As science has advanced, so has our ability to understand, and predict, our own health risks. Genetic testing plays a large role in this prediction model. Genetic testing looks for specific inherited changes (mutations) in a person’s chromosomes, genes or proteins. Mutations that are harmful may increase a person’s chance of developing cancer. Inherited mutations are thought to play a role in about 5 to 10 percent of all cancers. In this article we explore genetic testing to assess cancer risk.
Does inheriting the gene mean you’ll get cancer?
Genetic testing can confirm whether an individual has a certain defective gene. However, having the inherited defective gene does not assure you will get cancer. Inherited genetic mutations can increase a person’s risk of developing cancer, but there are multiple factors that influence whether a person will develop cancer, including variations in how the gene is inherited.
Autosomal dominant inheritance – a person has a single altered copy of the gene. This is enough to increase a person’s chances of developing cancer.
Autosomal recessive inheritance – a person has an increased risk of cancer only if he or she inherits a mutant copy of the gene from each parent.
X-linked recessive inheritance – a female with a recessive cancer-predisposing mutation on one of her X chromosomes and a normal copy of the gene on her other X chromosome is a carrier but will not have an increased risk of cancer. Her sons, however, will have only the altered copy of the gene and will therefore have an increased risk of cancer.
We discussed the 10 most common inherited cancers, the defective gene and how to manage risk in a series we did in 2017. These include colorectal, breast, kidney, melanoma, ovarian, prostate, pancreatic, stomach and thyroid cancers
Why I tested – I didn’t want to be a ticking time bomb
Jenny Field has a lot of cancer on her paternal side — an aunt and second cousin had breast cancer, her grandfather prostate, lung and brain. So it was recommended that their entire family get genetic testing done. Jenny’s test – and the tests of three other members of her family — came back positive for the BRCA2 breast cancer mutation. Her lifetime risk of getting an inherited cancer was assessed at 86%. Her choices, as she saw it, were to alternate MRI and mammography screening every 6 months or to be proactive and have surgery. Jenny chose a prophylactic double mastectomy and a hysterectomy. She made this choice in lieu of a lifetime of anxiety and worry over if and when she would get breast and ovarian cancer, two cancers associated with the BRCA2 gene. The more knowledge Jenny had, the more power she had to manage her health and take control of her future.
Who should get tested?
Genetic testing to assess cancer risk isn’t for everyone. Experts and the National Cancer Institute recommend all three of these criteria be met first:
- Personal or family history that suggests an inherited cancer risk condition
- The test results can be adequately interpreted (that is, they can clearly tell whether a specific genetic change is present or absent)
- The results provide information that will help guide future medical care
How can you tell if your family history suggests risk? If one or more of these factors come into play, hereditary risk is indicated:
- Cancer diagnosed at an unusually young age
- Several different types of cancer that have occurred independently in the same person
- Cancer that has developed in both of paired organs, such as both kidneys or both breasts
- Several close blood relatives that have the same type of cancer (for example, a mother and sister with breast cancer)
- