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Definition

The genes in our cells play important roles. They affect hair and eye color and other traits passed on from parent to child. Genes also tell cells to make proteins to help the body function.

Cancer occurs when cells begin to act abnormally. Our body has genes that prevent rapid cell growth and tumors from forming. Changes in genes (mutations) may allow cells to divide rapidly and stay active. This leads to cancer growth and tumors. Gene mutations may be the result of damage to the body or something passed down in the genes in your family.

Genetic testing can help you find out if you have a genetic mutation that may lead to cancer or that may affect other members in your family. Learn about which cancers have testing available, what the results mean, and other things to consider before you get tested.

Which Cancers May Be Genetic

Today, we know specific gene mutations that can cause over 50 cancers, and the knowledge is growing.

A single gene mutation may be tied to different types of cancer, not just one.

• For example, mutations in the BRCA1 and BRCA2 genes are linked with breast cancer, ovarian cancer, and several other cancers, in men and women. Around one half of women who inherit BRCA1 or BRCA2 genetic mutations will develop breast cancer by the age of 70.
• Polyps or growths on the lining of the colon or rectum may be linked to cancer and at times may be part of an inherited disorder.

Genetic mutations are linked with some cases of the following cancers:

• Breast (male and female)
• Ovarian
• Prostate
• Pancreatic
• Bone
• Leukemia
• Adrenal gland
• Thyroid
• Endometrial
• Colorectal
• Small intestine
• Renal pelvis
• Liver or biliary tract
• Stomach
• Brain
• Eye
• Melanoma
• Parathyroid
• Pituitary gland
• Kidney

Signs that cancer may have a genetic cause include:

• Cancer that is diagnosed at a younger than normal age
• Several types of cancers in the same person
• Cancer that develops in both paired organs, such as both breasts or kidneys
• Several blood relatives who have the same type of cancer
• Rare cases of a specific type of cancer, such as breast cancer in a man
• Birth defects that are linked to certain inherited cancers
• Being part of a racial or ethnic group with a high risk for certain cancers along with one or more of the above

About Genetic Testing

You may first have an assessment to determine your level of risk. A genetic counselor will order the test after talking with you about your health and needs. Genetic counselors are trained to inform you without trying to guide your decision. That way you can decide whether testing is right for you.

How testing works:

• Blood, saliva, skin cells, or amniotic fluid (around a growing fetus) can be used for testing.
• Samples are sent to a lab that specializes in genetic testing. It can take several weeks to get the results.
• Once you get the results, you will talk with the genetic counselor about what they may mean for you.

While you may be able to order testing on your own, it is a good idea to work with a genetic counselor. They can help you understand the benefits and limitations of your results, and possible actions. Also, they can help you understand what it may mean for family members, and counsel them as well.

You will need to sign an informed consent form before testing.

What Genetic Testing Can Tell you

Testing may be able to tell you if you have a genetic mutation that is linked with a group of cancers. A positive result means you have an increased risk of getting those cancers.

However, a positive result does not mean you will develop the cancer. Genes are complex. The same gene may affect one person differently from another.

A negative result does not mean you will never get cancer. You may not be at risk due to your genes, but you could still develop cancer from a different cause.

Your results may not be as simple as positive and negative. The test may discover a mutation in a gene that experts have not identified as a cancer risk at this point. You may also have a strong family history of a certain cancer and a negative result for a gene mutation. Your genetic counselor will explain these types of results.

There also may be other gene mutations not yet identified. You can only be tested for the genetic mutations we know about today. Work continues on making genetic testing more informative and accurate.

Who Should Consider Testing

Deciding whether to have genetic testing is a personal decision. You may want to consider genetic testing if:

• You have close relatives (mother, father, sisters, brothers, children) who have had the same type of cancer.
• People in your family have had cancer linked to a gene mutation, such as breast or ovarian cancer.
• Your family members had cancer at a younger age than normal for that type of cancer.
• You have had cancer screening results that may point to genetic causes.
• Family members have had genetic tests and had a positive result.

Testing can be done in adults, children, and even in a growing fetus and embryo.

Possible Benefits of Testing

The information you get from a genetic test may help guide your health decisions and lifestyle choices. There are certain benefits of knowing if you carry a gene mutation. You may be able to lower your risk for cancer or prevent it by:

• Having surgery.
• Changing your lifestyle.
• Starting cancer screenings. This can help you catch cancer early, when it can be treated more easily.

If you already have cancer, testing may help guide targeted treatment.

Questions to Consider Before Testing

If you are thinking about testing, here are some questions you may want to ask your health care provider or genetic counselor:

• Is genetic testing right for me?
• What testing will be done? How accurate is the testing?
• Will the results help me?
• How might the answers affect me emotionally?
• What is the risk of passing a mutation onto my children?
• How will the information affect my relatives and relationships?
• Is the information private?
• Who will have access to the information?
• Who will pay for the testing (which can cost thousands of dollars)?

Before getting tested, be sure you understand the process and what the results may mean for you and your family.

When to Call the Doctor

Contact your provider if you:

• Are considering genetic testing
• Would like to discuss the results of genetic testing

References

American Cancer Society website. Understanding genetic testing for cancer risk. www.cancer.org/cancer/cancer-causes/genetics/understanding-genetic-testing-for-cancer.html. Updated September 22, 2022. Accessed October 28, 2022.

National Cancer Institute website. BRCA mutations: cancer risk and genetic testing. www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet. Updated November 19, 2020. Accessed October 28, 2022.

National Cancer Institute website. Genetic testing for inherited cancer susceptibility syndromes. www.cancer.gov/about-cancer/causes-prevention/genetics/genetic-testing-fact-sheet. Updated March 15, 2019. Accessed October 28, 2022.

Walsh MF, Cadoo K, Salo-Mullen EE, Dubard-GaultM, Stadler ZK, Offit K. Genetic factors: hereditary cancer predisposition syndromes. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 13.

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