A majority of women with early breast cancer experienced a sustained immune response after immunization with a vaccine that fights human epidermal growth factor receptor 2 (HER2), and this response may reduce their risk of developing more invasive cancer later.

In the small study, published in Journal of Immunotherapy (2012;35[1]:54-65), 27 women with HER2 positive ductal carcinoma in situ (DCIS) received four weekly shots of a personalized anti-HER2 vaccine. The vaccine was made partly from the patient’s own dendritic cells, which are key regulators of the immune system, and were primed with small pieces of HER2/neu, a protein critical for the survival of early breast cancers. Two weeks after the vaccination regimen ended, patients had surgery to remove any remaining disease, as is standard in DCIS.

When prevaccination biopsy samples were compared with postvaccination surgical samples, five patients had no disease visible at the time of surgery, indicating that their immune system had eradicated the tumor. HER2 expression was eliminated in 11 other patients and reduced by 20% or more in another two women.

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Most of the women (85%) had HER2-reactive CD4 and CD8 T cells, suggesting that they had developed a robust and relatively complete immune response following vaccination. Perhaps most important, some patients maintained this response for as long as 52 months, giving them some protection from recurrence of HER2-positive disease.

Only low-grade side effects were reported with vaccine use, the most common being malaise in 72% of the recipients, injection-site soreness in 59%, chills or rigor in 38%, fever in 28%, and headaches in 24%.