Inclusion Criteria

DISEASE CHARACTERISTICS:

- Meets at least 1 of the relative risk factors based on age as follows:

- 45 to 70 years of age:

- First-degree relative who developed breast cancer at ≤ 50 years of age

- First-degree relative who developed bilateral breast cancer

- Two or more first- or second-degree relatives who developed breast cancer
or ovarian cancer

- Participants having both relatives who are second degree and on the
opposite sides of the family must have at least one that was diagnosed
at ≤ 50 years of age

- Nulliparous (or first birth at ≥ 30 years of age) and a first-degree
relative who developed breast cancer

- Benign biopsy with proliferative disease and a first-degree relative who
developed breast cancer

- Mammographic opacity covering at least 50% of the breast in the absence of
hormone replacement therapy within the past 3 months

- 60 to 70 years of age:

- First-degree relative with breast cancer at any age

- Age at menopause ≥ 55 years

- Nulliparous or age at first birth ≥ 30 years

- 40 to 44 years of age:

- Two or more first- or second-degree relatives who developed breast cancer
or ovarian cancer at ≤ 50 years of age

- First-degree relative with bilateral breast cancer who developed the first
breast cancer at ≤ 50 years of age

- Nulliparous (or first birth at ≥ 30 years of age) and a first-degree
relative who developed breast cancer at ≤ 40 years of age

- Benign biopsy with proliferative disease and a first-degree relative who
developed breast cancer at ≤ 40 years of age

- All age groups (40 to 70 ears of age) with a 10-year risk > 5% who do not fit into
the above categories are allowed

- Clearly apparent family history AND/OR other risk factors indicating appropriate
increased risk of breast cancer for age

- The following prior breast conditions are allowed (for all age groups):

- Lobular carcinoma in situ

- Atypical ductal or lobular hyperplasia in a benign lesion

- Ductal carcinoma in-situ (DCIS), diagnosed within the past 6 months, and treated
by mastectomy

- No evidence of breast cancer on mammogram within the past year

- Hormone receptor status:

- For patients with prior DCIS, estrogen- or progesterone-receptor status must
have been positive

- Must have had greater than or equal to 5% positive cells

PATIENT CHARACTERISTICS:

Age

- 40 to 70

Sex

- Female

Menopausal status

- Postmenopausal, defined as at least 1 of the following:

- Over 60 years of age

- Bilateral oophorectomy

- ≤ 60 years of age with a uterus and amenorrhea for at least 12 months

- ≤ 60 years of age without a uterus and with follicle-stimulating hormone levels
> 30 IU/L

Performance status

- Not specified

Life expectancy

- At least 10 years

Hematopoietic

- Not specified

Hepatic

- Not specified

Renal

- Not specified

Other

- Psychologically and physically suitable to receive 5 years of anti-estrogen therapy

- No cancer within the past 5 years except non-melanoma skin cancer or carcinoma in
situ of the cervix

- No evidence of osteoporosis or fragility fractures within the spine

- Participants with a T-score > minus 4 and no more than 2 fragility fractures are
allowed

- No concurrent severe disease that would place the participant at unusual risk or
confound the results of the study

- No other medical condition that would preclude the ability to receive the study
treatment

PRIOR CONCURRENT THERAPY:

Biologic therapy

- Not specified

Chemotherapy

- Not specified

Endocrine therapy

- No prior tamoxifen, raloxifene, or other selective estrogen receptor modulator (SERM)
use for more than 6 months in duration unless an IBIS-I participant (must have been
off trial therapy for at least 5 years.

- No concurrent tamoxifen, raloxifene, or other SERM

- No concurrent estrogen-based hormone replacement therapy

- No concurrent systemic estrogen replacement therapy, including vaginal estrogen
preparations

Radiotherapy

- Not specified

Surgery

- See Disease Characteristics

- No prior prophylactic mastectomy

- No concurrent prophylactic mastectomy

Other

- More than 6 months since prior investigational drugs