Precision Oncology: Biomarker Testing and Personalized Treatment

Precision oncology is an approach to cancer care that uses biomarker testing to better understand a person’s tumor and help choose the most appropriate treatment. By looking at genetic, protein, or other molecular features, doctors may be able to match therapies more closely to the biology of the cancer.

Overview

Precision oncology is a modern approach to cancer care that aims to tailor treatment to the unique characteristics of a person’s tumor. Instead of relying only on where the cancer started in the body, doctors also study molecular features such as gene changes, proteins, and other biomarkers. This can help explain how the cancer behaves and which treatments may be more likely to help.

Biomarker testing is a central part of precision oncology. A biomarker is a measurable feature in cancer cells or sometimes in blood that gives information about the disease. Some biomarkers can predict whether a targeted drug or immunotherapy might work, while others help estimate prognosis or support diagnosis.

Personalized treatment does not mean that every patient receives a completely unique medicine. In practice, it means choosing from available therapies in a more informed way. For example, two people with the same type of cancer may receive different treatments if their tumors have different molecular changes.

Precision oncology is now used in many cancers, including lung, breast, colorectal, melanoma, ovarian, and some blood cancers. It is also becoming more important in advanced cancer, recurrent disease, and situations where standard treatments have not worked as expected.

How biomarker testing works

Biomarker testing looks for features that may influence treatment decisions. These may include gene mutations, gene fusions, extra copies of certain genes, protein expression, microsatellite instability, or other molecular patterns. Depending on the cancer, doctors may test one biomarker at a time or use broader molecular profiling to examine many markers together.

Testing is often performed on a sample from a biopsy or surgery. A pathologist examines the tumor, and specialized laboratory methods are used to analyze the tissue. Common techniques include immunohistochemistry, polymerase chain reaction, fluorescence in situ hybridization, and next-generation sequencing. Each method answers slightly different questions, so the choice depends on what doctors need to know.

In some cases, biomarker testing can also be done through a blood sample, sometimes called a liquid biopsy. This may detect tumor DNA circulating in the bloodstream. Liquid biopsy can be helpful when tissue is limited, when a repeat biopsy is difficult, or when doctors want to look for changes that developed over time during treatment.

Results usually take days to a few weeks, depending on the type of test and how complex it is. The report may show actionable findings, meaning there is a treatment or clinical trial linked to the result. It may also show no clearly actionable biomarker, which can still be useful because it helps narrow treatment options and avoid therapies that are unlikely to help.

Who may benefit from precision oncology

Precision oncology can be useful at several points in cancer care. It is often considered when a person is newly diagnosed with certain cancers where biomarker-guided treatment is part of standard care. It is also commonly used in metastatic or advanced cancers, in recurrent disease, and when previous treatment has stopped working.

Not every person with cancer will need the same type or extent of testing. The benefit depends on the cancer type, stage, available tissue, and which treatments are being considered. For example, biomarker testing is especially important in some forms of lung cancer, breast cancer, colorectal cancer, melanoma, and ovarian cancer, where specific markers may open the door to targeted therapies or immunotherapy.

Doctors may also recommend broader testing when the cancer is rare, has unusual features, or does not respond as expected to standard treatment. In these situations, molecular profiling may reveal less common changes that suggest a different treatment approach or eligibility for a clinical trial.

Even when testing does not identify a targetable change, the information can still support care decisions. It may clarify the diagnosis, help estimate whether immunotherapy is more or less likely to work, or guide future planning if the cancer changes over time.

Common biomarkers and what they may mean

Different cancers are linked to different biomarkers. In some lung cancers, doctors may test for changes such as EGFR, ALK, ROS1, BRAF, MET, RET, KRAS, or NTRK. In breast cancer, testing may include hormone receptors and HER2. In colorectal cancer, biomarkers such as RAS, BRAF, mismatch repair deficiency, and microsatellite instability can influence treatment choices. These are only examples, and the appropriate panel depends on the specific diagnosis.

Some biomarkers are called predictive biomarkers because they help predict whether a treatment may work. For instance, high PD-L1 expression or mismatch repair deficiency may support the use of certain immunotherapy medicines in selected cancers. HER2 overexpression may indicate that HER2-targeted therapy could be useful in cancers where this marker is relevant.

Other biomarkers are prognostic, meaning they give information about how the cancer may behave overall, even if they do not directly point to one treatment. Some markers are diagnostic and help confirm the exact type or subtype of cancer. This distinction matters because not every positive test result automatically changes treatment.

Biomarker results should always be interpreted in context. A mutation found in one cancer type may have a different meaning in another. Also, some alterations are well established with approved treatments, while others are still being studied. For this reason, patients often benefit from discussion in a multidisciplinary tumor board that includes oncologists, pathologists, radiologists, and genetics specialists when needed.

Diagnosis and treatment planning

Precision oncology is one part of a larger diagnostic process. Doctors also consider the cancer’s location, stage, grade, imaging findings, pathology results, symptoms, and the person’s overall health. Biomarker testing does not replace these steps; rather, it adds another layer of detail that can help refine the treatment plan.

