How biomarker testing works

How is biomarker testing done?

Biomarker testing happens in a few key steps. Below is a high-level overview of the process, followed by a closer look at each step and what it could mean for your care. Understanding what to expect at each stage can help you feel more informed and can clarify what to expect from the experience.

Step 1. Sample collection
Doctors collect a sample of cancer cells through one of two types of biopsies: a tissue biopsy, which involves removing a small piece of tissue from the body, usually from a tumor or another area where cancer is present, or a liquid biopsy, which includes things like a blood draw or urine sample. These samples contain cells that can reveal important clues about the cancer.

Step 2. Laboratory Analysis
Specialized labs analyze the sample using techniques like pathology and molecular testing. Scientists look for biomarkers, which help determine how the cancer behaves and which treatments may work best.

Step 3. Reporting Results
It may take a week or longer to get the results, depending on which tests are being done and whether the samples need to be sent to another lab. While some cancer centers perform testing in-house, others may need to send samples to centralized laboratories for analysis.

Once testing is complete, results are shared with your care team. These findings help guide treatment decisions, such as whether targeted therapy or immunotherapy is appropriate. Your doctor will discuss the results with you to help you understand how your results can impact your treatment plan.

What’s the difference between biomarker testing and genetic testing

Although biomarker testing and genetic testing are often mentioned together, they serve different purposes and may be referred to by different names:

Biomarker testing

• Somatic testing
• Tumor genetic testing
• Tumor subtyping
• Genomic testing

Genetic testing

• DNA testing
• Inherited genetic testing
• Genomic testing
• Germline testing

Biomarker testing focuses on the cancer itself. It examines changes in tumor cells, such as gene mutations, protein levels, or other molecular markers, that influence how the cancer behaves and which treatments may work best. Biomarker testing is typically done after a cancer diagnosis to guide therapy decisions.

Genetic testing looks for abnormal DNA passed down from family members. These tests identify whether you carry mutations that increase your risk of developing certain cancers (for example, BRCA1 or BRCA2 mutations). Genetic testing is often used to assess cancer risk and prevention, but not for choosing treatments for an existing cancer.

In other words, biomarker testing informs current treatment choices, while genetic testing helps predict future cancer risk and may guide screening or preventive measures. Ask your doctor whether biomarker testing could be helpful for you and consider using the following discussion guide to plan for your discussion.

What do biomarker tests look for?

Biomarker tests examine cancer cells for certain signals that help show how the disease is behaving. This information can provide insight into how quickly the tumor is growing, how it might respond to treatment, and whether precision‑medicine could be a good option. Depending on the type of cancer, testing may focus on:

• Gene mutations: Changes in the sequence of DNA cancer cells can drive tumor growth.
• Protein levels: Abnormal amounts of specific proteins can indicate how aggressive a cancer is or whether certain treatments, like targeted therapies, can help.
• DNA damage: Breaks or errors in DNA strands can lead to uncontrolled cell growth. Detecting DNA damage helps identify cancers that may respond to drugs targeting repair mechanisms.
• Gene fusions: When two separate genes join together, they create a fusion gene that can promote cancer development. These fusions often guide the use of targeted therapies.
• Immunotherapy markers: Indicators such as PD-L1 show whether a cancer might respond to immunotherapy, which helps the immune system attack cancer cells.
• Hormone receptors: Proteins on cancer cells can bind to hormones like estrogen or progesterone. Their presence often determines whether hormone treatments may be effective.