The purpose of this study is to compare the changes in a proliferation biomarker in subjects receiving Anastrozole or Anastrozole/ZD1839 combination.

Inclusion Criteria:

• Measurable (stage I-IIIB) non meta static non inflammatory breast cancer
• Patients must post menopausal women who in the opinion of investigator would be likely to benefit from endocrine therapy. Postmenopausal patients are defined as:
• Natural menopause with last menses > 1 year ago,
• Radiation induced oophorectomy with last menses > 1 year ago,
• Serum FSH and LH levels clearly in the postmenopausal range for the institution.
• Bilateral oophorectomy

Exclusion Criteria:

• Other current or previous (to last 5 years) malignancies, other metastases, abnormal blood chemistry, lung/ heart/kidney/liver abnormalities,
• Hormonal treatment within the last 2 weeks, previous hormonal treatment for invasive cancer