Genetic Testing for Cancer Risk: What Your Results Mean

When it comes to optimising cancer treatment and increasing your odds of survival, early detection is key. While various screening tools, such as colonoscopies and mammograms, can help to detect cancer, genetic testing can show your risk level of developing cancer, which can then prompt more frequent screenings and encourage a change in lifestyle habits. Understanding your cancer risk profile can be a powerful resource for improving your health.

Genetic Testing for Cancer Risk

Genetic testing looks for certain mutations in a person’s genes. In the case of genetic testing for cancer risk, the tests look for gene mutations that are associated with cancer development.

Cancer itself begins at the cellular level when the genes in a cell become abnormal. As a result, the instructions for the cell become mixed up, causing it to grow and divide out of control. In some cases, these mutations are inherited, which is why a common cancer risk is having a family member who had cancer. In fact, estimates place 10-20% of all cancers as resulting from an inherited mutation.

Of note, these mutations do not guarantee that you will develop cancer; they just mean that you are at a higher risk.

Predictive genetic testing can help see who is at a higher risk of cancer, and may be suggested for:

Someone with a family history of cancer Predictive genetic testing can help identify whether they carry a gene mutation that increases their risk of cancer.
Those already diagnosed with cancer It may seem counterintuitive to test for cancer risk in someone already diagnosed, but this testing can help determine if they are at a higher risk of developing any other cancers. If it is discovered that an inherited mutation caused the cancer, it may also help other family members decide to be tested, as well.
Family members of someone with a known heritable gene mutation Testing for these mutations can help family members determine if they also carry the mutation.

The Steps of Genetic Testing for Cancer Risk

The following are some of the standard steps when undergoing genetic testing:

Step 1: Information Gathering

Before undergoing testing, your healthcare professional will collect information about your personal and family medical history. This may include any cancer screening tests you have undergone, biopsies or surgeries you have had, and lifestyle factors. You will also be asked to provide a detailed review of your family medical history, such as how many relatives have had cancer, the type of cancer, and their age at diagnosis.

Step 2: Risk Evaluation

Once the information has been gathered, the healthcare professional will use it to determine your risk of developing cancer, whether genetic testing may be beneficial, and which gene changes to check for. In some cases, the doctor may recommend looking at just one gene, while at other times they may test for a panel of gene changes.

Step 3: Education

At this point, the healthcare professional will explain how some inherited genes can increase cancer risk, and what the benefits, risks, costs, and limitations of genetic testing are. They will also discuss if anyone else in the family should consider being tested. This stage also discusses what can come following genetic testing, including ways to cope with the results.

Step 4: Informed Consent

Once you have all the information regarding why genetic testing is being done, how the results may impact your life, and your risk status, you can make an informed decision regarding whether you’d like to proceed with genetic testing.

Step 5: Specimen Collection and Lab Testing

Genetic tests for cancer are typically performed using a sample of saliva, blood, cheek cells (obtained by swabbing the inside of the mouth), and in some cases urine or stool. The samples are sent to the lab for testing, and once the results are ready, which may take a few weeks, your genetic counsellor will share the results with you.

Understanding the Results of Genetic Testing for Cancer Risk

There are three possible results for your genetic testing: positive, negative, or variant of uncertain significance.

Receiving a positive result means that you have a mutated gene that can increase your risk of developing a certain type of cancer. It does not, however, mean that you have cancer. Once you receive this result, you can discuss with your healthcare professional the steps you can take to help lower your risk of these cancers or screening tests that you can undergo to catch them at an early stage.

For those with cancer who undergo genetic testing and receive a positive test, the mutated gene may be behind the development of the cancer. Receiving this positive result can also be informative about cancer treatment pathways for certain cancers.

If the test result is negative, it means that no mutation was found in the genes that were tested. However, this does not mean that your risk of cancer is zero; it just means that you have the same average risk as most people. Additionally, genetic testing does not look for all possible gene mutations, so you may still have a mutation of another gene. Knowing this, it is still important to undergo regular screening for cancer as suggested by healthcare professionals.

If the test comes back as a variant of uncertain significance (VUS), it means that the genetic testing detected a change in a gene, but it is unknown if this change affects cancer risk. In most cases, VUSs are later found to be benign, but your genetic counsellor can help you work through this finding and what it means for you.

Why Receive Genetic Testing?

When it comes to the fight against cancer, knowledge is power. This includes knowledge of whether or not you are at a higher risk of developing cancer.

Knowing that you carry a genetic mutation that increases cancer risk can help prompt early screening tests to detect cancer early. It can also act as the driver for lowering cancer risk by making lifestyle changes to reduce cancer risk, taking medicines to help reduce risk, or undergoing preventive surgery to try and keep cancer from setting in.

Cancer is a significant health concern in Hong Kong but genetic testing can provide you with more information about your health.

References

N. Jewel Samadder, Riegert-Johnson, D., Boardman, L., Rhodes, D., Wick, M., Okuno, S., Kunze, K.L., Golafshar, M., Pedro, Mountjoy, L., Ertz-Archambault, N., Patel, N., Rodriguez, E.A., Lizaola-Mayo, B., Lehrer, M., Thorpe, C.S., Yu, N.Y., Esplin, E.D., Nussbaum, R.L. and Sharp, R.R. (2020). Comparison of Universal Genetic Testing vs Guideline-Directed Targeted Testing for Patients With Hereditary Cancer Syndrome. JAMA Oncology, 7(2), pp.230–230. doi:https://doi.org/10.1001/jamaoncol.2020.6252.
Crowley, F., Gandhi, S., Rudshteyn, M., Mantej Sehmbhi and Cohen, D.J. (2023). Adherence to NCCN Genetic Testing Guidelines in Pancreatic Cancer and Impact on Treatment. The Oncologist, 28(6), pp.486–493. doi:https://doi.org/10.1093/oncolo/oyad044.
Cancers May be Caused by Inherited Mutations. (2025). Facing Our Risk of Cancer Empowered. Available at: https://www.facingourrisk.org/info/hereditary-cancer-and-genetic-testing/hereditary-cancer/types-of-hereditary-cancers.
Hong Kong Genome Institute -. (2021). Hereditary Cancer - Hong Kong Genome Institute. Available at: https://hkgp.org/en/discover-genomics/hereditary-cancer/.