The investigative vaccine E75 may have survival benefits for patients with breast cancer that has low expression of the human epidermal growth factor receptor 2 (HER2). These results were recently presented at the 2008 annual meeting of the American Association for Cancer Research.
The HER2 pathway is a biological pathway within cells that is involved in cellular replication and growth. Approximately 25–30% of breast cancers overexpress the HER2 protein on the surface of the cell; these cancers are referred to as HER2-positive or HER2-overexpressing breast cancer.
The HER2 protein provides a target for cancer therapy. Herceptin® (trastuzumab) and Tykerb® (lapatinib) are the two agents approved for HER2-positive breast cancer. These agents both tend to provide greater anticancer activity among breast cancer with greater expression of HER2. Patients whose cancer recurs following therapy with either agent, however, have limited treatment options. Researchers continue to evaluate novel ways to treat HER2-positive breast cancer.
The E75 vaccine is an investigative vaccine that stimulates the immune system to attack cells that express the E75 peptide (protein) found on HER2-overexpressing cells. The vaccine consists of E75 plus granulocyte macrophage-colony stimulating factor (GMSF), an agent that helps the immune system to recognize compounds as “foreign”, which triggers the immune system to attack the foreign agent.
Researchers from the Brooke Army Medical Center in San Antonio, Texas, recently completed a subgroup analysis from a clinical trial evaluating the E75 vaccine. The original trial included women with HER2-overexpressing early breast cancer. Patients had received standard therapy for early cancer and had no remaining evidence of cancer at the time of the trial. They were then treated with the vaccine or no vaccine (control group). The subgroup analysis of this trial included 203 patients from the trial; 92 patients who received the vaccination and 71 patients in the control group. The purpose of the subgroup analysis was to evaluate outcomes between different levels of HER2-expression and responses to the vaccine. The median follow-up was 30 months.
- Mortality rates were 3.4% among patients treated with the vaccine compared with 9.1% among the control group.
- Among patients who expressed low levels of HER2 (low-expressers), there were no deaths among those who had received the vaccine, while the mortality rate was 6.8% for those in the control group.
- Cancer recurrence rates were 13.8% in the vaccine-treated group and 18.2% in the control group.
- Among patients who experienced a recurrence and overexpressed HER2, mortality rates were 25% in the vaccine group and 50% in the control group.
- Among low-expressers who experienced a recurrence, mortality rates were 0% for those who received the vaccine and 38% for the control group.
- Side effects included minimal flu-like symptoms in less than 20% of women.
The researchers concluded that it appears that the E75 vaccine may provide survival benefit for patients with HER2 low-expressing breast cancer. However, this trial included only a small number of patients and further trials are necessary to confirm these results. A Phase III trial (the last phase prior to FDA review) is planned for the E75 vaccine.
Patients with breast cancer may wish to speak with their physician regarding ongoing clinical trials evaluating novel therapeutic approaches for breast cancer. Two sources of information regarding ongoing clinical trials include the National Cancer Institute (www.cancer.gov) and www.eCancerTrials.com.
Reference: Benavides LC, et al. Response to a preventive HER2/neu peptide (E75) vaccine based on HER2/new status. 2008 annual meeting of the American Association for Cancer Research*.* Abstract 2545.
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