Tamoxifen is an antiestrogen medication that works by competing with estrogen for binding sites in target tissues, such as breast tissue, and blocking estrogen’s effects there. By interfering with estrogen activity, tamoxifen helps slow or stop the growth of certain types of breast cancer cells that depend on estrogen to grow.

Tamoxifen is used for several important purposes:

Treatment of breast cancer — especially hormone receptor-positive breast cancers.
Prevention of breast cancer — in women who are at high risk of developing the disease.
Post-surgical therapy — to lower the risk of invasive breast cancer in women who have undergone surgery and radiation therapy for ductal carcinoma in situ (DCIS), a non-invasive form of breast cancer.

Because of its ability to target hormone-driven cancers, tamoxifen remains a cornerstone of breast cancer management and prevention strategies.