This page provides information about how genomics is used in cancer diagnosis and treatment.

It may be useful for people whose oncologists have recommended genomic testing or people with a family history of cancer.

Oncologists are using genomics to help inform cancer diagnosis and care. Two experts from the Peter MacCallum Cancer Centre answer some common questions about genomics and cancer, and provide some helpful resources for support and information.

Our genes are one piece of the puzzle in cancer care. Genomic tests can help diagnose cancers and can give us information about inherited cancer risk. Read on to find out more.

How are genes involved in cancer?

Cancer happens when an individual cell in a person’s body grows out of control, and the immune system is unable to remove this abnormal cell. This happens when there are changes in this cell’s genome – its DNA. Genomics England’s webpage on cancer genomics can help you understand how cancer develops.

Overtime, the DNA in our body can produce small changes in its code. Genes are the ‘building blocks’ of your DNA. Not all changes in DNA cause cancer. When lots of little changes develop in our DNA over time, or the changes cause a big enough re-arrangement in our DNA code, it can result in a cumulative change in the way the cell works. When this happens, genes can function differently to before, which can sometimes lead to cancer.

Although most cancers are not inherited, our genes can play a role in developing some cancer types. This means that there are broadly two types of cancers:

  1. Cancers that happen purely by chance or environmental factors.
  2. Cancers caused by gene changes that are passed down through families.

We explain the difference between these types of gene changes below. You can also read more in this article on germline vs somatic testing.

Cancer can happen in any part of the body, which means there are many different types of cancer. These different types of cancer often have different types of gene changes.

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How is genomics used in cancer care?

Genomics is the area of health that investigates many, or all, of your genes.

Genomics has an increasing role in the management of cancer, new technology means that doctors are developing ways to:

  • Diagnose the specific type of cancer by finding the cancer-causing gene change
  • Choose the most suitable treatment options for cancer patients
  • Determine the possibility or likelihood of developing cancer in the future
  • Check if biological relatives of a cancer patient carry the same gene change, which may put them at a higher risk of developing cancer
  • Treat certain types of cancer early
  • Check how you’re responding to the treatments over time

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Genomic testing for cancers

What is a somatic mutation?

In cancer, somatic mutations refer to the acquired gene changes in the DNA of cancer cells. These changes are like a glitch in the instructions that tell the cells what to do and how to behave. Unlike germline – or inherited – gene changes, these changes aren’t in every cell of the body. Because of this, it means that somatic gene changes can’t be passed down through families to anyone else.

Somatic gene changes develop over time due to factors such as aging, exposure to harmful substances, or other unknown reasons. Most cancers are due to somatic gene changes.

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Testing cancers cells for gene changes

Generally, there are two kinds of genomic tests used in cancer. There are tests that look for gene changes you inherit from your biological parents, and tests that look at the cancer’s DNA.

Tests that look at the cancer’s  DNA can help doctors understand what is causing the growth of cancer or may provide information on an ideal treatment. Identifying the specific cause of a patient’s cancer can guide treatment. This test is ideally done by collecting a sample of the cancer tissue in surgery or via biopsy. If surgery is not an option, this test may also be done by collecting the patient's blood, known as a ctDNA test.

This resource from NHS England explains genomic testing for suspected cancer, with an easy-read option available.

The genomic testing process can be complicated and involves many experts. This page can help you understand the steps involved in a genomic test.

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How can genomics help inform cancer treatment?

Doctors may be able to use the information from a genomic test to determine which treatment options will be best suited for each patient. This is often referred to as genomic medicine, or even precision medicine.

The best course of treatment will differ for each patient, as it depends on the type of cancer they have, the gene change driving the cancer, and the patient’s physical condition.

For more information on specific cancers, the Cancer Council has guides to best cancer care. They can give you an idea of what to ask your doctor, and the possibly pathways for each type of cancer.

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How can I access cancer genomic testing and how much will it cost?

It’s important to speak to your doctor about getting a genomic test, as genomic testing is not recommended for every type of cancer.

The exact type and cost of the test will vary depending on which test is most suitable for you and your condition. Some people with some cancers may be eligible for a Medicare rebate. Generally, the cost of a self-funded test can range from a few hundred dollars to several thousand dollars depending on what test is needed. This booklet from NSW Health explains some of the public and private options for genetic testing for cancer.

You may be able to access genomic testing by participating in a clinical trial. Australian Cancer Trials connects consumers with the trials currently available in Australia.

