for the first 03 chemotherapy cycles.
• Patients with baseline ANC ≥ 1.5 x 109/L, PLT ≥ 100 x 109/L, HgB ≥ 9 g/dL, WBC ≥ 3,000/mL and albumin ≥ 3.0 g/dL.
• Performance status as per ECOG (Eastern Cooperative Oncology Group) score 0, 1 or 2.
• Willing to give written and signed informed consent

Exclusion Criteria:

• Patients with prior exposure of G-CSF or GM-CSF or its pegylated products in clinical development less than 6 months prior to randomization.
• Myelotoxic concomitant treatment such as chloramphenicol, methotrexate, immunomodulating agents, interferons during 10 days before randomization.
• Received systemic antibiotic treatment within 72 hours of chemotherapy.
• Chronic use of corticosteroids, prior bone marrow or stem cell transplant.
• Patients who had an immediate/ concurrent exposure to radiotherapy or surgery (within 4 weeks).
• Severe medical disease: cardiovascular, hepatic, renal, pulmonary…
• Known cases of hematological disease (sickle cell anemia, AML…)
• History of HIV positive, active hepatitis.
• Pregnant and lactating women or patients planning to become pregnant.
• Known allergic reactions to study medications.
• Positive to anti-pegfilgrastim antibody test.

Breast cancer