Feasibility Study of Presurgical Hormone Therapy (Anastrozole) in Breast Cancer Patients

Inclusion Criteria: 1. Newly diagnosed postmenopausal women (Women are considered post-menopausal and not of child bearing potential if they have had 12 months of natural (spontaneous) amenorrhea with an appropriate clinical profile (e.g., age appropriate, history of vasomotor symptoms) or six months of spontaneous amenorrhea with serum FSH levels \> 40 mIU/mL and estradiol \< 20 pg/mL or have had surgical bilateral oophorectomy (with or without hysterectomy) at least six weeks ago.) 2. Confirmation of estrogen receptor positive invasive carcinoma on core biopsy 3. Patients whose cancers are palpable and have been deemed to be "operable" by the surgeon 4. Surgery is planned for the next 2-8 weeks. Exclusion Criteria: 1. History of hormone replacement therapy in the last 6 months 2. Previous treatment by tamoxifen or aromatase inhibitor treatment in six months 3. Known hypersensitivity or contraindications to aromatase inhibitors 4. Known metastatic disease on presentation 5. Recurrent breast cancer 6. Inability to give informed consent