Nexavar® May Overcome Resistance to Arimidex® in Breast Cancer
The addition of Nexavar® (sorafenib) to Arimidex® (anastrozole) helps restore sensitivity to Arimidex among women with breast cancer. These results were recently presented at the 2008 annual American Society of Clinical Oncology (ASCO) breast cancer symposium.
The majority of breast cancers are hormone positive, meaning that the cancer cells are stimulated to grow from exposure to the female hormones estrogen and/or progesterone. Women with hormone-positive breast cancer receive hormone therapy, which prevents estrogen from forming in the body or blocks the exposure of cancer cells to estrogen.®
Arimidex is a hormone therapy that prevents the formation of estrogen in the body. It is commonly used among postmenopausal women with hormone-positive breast cancer. Unfortunately, some women can become resistant to Arimidex, meaning that their cancer continues to grow despite treatment, whereas others may never respond to Arimidex. Reasons for this lack of response are not clear. Researchers continue to evaluate ways to work around this resistance, such as targeting other biologic pathways associated with cancer.
Nexavar is an agent that has multiple targets involved in several biologic pathways associated with cancer. Used alone, Nexavar has not demonstrated anticancer responses in the treatment of breast cancer; however, researchers have speculated that Nexavar may aid in reversing the resistance to Arimidex or other hormone agents.
Researchers from Georgetown University recently conducted a clinical trial to explore the potential effectiveness of the combination of Nexavar and Arimidex in the treatment of advanced breast cancer that has stopped responding to Arimidex. This trial included 27 postmenopausal women with hormone-positive breast cancer who had no more than two prior chemotherapy regimens for their disease and who had stopped responding to prior therapy with Arimidex.
- Over 26% of patients achieved either partial regression of their cancer or stabilization of their cancer for at least six months.
- A reduction in specific cells (endothelial cells) in the circulating blood during the first week of treatment predicted a response to therapy.
The researchers concluded that the addition of Nexavar to Arimidex may help overcome resistance to Arimidex in postmenopausal women with hormone-positive advanced breast cancer. Ultimately, these results support the idea that targeted therapies may be able to restore sensitivity to certain effective therapies in several types of cancers. Future trials further evaluating this approach are warranted.
Patients with breast cancer who have stopped responding to certain therapies may wish to speak with their physician regarding their individual risks and benefits of participation in a clinical trial further evaluating combined therapies or other promising therapeutic approaches. Two sources of information regarding ongoing clinical trials include the National Cancer Institute (www.cancer.gov) and www.eCancerTrials.com.
Reference: Subramaniam D., et al. Sorafenib in hormone-receptor positive (ER/PR+) metastatic breast cancer (MBC) resistant to aromatase inhibitors (AIs). Proceedings from the 2008 ASCO Breast Cancer Symposium. Abstract #162.