For women with HER2-positive breast cancer that worsens in spite of treatment with Herceptin® (trastuzumab), treatment with a combination of Herceptin and Afinitor® (everolimus) may provide a benefit. These results were published in the Journal of Clinical Oncology.
Approximately 20-25% of breast cancers overexpress (make too much of) the HER2 protein. HER2-targeted therapies such as Herceptin have dramatically improved outcomes for women with HER2-positive breast cancer, but researchers continue to explore new approaches to treatment. One important focus of research is the treatment of cancer that has progressed after prior HER2-targeted therapy.
Afinitor is an oral medication that works by inhibiting a protein known as mTOR. The mTOR protein plays an important role in regulating cancer cell division and blood vessel growth. Currently, Afinitor is used for the treatment of selected patients with kidney cancer, pancreatic neuroendocrine tumors, and subependymal giant cell astrocytoma (SEGA).
To evaluate the combination of Herceptin and Afinitor, researchers combined information from two clinical trials that were conducted concurrently. Information was available for 47 women with HER2-positive metastatic breast cancer that had progressed during treatment with Herceptin. Study participants received Herceptin every three weeks in combination with daily Afinitor.
- Seven patients (15%) had a partial response to treatment (a reduction in detectable cancer).
- An additional nine patients (19%) experienced stable disease for six months or longer.
- Median duration of survival without cancer progression was 4.1 months.
- Side effects included fatigue, infection, and mouth sores (mucositis).
These results suggest that the combination of Afinitor and Herceptin may benefit women with HER2-positive, advanced breast cancer that has worsened in spite of Herceptin treatment. Afinitor has been approved by the US Food and Drug Administration for other purposes, but has not yet been approved for breast cancer. At this time, the use of Afinitor would only be appropriate for women with HER2-positive breast cancer in the setting of a clinical trial. Additional, ongoing studies are evaluating the combination of Herceptin, Afinitor, and chemotherapy in the first- and second-line treatment of metastatic breast cancer.
Reference: Khanh Morrow P, Wulf GM, Ensor J et al. Phase I/II study of trastuzumab in combination with everolimus (RAD001) in patients with HER2-overexpressing metastatic breast cancer who progressed on trastuzumab-based therapy. Journal of Clinical Oncology. Early online publication July 5, 2011.