Hormones are special chemical messengers made by endocrine glands that occur naturally in the body. One of the many jobs they have on the body is the controlling of the growth and activity of certain hormone sensitive tissues and cells, such as breast and prostate tissue. Sometimes, cancer cells found in these tissues become hormone sensitive or hormone dependent, meaning they rely on hormones to grow or develop, and the cancer’s growth then may be caused by the body’s own hormones.
In cases such as these, blocking the action of hormones or altering the way they work could stop the cancer from growing. Drugs used in hormonal therapy block hormone production or change the way hormones work, and/or removal of organs that secrete hormones, such as the ovaries or testicles, are ways of fighting cancer. Similar to chemotherapy, hormone therapy is considered a systemic treatment in that it is designed to have a widespread effect on the cancer cells in the body.