A new breast cancer vaccine that is derived from the HER2 protein may help prevent recurrence in patients with HER2-positive disease and appears safe. Phase II study results of the vaccine were released at the 2014 Breast Cancer Symposium, September 4–6, in San Francisco.
The HER2 protein, also known as human epidermal growth factor receptor 2, is found on the surface of certain cancer cells, including breast cancer. In normal cells HER2 helps control cell growth. Cancer cells, however, can make too much of the protein, which can cause cells to grow more quickly and be more likely to spread to other parts of the body.
The HER2-derived vaccine, known as GP2, is designed to provoke the body’s immune system to fight cancer by recognizing tumor cells that express HER2. It is administered in addition to standard breast cancer treatment, such as Hercpetin® (trastuzumab), with the goal of preventing recurrence.
To measure how effectively the GP2 vaccine might help prevent recurrence in women with HER2-postive breast cancer, researchers evaluated patients who were disease free after treatment with Hercpetin. A portion of participants (89) was randomly selected to receive the GP2 vaccine plus granulocyte-macrophage colony-stimulating factor (GM-CSF), an immunotherapy to stimulate an immune response, and another 91 patients received GM-CSF alone. Patient characteristics—including age, node status, tumor size, hormone receptor status, and HER2 expression—were similar between treatment groups. Both groups initially received six monthly vaccinations and then four boosters every six months.
At a median follow-up of 34 months, there were no recurrences among patients with the highest expression of HER2 who had received the GP2 vaccine. When the researchers analyzed results using an intend-to-treat method (meaning they included results for all patients who should have received a treatment regimen, even those who for whatever reason did not), they found that the disease-free survival rate was higher among those who received the GP2 vaccine: 88% versus 81% for those who received GM-CSF alone. This translated to a 37% reduction in recurrence. When the researchers excluded outcomes for patients who had a recurrence during their primary vaccination series or developed a second malignancy, the disease-free survival rate for patients who received the GP2 vaccine was 94% compared with 85% in unvaccinated patients; this meant that vaccinated patients had a 57% reduction in risk of recurrence. The GP2 vaccine appeared to be well tolerated, with similar toxicity (harmful effects) as GM-CSF alone (most were low grade and improved after taking acetaminophen).
Based on these findings, the GP2 vaccine appears promising in addition to standard therapy in women with HER2-positive breast cancer, as it might have the potential to safely and effectively prevent recurrences. The researchers also speculate that GP2 works with Herceptin in a specific way to stimulate immune response and that further research into this interaction is warranted.
Reference: Schneble EJ, Perez SA, Murray JL, et al. Primary Analysis of the Prospective, Randomized, Phase II Trial of GP2+GM-CSF Vaccine Versus GM-CSF Alone Administered in the Adjuvant Setting to High-Risk Breast Cancer Patients. 2014 Breast Cancer Symposium; September 4–6, 2014; San Francisco, CA. Abstract 134.
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