Hormone therapy. Hormone therapy is used to prevent the growth,
spread, and recurrence of breast cancer. The female hormone
called estrogen can increase the growth of breast cancer cells
in some women. Hormones are chemicals produced by glands, such
as the ovaries and testicles. Hormones help some types of cancer
cells to grow, such as certain breast cancers and prostate
cancer. Hormone therapy may be considered for women whose breast
cancers test positive for estrogen or progesterone receptors. A
hormone receptor test measures the amount of certain proteins
(called hormone receptors) in cancer tissue. Hormones (such as
estrogen and progesterone that naturally occur in the body) can
attach to these proteins. If the test is positive, it indicates
that the hormone is probably helping the cancer cells to grow.
In this case, hormone therapy may be given to block the way the
hormone works and/or help keep the hormone from attaching to the
receptors on the cancer cells. If the test is negative, the
hormone does not