Tamoxifen is a drug widely prescribed throughout the world for treatment of breast cancer. In breast tissue, tamoxifen blocks the action of the hormone estrogen. Estrogen stimulates some breast cancer cells to grow and divide by attaching to proteins inside the cells called estrogen receptors. Tamoxifen also binds to these receptors and prevents attachment of estrogen, depriving cancer cells of growth signals.
Not all breast cancer cells have estrogen receptors, and tamoxifen is most useful for patients whose cancers do have them. The drug helps prevent reappearance of cancer in women whose tumors have been removed surgically. In patients whose cancer has already reappeared, tamoxifen can slow the growth of tumors and prolong life. Some women with cancer in one breast have an increased risk that a new cancer will develop in their other breast. Tamoxifen lowers the risk that these new cancers will form. Studies show that tamoxifen is even more effective when given with another estrogen-suppressing drug called letrozole. Some studies suggest that tamoxifen also significantly reduces the likelihood that breast cancer will develop in healthy women who have an increased risk for the disease.
The main side effects of tamoxifen are nausea, vomiting, and hot flashes (sudden, intense sensations of body heat). In some tissues, tamoxifen behaves like estrogen rather than blocking its action. Like estrogen, tamoxifen increases the risk of developing cancer of the uterus. But the risk is still small, and most experts agree that the benefits of tamoxifen far outweigh this risk for women with breast cancer. Some studies suggest that tamoxifen can help prevent osteoporosis << `os` tee oh puh ROH sihs >> , a loss of bone tissue as people age. Tamoxifen may also help lower cholesterol levels.
