Inclusion Criteria:

• Pathologically confirmed breast cancer, determined to be a candidate for primary systemic (neoadjuvant) therapy and for surgical resection of residual primary tumor following completion of neoadjuvant therapy
• Tumor size >2cm, measured on imaging or estimated by physical exam
• No obvious contraindications for primary chemotherapy with docetaxel, adriamycin, or cyclophosphamide
• Residual tumor planned to be removed surgically following completion of neoadjuvant therapy
• Able to lie still for 1.5 hours
• Age 18 years or older.
• leukocytes ≥ 3,000/μl
• absolute neutrophil count ≥ 1,500/μl
• platelets ≥ 100,000/μl
• total bilirubin within normal institutional limits
• AST(SGOT)/ALT(SGPT) ≤ 2.5 times the institutional upper limit of normal
• creatinine within normal institutional limits OR, for patients with creatinine levels above institutional normal, or clearance ≥ 60 mL/min/1.73 m2
• If female, postmenopausal for a minimum of one year, or surgically sterile, or not pregnant, confirmed by ß-HCG blood test

Exclusion Criteria:

• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Medically unstable
• Condition requiring anesthesia for PET scanning
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to F-18 fluorothymidine