Tamoxifen inhibits estrogen receptor activity in some organs (AE = antiestrogenic) but stimulates estrogen receptor activity in others (E = estrogenic). In organs such as the breast, the AE action of tamoxifen is favorable (+), while in others, such as the brain and vaginal mucosa, it produces unwanted side-effects, and the effect is unfavorable (-). Likewise, in some organs such as bone, the E activity of tamoxifen is favorable (+), while in others, such as the endometrium, it is unfavorable (-). In liver, the E activity is both favorable (lower cholesterol and decreased risk of coronary artery disease) and unfavorable (higher clotting protein levels and increased risk of deep venous thrombosis).
New directions in research Scientists are investigating a number of potential preventive therapies for breast cancer, including: Retinoids. Natural or synthetic forms of vitamin A (retinoids) may have the ability to destroy or inhibit the growth of cancer cells. Unlike other experimental therapies, retinoids may be effective in premenopausal women and in those whose tumors aren't estrogen positive. Research is ongoing. Flaxseed. Flaxseed is high in lignan, a naturally occurring compound that lowers circulating estrogens in your body. Flaxseed appears to decrease estrogen production — acting much like tamoxifen does — which may inhibit the growth of breast cancer tumors. Lignans are also antioxidants with weak estrogen-like characteristics. These characteristics may be the mechanism by which flaxseed works to decrease hot flashes. Further research should clarify the connection.