Breast Cancer Biomarker Testing

At Rocky Mountain Cancer Centers, we are committed to providing individualized breast cancer treatment using cutting-edge technologies. One of the most advanced techniques for creating a personalized treatment plan is biomarker testing.

Biomarkers are genetic mutations, proteins, or other substances known to cause breast cancer cell growth. They’re found through testing a tissue or blood sample. Biomarker testing might also be referred to as genomic testing or molecular testing. 

Why Is Biomarker Testing Important?

The goal of biomarker testing is to give your breast cancer doctor a clearer picture of what is causing the cancer to grow and, ultimately, which treatments will counteract these genetic changes. 

Biomarker testing makes it possible to:

1. Personalize your treatment plan: By understanding the specific biology of your cancer, your care team can tailor treatments to more effectively target the tumor.
2. Identify targeted therapies most likely to work: Biomarker testing reveals which treatments the cancer will likely respond to best. This is used most often for metastatic breast cancer. 
3. Avoid unnecessary treatments: Biomarker testing helps avoid treatments that are unlikely to be effective for your specific type of cancer.
4. Estimate the likelihood of cancer recurrence after early-stage breast cancer treatment is complete. 

Types of Biomarker Tests for Breast Cancer

Thanks to clinical research, new genetic changes related to breast cancer are being discovered, as well as new treatments for these mutations. Here are several types of biomarker tests currently used to guide breast cancer treatment:

HER2 Testing

The HER2 biomarker (human epidermal growth factor receptor 2) is a protein that promotes the growth of cancer cells. Tumors that are HER2-positive produce higher levels of this protein, making them grow faster.

• Why It’s Important: HER2 testing helps identify whether targeted therapies, such as trastuzumab or pertuzumab, will be helpful in the treatment plan.
• How It’s Done: HER2 testing is typically performed on a tissue sample using an immunohistochemistry (IHC) test to measure HER2 protein levels on the tumor’s surface or in situ hybridization (ISH), which looks for extra copies of the HER2 gene in the cancer cells.

Learn more about hormone receptors and HER2 overexpression. 

Hormone Receptor (HR) Testing

Hormone receptor testing determines if the cancer cells have receptors for estrogen or progesterone.

• Why It’s Important: Tumors with hormone receptors (HR-positive) are likely to respond to hormone therapies that block estrogen or progesterone from attaching to the cancer cells and helping them grow.

Related read: What Is Molecular Subtyping Of Breast Cancer And Why Is It Important?

Early-Stage Breast Cancer Biomarker Testing

Several tests exist, such as Oncotype DX and the Mammaprint test, also called assays, that focus on the likelihood of early-stage or estrogen-positive, HER2-negative breast cancer recurring. 

Advanced or Metastatic Breast Cancer Biomarker Testing

While HER2 and hormone receptor tests are performed for nearly all breast cancer patients, only those who have stage IV breast cancer are likely to have additional biomarker testing done to identify targeted therapies or clinical trials that you may be suited for.

PD-L1 Testing

The PD-L1 biomarker looks for an overexpression of a protein that allows cancer cells to evade detection by the immune system. For patients who have metastatic, triple-negative breast cancer and are PD-L1  positive, the cancer is likely to respond to an immunotherapy that blocks PD-L1. This makes it possible for your immune system to identify and attack cancer cells.

Learn more about immunotherapy for breast cancer.

ESR1 Testing

If you are positive for the estrogen-receptor 1 mutation, the cancer is no longer as responsive to some hormone therapy drugs, especially aromatase inhibitors. There are other hormone therapy drugs known to work better in patients with this mutation. 

Microsatellite Instability High (MSI-H)

Patients are tested to see if the breast cancer cells have many mutations in short, repeated DNA sequences (called microsatellites). MSI-H breast cancer cells are less likely to correct DNA mistakes, which leads to the development of more cancer cells. MSI-H patients may be treated with immunotherapy, making it easier for the body to attack and destroy cancer cells. 

Additional Gene Testing Determines the Right Combination of Drug Therapies

Many other genes are tested during biomarker testing of advanced or metastatic breast cancer cells. The results help the oncologist determine the correct set of therapies. Some of the additional biomarkers tested include:

• AKT1 gene - When this gene mutates in breast cells, the cells can grow and divide without control. 
• PIK3CA gene - This gene is critical for cell function.
• PTEN gene - A change in this gene blocks an enzyme that prevents cells from dividing and growing out of control. 
• NTRK fusion - The NTRK gene fuses with a gene on another chromosome, causing abnormal protein production that leads to cancer cell growth.  

Advancing Breast Cancer Care in Colorado Using Biomarker Testing

The treatment planning process at Rocky Mountain Breast Specialists includes biomarker testing as a critical step in providing precise, personalized care. By understanding the unique characteristics of your breast cancer, we can tailor your treatment plan to meet your specific needs while minimizing side effects as much as possible.

Our team is here to guide you through every step of the way. If you were diagnosed with breast cancer or your cancer has recurred, request a consultation with one of our specialists located throughout Colorado, including Denver, Colorado Springs, and the Boulder area.