When results identify an actionable biomarker, treatment options may include targeted therapy, immunotherapy, hormone therapy, standard chemotherapy, radiation therapy, surgery, or combinations of these. In some cases, the result may point toward a treatment approved specifically for that cancer type. In others, it may support referral to a clinical trial evaluating newer options.

Timing is important. In some cancers, biomarker testing should be done before starting first-line systemic treatment so that the best option is not missed. In other situations, repeat testing later may be useful if the cancer returns or becomes resistant to treatment, because tumors can evolve and develop new molecular changes over time.

Patients may hear terms such as companion diagnostic, actionable mutation, or comprehensive genomic profiling. A companion diagnostic is a test linked to a particular medicine. Actionable means the result may influence management. Comprehensive profiling refers to testing many genes or markers at once. Understanding these terms can make discussions with the oncology team clearer and less overwhelming.

Benefits, limits, and possible concerns

The main benefit of precision oncology is that it can help match treatment more closely to the biology of the cancer. This may improve treatment selection, reduce trial-and-error prescribing, and identify options that might not otherwise be considered. For some people, it can also open access to clinical trials or newer therapies based on a specific molecular finding.

At the same time, biomarker testing has limits. Not all cancers have biomarkers with a proven treatment match. Some findings are uncertain, meaning their clinical significance is not fully understood. In other cases, a relevant biomarker may be present, but the corresponding treatment may not be suitable because of side effects, other health conditions, or the stage of disease.

Another important point is that tumor biology can change. A test result reflects the sample collected at a certain time. If the cancer progresses, repeat biopsy or liquid biopsy may sometimes reveal new resistance mutations or different features that affect treatment. This is especially relevant in cancers treated over a long period.

Patients may also have questions about inherited genetic risk. Tumor biomarker testing is different from germline genetic testing, which looks for inherited changes in genes present in all cells of the body. Sometimes a tumor result suggests that germline testing should also be considered, especially if there is a strong family history or a known cancer predisposition syndrome. The care team may recommend genetic counseling in these cases.

Questions to ask and when to seek specialist care

It is reasonable for patients and families to ask whether biomarker testing is recommended, what type of sample will be used, and how the results may change treatment. Other helpful questions include how long testing will take, whether retesting may be needed later, and whether any clinical trials are relevant. Clear communication can help patients feel more informed and involved in decisions.

Specialist care may be particularly helpful when the diagnosis is rare, the cancer is advanced, or test results are complex. Multidisciplinary cancer centers often bring together medical oncologists, surgeons, radiation oncologists, pathologists, radiologists, molecular specialists, and genetics experts to review each case. This team-based approach can help place biomarker findings in the right clinical context.

People should contact their doctor if they have a new cancer diagnosis, if current treatment is not working as expected, or if they are told the cancer has returned. These are common times when biomarker testing may become especially important. Patients should also ask about supportive care needs, side effect management, and second opinions when appropriate.

For international patients seeking evaluation, Acibadem International’s multidisciplinary specialists at JCI-accredited hospitals diagnose and treat cancer using modern testing and personalized treatment planning. Depending on the diagnosis, care may include advanced imaging such as PET-CT scanning along with systemic therapies and coordinated oncology follow-up.

Frequently asked questions

What is precision oncology in simple terms?

Precision oncology is a way of treating cancer based on the specific features of a person’s tumor. Doctors use biomarker testing to look for molecular changes that may help them choose the most appropriate treatment.

Is biomarker testing the same as genetic testing?

Not exactly. Biomarker testing usually examines the tumor itself to look for changes that may guide treatment. Genetic testing can also refer to inherited, or germline, testing, which looks for gene changes passed through families and may have different goals.

Does every cancer patient need biomarker testing?

No, not every cancer requires the same testing. Whether it is recommended depends on the cancer type, stage, available treatments, and whether results are likely to affect care decisions. An oncologist can explain which tests are useful in a specific situation.

Can biomarker testing be done with a blood test?

Sometimes. A liquid biopsy uses a blood sample to look for tumor DNA circulating in the bloodstream. It can be helpful when tissue is limited or when doctors want to check for changes that may have developed during treatment, but it does not replace tissue testing in every case.

What happens if no actionable biomarker is found?

This does not mean treatment options are gone. Standard treatments such as surgery, chemotherapy, radiation therapy, hormone therapy, or immunotherapy may still be appropriate depending on the cancer. The result can also help avoid treatments that are unlikely to help and guide future testing if the cancer changes.

Can biomarker results change over time?

Yes. Cancer cells can evolve, especially after treatment, and new molecular changes may appear. That is why doctors sometimes recommend repeat biopsy or liquid biopsy if the cancer returns or stops responding.

References

• World Health Organization
• National Cancer Institute
• American Society of Clinical Oncology
• European Society for Medical Oncology
• U.S. Food and Drug Administration

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.