Molecular testing for cancer can help doctors understand specific characteristics of a tumor that may influence treatment decisions. Two people can have the same type of cancer and even the same stage, but their cancers may behave differently because of differences in their tumour biology.

In selected cancers, molecular testing in cancer can identify biomarkers, gene changes or proteins that may help doctors decide whether treatments such as targeted therapy or immunotherapy could be appropriate.

This does not mean every patient needs molecular testing or that chemotherapy can always be avoided. The purpose of testing is to understand the cancer more precisely and use that information, when relevant, to guide treatment.

What is molecular testing for cancer?

Molecular testing in cancer examines cancer cells for specific biological changes that may provide information about how the cancer behaves and which treatments may be suitable.

It may look for:

• Changes in specific genes
• Certain proteins
• Molecular alterations involved in cancer growth
• Biomarkers linked to particular treatments

Terms such as cancer molecular testing, molecular profiling for cancer, biomarker testing for cancer, cancer biomarker testing and tumor profiling may be used when discussing these tests.

Some tests examine one specific biomarker. Others assess several genes or molecular alterations at the same time using broader testing methods such as multigene panels or next-generation sequencing.

The important question is not simply whether a mutation is present. Doctors need to know whether that finding has a meaningful role in deciding treatment.

Can cancer molecular testing change treatment?

Yes, molecular testing in cancer can change the treatment in selected patients. If testing identifies a molecular alteration for which an appropriate treatment is available, the oncologist may consider a therapy designed to target that particular feature of the cancer.

For example, two patients may have the same type and stage of cancer. One tumour may contain an actionable biomarker while the other may not. Their cancer treatment plans can therefore be different even though their basic diagnosis appears similar. However, molecular testing does not decide treatment on its own. Cancer type, stage, previous treatment, overall health, and other clinical factors also need to be considered for cancer molecular testing.

How does molecular testing help choose cancer treatment?

A common question that patients ask is, “How does molecular testing help choose cancer treatment?” The answer is that it can add another layer of information beyond the cancer’s name and stage.

1. It may identify a treatment target

Some cancers contain specific molecular changes that help cancer cells grow or survive. If there is an approved treatment that acts on that target, targeted therapy may become one of the treatment options.

2. It may help identify patients for targeted therapy

Targeted treatments are designed to interfere with specific proteins or pathways involved in cancer growth. Depending on the medicine, targeted therapy may be given as a tablet, capsule, or intravenous treatment.

3. It may provide information relevant to immunotherapy

In some cancers, certain biomarkers may help doctors determine whether immunotherapy should be considered. This is why molecular and biomarker information can sometimes affect treatment selection. 

Can biomarker testing help choose cancer treatment?

Biomarker testing can help choose cancer treatment when the cancer contains a biomarker that has an established treatment implication. However, not every biomarker leads to a treatment option.

A test may show:

• A biomarker linked to an available treatment
• A molecular change for which no approved treatment is currently appropriate
• A finding whose significance is still uncertain
• No actionable molecular alteration

Even when an actionable biomarker is found, treatment response cannot be guaranteed. Biomarker testing should therefore be considered one part of the complete cancer treatment decision.

Is molecular testing needed before cancer treatment?

Molecular testing for cancer before treatment is useful in some cancers but is not automatically required for every patient. Whether molecular testing is appropriate depends on several factors, including the type and stage of cancer, whether the disease has spread or returned, the treatment options currently available, any previous treatments the patient has received, and the clinical guidelines relevant to that particular cancer.

In some cancers, biomarker testing has become an established part of deciding treatment. In other situations, it may not change the treatment plan and therefore may not be necessary. Your oncologist can determine whether molecular testing is relevant to your specific diagnosis.

Is molecular testing needed before chemotherapy?

Patients also frequently ask about molecular testing before chemotherapy. The answer depends on the cancer. In some situations, molecular testing may identify a targeted treatment option that affects whether chemotherapy is used, when it is used, or what other treatments are combined with it. But finding a target does not automatically mean chemotherapy can be avoided.

Depending on the type of cancer and its molecular characteristics, targeted therapy may be used instead of chemotherapy, before or after chemotherapy, or alongside other cancer treatments as part of the overall treatment plan. The objective of cancer molecular testing is not simply to avoid chemotherapy. It is to help doctors select the most appropriate treatment strategy for that particular cancer.

What is the difference between targeted therapy and chemotherapy?

Chemotherapy generally works by killing or slowing cells that divide rapidly. Whereas targeted therapy works differently. It is designed to interfere with specific molecular targets or pathways involved in the growth and survival of cancer cells. This difference does not mean one treatment is always better than the other.

Chemotherapy continues to be an important part of cancer treatment for many patients. Modern cancer treatment may involve chemotherapy, targeted therapy, immunotherapy, surgery, radiation, or a combination of approaches. The right sequence depends on the individual cancer.

Can molecular testing help you get cancer treatment tablets?

Some targeted cancer medicines are available as tablets or capsules, but there is no single tablet that can treat every type of cancer. The right medicine depends on several factors, including the type and stage of cancer, its molecular characteristics, any previous treatments, the patient’s overall health, and whether that particular medicine is clinically appropriate for the cancer.

This is why searching only for a “cancer tablet” or a cancer tablet name can be misleading. A medicine should be selected because it is appropriate for the cancer, not simply because it is available in tablet form.

Who should consider molecular testing for cancer?

The need for molecular profiling for cancer varies from patient to patient. Testing may be particularly relevant in certain advanced or recurrent cancers and in cancer types where biomarker-directed treatments are already part of treatment planning.

However, molecular testing is not a test that every cancer patient automatically requires. A more useful question would be, “Will molecular or biomarker testing provide information that could change my treatment?” Your oncologist can answer this based on your cancer type, stage, and current treatment options.

What if molecular testing does not find a treatment target?

A negative or non-actionable result does not mean there are no treatment options. Sometimes tumour profiling does not identify a molecular alteration that matches an available targeted treatment. In other cases, it may find a change whose clinical importance is not yet clear.

Cancer can also contain different groups of cells, and its molecular characteristics may change over time. For these reasons, molecular testing provides useful information, but it cannot guarantee that a targeted treatment will be available or effective.

What should you ask your oncologist about molecular testing?

You do not need to remember complicated gene names. A useful question to ask is, “Is molecular or biomarker testing relevant for my cancer, and could the result change my treatment?” For the right patient, molecular testing for cancer can provide important information about tumor biology and help doctors make more precise treatment decisions.

Cancer treatment today is not based only on identifying the cancer and its stage. In selected cases, understanding the molecular characteristics of the tumor can also help answer an equally important question, “Which treatment is most appropriate for this particular patient?”