This phase IIA trial compares the effect of acolbifene versus low dose tamoxifen in preventing breast cancer in premenopausal women at high risk for developing breast cancer. The usual approach for patients at increased risk for breast cancer is to undergo yearly breast magnetic resonance imaging or ultrasound in addition to yearly mammogram. Premenopausal women at very high lifetime risk for breast cancer (greater than 50%) can consider preventive removal (mastectomy) of both breasts. Premenopausal women age 35 or older with a prior diagnosis of atypical hyperplasia, lobular carcinoma in situ, or an estimated 10-year risk of greater than or equal to 3% or estimated 10-year risk of greater than or equal to 2-5 times that of the average woman (depending on age) may be advised to consider five years of standard dose tamoxifen. Standard dose tamoxifen is four times the dose used in this study. Estrogen can cause the development and growth of breast cancer cells. Acolbifene and tamoxifen blocks the use of estrogen by breast cells. This study may help researchers measure the effects of acolbifene and low dose tamoxifen on markers of breast cancer risk in mammogram imaging, breast tissue, and in blood samples.
Age >= 35 years
Considered clinically premenopausal
Having regular menstrual cycles (between 21 and 35 days) unless a contraceptive device such as progestin containing intrauterine device (IUD) (e.g., Mirena IUD) is being used which suppresses menstrual periods, or premenopausal women who have undergone a hysterectomy, but ovaries are intact
Not considering pregnancy for at least 12 months
Bilateral breast implants (danger of implant puncture with RPFNA)
Women who are pregnant
Currently breastfeeding (concern that tamoxifen or acolbifene may be in breast milk) or nursing within the past 12 months (concern about milk fistula with RPFNA)
Prior invasive breast cancer within the past 5 years