What are cancer biomarkers, and how do they guide treatment?

Cancer care is no longer one-size-fits-all. Today, doctors can tailor treatment based on the specific characteristics of each patient’s tumor, and cancer biomarker testing plays a key role in making that possible.

Biomarkers help doctors understand what is driving a cancer and how it may respond to treatment. This approach is a key part of precision medicine and continues to evolve.

“Biomarker testing is now a fundamental part of how we care for many patients with cancer,” says Funda Meric-Bernstam, M.D., chair of Investigational Cancer Therapeutics. “It helps us understand each tumor at a deeper level and continue refining treatment as new discoveries emerge.”

At UT MD Anderson, we do biomarker testing for many patients as a part of their care. Our doctors use molecular profiling to help match patients with therapies and clinical trials based on a tumor’s specific characteristics.

For patients, this means treatment decisions are increasingly based on the unique features of their cancer, not just the cancer type.

What are cancer biomarkers?

Cancer biomarkers are biological molecules found in your body or tumor. Biomarker testing provides detailed information about a cancer, including what may be driving its growth. Biomarkers can include changes in DNA, RNA patterns, protein levels or immune system markers related to how the body responds to the tumor.

Together, these biomarkers help identify the specific characteristics of a patient’s cancer and what is fueling its behavior.

Biomarkers can be grouped into several categories based on how they are used in care and research. These categories are:

• Susceptibility or risk biomarkers help identify the likelihood of developing cancer. Some biomarkers can also detect higher risk of side effects from certain drugs.
• Diagnostic biomarkers help detect or confirm cancer.
• Monitoring biomarkers can help detect early recurrence and track how a disease changes over time or responds to treatment.
• Prognostic biomarkers provide information about how cancer may behave, such as the risk of recurrence.
• Predictive biomarkers help determine which treatments are most likely to work.
• Pharmacodynamic or response biomarkers show that treatment is having an effect on the body.
• Safety biomarkers help identify or monitor side effects from treatment.

How biomarker testing is used in cancer treatment

Biomarker testing is now widely used in cancer care. It plays an important role in several areas.

Selecting targeted therapies

Biomarker testing can identify specific genetic changes in a tumor that doctors can target with certain drugs. These targeted therapies are often more precise and may be more effective for certain patients.

Guiding immunotherapy decisions

Some biomarkers can help predict whether a patient is more likely to benefit from immunotherapy. While not all patients respond in the same way, these markers help inform treatment planning.

Helping create personalized treatment plans

Biomarker results help doctors select treatments that are most appropriate for each patient’s cancer, reducing a trial-and-error approach.

Matching patients to clinical trials

In some cases, biomarker testing may help identify clinical trials that match the molecular features of a patient’s tumor, providing access to new and emerging therapies.

What are liquid biopsies and MRD testing?

Some advances involve blood-based tools, including liquid biopsies. These blood tests can detect fragments of tumor DNA circulating in the bloodstream, known as circulating tumor DNA (ctDNA).

Liquid biopsy may be used to:

• Identify genomic changes in a tumor without a tissue biopsy
• Monitor how cancer is responding to treatment
• Detect new genetic changes as cancer evolves

Another key tool is measurable residual disease (MRD) testing. MRD testing looks for very small amounts of cancer that may remain after treatment, even when imaging or exams show no visible disease. This information may help guide decisions about whether additional treatment or closer monitoring is needed.

Some of the most common cancer biomarkers

Some biomarkers are used more often because they play a key role in guiding treatment across multiple cancer types. These are some of the most commonly tested biomarkers in cancer care:

Tumor-based biomarkers

HER2

Most commonly tested in breast and stomach cancers but may have high levels in multiple tumor types. Helps determine whether targeted therapies or antibody-drug conjugates (antibodies carrying chemotherapy) may be effective.

Hormone receptors (estrogen and progesterone)

Often tested in breast cancer. Helps determine whether hormone therapy is an option.

Genetic mutations

EGFR

Found in some lung cancers. Helps guide targeted treatment options.

KRAS

Commonly tested in colorectal and pancreatic cancers. Helps guide treatment decisions. KRAS mutations may make certain drugs ineffective. KRAS inhibitors are approved for certain diseases and in clinical trials for many others.

BRCA1 and BRCA2

Germline (hereditary) and somatic (in the tumor only) gene changes linked to several cancers. May influence treatment options.

BRAF

More commonly seen in cancers like melanoma and colorectal cancer but detected in many tumor types. Some mutations can be treated with targeted therapies regardless of where the cancer started.

ALK fusions

Found in a small number of lung cancers. Can be treated with specific targeted drugs.

NTRK gene fusions

Rare but important across cancer types. Can be treated with targeted therapies designed to work regardless of where the cancer started.

RET gene mutations and fusions

Found more commonly in thyroid and lung cancer. RET fusions on other tumor types are rare but important. Can be treated with targeted therapies designed to work regardless of where the cancer started.

Immunotherapy-related biomarkers

PD-L1

Used in several cancers, including lung cancer. Helps determine whether immune checkpoint inhibitor therapies may be effective in some tumor types.

MSI or MMR deficiency

Identified in several cancer types. Helps determine whether immunotherapy may be effective.

Tumor mutational burden (TMB)

Identified in several cancer types. High levels of tumor mutational burden suggest the tumor may be detected more by the immune system. Helps determine whether immunotherapy may be effective.

Artificial intelligence (AI) and the future of biomarker discovery

Researchers are using AI to better understand cancer and discover new biomarkers. These advances are helping researchers analyze large amounts of data from tumors.

These tools can:

• Identify patterns in tumor biology that may not be visible using traditional methods
• Integrate multiple types of data, including DNA, RNA, proteins and immune signals
• Help uncover new biomarkers and potential treatment targets

As these technologies continue to develop, they may further improve how cancers are classified and treated in a more personalized way.

Why biomarker testing matters for patients

Biomarker testing is helping to make cancer care more precise and individualized. For many patients, biomarker testing can provide clearer answers during an uncertain time., including

• More targeted treatment options
• A reduced likelihood of receiving therapies that may not be effective
• Greater opportunity to participate in clinical trials
• A deeper understanding of how their cancer may behave over time

If you’ve been diagnosed with cancer, ask your care team:

• Should I have biomarker testing?
• What biomarkers are relevant for my cancer?
• How could the results affect my treatment options?

The future of cancer biomarkers

“As our ability to analyze tumors becomes more refined, biomarker testing is increasingly helping us match the right treatment to the right patient at the right time, while also allowing us to better understand how cancers evolve,” Meric-Bernstam says.

At UT MD Anderson, biomarker testing is integrated into patient care while research continues to expand how these tools are used. As advances continue, this approach is helping make cancer care more precise, more personalized and better informed.

Request an appointment at UT MD Anderson online or call 1-877-632-6789.