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Antiestrogens are a group of medications that block the effect that estrogen has on the growth of a tumor.


Antiestrogens refer to a group of drugs that are used to treat advanced hormone-sensitive breast cancers. Many breast cancer tumors grow due to normal levels of estrogen, a hormone found in the bloodstream. Some patients have tumors that are extra-sensitive to this normal estrogen level. The estrogen attaches to the area on the outside of the tumor cells and sends a signal to the cell that causes it to grow and multiply. Antiestrogens block the protein on the outside wall of the estrogen-sensitive breast cancer cell. By blocking this protein, known as the estrogen receptor, the free-floating estrogen cannot stimulate the cancer cells to grow and multiply any further.

The drug tamoxifen is a common antiestrogen that has proven to have a positive effect in breast cancer patients for both treatment and prevention.

Nancy J. Beaulieu, RPh., BCOP