How Your Genes Affect Your Cancer Risk

July 12, 2016 Sandra Brown, MS, LCGC

how-genes-affect-cancer-riskResearch shows there are more than 100 different types of cancer, making it the second leading cause of death in the United States. Although not all cancers are hereditary, genetic testing has become an increasingly popular topic of interest among patients and cancer experts.

According to the National Cancer Institute, cancer is a genetic disease caused by mutations or changes to genes that occur over a person’s lifetime. These changes affect the way cells behave, grow and divide, and can result in the development of a tumor. About 5 to 10 percent of all cancers are due to an inherited mutation that significantly increases the likelihood of developing cancer.

Sandra Brown, MS, LCGC, genetic counselor and manager of the Cancer Genetics Program at The Center for Cancer Prevention and Treatment at St. Joseph Hospital, Orange, explained that some people have an increased risk of developing specific types of cancer due to inherited mutations in specific genes that are associated with different hereditary cancer syndromes.

“For instance, inherited mutations within the Lynch Syndrome genes primarily cause increased risks of developing colon, uterine and ovarian cancers,” said Brown.

In fact, inherited genetic mutations account for more than 50 types of hereditary cancer syndromes. While this number may seem alarming, it is important to understand most people do not carry inherited genetic mutations and hereditary cancer syndromes
are relatively rare.

“If you have a strong family history of cancer and a genetic test confirms that you have inherited a mutation, it does not mean that you will develop cancer. However, it does mean you have inherited an increased risk of developing cancer in your lifetime. Whether your test results are positive or negative, we can assess your cancer risks and inform you of recommended options to help prevent cancer,” said Forum Shah, MS, LCGC, genetic counselor at The Center for Cancer Prevention and Treatment.


A number of factors are considered before genetic counseling is recommended:

  • Cancer occurring younger than expected (typically before age 50)
  • More than one type of cancer in the same person
  • Two or more family members with the same type or related types of cancer
  • A rare or unusual type of cancer

Patients are encouraged to speak with their primary care physician to determine if genetic counseling is appropriate based on their personal and/or family history of cancer.

“Genetic counseling provides patients with the information and support to help them manage their cancer risks. While a positive genetic test result can be daunting for many patients, that information along with genetic counseling can help patients feel reassured and empowered to make informed decisions about their medical care,” said Lisa Mohler, MS, LCGC, genetic counselor at The Center for Cancer Prevention and Treatment.


Genetic test results also have implications for family members. For example, if a patient has been diagnosed with breast cancer and tests positive for a mutation within the BRCA1 gene, then the patient’s children have a 50 percent chance of carrying the same mutation. The patient’s close family members may also carry the same gene mutation.

“The goal of genetic counseling is to help patients interpret their family history, discuss the option of genetic testing, clarify the risk of developing cancer and determine the best management recommendations to help prevent cancer. Genetic counselors also help patients recognize how their results could impact their family members and how they can effectively share this information with their relatives,” Brown said.

For more information, visit or call (714) 734-6229. 

This information is not intended as a substitute for professional medical care. Always follow your health care professional's instructions.


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