Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of invasive breast cancer

- Clinical stage I, II, or III disease

- Resectable disease

- Measurable disease, defined as a mass that can be reproducibly measured by physical
examination and/or ultrasound and is at least 1 cm in size by ultrasound

- Patients with measurable residual tumor at the primary site allowed

- Estrogen receptor-positive tumor by immunohistochemistry (IHC)

- HER2-negative tumor by Herceptest (0 or +1) OR HER2 not overexpressed by fluorescence
in situ hybridization (FISH)

- Planning to undergo surgical treatment with either segmental resection or total
mastectomy with or withoutlymph node evaluation

- Must have core biopsies from the time of diagnosis available (may include sections of
paraffin-embedded material)

- Prior contralateral breast cancer allowed provided there is no evidence of recurrence
of the initial primary breast cancer

- Patients with locally advanced disease who are candidates for preoperative
chemotherapy at the time of initial evaluation are not eligible

- Locally advanced disease is defined by any of the following:

- Primary tumor ≥ 5 cm (T3)

- Tumor of any size with direct extension to the chest wall or skin (T4a-c)

- Inflammatory breast cancer (T4d)

- Fixed axillary lymph node metastases (N2)

- Metastasis to ipsilateral internal mammary node (N3)

- No locally recurrent disease

- No evidence of distant metastatic disease (i.e., lung, liver, bone, or brain
metastases)

PATIENT CHARACTERISTICS:

- ECOG performance status 0-1

- Postmenopausal, as defined by any of the following:

- 55 years of age and over

- Under 55 years of age and meets 1 of the following criteria:

- Amenorrheic for at least 12 months

- Follicle-stimulating hormone (FSH) ≥ 40 IU/L and estradiol levels ≤ 20 IU/L

- Has undergone prior bilateral oophorectomy or radiation castration AND has been
amenorrheic for at least 6 months

- Bilirubin ≤ 1.5 times upper limit of normal (ULN)

- SGOT and SGPT ≤ 1.5 times ULN

- Creatinine ≤ 1.5 t times ULN

- Able to swallow and retain oral medication

- No serious medical illness that, in the judgment of the treating physician, places
the patient at high risk for operative mortality

- No malabsorption syndrome, ulcerative colitis, or other disease significantly
affecting gastrointestinal function

- No other malignancy within the past 5 years except for completely resected
nonmelanoma skin cancer or successfully treated in situ carcinoma

- No dementia, altered mental status, or any psychiatric condition that would preclude
the understanding or rendering of informed consent

- No severe uncontrolled malabsorption condition or disease (i.e., grade II/III
diarrhea, severe malnutrition, or short gut syndrome)

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- At least 21 days since prior tamoxifen or raloxifene as a preventive agent

- At least 7 days since prior hormone replacement therapy (e.g., conjugated estrogens
[Premarin])

- No prior resection of the stomach or small bowel

- More than 30 days or 5 half-lives, whichever is longer, since prior investigational
drugs

- No prior chemotherapy for this primary breast cancer

- No other concurrent investigational agents

- No other concurrent anticancer therapy (e.g., chemotherapy, radiotherapy,
immunotherapy, hormonal therapy, or any other biologic therapy)