Genetic Testing for Cancer

In the fight against cancer, understanding your individual risk of developing cancer is key. If you can understand your risk earlier, you can make informed decisions about how to manage future risks of cancer. One way to better know your risk for cancer is through genetic testing.  Our guest post for this month is from Dr. Susan Miesfeldt – director of the Maine Medical Center’s Cancer Risk and Prevention Clinic.  She’s here to fill us in about what genetic testing is and how to know if it’s right for you.

What is genetic testing?

Cancer is triggered by mutations (changes) in the genes of a cell that result in uncontrolled, abnormal cell growth.  Most often this is caused by exposure to cancer-causing agents (like tobacco), lifestyle (like obesity, poor diet and lack of exercise), or chance.  Occasionally, it is caused by gene mutations that are passed down from one generation to the next.  You may hear people say certain conditions “run in the family.” In some cases, cancer can run in the family too. Genes are what affect inherited traits passed on from a parent to a child, such as hair color, eye color, and height. They also affect whether a person is likely to develop certain diseases, such as cancer. Genetic testing is one way to help you understand if you are at a higher risk for developing certain cancers.

Who should consider genetic testing?

Cancer genetic testing is not for everyone.  Only about 10-15% of cancers are related to inherited factors.  There are certain personal and family history features that impact whether or not you will test positive for a mutation (change) in an inherited cancer gene. If you are aware of any of these risk factors, you may want to talk to your doctor about genetic testing:

  1. You and/or several first degree relatives (mother, father, sisters, brothers, children) have or have had cancer, especially if it is all the same type of cancer.
  2. You or family members had cancer at a younger age than normal for that type of cancer (for example, breast or colon cancer diagnosed before the age of 50).
  3. You or close relatives have or have had rare cancers that are linked to inherited cancer syndromes (such as Lynch Syndrome).
  4. You or family members have had more than one type of cancer or more than one cancer of a given type (for example, two separate breast cancers).
  5. A known genetic mutation in one or more family members who have already had genetic testing

Weighing the pros and cons of genetic testing

There are many benefits of genetic testing for both you and for your family.

For you:

  • Test results may make you feel better and less worried.
  • Test results may give you more information about your cancer risks and help your doctor plan your care. If your test results show that you have a mutation, you can choose which steps to take to find cancers earlier or to lower your risks of cancer.

For others:

  • Test results may help a family understand its cancer history.
  • These results may give more information to your family members about their cancer risks and help their doctors plan for their care.
  • You may learn about the chances your children, or other relatives have for a mutation.

There are also negative outcomes you need to consider before you decide to move ahead with testing.

For you:

  • Test results could upset you and make you feel worried or depressed.
  • You may feel pressure to make hard medical decisions.
  • A positive result may make you worry about others in your family.

For others:

  • A positive result may cause strain in your relationships with other family members.
  • A negative result may cause stress and guilt in a family if there are other family members with positive results.

What will the test results mean?

Personal and family medical history plays a large role in understanding your genetic test results. The advice of your doctor is also important in understanding what your genetic test results mean for your future health. A genetic test can come back with these results: positive, negative, or uncertain.


A mutation (change) was found. This result means that you have a higher risk for cancer.


No mutation (change) was found. This result means that you may still have a higher risk for cancer based on your personal and family medical history. For example, there might still be a chance that you have a mutation that you were not tested for or that the test could not pick up.


A genetic change was found but it is not clear whether the change is related to a higher risk of cancer. This result means that you may still have a higher risk for cancer based on your personal and family medical history.

It is important to remember that genetic testing is a very personal choice. If you need help figuring out if it is right for you, your doctor can refer you to a genetic counselor. Genetic counselling is a great way to talk to a trained specialist about your options. Visit the Cancer Risk and Prevention Clinic website to learn more


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