Hormone (endocrine) therapy is a systemic, targeted treatment available for certain women who have estrogen positive (ER+ (ER positive, estrogen receptor positive) or PR+ (PR positive, progesterone receptor positive)) tumors. It can be given along with chemotherapy, or in place of it. It is used to prevent estrogen from fueling the growth of those tumors or any residual or recurrent tumor cells in the body. These therapies do not work for estrogen and progesterone negative tumors. Although standard treatment is 5 years, it has been extended in many circumstances to 10 years based on the risk of tumor recurrence.
A woman with early stage hormone receptor positive cancer can be treated with aromatase inhibitors like Arimidex (anastrozole) Aromasin (exemestane) or Femara (letrozole), which reduce estrogen by blocking an enzyme called aromatase and keeping it from converting androgens into estrogen; or Tamoxifen, which occupies estrogen receptors so that estrogen can’t get to the cell.
