Inclusion Criteria

Criteria:

- At increased risk for breast cancer, as indicated by >= 1 of the following risk
factors:

- BRCA1/2 mutation characterized as deleterious or of uncertain significance

- Prior atypical ductal hyperplasia, ductal carcinoma in situ, or lobular carcinoma in
situ

- Prior random periareolar fine needle aspiration (RPFNA) showing atypical hyperplasia

- Family history consistent with hereditary breast cancer, as indicated by 1 of the
following criteria:

- >= 4 relatives with breast cancer

- >= 2 relatives diagnosed with breast cancer at ≤ 50 years of age

- Breast and ovarian cancer diagnosed in same relative

- No suspicion for breast cancer on baseline mammogram performed between days 1-10 of
menstrual cycle within 3 months prior to screening baseline RPFNA

- Exhibits hyperplasia with or without atypia (Masood score >= 14) with >= 500 cells
AND Ki-67 positivity >= 2% by RPFNA performed within 6 months prior to initiation of
study drug

- Estimated visual mammographic breast density category >= 5% on mammogram performed
within 6 months prior to initiation of study drug

- Has regular menstrual cycles (between 21 and 35 days) unless using extended regimen
oral contraceptives or a contraceptive device (e.g., Mirena IUD)

- Absolute granulocyte count > 1,000/mm^3

- Platelets > 100,000/mm^3

- Hemoglobin > 10 g/dL

- Bilirubin < 2.0 mg/dL

- AST < 2 times upper limit of normal (ULN)

- Albumin > 3.0 g/dL

- Creatinine < 1.5 mg/dL

- Not pregnant or nursing

- No nursing within the past 6 months

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 3 months after
completion of study treatment

- Willing to ingest recommended dose of calcium and vitamin D for premenopausal bone
health (1,200 mg calcium and 800 IU vitamin D daily)

- Alkaline phosphatase < 2 times ULN

- No known osteoporosis or severe osteopenia (T-score -2 or worse by DEXA)

- No history of symptomatic endometriosis with pelvic pain, poorly controlled
migraines, or hot flashes

- No history of deep venous thrombosis

- No history of allergic reactions attributed to compounds of similar chemical or
biological composition to the study agent

- No other condition or concurrent illness that, in the opinion of the investigator,
would make the patient a poor candidate for RPFNA

- At least 1 year since prior and no concurrent aromatase inhibitors (e.g.,
anastrozole, exemestane, or letrozole) or selective estrogen receptor modulators
(e.g., tamoxifen citrate, raloxifene, or arzoxifene hydrochloride)

- Concurrent hormonal contraceptives allowed provided patient remains on the same
hormonal regimen from 3 months prior to baseline aspiration until the completion of
study treatment

- No other concurrent chemopreventive agents

- No concurrent anticoagulants

- Gail risk >= 1.7% and/or relative risk >= 3 times that for 5-year age group

- No other concurrent investigational agents

- Premenopausal

- No bilateral breast implants

- More than 6 months since initiating or discontinuing oral contraceptives