Why Test Tumor Markers?
- Testing the estrogen receptor (ER), progesterone receptor (PR), and the human epidermal growth factor receptor (HER2) after a breast cancer diagnosis or recurrence is essential.
- This is commonly referred to as “marker,” “tumor marker,” or “biomarker” testing by physicians.
- This testing can determine the subtype of your tumor, which can help guide treatment.
- It can also determine what other tests may be beneficial for you.
- Germline or genetic testing can also be helpful for many patients at all stages of breast cancer.
Why Tumor Markers Matter
Different types of breast cancer react differently to various treatments. Hormone receptor-positive breast cancer can be treated with hormone therapy, while breast cancers that do not have hormone receptors will require other kinds of treatments, such as chemotherapy. Once diagnosed, your doctor will likely test your cancer for these important hormone receptors and proteins:
- Estrogen Receptor (ER)
- Progesterone Receptor (PR)
- Human Epidermal Growth Factor Receptor 2 (HER2)
- Estrogen Receptor-Positive. This means your breast cancer cells have estrogen receptors. It may also be called ER+ breast cancer.
- Progesterone Receptor-Positive. This means your breast cancer contains progesterone receptors. It may also be called PR+ breast cancer.
- Human Epidermal Growth Factor Receptor 2-Positive: This means your breast cancer is positive for the HER2 gene mutation. It is commonly referred to as HER2+ breast cancer.
- Human Epidermal Growth Factor Receptor 2-Negative: This means your breast does not have the HER2 gene mutation. It is commonly referred to as HER2- breast cancer.
How Will My Doctor Use My Test Results?Knowledge is power; the more information your doctors have, the better they can plan your breast cancer treatment. Since breast tumor marker tests can measure the type of breast cancer cells in your body, they can help your doctor in several ways:
- Determine which treatment will work best for your type of cancer.
- See whether your treatment is working – and perhaps lead your doctor to try a different treatment.
- Measure the progression or recurrence of your breast cancer.
- Help to predict how likely your cancer will come back after treatment.
How is the Test Conducted?A test called immunohistochemistry (IHC) is used to determine whether your breast cancer cells have HER2 receptors and/or hormone receptors on their surface. It is conducted with a special staining process using a breast cancer biopsy sample.
The test will show whether you are:
- Hormone receptor-positive (HR+), which means that you have either estrogen (ER) or progesterone (PR) receptors. You may also have both. If this is your type of cancer, you can be treated with hormone therapy drugs that either lower levels of estrogen or block your estrogen receptors. This type of breast cancer will tend to grow more slowly than if you tested receptor-negative. Although receptor-positive breast cancers may return many years after treatment is completed, the outlook is optimistic in the short term.
- Hormone receptor-negative (HR-) means that your cancer cells don’t have estrogen or progesterone receptors. In this case, hormone therapy drugs would not be effective. This type of breast cancer tends to grow more quickly and is more common in women who have not yet gone through menopause. If the cancer returns, it’s more often in the first few years after treatment is completed.
- Triple-positive means that your cancer cells are ER-positive, PR-positive, and HER2-positive, and your breast cancer can be treated with hormone drugs. In addition, drugs that specifically target HER2 can also be used.
- Triple-negative means that your breast cancer cells have neither estrogen nor progesterone cells, nor do they make too much of the protein called HER2.
Triple-Negative Breast Cancer
Triple-negative breast cancer grows and spreads faster than other types. Since these types of breast cancer cells don’t have hormone receptors, hormone therapy treatments will not work, nor will drugs aimed at HER2 receptors. However, chemotherapy can still be helpful. These cancers are more common in African-American women younger than forty years old.
“Another particular marker we look at specifically in metastatic triple-negative breast cancer is the PD-L1 marker. The PDL-1 marker helps us determine whether your tumor will respond to immunotherapy,” Dr. Abdou explains. “This marker is specifically checked in patients who have metastatic triple-negative breast cancer to determine what type of therapy you’ll be eligible for.”
How Results Determine the Next Steps in Treatment
When your doctor knows whether or not your breast cancer carries hormone receptors, this knowledge will inform the decision about treating your cancer with hormone therapy drugs or not.
“In hormone-positive breast cancer, we sometimes order something called genomic assay. Examples of these include Oncotype DX, Prosigna. These tests look at level of activity in groups of genes in cancer cells to determine how likely the cancer is going to recur and how likely it is to respond to chemotherapy. So, this test really helps us tailor treatments according to that genomic assay,” Dr. Abdou explains.
Germline or genetic testing looks for inherited mutations that are present in every cell of the body since birth. Germline testing can be done with a cheek swab, spit sample, or drawing blood.
“It determines whether you have inherited genes that could increase your risk of developing another breast cancer down the line or other types of breast cancer,” Dr. Abdou says. “Examples of such genes include BRCA one and BRCA two mutations. You could have received these inherited mutations from your parents and could pass them on to your children. So, it’s important to identify these genes. We also have targeted therapies for these particular defects that you might be eligible for in your treatment course.”
Questions to Ask Your Doctor
It’s key to have good communication with your healthcare provider. If your doctor suggests hormone receptor testing for your breast cancer, you may want to ask:
- What will I be tested for, and how often?
- What do you hope to learn from the testing? How will you use it?
- What are the costs of the test, and is it covered by my private insurance, Medicare or Medicaid?
- What is the percentage of false positives or false negatives?
As a patient recently diagnosed with breast cancer, you may feel overwhelmed with an exhausting list of procedures and tests. But try not to feel pressured into agreeing to the road ahead until your medical provider explains each step’s purpose.