According to an article recently published in the Journal of the National Cancer Institute, among breast cancer patients with HER2-overexpressing cancer cells, those whose cells express a receptor called p95HER2 have poor anticancer response rates to Herceptin® (trastuzumab).
Approximately 25–30% of breast cancers overexpress a protein referred to as the human epidermal growth factor receptor 2 (HER2). The HER2 receptor is involved in a biologic pathway that is responsible for the growth and spread of a cell. Herceptin is an agent that is targeted against the HER2 receptor and helps to slow or stop the spread of cancer cells that overexpress HER2. Although the addition of Herceptin to treatment of HER2-overexpressing breast cancer can improve outcomes, some women do not have anticancer responses to Herceptin.
Researchers from Spain recently conducted a clinical study to evaluate the potential predictive value of the receptor p95HER2 in the response to Herceptin among patients with HER2-overexpressing breast cancer. Forty-six patients with metastatic breast cancer (cancer that has spread from the breast to distant sites in the body) were treated with Herceptin; nine patients had cancer cells that expressed p95HER2, and 37 patients did not express p95HER2.
- Of the patients who expressed p95HER2, only one (11.1%) demonstrated an anticancer response to Herceptin.
- Of the patients who did not express p95HER2, more than half (51.4%) demonstrated anticancer responses to Herceptin.
- In laboratory testing of cancer cells that expressed p95HER2, treatment with the targeted agent Tykerb® (lapatinib) demonstrated anticancer activity while treatment with Herceptin did not demonstrate anticancer activity.
The researchers concluded that patients with HER2-overexpressing breast cancer who also express p95HER2 appear to be more resistant to treatment with Herceptin and “may require alternative or additional anti-HER2–targeting strategies.” Patients with HER2-overexpressing breast cancer may wish to speak with their physician regarding their individual risks and benefits of participating in a clinical trial further evaluating biologic markers that may help predict responses to certain therapies.
Reference: Scaltriti M, Rojo F, Ocana A, et al. Expression of p95HER2, a truncated form of the HER2 receptor, and response to anti-HER2 therapies in breast cancer. Journal of the National Cancer Institute. 2007; 99: 628-638.
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