The Columbia Encyclopedia, Sixth Edition. 2001-07.
tamoxifen
(tmk´sfn´´) (KEY) , synthetic hormone used in the treatment of breast cancer. Introduced in 1978, tamoxifen is used to prevent recurrences of cancer in women who have already undergone surgery to remove their tumors. In 1998, a large study of healthy women at high risk for breast cancer showed that tamoxifen can also prevent first occurrence of the disease: women who took the drug had a 45% lower incidence of cancer that those who received a placebo. However, adverse effects (including uterine cancer) and other concerns await further study.