Hormone Therapy |
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About two-thirds of all breast cancers are hormone-receptor positive, meaning they carry receptors for the hormones estrogen or progesterone. Two basic types of hormone therapy are available for such tumors: one stops estrogen from acting on breast cancer cells; the other lowers overall estrogen levels in the body or within the cancer cell.
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Tamoxifen and similar drugs are used to block the estrogen receptor on tumor cells, preventing them from receiving growth signals. Adults with invasive, hormone receptor-positive breast cancer generally take tamoxifen for five to 10 years after surgery to reduce the chances that the cancer will come back. To reduce estrogen production within cancer cells, doctors may prescribe drugs known as aromatase inhibitors, which block an enzyme that helps produce a small amount of estrogen in breast cancer cells, as well as other parts of the body, such as fat and muscle. Because such drugs don’t stop the ovaries from making estrogen, they’re effective only in adults whose ovaries no longer function, such as in post-menopausal adults.
Patients diagnosed prior to menopause with an early stage of hormone receptor-positive breast cancer are often treated with tamoxifen, and may receive an aromatase inhibitor if they go through menopause during treatment. In addition, young adults may benefit from reducing the amount of estrogen produced from the ovaries by suppressing the ovarian function through medications or surgery. However, tamoxifen or an aromatase inhibitor is always given in addition to ovarian suppression.
