S-equol in Women With Triple Negative Breast Cancer

After a baseline breast tumor core biopsy, eligible women with triple negative breast cancer (ER- alpha, PR and HER-2 receptor negative) will be treated with S-equol at a dose of 50 mg twice daily for a period of about 14 days (10-21 day range). After completion of treatment, a second breast tumor sample will be obtained to compare molecular changes between the two specimens. The second pathology specimen may be from the surgical resection of the breast tumor, or a repeat core needle biopsy, if no further surgery is planned. The primary endpoint will be the absolute change in the Ki67, which is a validated marker of tumor proliferation in breast cancer. Secondary endpoints will include assessment of total ER-beta and pY36 levels as measured by immunohistochemical staining and their correlation with S-equol effects. Further treatment after surgical resection or second core needle biopsy of the tumor will be guided by tumor size, nodal status and other standard parameters, and is at the discretion of the treating physician. The Investigator hypothesizes that S-equol will cause a measurable decrease in Ki-67 in estrogen receptor beta expressing triple negative breast cancers, indicating its potential efficacy in this tumor type.