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Genes are pieces of DNA (deoxyribonucleic acid) inside our cells that tell the cell how to make the proteins the body needs to function. DNA is the genetic “blueprint” in each cell. Genes affect inherited traits passed on from a parent to a child, such as hair color, eye color, and height.
An abnormal change in a gene is called a mutation and certain mutations can cause cells to grow out of control, which can lead to cancer. Only about 5% to 10% of all cancers are thought to be strongly related to an inherited gene mutation.
Most cancers start because of acquired gene mutations that happen during a person’s lifetime. Sometimes these gene changes have an outside cause, such as exposure to sunlight or tobacco. But gene mutations can also be random events that sometimes happen inside a cell, without a clear cause.
Genetic information provides a means of identifying people who have an increased risk of cancer. Sources of genetic information include biologic samples of DNA, information derived from a person’s family history of disease, findings from physical examinations, and medical records.
Who Needs Genetic Testing?
A healthcare provider may recommend counseling for several reasons.
You may be a candidate for genetic testing if you have:
- Several first-degree relatives (parents, siblings, or children) who have or have had cancer
- Multiple relatives with cancer
- Family members who had cancer at a young age
- A family member with a rare cancer, such as male breast cancer
- A physical finding from a different test that could be linked to a hereditary cancer, such as finding many colon polyps during a routine colonoscopy
- A family member who already underwent genetic testing and found a mutation
- A birth defect that’s known to be associated with hereditary cancers syndromes, such as certain noncancerous skin growths that are associated with neurofibromatosis
- Ancestry or ethnicity that’s linked to an increased risk of some inherited cancers, such as Ashkenazi Jewish ancestry (linked to ovarian and breast cancers)
Your provider may also recommend testing if you have already been diagnosed with cancer. This can help them make decisions about your treatment plan.
Most cancer-causing genetic changes are acquired — the result of errors that occur when cells divide or from exposure to substances like cigarette smoke that are known to cause cancer.
Less commonly, cancer can be the result of germline mutations. These are changes that occur in the sperm or egg cells. As a baby grows in the womb, the mutation from their parent’s original sperm or egg cell gets copied into every cell within the baby’s body. When germline mutations cause cancer, it’s called inherited cancer. Inherited cancer only plays a significant role in about 5 to 10% of all cancer cases.
Germline Mutations and Inherited Cancer
Germline mutations are associated with more than 50 hereditary cancer syndromes — disorders that can predispose someone to developing certain cancers.
For example, the TP53 gene is the most commonly mutated gene in all types of cancer. The p53 gene creates a protein called tumor protein p53. This protein plays a key role in controlling cell division and cell death, including keeping cancer cells from growing. Changes to the p53 gene can interfere with that role and allow cancer cells to grow and spread throughout the body.
Changes to this gene can also cause a genetic condition called Li-Fraumeni syndrome — a disorder that can greatly increase the risk of getting certain types of cancer, such as breast cancer and leukemia.
Where Does Genetic Testing Fit In?
Genetic testing searches for specific changes in your genes, proteins, or chromosomes. Testing can be used to assess your risk of developing certain conditions, from heart disease to epilepsy to cancer. It can also help your provider choose the best treatment plan.
When it comes to cancer, there are several uses for genetic testing, including:
- Estimating your likelihood of developing certain types of cancer at some point in your life
- Determining if you have genes that you could pass onto your child which could increase their risk of having cancer
- Providing information that your provider can use to help you manage your risk or guide your treatment
And What About Genetic Counseling?
Genetic counseling provides you with information about your genes and how they could affect the risk of developing cancer in you or your family. A genetic counselor will help you understand your risks, determine if you need genetic testing, and work with you on the next steps.
Getting Your Results
There are three possible results of genetic testing:
- Positive, which means the test found a gene change that is known to increase cancer risk.
- Negative, which means the test did not find a change in any of the particular genes studied in your test.
- Inconclusive or a variant of uncertain significance, which means that the test did find a change in at least one gene, but it’s not entirely clear if the change could increase your risk for cancer.
Positive Results: The Next Steps
There’s no doubt about it that learning that you have an increased risk of developing cancer can be overwhelming and scary.
But take a deep breath — there are also several upsides of receiving a positive result:
- You can learn about risk factors that you can control — such as quitting smoking or maintaining a healthy weight — and get a head-start on taking preventive measures to control those risk factors.
- Cancer is typically easiest to treat when it’s found in its early stages. But many times, cancer doesn’t cause symptoms until it’s more advanced. Learning that you’re at risk can help you be more proactive about getting regular screenings, like mammograms or colonoscopies, so you can find cancer early and have a better chance of treating it successfully.
- Since genes are passed down from one generation to the next, learning about your risk provides an opportunity for your family members to learn more about their risks, too.
- You can start to mentally prepare yourself for a more rigorous health journey ahead, such as more extensive testing.
And remember — genes change frequently, and the changes aren’t always harmful. Finding out that you’re at higher risk for developing cancer doesn’t mean it’s a guarantee. While it’s important to get a move on taking precautions to reduce your risk, you don’t need to panic.
Instead, start working with your provider to learn what you can do. You don’t need to tackle this alone.
Negative or Inconclusive Results: The Next Steps
If your results are negative or inconclusive, your provider may or may not recommend additional testing.
Just remember that while it can be a relief to not have a positive result, that doesn’t mean you will never be at risk of getting cancer. Genes can change and start to cause cancer at any point in your life, so it’s important to still take steps to reduce your risk. These steps include:
- Staying at a healthy weight
- Getting regular physical activity
- Quitting smoking
- Limiting or stopping alcohol use
- Using sunscreen
- Getting any recommended screenings (like mammograms or colonoscopies), in order to increase your chance of finding cancer earliest, when it’s easiest to treat
Keep up regular visits with your primary care provider (PCP) to learn more about what you can do to lower your risk of developing cancer. If cancer runs in your family, but you had a negative or inconclusive test result, your PCP may recommend that you still meet with a genetic counselor about the next steps.
Genetic Counseling and Testing at UI Health
At UI Health, the first step is meeting with a genetic counselor to get a personalized assessment and determine whether or not you need genetic testing.
Genetic Counseling & Testing Clinic