The purpose of this study is to assess the relative dose intensity (RDI) of intravenous (IV) CMF on a Day 1 and 8 schedule given every 28 days with pegfilgrastim support in subjects with stage I-III breast cancer.

Inclusion Criteria: - Histologically confirmed breast cancer Stage I, II or III - Candidate for IV CMF chemotherapy (every 4 weeks) for a total of 6 cycles - Chemotherapy naïve (prior treatment with hormone therapy or with anti-HER2 monoclonal antibody therapy is permitted as long as treatment has been stopped prior to enrollment into the study) - Absolute neutrophil count (ANC) greater than or equal to 1.5 x 10^9/L - Platelet count greater than or equal to 100 x 10^9/L - Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 - Written informed consent before any study specific procedure Exclusion Criteria: - AST and/or ALT greater than 1.5 x upper limit of normal (ULN) concomitant with alkaline phosphatase greater than 2.5 x ULN according to institutional standard - Bilirubin greater than 2 x ULN according to institutional standard - Inadequate renal function (creatinine greater than 1.5 x ULN according to institutional standard) - Any premalignant myeloid condition or any malignancy with myeloid characteristics (e.g., myelodysplastic syndromes, acute or chronic myelogenous leukaemias) - History of prior malignancy other than breast cancer with the exception of curatively treated basal cell or squamous cell carcinoma of the skin, in situ cervical carcinoma, or other surgically cured malignancy - Prior radiotherapy - Scheduled concomitant radiotherapy (e.g., radiotherapy administration while on study) - Documented active infection at the time of enrolment requiring use of systemic anti- infectives - Documented positive test for human immunodeficiency virus (HIV) infection - Known hypersensitivity to E coli derived products [e.g., Filgrastim (Neupogen®), pegfilgrastim (Neulasta®), HUMULIN® Insulin, L-Asparaginase, HUMATROPE® Growth Hormone, INTRON A®] - Subject is currently enrolled in or 30 days have not passed since completing other investigational device or drug trial(s) or is receiving other investigational agent(s) other than placebo (confirmation of prior treatment must be documented) - Pregnant or breast-feeding (for subjects of child bearing potential) - Not using adequate contraception (for subjects of child bearing potential) - Previous participation in this study - Inability or unwillingness to comply with the protocol procedures