Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed invasive carcinoma of the breast by core needle or final
pathological evaluation of the surgical specimen

- Clinical stage I, II, or IIIA primary tumor for patients who received
neoadjuvant chemotherapy

- Primary tumor t1-3 on pathologic evaluation and ipsilateral nodes pN0, pN1
(pN1mi, pN1a, pN1b, pN1c), pN2a, pN3a, or pN3b for patients who received
adjuvant chemotherapy

- Received adjuvant hormonal therapy after breast cancer diagnosis for a duration of
57-63 months from the first dose (regardless of the number of missed doses) with 1 of
the following:

- Aromatase inhibitor* (AI)

- Combination of up to 3 years of tamoxifen citrate followed by an AI for a total
of 5 years

- No tamoxifen citrate during years 4 and 5 of 5-year adjuvant hormonal
therapy NOTE: *Adjuvant AI therapy must be discontinued at the time of
randomization

- Must have completed adjuvant hormonal therapy within the past 6 months

- Must have undergone a bilateral mammogram within the past year (unilateral if patient
had a mastectomy)

- Mammogram not required if patient has a prophylactic contralateral mastectomy

- Must have undergone a bone mineral density test within the past year

- Must have undergone a lumpectomy with axillary nodal staging followed by breast
radiotherapy OR a total mastectomy with axillary nodal staging

- Nodal staging with sentinel node biopsy alone is allowed provided sentinel nodes
were negative on H&E staining

- No evidence of recurrent breast cancer by history and physical within the past 3
months

- No diagnosis of bilateral breast cancer, including ductal carcinoma in situ
(synchronous or metachronous)

- Estrogen receptor (ER)-positive and/or progesterone receptor-positive tumor

- Patients with a tumor considered to be borderline hormone receptor-positive that
was treated with tamoxifen citrate and/or AI are allowed

PATIENT CHARACTERISTICS:

- Female

- Postmenopausal as defined by any of the following criteria:

- Age ≥ 56 years with no spontaneous menses for ≥ 12 months prior to study entry

- Age ≤ 55 years with no spontaneous menses for ≥ 12 months prior to study entry
(e.g., spontaneous or secondary to hysterectomy) AND a documented estradiol
level in the postmenopausal range

- Prior documented bilateral oophorectomy

- ECOG performance status 0 or 1

- Cholesterol ≤ grade 1 (with or without cholesterol-lowering therapy) meeting 1 of the
following criteria:

- Criteria must be met within the past year if patient has any of the following:

- History of hypercholesterolemia controlled with cholesterol-lowering
therapy and/or therapeutic lifestyle changes

- History of ≥ 1 of the following risk factors for cardiovascular events:

- Diabetes

- Hypertension

- Obesity

- Tobacco use

- Hypertriglyceridemia

- Documented coronary artery disease

- Family history of premature coronary heart disease

- Criteria must be met within the past 2 years for all other patients

- Not pregnant or nursing

- No history of nontraumatic osteoporotic fracture of the wrist, hip, or spine

- No other malignancies unless disease-free for ≥ 5 years and, in the opinion of the
investigator, at low risk for recurrence

- No other prior malignancy within the past 5 years except for the following:

- Carcinoma in situ of the cervix

- Colon carcinoma in situ

- Melanoma in situ

- Basal cell or squamous cell carcinoma of the skin

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- No other investigational agent within the past 30 days

- No other concurrent anticancer therapy

- No concurrent participation in any other hormonal therapy or placebo-controlled
supportive therapy clinical trial

- No other concurrent hormonal therapy, including any of the following:

- Hormonal agent for management of osteoporosis (e.g., raloxifene)

- Selective estrogen receptor modulators (e.g., raloxifene)

- Sex hormonal therapy (e.g., estrogen- or progesterone-replacement therapy,
including low-dose estrogen in the form of vaginal cream) or oral contraceptives

- Luteinizing hormone-releasing hormone agonists/antagonists (e.g., goserelin)

- Estradiol acetate

- Conjugated estrogen ring or estradiol hemihydrate vaginal tab allowed

- Other aromatase inhibitors

- Concurrent bisphosphonates allowed provided dose is as recommended for bone
protection, not anticancer therapy