What is HER2-positive breast cancer?
When you have been diagnosed with breast cancer, doctors check if you have HER2-positive breast cancer or HER2-negative cancer.
Breast cancer is the most common cancer affecting women in the United States. Based on what type of proteins of breast cells are responsible for breast cancer, breast cancer is divided into two types:
- Human epidermal growth factor receptor 2 (HER2)-positive breast cancer
- HER2-negative cancer or hormone-receptive breast cancer (either estrogen-receptive or progesterone receptive cancer)
The HER2 is a kind of protein found on the surface of breast cells. It is involved in the normal growth of breast cells. The HER2 gene controls the production of the HER2 protein. When there is a defect in this gene, it makes more than the required copies of HER2. Excess of HER2 results in overgrowth of breast cells, giving rise to HER2 positive cancer. More the copies of the HER2 gene, the more aggressive is the HER2-positive breast cancer.
When you have been diagnosed with breast cancer, doctors check if you have HER2-positive breast cancer or HER2-negative cancer. The type of breast cancer diagnosed is based on tests that check for the presence of overexpression of HER2 protein in the breast tissue. If the test is positive, it means you have HER2-positive cancer; if the test results are negative, it means you have HER2-negative cancer. HER2-negative cancer means either you have estrogen-positive cancer or progesterone-positive cancer.
Nearly one in five women with breast cancer have HER2-positive breast cancer.
How is HER2-positive breast cancer diagnosed?
Doctors use a surgical procedure known as breast biopsy to determine the HER2 status of your breast cancer. It involves the removal of the cancerous portion from the breast tissue. The biopsy is sent for laboratory testing to measure either HER2 protein breast cancer cells or extra copies of the HER2 gene, or both. HER2-positive breast cancer means either you have extra HER2 proteins or extra copies of the HER2 gene or both; its absence suggests you have HER2-negative cancer. Further testing can help identify whether it is estrogen-positive or progesterone-positive cancer.
You may even get your biopsy report as triple-negative cancer or triple-positive cancer. Triple-negative breast cancers are negative for HER2, estrogen, and progesterone whereas triple-positive breast cancers are positive for all three.
Is HER2-positive breast cancer good or bad?
HER2-positive cancer tends to be poorer in terms of prognosis than HER2-negative cancer because:
- It grows faster.
- It is more likely to spread to the lymph nodes fast.
- It is at least two times more likely to return than HER2-negative tumors.
The reason behind the entire concept of testing for HER2 status is to decide the kind of treatment. Some drugs have been developed to specifically target HER2-positive breast cancer. This kind of treatment is known as targeted therapy and in this case, it is referred to as HER2-targeted therapy.
HER2-negative breast cancer, particularly estrogen-positive breast cancer benefits from hormonal therapy, but this same hormonal therapy does not work for HER2-positive cancer.
Before the use of HER2-targeted drugs in the treatment of HER2-positive cancer, the chances of survival were not as good as they were for HER2-negative breast cancer. Thanks to these drugs, the prognosis for HER2-positive breast cancer has changed from bad to good.
The HER2-targeted drugs include:
- Herceptin (trastuzumab)
- Perjeta (pertuzumab)
- Nerlynx (neratinib)
A study showed that a combination of Herceptin (trastuzumab) and chemotherapy is more effective than chemotherapy alone. The combined approach works by slowing down the growth of HER2-positive breast cancer. For some, the use of Herceptin with chemotherapy has increased the disease-free years of survival.
Every breast cancer is different. The survival rates can also predict how long you are likely to live with the disease. Remember, it may happen HER2-positive cancer may become HER2-negative after it recurs. Whether it is HER2-positive cancer or HER2-negative cancer, the prognosis also depends on the size of the breast tumor. Based on your tumor size, response to cancer therapy, and preferences, your doctor will plan a treatment tailored to your needs. Make sure you follow all their instructions carefully and follow up with them as scheduled.