This phase II trial evaluates response-guided low-dose tamoxifen for reducing breast density in women who are at higher than average risk for breast cancer. Increasing breast density is a well established risk factor for breast cancer. Tamoxifen is a selective estrogen receptor modulator. It works by blocking the effects of the hormone estrogen in the breast. Tamoxifen has been shown to reduce breast density, even at reduced dosages, and is approved for the prevention of breast cancer.
Age under 50 years and regular menstruation (most recent period within the past 3 months)
Age under 50 years and continuous hormonal contraception use and at least one intact ovary
Women who are not postmenopausal based on serum hormone levels. Women with estradiol =< 30 pg/mL, follicle-stimulating hormone (FSH) >= 30 IU/mL are eligible
A history of unilateral estrogen receptor (ER) positive ductal carcinoma in situ (DCIS) with local therapy completed (as determined by treating physician recommendation and patient acceptance) at least 1 month prior to study entry. (The untreated breast will be the study breast, for both imaging and optional biopsy)
BIRADS breast density category A on most recent mammogram
Use was less than 6 months duration in the past 5 years and not used in the 1 year prior to enrollment OR
Use was no greater than 2 months duration in the past 1 year and not used in the 6 months prior to enrollment
History of invasive breast cancer