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