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