Hormones are natural substances produced by the body that control reproduction, growth, and metabolism.
Certain body tissues, such as breast and prostate, require hormones to develop. When cancer originates in these tissues, it responds to hormones. This means that the cancer responds to hormonal manipulation, which includes the administration of hormones, the withdrawal of hormones, or interference with hormone function. For example, by using chemicals that block the action of these hormones, it is possible to slow down, or even stop, the growth of cancer cells.
Rarely given as a single agent to attempt to cure cancer, hormones are often used to prevent or delay recurrence of cancer after other modalities of treatment have removed the gross primary tumor and chemotherapy or radiation therapy have treated systemic and regional micrometastases.
An example is a breast cancer patient who had the primary tumor and positive axillary nodes removed surgically, received systemic chemotherapy and regional radiation, and was placed on tamoxifen, a synthetic antiestrogen, to prevent or delay recurrence.
Hormones can be administered orally, intravenously, or intramuscularly. Surgery may also be used to prevent the body from producing hormones. For example, a patient with prostate cancer may have an orchiectomy to prevent the production of testosterone.
Some types of cancer may originate from organs that require hormones to develop, but they may not be treated with hormonal therapy. A sample of the tumor can be sent to a special lab to determine if hormonal therapy is likely to be effective.