Tumor Genetic Testing

What Is Tumour Genetic Testing?

Cancers develop when mutations (or changes) occur in the DNA sequence of genes, causing harmful consequences. Tumour genetic testing refers to the process of analysing and identifying genetic mutations that are present in cancer cells. This will include both acquired as well as inherited mutations. Most cancers occur due to acquired mutations. Acquired mutations are changes that are not present at birth but develop later on in life and are usually found only in cancer cells but not in other normal cells in a cancer patient. Acquired mutations cannot be passed from parent to child (i.e., not heritable).

Why Is This Test Important?

Some of the mutations present in a cancer cell are ‘targetable’. This means that there exists a drug that specifically targets a particular pathway to stop the cancer from growing uncontrollably. Other mutations serve as important biomarkers that can help doctors personalise your cancer treatment.

How Is Tumour Genetic Testing Done?

A sample of your tumour will be required. If you previously had a biopsy or surgery for your tumour and the sample has been stored by the hospital, you can check if this archived sample is available in the laboratory and is suitable to be used for tumour genetic testing.

If unsuitable, you might be required to go for a biopsy to obtain a new tumour sample for the test. If you require a fresh biopsy, your doctor will discuss with you how best to do that. If a re-biopsy is not an option, your doctor can discuss the option of liquid biopsy with you.

Liquid biopsy analyses a blood sample for the presence of circulating tumour DNA or ctDNA; as cancer cells go through their life cycle, fragments of DNA can enter the bloodstream. These fragments of DNA are known as ctDNA.

Samples of your tumour or blood (ctDNA) will be sent to specialised laboratories for tumour genetic testing. Some tumour genetic tests use a more targeted approach, testing only specific gene mutations, while others test multiple cancer genes. Your doctor/ Cancer Genetics Clinic will be able to advise you on which test would be most suitable for your cancer.

Check out - How Cancer Starts, Grows and Spreads?

How Long Do the Results of the Tumour Genetic Testing Take?

The results may take 14-45 working days to return, depending on the type of test offered. Your testing laboratory will advise you further.

Other Important Considerations

While most mutations found in cancer cells are acquired mutations, in some situations, a mutation detected in cancer cells may be an incidental heritable mutation. A proportion of cancer patients developed cancer because they inherited a cancer-predisposing gene mutation. These heritable mutations can be passed from parent to child and are present in all cells. When these individuals undergo tumour genetic testing, the heritable mutations may be detected in the cancer cells.

Unfortunately, tumour genetic testing alone is unable to definitively distinguish heritable from acquired mutations. If your Geneticist suspects that one or more of the mutations detected in your tumour are potentially heritable mutations, you may benefit from genetic counselling and further genetic testing using blood or saliva to confirm the nature of the mutation. Your Geneticist will advise you accordingly.

Is Genetic Tumour Testing for All Tumour Types?

With advancements in cancer research and understanding of important biomarkers, the role of tumour genetic testing is increasing. There is an ever-growing list of cancers for which tumour genetic testing is considered routine as the information is critical to guide the choice of drug treatment for the patient.

These tumour types include but are not limited to Lung, Breast, Ovarian, Prostate, Biliary tract, and Colorectal cancers.

Book an appointment with the Cancer Genetic Specialist to find out more about whether tumour genetic testing would be useful for your cancer!