Cancer Biomarker Testing: How It Helps Doctors Choose the Right Treatment

Every cancer is different. Even when two people have the same type of cancer, the biological changes inside their cancer cells may not be identical. These differences can influence how a cancer grows and which treatments may be effective.

This is where cancer biomarker testing becomes important. By examining specific genes, proteins and other biological features, doctors can gain valuable information that may help guide cancer treatment decisions.

In this article, we explain what cancer biomarker testing is, how it works, which tests are commonly used, and how the results can help doctors develop a more personalised treatment plan.

What Is Cancer Biomarker Testing?

Cancer biomarker testing is a medical process used to identify specific biological characteristics associated with a tumour or cancer cells. These characteristics are known as biomarkers.

Biomarkers may include genetic changes, abnormal proteins or other substances that provide information about a cancer. Depending on the test, the results may help doctors select treatments, understand certain features of the disease or monitor how cancer responds to treatment.

Biomarker testing may also be called tumour profiling, molecular testing, genomic testing or molecular profiling.

It is important to distinguish tumour biomarker testing from inherited genetic testing. Tumour testing looks for changes associated with the cancer, while inherited genetic testing examines genetic changes that may have been passed down through a family.

How Does Cancer Biomarker Testing Work?

The testing process depends on the cancer type, the suspected biomarker and the information doctors need.

In many cases, the process involves the following steps.

Step 1: Collecting a Sample

Doctors may use a tissue sample obtained through a biopsy or surgery. In certain situations, a blood sample or another type of specimen may be suitable.

The appropriate sample depends on the suspected cancer and the test being performed.

Step 2: Analysing the Sample

A specialised laboratory examines the sample for particular genes, proteins or other biological features.

Different laboratory methods are used for different purposes. Some tests identify specific genetic mutations, while others measure protein expression or look for a wider range of genetic changes.

Step 3: Interpreting the Results

The laboratory provides a report describing the biomarkers identified and their potential clinical significance.

Not every detected change has an established treatment implication. Some findings may be uncertain or may not currently have a corresponding treatment.

Step 4: Discussing Treatment Options

The oncologist considers the test results alongside the cancer diagnosis, stage, previous treatments and the patient’s overall health.

If a clinically relevant biomarker is identified, a targeted treatment or another suitable treatment option may be considered.

What Are the Different Types of Cancer Biomarker Tests?

Several types of tests are used in cancer care. The choice depends on the clinical question being investigated.

1. Genetic Mutation Testing

Genetic mutation testing identifies changes in DNA that may influence cancer development or treatment response.

For example, certain EGFR mutations can help doctors determine whether an EGFR-targeted medicine may be appropriate for a patient with non-small cell lung cancer.

Other genetic changes, including selected BRCA1 and BRCA2 mutations, may help guide treatment decisions in particular cancers.

2. Protein Biomarker Testing

Some cancer treatments are selected according to the presence or level of specific proteins.

For example, HER2 testing can help guide treatment decisions in certain breast and other cancers. PD-L1 testing may also help determine whether particular immunotherapy options are appropriate in selected clinical settings.

The meaning of a result depends on the cancer type, the specific test and the treatment being considered.

3. Next-Generation Sequencing (NGS)

Next-generation sequencing is a laboratory technology that can analyse multiple genetic regions simultaneously.

Depending on the test, it may identify several potentially relevant genetic changes from a single tumour sample. This can help doctors evaluate multiple treatment possibilities without necessarily ordering separate tests for every individual gene.

However, NGS does not guarantee that an effective targeted treatment will be available. Some results may have uncertain significance or may not change the recommended treatment.

4. Liquid Biopsy

A liquid biopsy is a test that examines biomarkers in a body fluid, commonly blood. Some liquid biopsies look for circulating tumour DNA (ctDNA), which consists of DNA fragments released by cancer cells into the bloodstream.

Liquid biopsy may be useful in selected situations, such as identifying certain tumour mutations or monitoring changes during treatment.

However, a negative blood test does not always mean that a tumour lacks a particular biomarker. Some cancers release very little detectable tumour DNA, so tissue testing or additional investigations may still be necessary.

How Does Biomarker Testing Help Personalise Cancer Treatment?

Cancer biomarker testing can help doctors move beyond treatment decisions based only on the location of the cancer.

Its potential applications include:

Identifying targeted treatment options: Certain medicines work by acting on specific proteins or genetic changes found in cancer cells.

Assessing immunotherapy options: Particular biomarkers may help doctors determine whether certain immunotherapies are appropriate.

