Arimidex (chemical name: anastrozole) and Faslodex (chemical name: fulvestrant) are different types of hormonal therapies often used individually to treat hormone-receptor-positive metastatic breast cancer.
A study has found that postmenopausal women diagnosed with hormone-receptor-positive metastatic breast cancer and treated with a combination of Arimidex and Faslodex as the first treatment for metastatic disease lived about 6 months longer than women treated only with Arimidex. Women who got the Arimidex-Faslodex combination also lived about 2 months longer before the cancer grew (progression-free survival).
The study was published online on Aug. 2, 2012 by the New England Journal of Medicine. Read the abstract of “Combination Anastrozole and Fulvestrant in Metastatic Breast Cancer.”
Arimidex, an aromatase inhibitor, works by lowering the amount of estrogen in the body. Arimidex is used to treat both early-stage and advanced-stage hormone-receptor-positive breast cancer, including metastatic breast cancer, in postmenopausal women.
Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver.
Arimidex is a pill taken by mouth. Aromasin (chemical name: exemestane) and Femara (chemical name: letrozole) are also aromatase inhibitors.
Faslodex, an estrogen receptor downregulator, works by blocking the effect of estrogen on hormone-receptor-positive breast cancer cells. Faslodex is used to treat metastatic hormone-receptor-positive breast cancer in postmenopausal women who didn’t respond to or stopped responding to tamoxifen, another hormonal therapy medicine. Faslodex is given as an injection into muscle.
Because Arimidex and Faslodex work in different ways, the researchers wanted to see if taking the two medicines together would be more effective than Arimidex alone.
In this study, 694 postmenopausal women diagnosed with metastatic hormone-receptor-positive breast cancer were randomly assigned to receive a combination of Arimidex and Faslodex or Arimidex alone. Many of the women previously had received treatment for early-stage breast cancer, but they hadn’t received any treatment for metastatic cancer.
Overall survival (the amount of time the women lived whether or not the cancer grew) was more than 6 months longer for women treated with the Arimidex-Faslodex combination compared to women treated only with Arimidex (47.7 months compared to 41.3 months).
Some doctors were surprised by this result since a similar study published in 2010 found no difference in survival between women treated with the Arimidex-Faslodex combination and women treated only with Arimidex.
Progression-free survival (the time a woman lived without the cancer growing) was 1.5 months longer in women who got the Arimidex-Faslodex combination (15 months) compared to women who got only Arimidex (13.5 months).
Women who were getting only Arimidex and had the cancer grow were able to start taking the Arimidex-Faslodex combination. About 41% of the women getting only Arimidex switched to the Arimidex-Faslodex combination.
Women who were treated with the Arimidex-Faslodex combination had more serious side effects than the women treated only with Arimidex, but this difference wasn’t statistically significant, which means it could have been due to chance and not because of the differences in treatments.
If you’re a postmenopausal woman just diagnosed with hormone-receptor-positive metastatic breast cancer, you and your doctor will consider a number of treatment options. These may include hormonal therapy, chemotherapy, and/or a targeted therapy (for example, Herceptin if the cancer is HER2-positive). If hormonal therapy is recommended, the specific medicine will depend on a number of factors, including any past treatments you may have had if you were previously treated for early-stage breast cancer.
Right now, doctors are unlikely to recommend a combination of Arimidex and Faslodex based on currently available research results. Still, you might want to talk to your doctor about this study and the factors considered in making your hormonal therapy recommendation.
You can learn more about the potential benefits and side effects of hormonal therapy medicines, including Arimidex and Faslodex, in the Breastcancer.org Hormonal Therapy section.