Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed ductal carcinoma in situ (DCIS) of the breast

- Mixed DCIS and lobular carcinoma in situ (LCIS) allowed

- Must have undergone lumpectomy

- Margins must be histologically free of disease

- Re-excision to obtain tumor-free margins allowed

- No more than 84 days since prior lumpectomy or re-excision

- More than 1 area of DCIS allowed provided all disease is removed with tumor-free
margins

- Masses or clusters of calcification that are clinically or mammographically
suspicious must be biopsied

- No prior invasive breast cancer or DCIS

- Patients with a history of LCIS are eligible

- No prior or concurrent invasive (including microinvasive) breast cancer

- DCIS "suspicious" for microinvasion allowed

- No bilateral malignancy

- No mass or mammographic abnormality suspicious for malignancy in the opposite
breast unless not malignant as proven by biopsy

- No Paget's disease of the nipple

- No positive ipsilateral axillary or intramammary nodes

- No palpable nodes in the ipsilateral or contralateral axilla or palpable
supraclavicular or infraclavicular nodes unless not involved with tumor as
proven by biopsy

- Hormone receptor status:

- Estrogen- or progesterone-receptor positive as determined by
immunohistochemistry

- Borderline results are considered positive

PATIENT CHARACTERISTICS:

Age

- See Menopausal status

Sex:

- Female

Menopausal status:

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

- Prior documented bilateral oophorectomy

- At least 12 months without spontaneous bleeding

- Age 55 or over with prior hysterectomy without oophorectomy

- Age 54 or under with prior hysterectomy without oophorectomy with a documented
follicle-stimulating hormone level in the postmenopausal range

Performance status

- Zubrod 0-2

Life expectancy

- At least 10 years (excluding diagnosis of breast cancer)

Hematopoietic

- WBC normal

Hepatic

- AST normal

- Bilirubin normal

- Alkaline phosphatase normal

- No hepatic disease that would preclude administration of study drugs

Renal

- Creatinine normal

- No renal disease that would preclude administration of study drugs

Cardiovascular

- No prior documented cerebral vascular accident or transient ischemic attack

- No prior deep vein thrombosis

- No cardiovascular disease that would preclude administration of study drugs

- No uncontrolled hypertension (i.e., systolic blood pressure at least 180 mm Hg or
diastolic blood pressure at least 110 mm Hg based on the average of 2 or more
readings at each of 2 or more visits after initial screening)

- No uncontrolled atrial fibrillation

Pulmonary

- No pulmonary embolus

Other

- Not pregnant or nursing

- Patients with a history of non-breast malignancies are eligible provided they have
been disease-free for ≥ 5 years and are deemed by their physician to be at low risk
for recurrence

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

- No psychiatric or addictive disorders that would preclude informed consent

- No uncontrolled diabetes, defined as hemoglobin A1C greater than 9% (fasting glucose
200 mg/dL)

- No nonmalignant systemic disease that would preclude administration of study drugs

PRIOR CONCURRENT THERAPY:

Endocrine therapy

- No prior or concurrent aromatase inhibitors (e.g., exemestane or letrozole) or
tamoxifen

- No concurrent raloxifene or other selective estrogen receptor modulators

- No concurrent sex hormone therapy (e.g., estrogen or progesterone replacement
therapy, oral contraceptives, androgens, luteinizing hormone releasing hormone
analogs, prolactin inhibitors, or antiandrogens)

- Low-dose estrogen vaginal creams or Estring allowed

Radiotherapy

- Radiotherapy for this cancer initiated before study is allowed

Surgery

- See Disease Characteristics

- No prior or concurrent mastectomy for DCIS

- Prior sentinel node biopsy or axillary node dissection allowed provided nodes are
pathologically negative

Other

- No concurrent warfarin

- No other systemic therapy for this cancer initiated before study

- No other concurrent anticancer therapy unless permitted by the protocol investigator

- No concurrent participation in another clinical trial of therapy for DCIS

- Concurrent participation in protocol NSABP-B-39 allowed