Hormones are naturally occurring substances in the body that can stimulate or modulate the growth of hormone sensitive tissues, such as the breast or prostate gland. When cancer arises in certain tissues such as breast or prostate tissue, its growth and spread may be caused by the body's own hormones. Therefore, drugs that block hormone production or change the way hormones work are often very effective and tolerable ways of treating cancer. Hormone therapy, similar to chemotherapy, is a systemic treatment in that it is designed to affect cancer cells throughout the body.
