The finding of a decrease in contralateral breast cancer incidence following tamoxifen administration for adjuvant therapy led to the concept that the drug might play a role in breast cancer prevention. No liver cancers or increase in colon, rectal, ovarian, or other tumors was observed in the tamoxifen group.
Tamoxifen decreases the incidence of invasive and noninvasive breast cancer.
Despite side effects resulting from administration of tamoxifen, its use as a breast cancer preventive agent is appropriate in many women at increased risk for the disease. The National Cancer Institute has created a breast cancer risk assessment tool that quickly estimates a woman's individualized absolute risk of developing breast cancer. Understanding the magnitude of risk is important because recent data show that breast cancer incidence may be reduced. All women may improve their overall health and thus perhaps minimize breast cancer risk by maintaining a healthy weight, avoiding cigarettes, limiting alcohol consumption, getting regular exercise, and avoiding non-diagnostic ionizing radiation. Nevertheless, no lifestyle modifications have yet been proven to prevent or definitively lower the risk of breast cancer.