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Genomic testing for inherited cancers

How is cancer passed down in families?

Germline mutations are gene changes inherited from your biological parents. It's like inheriting a small typo in the family recipe book that predisposes you to certain types of cancer. These kinds of gene changes are present in every cell of the body from birth, making individuals more susceptible to developing certain types of cancer throughout their lifetime. These inherited gene changes are why some cancers can run in biological families.

However, not everyone with these mutations will develop cancer, as other factors play a role in whether cancer develops or not.

Some examples of cancer that can happen because of germline mutations that can be passed down through families include breast, ovarian and prostate cancers.

You may have heard of the BRCA1 and BRCA2 genes. While changes in these genes are known to play a role in having an increased risk of developing breast and ovarian cancer, not everyone with a family history of cancer will have a gene change associated with cancer.

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What does it mean to have a higher cancer risk?

A person with specific types of gene changes have a higher-than-average risk of developing cancer in their lifetime. This does not mean that they are born with cancer or that it is inevitable that they will develop cancer later in life.

Because they are born with a gene change associated with cancer, those with an inherited susceptibility can develop cancer with fewer external contributing factors than those with an average risk of cancer.

This page from Macmillan Cancer Support explains inherited cancer risk.

A genetic counsellor can help you assess your risk of developing cancer. They can work with you to create a preventative plan to manage and reduce your risk. This is a free service in familial cancer centres for certain types of cancers. Contact your doctor to find your local genetics service.

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Can you test for an inherited cancer gene?

Confirming if a cancer is inherited

Doctors can use genomic testing to confirm if a cancer is caused by an acquired or inherited gene change. Understanding the genetic change responsible for cancer can help guide treatment for the patient. It can also help determine if the patient’s biological relatives are at a higher risk of developing the same cancer.

Predictive genetic testing

Genetic testing can also be done to help doctors understand a person’s likelihood of developing cancer in the future. This can be done for family members of cancer patients who have a high risk due to family history and want to know if they carry the same inherited gene change. For example, changes in the BRCA1 and BRCA 2 genes can increase the risk of breast or ovarian cancer. This test checks for the presence of a specific gene change and is usually done by collecting a person’s blood.

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What about testing for cancer risk in family members?

It can be distressing to find out you or your loved one has a higher risk of developing cancer. Feeling concerned about risk is normal. It’s also okay to not want to know further about your genes.

Your doctor can refer you to a familial cancer centre, where a genetic specialist can help you understand your risk of developing cancer. This Q&A with a genetic counsellor breaks down cancer in families, including its implications for insurance. The Cancer Council also breaks down some frequently asked questions about cancer and life insurance and highlights some recent policy changes.

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What could genetic testing mean for my family?

While genomic testing may provide answers, it’s important to speak with your doctor to determine if genomic testing is right for you. Because you share DNA with your biological family, your test results may impact them. Cancer.Net breaks down some of the common factors to consider before getting a genomic or genetic test.

If you’re considering getting a genomic or genetic test for cancer, a genetic counsellor can help explain how it may impact you and your family. Speak to your doctor for a referral.

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What are familial cancer centres?

Familial – or family – cancer centres help support people who are worried about their risk of developing cancer due to their family history. These centres can provide family risk testing, genetic counselling, and medical advice.

Familial cancer centres have genetic experts and counsellors who can explain your cancer risk in detail, and walk you through what happens next. They can help you develop a health plan to manage your risk of cancer.

Speak to your doctor for a referral to a familial cancer centre. This page also lists the available cancer genetics services in Victoria. If you need support making an appointment, Gene Equal has resources on how to make a genetic appointment and how to get ready to go to the genetics clinic.

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Where can I find more information about genomics and cancer?

Attending medical appointments can be exhausting when you’re already feeling unwell. Likewise, the idea of having a higher risk of cancer can be stressful. The Cancer Council has phone lines with cancer nurses available for those diagnosed with cancer, as well as support for their families and friends, or anyone concerned about having a higher genetic risk of developing cancer.

Connecting with other patients and families can be helpful. You can find peer networks by:
  • Reaching out to a cancer support organisation
  • Searching the name of your condition and the area you live in on Facebook
  • Asking a genetic counsellor at your local familial cancer centre
There are great resources on genomics and cancer available online:

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Written by: Jessica InceConnect
Medically reviewed by: Dr Kortnye Smith and Dr Lavinia Tan
Insights provided by: Bonney Corbin, Jo Cockwill and Victoria Sharp

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