A study found that treating hormone-receptor-positive, HER2-positive metastatic breast cancer with the hormonal therapy medicine Femara (chemical name: letrozole) AND the targeted therapy medicine Tykerb (chemical name: lapatinib) offered more benefits than Femara alone. These results were presented at the 2008 San Antonio Breast Cancer Symposium.
Hormonal therapy medicines such as Femara often are used to treat hormone-receptor-positive metastatic breast cancers. About one-third of hormone-receptor-positive metastatic breast cancers will respond to hormonal therapy alone.
HER2-positive cancers have too many copies of the HER2/neu gene that makes too much of the HER2 protein. About 1 out of every 4 breast cancers is HER2-positive. Advanced-stage HER2-positive breast cancers that are also hormone-receptor-positive often are treated initially with just a hormonal therapy medicine, but these types of cancers often stop responding to the hormonal therapy medicine.
Researchers think that this lack of response by HER2-positive cancers to hormonal therapy medicines is caused by the HER2 protein. So they wanted to see if combining hormonal therapy with Tykerb, a medicine that specifically targets HER2-positive cancer cells, would make the treatment more effective.
More than 200 women diagnosed with metastatic hormone-receptor-positive, HER2-positive breast cancer participated in this study. The metastatic breast cancer had not been treated before in any of the women. About half of the women received Femara alone as a first treatment, while the other half of the women received Femara and Tykerb.
- Cancers treated with Femara AND Tykerb stopped growing 29% longer compared to cancers treated only with Femara.
- About 38% of the cancers treated with Femara AND Tykerb had a partial or a complete response to treatment, compared to only about 15% of cancers treated only with Femara.
- Almost 50% of the cancers treated with Femara AND Tykerb were stable for a period of time during treatment, compared to about 30% of the cancers treated only with Femara.
The women who got both Femara and Tykerb had side effects commonly associated with each treatment:
- Femara can cause muscle and joint pain, and sometimes hot flashes.
- Tykerb can cause diarrhea, vomiting, and fatigue.
Right now, Tykerb is approved by the U.S. Food and Drug Administration (FDA) to be used only in combination with the chemotherapy medicine Xeloda (chemical name: capecitabine) to treat HER2-positive, metastatic breast cancer that has stopped responding to Herceptin (chemical name: trastuzumab), another targeted therapy medicine that targets HER2-positive cancer cells. This study used Tykerb in a way that is not approved by the FDA. So while this research is very promising, more research is needed before Tykerb is used routinely to treat hormone-receptor-positive, HER2-positive metastatic breast cancer.
If you've been diagnosed with hormone-receptor-positive, HER2-positive metastatic breast cancer, you might want to talk to your doctor about this study. You may be able to be part of a clinical trial that does more research on Tykerb and Femara.
Visit the Breastcancer.org Targeted Therapies section to learn about the different targeted therapy medicines, how they work, when they are used, and possible side effects.