Precision Oncology: How Biomarker Testing Guides Treatment

Precision oncology is an approach to cancer care that uses biomarker testing to understand the unique features of a tumor. This information can help doctors choose treatments that are more closely matched to an individual patient’s cancer.

Overview: What Precision Oncology Means

Precision oncology is a personalized approach to cancer care. Instead of choosing treatment based only on where the cancer started in the body, doctors also look at the tumor’s molecular features. These features, often called biomarkers, can include gene mutations, protein levels, and other biological signals that influence how cancer grows and how it may respond to treatment.

Biomarker testing helps identify these features. The goal is to match a patient with the treatment most likely to work for that specific cancer biology. In some cases, this may mean a targeted medicine aimed at a particular mutation. In others, it may help determine whether immunotherapy is likely to be useful, or whether standard treatments such as surgery, chemotherapy, or radiation remain the best choice.

Precision oncology does not replace the fundamentals of cancer care. Doctors still consider the cancer type, stage, location, symptoms, previous treatments, and the patient’s overall health. Biomarker results add another layer of information that can make treatment planning more individualized and informed.

What Biomarker Testing Looks For

A biomarker is a measurable characteristic that provides information about a cancer. Some biomarkers are changes in DNA, such as mutations, rearrangements, amplifications, or deletions. Others are found at the protein level, for example when a tumor makes too much of a certain protein. Some biomarkers suggest how active the immune system is around the tumor, which may influence whether immunotherapy could help.

Testing may be done on a tissue sample taken during a biopsy or surgery. In some cases, a blood-based test, often called a liquid biopsy, may also be used to look for tumor DNA circulating in the blood. Tissue testing often remains the main method because it gives detailed information about the tumor itself, but blood testing can be useful when tissue is limited or when doctors want to monitor changes over time.

Common examples of biomarkers vary by cancer type. In some lung cancers, specific gene alterations can help guide the use of targeted medicines. In breast cancer, hormone receptor status and HER2 are important biomarkers. In colorectal cancer, tests for certain mutations or mismatch repair status may affect treatment planning. The exact tests recommended depend on the suspected or confirmed cancer diagnosis.

• DNA changes in cancer cells
• Protein markers on or inside tumor cells
• Immune-related markers linked to immunotherapy response
• Inherited changes, when appropriate, that may affect cancer risk or treatment

When Biomarker Testing Is Recommended

Biomarker testing is often recommended when it is likely to affect treatment decisions. This is especially common in advanced or metastatic cancers, where targeted therapy or immunotherapy may be an option. It may also be useful in some earlier-stage cancers to help choose the most appropriate treatment plan after diagnosis or surgery.

Not every patient needs the same testing. Some cancers have well-established biomarkers that are routinely checked, while others have fewer markers that currently change treatment. The treating team decides which tests are appropriate based on the cancer type, the amount and quality of tissue available, and whether the results are likely to guide care.

Testing can be performed at diagnosis, after cancer has returned, or if a treatment stops working. This is important because tumors can change over time. A cancer that did not show a particular biomarker earlier may develop a new alteration later, especially after exposure to treatment. Re-testing may therefore become part of ongoing care in selected patients.

How Results Guide Treatment Choices

Biomarker testing can help doctors choose among several treatment paths. If a tumor has a targetable mutation or protein marker, a targeted medicine may be considered. These medicines are designed to act on specific pathways that help cancer cells survive. In the right patient, they may be more precise than treatments that affect many fast-growing cells throughout the body.

Results can also help identify patients who may benefit from immunotherapy. Certain biomarkers suggest that the immune system may be more likely to recognize and attack the cancer when supported by specific medicines. In other situations, testing may show that standard options such as chemotherapy, hormone therapy, radiation, or surgery are more suitable than a biomarker-driven medicine.

Sometimes, results show that no currently actionable biomarker is present. This can still be useful because it helps narrow the options and avoid treatments unlikely to help. In addition, biomarker findings may point toward a clinical trial, giving patients access to emerging therapies being studied under carefully monitored conditions.

Depending on the cancer type, treatment planning may involve therapies such as immunotherapy, chemotherapy, or radiation therapy. Precision oncology works best when these choices are reviewed by a multidisciplinary team that can interpret test results in the context of the whole clinical picture.

Benefits and Limitations of Precision Oncology

One of the main benefits of precision oncology is that it can make treatment more individualized. When a biomarker clearly predicts response, patients may be directed toward therapies that are more relevant to their cancer and away from options less likely to help. This can support more informed decision-making and, in some cases, improve treatment efficiency.

