Phase II Multicenter, Double-Blind, Randomized Trial Comparing Anastrozole (ZD1033, Arimidex™)-Placebo to the Combination Anastrozole-ZD1839 (Gefitinib, IRESSA™) in Postmenopausal Patients With Estrogen Receptor (ER) and/or Progesterone Receptor (PgR) Metastatic Breast Cancer

Inclusion Criteria:

- Female postmenopausal patients aged 18 years or older with newly diagnosed metastatic
breast cancer.

- Patients with recurrent disease during or after adjuvant tamoxifen or patients who
are hormone therapy naïve are eligible for this trial.

- A paraffin embedded tumor tissue block or slides from either the metastatic or
primary tumor site is required.

Exclusion Criteria:

- Patients cannot be on hormone replacement therapy while on study.

- Prior chemotherapy received for metastatic disease is not allowed.

- Previous treatment with tyrosine kinase inhibitors or aromatase inhibitors is not
allowed.

- Patients who have evidence of an active interstitial lung disease are not eligible.