Avoiding unsuitable treatments: Some test results can indicate that a particular medicine is unlikely to be effective for a specific tumour.

Identifying clinical trials: In some cases, biomarker findings may help patients explore clinical trials investigating treatments for cancers with particular molecular characteristics.

Supporting treatment planning: The results provide additional information that can be considered alongside pathology reports, imaging, symptoms and other clinical findings.

Biomarker testing supports clinical decision-making, but it does not replace the judgement of the treating oncologist.

Which Cancers May Benefit From Biomarker Testing?

Biomarker testing is used in the management of several cancer types, although the relevant tests differ from one cancer to another.

Examples include:

• Breast cancer: HER2, hormone receptor status and selected genetic alterations may help guide treatment.
• Lung cancer: Certain EGFR mutations, ALK rearrangements and other molecular changes may help identify targeted treatment options.
• Colorectal cancer: Tests such as RAS, BRAF, mismatch repair and microsatellite instability testing may inform treatment decisions.
• Prostate cancer: Selected BRCA1/BRCA2 and other DNA repair gene alterations may be relevant to treatment selection in appropriate patients.
• Blood cancers: Certain genetic abnormalities can help establish a diagnosis, guide treatment and monitor disease.
• Other solid tumours: Depending on the diagnosis, additional biomarkers may help identify targeted treatments or immunotherapy options.

Not every patient requires the same panel of tests. The appropriate investigations depend on the cancer type, stage, clinical circumstances and available treatment options.

What Is the Difference Between Biomarker Testing and Precision Oncology?

Biomarker testing and precision oncology are closely related, but they are not the same thing.

Biomarker testing is the process of identifying relevant biological features of a cancer. Precision oncology is the broader approach of using information about a patient’s cancer, including biomarkers, to help guide treatment decisions.

For example, a biomarker test may identify a specific genetic alteration in a tumour. The oncologist can then assess whether an established treatment targets that alteration and whether the treatment is appropriate for the patient.

This approach aims to make treatment decisions more individualised rather than assuming that every cancer of the same type will respond identically.

Are There Any Limitations to Cancer Biomarker Testing?

Although biomarker testing can provide valuable information, it has limitations.

Not every cancer has an actionable biomarker. A test may identify changes for which no established targeted treatment is available.

Results can be inconclusive. Some findings have uncertain clinical significance and cannot reliably guide treatment.

Samples may not capture the entire tumour. Different areas of the same cancer can sometimes contain different genetic changes.

A negative result is not always definitive. The test may not detect a biomarker because of sample limitations or the amount of tumour material available.

Testing can involve costs and waiting times. Availability, laboratory methods and turnaround times vary.

Patients should discuss the meaning of their results with their oncologist before making treatment decisions.

Frequently Asked Questions About Cancer Biomarker Testing

Is biomarker testing the same as a cancer diagnosis?

No. Biomarker testing generally provides additional information about a cancer’s biological characteristics. Diagnosis usually involves other investigations, such as pathology examination, imaging and clinical assessment.

Does every cancer patient need biomarker testing?

No. Testing is recommended when it is relevant to the diagnosis or may influence treatment decisions. The need for testing depends on the cancer type, stage and clinical guidelines.

Is cancer biomarker testing performed using blood or tissue?

Both methods are possible. Tissue-based testing examines a tumour sample, while liquid biopsy may identify certain cancer-related biomarkers in blood. The appropriate method depends on the clinical situation.

Can biomarker testing identify the best cancer treatment?

It can help identify suitable options, but it cannot guarantee which treatment will work best. Doctors must also consider clinical evidence, the patient’s overall health, treatment history and potential side effects.

Can biomarker results change over time?

Yes. Some cancers develop additional genetic changes as they grow or respond to treatment. In selected situations, repeat testing may provide useful information about treatment resistance or new treatment options.

Conclusion

Cancer biomarker testing is an important part of modern cancer care. By identifying specific genetic changes, proteins and other biological features, these tests can help oncologists evaluate targeted therapies, selected immunotherapies and other treatment possibilities.

However, testing is only one part of the decision-making process. The results must be interpreted in the context of the patient’s diagnosis, medical history and overall treatment goals.

At Galaxy Super Speciality, we believe that access to clear, reliable medical information helps patients and families better understand developments in cancer care. Patients should consult a qualified oncologist to determine which tests and treatments may be appropriate for their individual circumstances.

Medical disclaimer: This article is intended for general educational purposes only. It does not replace professional medical advice, diagnosis or treatment.