Arimidex (chemical name: anastrozole) is an aromatase inhibitor approved by the U.S. Food and Drug Administration (FDA) to treat:
- postmenopausal women diagnosed with hormone-receptor-positive, early-stage breast cancer after surgery (or possibly chemotherapy and radiation) to reduce the risk of the cancer coming back
- postmenopausal women diagnosed with advanced-stage or metastatic hormone-receptor-positive breast cancer
Arimidex won’t work on hormone-receptor-negative breast cancer. Arimidex shouldn’t be taken at the same time as tamoxifen.
Arimidex is a pill taken once a day. Most doctors recommend taking Arimidex at the same time each day.
You should not take Arimidex if you are breastfeeding, pregnant, trying to get pregnant, or if there is any chance that you could be pregnant. Arimidex may cause damage to developing embryos. You should use an effective non-hormonal type of birth control — such as condoms, a diaphragm along with spermicide, or a non-hormonal I.U.D. – while you are taking Arimidex. Ask your doctor which type of non-hormonal birth control would be best for you, as well as how long you should use this type of birth control after you stop taking Arimidex.
Benefits of Arimidex
The large ATAC (Arimidex, Tamoxifen Alone or in Combination) trial compared Arimidex to tamoxifen after surgery. The researchers wanted to know how the medicines worked by themselves as well as together to see which combination would be the best treatment for postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer. Based on the results of this trial, giving Arimidex and tamoxifen at the same time isn’t recommended.
The ATAC study found that 5 years of Arimidex is better than 5 years of tamoxifen as the first hormonal therapy for postmenopausal women with early-stage, hormone-receptor-positive breast cancer. Arimidex is better than tamoxifen for:
- increasing the time before the cancer comes back in those who experience recurrence
- reducing the risk of the cancer spreading to other parts of the body
- reducing the risk of a new cancer developing in the other breast
Research presented at the 2013 San Antonio Breast Cancer Symposium showed that Arimidex can lower the risk of first-time, hormone-receptor-positive breast cancer in postmenopausal women at high risk who haven’t been diagnosed. Arimidex isn’t approved by the FDA for this use, but doctors may consider it a good alternative to other hormonal therapies approved to reduce risk in high-risk women.
It’s possible that the FDA may approve Arimidex to be used to reduce risk in high-risk postmenopausal women who haven’t been diagnosed.
Side effects of Arimidex
Because Arimidex lowers the amount of estrogen in the body, less estrogen reaches bone cells, which can lead to bone thinning and weakening and a higher-than-average risk of broken bones. This side effect can be very troubling for some women. If you have osteoporosis, your doctor may recommend that you take tamoxifen rather than Arimidex because of this possible side effect.
The ATAC results reported in 2007 showed a finding that hadn’t been seen before. The higher risk of broken bones associated with Arimidex disappeared after the women stopped taking Arimidex. The researchers will see if this result continues as more data is collected and analyzed.