Just as there are different types of breast cancer based upon where the cancer begins, there are different types based on receptors that help control the growth and repair of breast cells. One of those is HER2.
HER2, shorthand for human epidermal growth factor receptor 2, is a gene found on the surface of healthy cells. When it mutates, the body makes too many HER2 proteins, which can lead to breast cancer. In some pathology reports, HER2 is referred to as HER2/neu or ERBB2 (Erb-B2 receptor tyrosine kinase 2).
For years, scientists have tried to answer the question: why do some cancers grow quickly and spread rapidly while others do not? While seeking an answer, in the 1980s researchers discovered that breast cancer cells containing abnormally high levels of HER2 are more likely to spread to other organs in the body.
Compared to other breast cancer types, HER2 grows rapidly, is biologically more aggressive and is more likely to metastasize. But we now have drugs designed to target the HER2 protein. The introduction of Herceptin® (trastuzumab) was a watershed moment. I believe the most monumental advancement in the treatment of breast cancer within the past 20 years is the identification of HER2 and development of HER2-targeted treatment.
In 1998, the FDA approved trastuzumab, an antibody that binds to HER2 to kill breast cancer cells. Today, treatments for HER2 positive breast cancer include:
- Ado-trastuzumab emtansine (Kadcyla)
- Lapatinib (Tykerb)
- Neratinib (Nerlynx)
- Pertuzumab (Perjeta)
- Trastuzumab (Herceptin)
Research published in the New England Journal of Medicine in July reported that “pertuzumab significantly improved the rates of invasive-disease–free survival among patients with HER2-positive, operable breast cancer when it was added to trastuzumab and chemotherapy.”
About 1-in-5 women are diagnosed with HER2 positive breast cancer. Research suggests that younger women were more likely to have HER2-positive cancer.
About half of HER2-positive cancers also have hormone receptors for estrogen and/or progresterone.