With some cancers, patients are given hormone therapy as soon as cancer is diagnosed, before any other treatment. It may shrink a tumor, or it may halt the advance of the disease. In some cancers, such as prostate cancer, hormone therapy helps ease the painful and distressing symptoms of advanced disease.

The female hormones estrogen and progesterone promote the growth of some breast tumors. Hormonal therapy may be given to block these hormones from stimulating tumor growth.