Precision Oncology: What Biomarker Testing Can Change

Precision oncology uses biomarker testing to look for specific changes in a tumor or in the body that may help guide cancer care. These results can support diagnosis, estimate likely treatment response, and help doctors choose more personalized options.

Overview

Precision oncology is an approach to cancer care that uses detailed information about a person’s tumor to help guide decisions. Instead of choosing treatment based only on where the cancer started, doctors may also study the tumor’s genes, proteins, and other molecular features. This process is often called biomarker testing, molecular profiling, or genomic testing.

A biomarker is a measurable characteristic that gives information about a cancer. Some biomarkers show how a tumor is likely to behave, while others suggest whether a certain treatment may work better than another. In practice, this can help doctors decide whether chemotherapy, targeted treatment, immunotherapy, hormone treatment, surgery, or radiation is most appropriate.

Precision oncology does not mean every treatment is unique for every person, and it does not replace standard cancer care. Rather, it adds another layer of information that may make treatment more precise. For some patients, biomarker testing identifies a clearly matched therapy. For others, it helps rule out treatments less likely to help, which can also be valuable.

What biomarker testing looks for

Biomarker testing can examine several types of tumor features. One common focus is DNA changes, such as mutations, fusions, amplifications, or deletions in cancer-related genes. Some of these changes drive tumor growth and may be targets for specific medicines.

Testing may also look at proteins found on tumor cells or immune cells. Examples include receptors or immune markers that help predict whether a cancer may respond to a certain drug. In other cases, doctors assess broader patterns such as microsatellite instability, mismatch repair deficiency, or tumor mutational burden, which can be important in treatment planning.

Biomarkers are not all used in the same way. Some are diagnostic, helping confirm the type of cancer. Some are prognostic, giving information about how the disease may behave. Others are predictive, meaning they can suggest whether a person is more or less likely to benefit from a particular treatment. A single test report may contain more than one type of information.

Biomarker testing can be especially important in cancers where targeted therapies are established, such as certain lung, breast, colorectal, melanoma, and blood cancers. It can also help doctors distinguish between related conditions, including some cases of lung cancer or breast cancer, where treatment options may depend strongly on tumor biology.

How testing is done

Doctors may perform biomarker testing on a sample of tumor tissue collected during a biopsy or surgery. A pathologist examines the tissue under a microscope and may request additional laboratory techniques, such as immunohistochemistry, fluorescence in situ hybridization, polymerase chain reaction, or next-generation sequencing. Each method is designed to answer different questions.

In some situations, testing can also be done with a blood sample, often called a liquid biopsy. This looks for tumor DNA or other tumor-related material circulating in the bloodstream. Liquid biopsy can be useful when a tissue sample is hard to obtain, when more information is needed after treatment starts, or when doctors are monitoring for new resistance changes.

Different tests may be ordered at different times. Some patients have focused testing for one or a few biomarkers, while others have broader panel testing that examines many genes at once. The choice depends on the type of cancer, the amount of tissue available, whether the disease is newly diagnosed or recurrent, and what treatment decisions need to be made.

Because results can be complex, they are often reviewed by a multidisciplinary team. This may include a medical oncologist, pathologist, molecular biologist, surgeon, radiologist, and other specialists involved in cancer treatment. Their combined interpretation helps place the findings in the context of the whole clinical picture.

What biomarker testing can change in treatment decisions

The most important change biomarker testing can bring is a better treatment match. If a tumor has a targetable change, a doctor may recommend a medicine designed to block that specific pathway. These treatments may be more effective for the right patient than a less targeted approach, although response still varies from person to person.

Testing can also help identify whether immunotherapy is more likely to be useful. Certain biomarkers suggest that a tumor may respond better to immune-based treatments, while others suggest a lower chance of benefit. This information may influence whether immunotherapy is used alone, combined with other treatment, or not recommended.

Sometimes biomarker testing changes the diagnosis or clarifies the cancer subtype. This matters because cancers that look similar under the microscope may behave differently and require different care plans. In advanced disease, repeat testing may show that the tumor has changed over time, which can explain why a treatment stopped working and what to consider next.

Biomarker results may also open the door to clinical trials. If standard treatments are limited, a trial can provide access to therapies being studied for cancers with certain molecular features. Even when there is no immediately actionable result, the report can still help doctors avoid unsuitable options and plan the next steps more efficiently.

Who may benefit and when testing is recommended

Biomarker testing is not used the same way for every cancer. In some cancer types, guidelines recommend testing routinely at diagnosis, especially if advanced disease is present. In other situations, testing is considered when the cancer returns, spreads, or does not respond as expected to treatment.

People with metastatic or recurrent cancer are often among those most likely to benefit because the results may directly affect systemic treatment choices. Testing may also be important for early-stage cancers in selected cases, such as when certain biomarkers help determine whether targeted treatment, hormone treatment, or immunotherapy should be added after surgery.

