Inclusion Criteria

DISEASE CHARACTERISTICS:

- At increased risk for the development or recurrence of breast cancer, defined as an
estradiol level ≥ 9 pg/mL

- No evidence of suspicious or malignant disease, based on the following examinations:

- Clinical bilateral breast examination within the past 6 months

- Bilateral* mammogram within 3 months before randomization OR within 30 days
after randomization

- Pelvic exam normal within the past 5 years

- General physical exam within the past 6 months NOTE: *Unilateral mammogram of
the uninvolved breast for patients with prior invasive breast cancer or ductal
carcinoma in situ (DCIS)

- Bone density scan within 2 standard deviations from normal within the past 30 days

- Bone density scan ≥ 2 standard deviations below normal allowed if approved by
the study physician

- At least 1 breast that has not been previously treated with radiotherapy or surgery
(for patients with prior invasive breast cancer or DCIS)

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

Age

- 35 and over

Sex

- Female

Menopausal status

- Postmenopausal, defined by any of the following criteria:

- At least 12 months without spontaneous menstrual bleeding

- Prior hysterectomy and bilateral salpingo-oophorectomy

- ≥ 55 years of age with a prior hysterectomy with or without oophorectomy

- < 55 years of age with a prior hysterectomy without oophorectomy OR the status
of the ovaries is unknown AND follicle-stimulating hormone (FSH) level is in the
postmenopausal range

Performance status

- Normal activity must not be restricted for a significant portion of the day

Life expectancy

- At least 10 years

Hematopoietic

- Complete blood count with differential normal

- Prior benign neutropenia allowed provided the granulocyte count is ≥ 1,500/mm^3

Hepatic

- Bilirubin normal

- Alkaline phosphatase normal

- SGOT and SGPT normal

Renal

- Creatinine normal

Cardiovascular

- No uncontrolled cardiovascular disease

Other

- Not pregnant

- No other malignancy within the past 5 years except basal cell or squamous cell skin
cancer or carcinoma in situ of the cervix

- No osteoporosis

- No hyperlipidemia

- No mental health status resulting in cognitive or emotional impairment that would
preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

- Not specified

Chemotherapy

- Not specified

Endocrine therapy

- More than 30 days since prior AND no concurrent use of any of the following hormonal
agents:

- Estrogen or progesterone replacement therapy

- Oral contraceptives

- Raloxifene or other plasma estrogen receptor modulators (SERMs)

- Androgens (e.g., danazol)

- Luteinizing hormone-releasing hormone (LHRH) analogs (e.g., goserelin or
leuprolide)

- Prolactin inhibitors (e.g., bromocriptine)

- Antiandrogens (e.g., cyproterone)

- More than 60 days since prior AND no concurrent tamoxifen

- No prior aromatase inhibitors (for patients with prior invasive breast cancer or
DCIS)

- No concurrent phytoestrogenic dietary supplements (e.g., soy, ginseng, or other
natural products)

- Dietary soy allowed

Radiotherapy

- See Disease Characteristics

Surgery

- See Disease Characteristics

- No prior bilateral mastectomy

Other

- More than 60 days since prior treatment for invasive breast cancer or DCIS

- More than 30 days since prior bisphosphonates or calcitonin

- No prior or concurrent participation on a treatment study for invasive breast cancer
or DCIS

- No concurrent participation in any other cancer prevention study or osteoporosis
prevention study involving pharmacologic agents

- No concurrent calcitonin

- No concurrent bisphosphonate therapy

- Concurrent cholecalciferol (vitamin D) and calcium to augment bone mineral density
allowed