Soy Isoflavones Supplementation in Treating Women at High Risk For or With Breast Cancer

PRIMARY OBJECTIVES: I. To assess whether magnetic resonance imaging (MRI) volume (equivalent
to 3-dimensional mammographic density) is reduced in high-risk women or those with invasive
breast cancer or DCIS who are supplemented daily with soy (5p mg total isoflavones as
aglycone) compared to placebo (microcrystalline cellulose) tablets for 1 year.II. To assess
whether cell proliferation and apoptosis, as measured by Ki67 and caspase 3 staining,
respectively, of breast epithelial cells is altered with soy treatment.SECONDARY OBJECTIVES:
I. To assess whether other intermediate molecular markers including estrogen receptor alpha
(ER alpha) and ER beta differ between women supplemented with soy vs placebo. OUTLINE:
Patients are randomized to 1 of 2 treatment arms.ARM I: Patients receive oral soy isoflavones
supplement once daily for12 months in the absence of disease progression.ARM II: Patients
receive oral placebo once daily for 12 months in the absence of disease progression.

Inclusion Criteria:

- Women at high risk for breast cancer, defined as any of the following groups:

- Five year Gail risk > 1.7%

- Known BRCA1/BRCA2 mutation carrier

- Family history consistent with hereditary breast cancer

- Prior biopsy exhibiting atypical hyperplasia or lobular carcinoma in situ (LCIS)

- History of invasive breast cancer or ductal carcinoma in situ (DCIS) and have
completed standard therapy including tamoxifen/aromatase inhibitor or will not be
treated with tamoxifen/aromatase inhibitor

- Signed Informed Consent

Exclusion Criteria:

- Metastatic breast cancer

- Undergoing treatment (chemotherapy, radiation, or SERMs)

- Pregnancy or breast-feeding, or planning to become pregnant within one year prior to
study entry

- Regular soy consumers (i.e., < once per week of soy food, soy supplements or other
products)

- Known food allergies such as to soy or nuts

- Not willing to avoid soy foods/supplements during study period

- Current users of exogenous hormones or oral contraceptive or planning to use exogenous
hormones during the duration of the study

- Cannot stop taking aspirin or NSAIDs within a week of breast biopsy

- Active participant in other ongoing trials