Breast cancer is often discussed as a general condition, but there are several different types that require different treatments.
One way to distinguish breast cancer cells is through your genes. When you’re diagnosed with breast cancer, your doctor will test the cancerous cells to determine their genetic makeup.
Read through to learn what it means if the genes in your cancer cells have more HER2 protein than they should.
HER2 is a protein that stimulates the growth of breast cancer cells. It can be found in your blood and urine. Sometimes it’s referred to as a “tumor marker.”
Tumor markers like HER2 can’t be used for cancer diagnosis, but they can provide other important information. For example, the presence of HER2 can help your doctor predict how your breast cancer is likely to respond to treatment.
The Mayo Clinic estimates that about 20 percent of breast cancers are HER2-positive. Younger women are more likely to be HER2-positive than older women.
HER2-positive breast cancer tends to be more aggressive and to spread more quickly than other cancers. That’s why it’s important to find out if the cancer cells in your body contain this protein.
Your doctor will order a lab test to determine if your cancer is HER2-positive. The American Cancer Society (ACS) advises that all patients diagnosed with breast cancer should get tested for HER2.
If your breast cancer is HER2-positive, you have a much better chance of successful treatment with methods that target the HER2 protein specifically.
Routine testing for HER2 is important upon initial diagnosis and in recurring cases of breast cancer. The Mayo Clinic reports that cancer cells can develop HER2 in up to 30 percent of people, even if the protein wasn’t present originally.
Researchers at the University of Texas M.D. Anderson Cancer Center (MDACC) conducted a study to determine recurrence risk for HER2-positive patients. Results showed that those who tested positive for HER2 at an early stage of the condition — with tumors 1 centimeter (cm) or smaller — had a higher risk of recurrence.
The MDACC study found that those who were HER2-negative had a five-year survival rate of 93.7 percent.
Researchers also found that HER2-positive patients had:
- a 77.1 percent five-year survival rate, with no recurrence
- around five times the recurrence risk of those who were HER-2 negative
- close to three times the risk of recurrence of those who tested negative for HER2
The risk of recurrence with HER2-positive tumors is significantly higher than with HER2-negative tumors.
Tumors that are HER2-positive are more often associated with factors that increase recurrence rates. For example, HER2 tumors are more likely to occur in younger women and have higher nuclear grade. Generally, the higher the nuclear grade, the more aggressive the tumor.
HER2 tumors are also more likely to show positive margins during breast surgery. Positive margins occur when cancer cells extend beyond the edge of tissue that’s removed. HER2 tumors also have a higher likelihood of residual disease being found when additional tissue is removed.
According to The New England Journal of Medicine (NEJM), up to 70 percent of patients with HER2-positive breast cancer respond to treatment. However, total remission for the condition occurs in around 7 to 8 percent of patients.
Targeted treatments (medicines that target the HER2 protein) have improved the prognosis for HER2-positive patients. Remissions can also be lengthy, offering another bright spot in prognosis. NEJM reports that remission can last more than 15 years for some patients.
Being diagnosed HER2-positive brings special challenges to breast cancer patients. The HER2 protein can make your breast cancer more aggressive. It can also make it harder to treat with hormone treatments used for other types of breast cancer.
However, drugs like trastuzumab and lapatinib target HER2 directly — and effectively. A new drug, pertuzumab (Perjeta), was approved by the FDA in 2014. This drug, when used in combination with other drugs, shows some very promising results for improving prognosis and survival rates for patients with HER2 cancer.