Breast Cancer Biomarker Testing

Virginia Oncology Associates uses the latest advances in treatment to create personalized breast cancer treatment plans. One way we do this is by using biomarker tests to understand the molecular makeup of each patient’s breast cancer.

Biomarkers are measurable factors, such as gene mutations, hormones, proteins, or other substances that promote cancer cell growth. The test results provide insight into how each patient’s cancer behaves and how it is likely to respond to treatment. Testing may be performed on tumor tissue or a blood sample and is often referred to as genomic testing or molecular testing.

How Biomarkers Help Guide Breast Cancer Treatment Decisions

For many years, oncologists have understood that hormone-positive breast cancer responds well to hormone therapies that block the hormone receptors on breast cancer cells. Now we’re also able to test for other markers related to breast cancer growth. Biomarker tests today can detect several types of genetic changes. 

Biomarkers generally fall into two categories: prognostic or predictive. 

• Prognostic biomarkers provide information about the likely course of the disease, regardless of treatment. 

• Predictive biomarkers help determine which therapies are most likely to work for a specific patient.

Prognostic biomarker test results can help guide follow-up care, determine clinical trial eligibility, and estimate the risk of recurrence, particularly for patients with early-stage breast cancer.

Predictive results help oncologists select targeted therapies or hormone therapies that match the cancer’s genetic makeup, which can help reduce unnecessary treatments and side effects. 

Learn more about the various breast cancer types. 

Biomarker Tests Used in Breast Cancer Care

Ongoing research continues to uncover new genetic changes that influence breast cancer behavior and treatment response. These discoveries have led to new treatments designed to target those changes directly. Several types of biomarker tests are routinely used to guide breast cancer care.  

Hormone Receptor (HR) Testing

Hormone receptor testing determines whether cancer cells depend on estrogen, progesterone, or both. Tumors that are hormone receptor-positive (HR-positive) often respond well to therapies that block hormones from fueling cancer growth.

HER2 Status Testing

HER2 testing measures whether cancer cells produce excessive amounts of the human epidermal growth factor receptor 2 protein, which can lead to rapid cancer cell growth. HER2-positive breast cancers tend to grow faster compared to HER2-negative breast cancers.

Testing typically includes: 

• Immunohistochemistry (IHC) to measure HER2 protein levels on the tumor’s surface

• Fluorescence in situ hybridization (FISH) to detect extra copies of the HER2 gene in the cancer cells

If the tumor is HER2-positive, targeted therapies such as trastuzumab or pertuzumab may be included in the treatment plan to reduce HER2 protein production.

Learn more about hormone-positive breast cancer and HER2-positive breast cancer.

Biomarker Testing in Early-Stage Breast Cancer 

For certain early-stage breast cancers, particularly those that are estrogen receptor-positive and HER2-negative, specialized tests assess the likelihood of recurrence. Common examples include multi-gene tests such as Oncotype DX and the Mammaprint test (also called assays). Your oncologist will review these results with you and take action to monitor you carefully for breast cancer recurrence after treatment is complete.

Biomarker Testing for Advanced or Metastatic Breast Cancer 

While HER2 and hormone receptor testing are standard for nearly all breast cancer patients, additional biomarker testing is often recommended for stage IV or recurrent breast cancer. These tests help identify suitable targeted therapies or clinical trial options.

PD-L1 Testing

PD-L1 biomarker testing assesses whether cancer cells overexpress a protein that enables them to hide from the immune system. Patients with PD-L1-positive metastatic, triple-negative breast cancer are likely to respond to immunotherapy designed to enable the immune system to recognize and attack cancer cells more effectively.

ESR1 Testing

Changes in the Estrogen Receptor 1 gene can affect how breast cancers respond to certain hormone therapy drugs, particularly aromatase inhibitors. However, identifying this mutation helps oncologists select hormone therapy drugs that may be more effective for these patients.

Microsatellite Instability High (MSI-H)

Microsatellites are short, repeated sequences of DNA. During the DNA copying process, any mistakes that occur are usually corrected by our cells through a process known as mismatch repair. However, when this mismatch repair system fails, it can lead to microsatellite instability (MSI).

In breast cancer, cells with high levels of microsatellite instability (MSI-H) are less effective at correcting DNA mutations, which can lead to the development of more cancer cells. In these cases, immunotherapy may help the patient's immune system more effectively attack and destroy the cancer cells.

Additional Gene Testing Determines the Right Combination of Drug Therapies

For advanced or metastatic breast cancer, broader testing may evaluate multiple genes to determine the most effective combination of therapies. Common biomarkers that may be tested include:

• PIK3CA gene: This gene plays a central role in normal cell function.

• AKT1 gene: Mutations may drive uncontrolled cell growth and division.

• NTRK fusion: This can lead to the production of abnormal proteins that promote cancer cell growth.  

• PTEN gene: Changes can result in the inability to regulate cell growth.

Understanding these molecular features helps your oncologist choose the most appropriate therapy combinations for your cancer. 

Advancing Breast Cancer Care Using Biomarker Testing in Hampton Roads & Eastern North Carolina

At Virginia Oncology Associates, biomarker testing is an essential part of comprehensive breast cancer care. Understanding the genetic makeup of your breast cancer allows our breast cancer specialists to develop a treatment strategy tailored to meet your specific needs. The VOA breast cancer specialists are located in Chesapeake, Hampton, Newport News, Norfolk, Suffolk (Harbour View and Obici), Virginia Beach, Williamsburg, Virginia, and Elizabeth City, North Carolina.