Inclusion Criteria

DISEASE CHARACTERISTICS:

Inclusion criteria:

- Must have histologically confirmed invasive breast cancer, as defined by the
following TNM staging criteria:

- pT1, pT2, or pT3

- pNx, pN0, pN1, pN2, or pN3*

- Patients with positive sentinel node biopsies (pN1) must have subsequent
axillary dissection to be eligible

- Patients with negative sentinel node biopsies (pN0) do not require axillary
surgery for study eligibility

- M0, according to the following radiologic studies:

- Bone scan (required only if alkaline phosphatase is > 2 x institutional
upper limit of normal [ULN] and/or there are symptoms of metastatic
disease)

- A confirmatory x-ray or other imaging study, such as CT scan or MRI,
is required if the results from the bone scan are questionable

- Abdominal ultrasound or CT scan of the abdomen (required only if AST/ALT or
alkaline phosphatase is > 2 x ULN unless the elevation is in the bone
fraction)

- Chest x-ray NOTE: *Only when the sole basis for this classification is the
presence of 10 or more involved axillary nodes

- Completely resected disease

- Surgical margins must be clear of invasive carcinoma and ductal carcinoma in
situ or lobular carcinoma in situ

- Must have one intact, noncancerous breast with no history of previous breast surgery
in that breast (other than a breast biopsy)

- Mammogram of the intact, noncancerous breast required ≤ 6 months prior to study
registration (both a craniocaudal [top down] and mediolateral oblique view [side
view] must be available)

- Must be registered on this study ≥ 3 weeks but ≤ 3 months after completion of
chemotherapy OR primary surgery*

- Adjuvant chemotherapy and radiation therapy as prescribed by the local
institution is allowed provided patient is registered on this study and hormonal
treatment is begun as soon as patient has sufficiently recovered from
chemotherapy NOTE: *Primary surgery is defined as the last surgical procedure to
remove invasive or in situ disease

- Planning to receive anastrozole or exemestane for ≥ 1 year for treatment of breast
cancer

- Hormone receptor status:

- Estrogen receptor- and/or progesterone receptor-positive (defined as a tumor
receptor content of > 10 fmol/mg protein OR receptor-positive by
immunohistochemistry [ERICA or PgRICA])

PATIENT CHARACTERISTICS:

Inclusion criteria:

- Female

- Postmenopausal, defined by one of the following:

- Age > 60 years

- Age 45-59 years with spontaneous cessation of menses > 12 months prior to
chemotherapy (if no chemotherapy was given, then prior to study registration)

- Age 45-59 years with cessation of menses for a duration of < 12 months or
secondary to hysterectomy AND an FSH level in the postmenopausal range (or ≥
34.4 IU/L, if institutional range is not available) prior to chemotherapy (if no
chemotherapy was given, then prior to study registration)

- Age 45-59 years with an FSH level in the postmenopausal range according to
institutional laboratory standards (or > 34.4 IU/L, if the institutional range
is not available) prior to chemotherapy (if no chemotherapy was given, then
prior to study registration)

- Bilateral oophorectomy

- ECOG performance status 0, 1, or 2

- Life expectancy ≥ 5 years

Exclusion criteria:

- History of other (non-breast) malignancies, except adequately treated nonmelanoma
skin cancer, curatively treated in situ cancer of the cervix, or other curatively
treated solid tumors with no evidence of disease for > 5 years

- Any co-existing medical or psychiatric condition that is likely to interfere with
study procedures and/or results

PRIOR CONCURRENT THERAPY:

Inclusion criteria:

- See Disease Characteristics

Exclusion criteria:

- Hormone replacement therapy, oral contraceptives, tamoxifen, raloxifene, other
selective estrogen-receptor modulators, or gonadotropin releasing-hormone analogues ≤
6 months prior to the pre-registration mammogram

- Prior treatment with an aromatase inhibitor (e.g., anastrozole, exemestane,
letrozole)

- Planned surgery (other than core needle biopsy) to intact non-cancerous breast (e.g.,
preventive/prophylactic mastectomy)