Family history, age at diagnosis, and tumor characteristics can also influence whether doctors suggest inherited genetic testing in addition to tumor testing. These are different but related tools. Tumor testing looks at changes in the cancer itself, while inherited testing looks for changes present in the body’s cells that may affect cancer risk for the patient and sometimes relatives.

Patients often benefit from asking practical questions before testing begins, such as:

• What specific biomarkers are being tested?
• How could the results change treatment choices?
• Is tissue testing, liquid biopsy, or both recommended?
• Will the test also help identify clinical trial options?
• Do the results have implications for inherited cancer risk?

Limits, challenges, and how to understand the results

Although precision oncology is a major advance, it has limits. Not every cancer has a biomarker that can be matched to an approved treatment. Sometimes a tumor contains a mutation, but there is not yet a proven medicine for it. In other cases, a targetable change is found, but the patient’s overall condition or treatment history makes another approach more suitable.

Results can also be difficult to interpret. Some findings are clearly actionable, while others are classified as variants of uncertain significance. A report may list many gene changes, but only a small number may matter for treatment. This is why results should be discussed with an oncology team rather than interpreted in isolation.

Testing quality can be affected by sample size and tumor content. If the biopsy contains too few cancer cells, or if the cancer is biologically diverse in different areas, a test may miss important changes. Repeat biopsy or additional blood-based testing may sometimes be needed, especially if the cancer evolves during treatment.

It is also helpful to remember that biomarker testing informs care; it does not guarantee a response. Cancer treatment decisions still depend on stage, symptoms, general health, other medical conditions, and personal goals. Precision oncology works best as part of a thoughtful, individualized treatment plan, which may include immunotherapy or other therapies when appropriate.

Practical next steps for patients

Patients who are newly diagnosed or facing a change in treatment can ask their oncology team whether biomarker testing is recommended for their cancer type. Bringing pathology reports, imaging results, and a list of prior treatments to appointments can help doctors decide what testing is most useful and whether existing samples are adequate.

It can be helpful to request that results be explained in plain language. Patients may ask which findings are actionable now, which ones may matter later, and whether the report suggests standard treatment options or research studies. Some people also benefit from a second opinion at a center with experience in molecular tumor boards and complex cancer care.

Emotional support is important, too. Waiting for test results can be stressful, and reports may contain unfamiliar terms. A clear conversation with the care team can reduce uncertainty and help patients feel more involved in decisions. Support from family, counselors, and patient advocacy groups can also make the process easier.

When specialized evaluation is needed, Acibadem International’s multidisciplinary specialists and JCI-accredited hospitals support international patients with diagnosis and personalized oncology planning, including advanced testing and treatments such as robotic surgery when clinically appropriate.

When to speak with a doctor promptly

Patients should contact their doctor promptly if they have a new cancer diagnosis and are unsure whether biomarker testing should be part of the evaluation. A timely discussion can be important because some treatment decisions are best made after the molecular profile is known.

Medical advice should also be sought if cancer symptoms are worsening, if treatment seems to have stopped working, or if a new biopsy is being considered after recurrence. In these situations, repeat testing may sometimes provide useful information about resistance changes or new treatment options.

Urgent medical attention is needed for severe symptoms such as trouble breathing, uncontrolled pain, new confusion, heavy bleeding, high fever during cancer treatment, or signs of serious infection. These issues require immediate assessment and should not wait for test results or routine follow-up.

Frequently asked questions

What is precision oncology in simple terms?

Precision oncology is a way of treating cancer using detailed information about the tumor’s biology. Doctors look for biomarkers, such as gene changes or proteins, to help choose treatments that may be more suitable for that specific cancer.

Is biomarker testing the same as genetic testing?

Not exactly. Biomarker testing usually examines the tumor to find changes that may guide treatment, while inherited genetic testing looks for changes passed through families that may affect cancer risk. Sometimes both types of testing are recommended.

Does every person with cancer need biomarker testing?

No. Whether testing is useful depends on the cancer type, stage, and available treatments. In some cancers it is standard practice, while in others it is used only in selected situations.

Can a blood test replace a tumor biopsy?

A liquid biopsy can be very helpful, but it does not always replace tissue testing. Tissue biopsy may still be needed to confirm the diagnosis, study the tumor directly, or detect findings that a blood test might miss.

If a biomarker is found, does that guarantee treatment will work?

No. A biomarker can suggest that a treatment is more likely to help, but it cannot guarantee a response. Doctors use the result together with many other factors, including overall health, prior treatment, and how advanced the cancer is.

Can biomarker testing be repeated later?

Yes. In some cases, repeat testing is done if the cancer returns, spreads, or stops responding to treatment. This can show whether the tumor has developed new changes that affect future treatment choices.

References

• National Cancer Institute
• American Society of Clinical Oncology
• European Society for Medical Oncology
• World Health Organization
• National Comprehensive Cancer Network

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.