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 6 months longer than women treated only with Arimidex.
The results were presented at the 2011 San Antonio Breast Cancer Symposium.
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. Faslodex is given as an injection into muscle. Tamoxifen, a selective estrogen receptor modulator, is similar to Faslodex, also working by blocking the effect of estrogen on hormone-receptor-positive breast cancer cells. Tamoxifen is used to treat early-stage and advanced-stage hormone-receptor-positive breast cancer, including metastatic breast cancer, in pre- and postmenopausal women.
In this study, 700 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 was more than 6 months longer for women treated with the Arimidex and Faslodex combination compared to women treated with only Arimidex (47.7 months compared to 41.3 months). So among all women treated with Arimidex and Faslodex, half lived for more than 47.7 months and half lived for shorter periods of time. Among all women treated with only Arimidex, half lived for more than 41.3 months and half lived for shorter periods of time.
Some experts were surprised by this result since a similar study reported in 2010 found no difference in survival among women treated with the Faslodex and Arimidex combination compared to women treated with only Arimidex.
Progression-free survival (the time a woman lived without the cancer growing) was 1.5 months longer in women who got the Faslodex and Arimidex combination (15 months) compared to women who got only Arimidex (13.5 months).
The researchers also specifically looked to see if adding Faslodex to Arimidex improved survival in women who had been treated with tamoxifen when first diagnosed with early-stage breast cancer. They're not sure why, but there was no survival improvement in these women who had been previously treated with tamoxifen.
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 much more about the potential benefits and side effects of hormonal therapies, including Arimidex and Faslodex, in the Breastcancer.org Hormonal Therapy section.