Biomarker Testing for Breast Cancer
Cancer Care Centers of Brevard uses advanced technologies that allow patients to receive personalized treatment for breast cancer. This includes biomarker testing, which can be used to identify genetic changes that cause various types of cancer to grow, including breast cancer.
A biomarker is a measurable factor, such as a gene mutation, protein, or other substance, that tells oncologists more about how cancer is growing and, ultimately, how it can be treated most effectively. These biomarkers can be tested using tissue or blood samples. Biomarker testing is also known as genomic testing or molecular testing.
Why Biomarker Testing is Important
Biomarkers are classified as prognostic or predictive. Prognostic biomarkers indicate the patient’s most likely overall outcome, regardless of treatment. Predictive biomarkers help determine which therapy a patient will most likely respond to.
Targeted therapies and hormone therapies are then selected based on the predictive biomarker test results. By understanding what the patient will respond to best, unnecessary treatments and their side effects can be avoided.
Prognostic biomarker test results are more likely to be used to determine clinical trial eligibility, direct follow-up appointment frequency, and determine which tests should be used after cancer treatment to look for recurrence. For breast cancer patients, prognostic biomarker testing will give the oncologist a sense of whether recurrence is likely after treating early-stage breast cancer.
Learn more about the various breast cancer types.
Biomarker Tests Used for Breast Cancer
Understanding the human genome led to the discovery of genetic changes related to breast cancer. Advancements in clinical research brought us new treatments that specifically address these mutations, slowing cancer growth. Several types of biomarker tests are currently used to guide breast cancer treatment, including:
Hormone Receptor (HR) Testing
Hormone receptor testing determines whether cancer cells have receptors for estrogen, progesterone, or both. Tumors that are hormone receptor-positive (HR-positive) are likely to respond to therapies that block these hormones from attaching to the cancer cells and promoting their growth.
HER2 Testing
The HER2 biomarker (human epidermal growth factor receptor 2) indicates the overgrowth of the HER2 protein, which promotes the growth of cancer cells. HER2-positive breast cancers tend to grow faster than when the patient is HER2-negative.
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 detects extra copies of the HER2 gene in the cancer cells. If HER2-positive, targeted therapies such as trastuzumab or pertuzumab may be included in the treatment plan.
Learn about hormone receptor status in breast cancer.
Biomarker Testing for Early-Stage Breast Cancer
Several tests exist, such as Oncotype DX and the Mammaprint test (also called assays), which focus on assessing the likelihood of recurrence in early-stage or estrogen-positive, HER2-negative breast cancer.
Advanced or Metastatic Breast Cancer Biomarker Testing
While HER2 and hormone receptor tests are performed for nearly all breast cancer patients, additional biomarker testing is more common in patients with stage IV breast cancer to identify suitable targeted therapies or clinical trials.
PD-L1 Testing
The PD-L1 biomarker test looks for an overproducing protein that allows cancer cells to hide from the immune system. For patients with metastatic, triple-negative breast cancer who are PD-L1 positive, the cancer is likely to respond to immunotherapy that targets PD-L1. This enables the immune system to recognize and attack cancer cells more effectively.
ESR1 Testing
Patients who tested positive for the Estrogen Receptor 1 Mutation may become less responsive to certain hormone therapy drugs, particularly aromatase inhibitors. However, other hormone therapy drugs may be more effective for patients with this mutation.
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, the number of microsatellites can become unstable.
Breast cancer cells with a high level of microsatellite instability (MSI-H) are less effective at correcting DNA mistakes, which can lead to the development of more cancer cells. Patients with MSI-H breast cancer may benefit from immunotherapy, a treatment that enhances the body's ability to attack and destroy cancer cells.
Additional Gene Testing Determines the Right Combination of Drug Therapies
In advanced or metastatic breast cancer, many other genes are tested during biomarker analysis. The results guide oncologists in determining the most effective set of therapies. Some additional biomarkers that may be tested include:
PIK3CA gene: This gene is critical for normal cell function.
AKT1 gene: Mutations in this gene can lead to uncontrolled cell growth and division.
NTRK fusion: This occurs when the NTRK gene fuses with another gene on a different chromosome, resulting in abnormal protein production and cancer cell growth.
PTEN gene: Changes in this gene can block an enzyme that stops cells from dividing and growing uncontrollably.
Your breast cancer specialist can explain more about these biomarkers and their meaning so you can make informed decisions about your treatment options.
Advancing Breast Cancer Care Using Biomarker Testing in Brevard County, Florida
Cancer Care Centers of Brevard understands the importance of biomarker testing in providing personalized breast cancer treatment. By gaining a deeper understanding of breast cancer's unique characteristics, your treatment plan can be tailored to meet your specific needs.
If you or a loved one was diagnosed with breast cancer or recurrent breast cancer, our oncologists in Melbourne, Merritt Island, Palm Bay, and Rockledge, Florida, are available to discuss the best treatment plan for you.