DISEASE CHARACTERISTICS:

• Diagnosis of invasive breast cancer

  • Clinical stage I or II (T1c or T2, N0 or N1) 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 lymph 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

PRIOR CONCURRENT THERAPY:

• At least 21 days since prior tamoxifen or raloxifene as a preventive agent
• At least 1 month 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)