Aromatase Inhibitor Therapy

Colorful pills.

Prior to a diagnosis, a biopsy is usually performed to confirm the presence of cancer cells in the breast. Once a formal diagnosis has been made, other tests are typically performed on the tissue obtained by the biopsy to determine whether the tumor is hormone receptor positive or negative. Knowing this information allows the treating oncologist to determine the best and most effective treatment path moving forward.

If the tumor is hormone receptor positive, it means the breast cancer relies on the hormones estrogen and progesterone to grow. Treatments called hormone therapies are typically used in hormone-positive breast cancers because these treatments work to block the cancer cells from using estrogen and progesterone.

Aromatase inhibitors are one type of hormone therapy that women with breast cancer may be treated with following surgery. These therapies are typically given to women who have already gone through menopause because they actually are not able to stop the ovaries from making estrogen. Aromatase inhibitor therapies work by preventing the body from making estradiol, a form of estrogen.

Arimidex (anastrazole), Aromasin (exemestane) and Femara (letrozole) are three types of aromatase inhibitors used to treat breast cancer. These therapies are approved for three different uses. The first is as an adjuvant therapy (treatment following surgery or radiation) in postmenopausal women with early breast cancer. Second is as an initial treatment for hormone-positive or hormone receptor-unknown locally advanced or metastatic breast cancer. The third is for use to treat advanced breast cancer that has progressed following treatment with another hormone therapy called tamoxifen.

None of these aromatase inhibitors have been approved to prevent the development of breast cancer.

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