However, biomarker testing also has limits. Not all cancers have an actionable biomarker. Even when a biomarker is found, an appropriate medicine may not be available, may not be suitable for that patient, or may stop working over time as the tumor develops resistance. A test result is therefore informative, but it is not a guarantee of treatment success.

Another challenge is that interpreting molecular results can be complex. Some findings are clearly meaningful, while others are less certain. This is why patients benefit from discussing results with oncology specialists who can explain what is known, what remains unclear, and how testing fits into the overall treatment strategy.

How Testing Is Performed and What Patients Can Expect

Biomarker testing usually begins after a cancer diagnosis has been confirmed. A pathologist examines tissue from a biopsy or surgery, and additional laboratory methods may then be used to analyze genes, proteins, or other markers. Some tests focus on one or two specific biomarkers, while broader panels evaluate many genes at the same time.

The waiting period for results varies depending on the type of test and how specialized it is. During this time, doctors may proceed with parts of care that cannot be delayed, or they may wait for results if they are expected to strongly influence the treatment plan. Patients can ask whether enough tissue is available, whether a blood test may also be helpful, and how the results could affect next steps.

In some cases, genetic counseling is recommended, especially if results suggest an inherited change that could affect family members as well as the patient. It is important to understand the difference between tumor testing, which looks for changes in cancer cells, and germline testing, which looks for inherited changes present in most cells of the body. Both can be valuable, but they answer different questions.

For patients diagnosed with conditions such as lung cancer or breast cancer, biomarker testing is often a routine part of modern treatment planning. The exact timing and type of test depend on the individual case.

Questions to Ask the Care Team

Patients often feel more confident when they understand why a test is being ordered and how the results may be used. Asking clear questions can make the process easier and help people take an active role in decisions. It is reasonable to request simple explanations of medical terms and to ask whether there are different testing options.

Helpful questions may include:

• Which biomarkers are being tested for and why?
• Will the test be done on tissue, blood, or both?
• How might the results change the treatment plan?
• Is repeat testing ever needed if the cancer changes or returns?
• Could the findings suggest a clinical trial or inherited risk?

Many patients also want to know whether biomarker testing should be done before starting treatment or whether it can be performed later if needed. The answer depends on the cancer type and urgency of care. A thoughtful discussion with the oncology team can help balance timely treatment with the value of waiting for important molecular information.

When to Seek Specialist Advice

Specialist advice is especially important when a diagnosis is new, when cancer returns, or when there are questions about whether a targeted therapy or immunotherapy may be appropriate. Patients may also benefit from a second opinion if test results are complex or if treatment options are unclear. Molecular tumor boards and multidisciplinary cancer teams can be particularly helpful in difficult cases.

People should contact their doctor promptly if symptoms worsen, if new symptoms appear during treatment, or if they have concerns about side effects or delays in testing. Ongoing communication helps ensure that test results are interpreted correctly and that treatment remains aligned with the patient’s needs and goals.

At the end of the process, precision oncology is about using the best available evidence to tailor care as much as possible. For international patients, Acibadem International’s multidisciplinary specialists in JCI-accredited hospitals diagnose and treat cancer using modern imaging, pathology, and personalized treatment planning, including medical oncology when appropriate.

Frequently asked questions

What is precision oncology?

Precision oncology is a way of planning cancer treatment based on the biological features of a person’s tumor. It uses biomarker testing to help identify therapies that may be more closely matched to that cancer.

Is biomarker testing the same as genetic testing?

Not exactly. Biomarker testing often looks for changes in the tumor itself, while genetic testing can also refer to inherited changes passed through families. In some situations, a doctor may recommend both because they provide different kinds of information.

Does every cancer patient need biomarker testing?

No. Testing is most useful when the results are likely to affect treatment decisions, and this varies by cancer type and stage. The oncology team decides which tests are appropriate for each patient.

Can biomarker testing be done with a blood sample?

Sometimes. A liquid biopsy can look for tumor DNA in the blood and may be helpful when tissue is limited or when doctors want to monitor changes over time. However, tissue testing is still often needed because it can provide more complete information.

Does finding a biomarker mean a targeted treatment will work?

Not always. A biomarker may suggest that a treatment is worth considering, but response can vary from person to person. Other factors, such as overall health, previous treatment, and how the cancer behaves, also matter.

Can biomarker results change over time?

Yes. Tumors can evolve, especially after treatment, and new molecular changes can appear. That is why repeat testing may sometimes be recommended if the cancer returns or stops responding to treatment.

References

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

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.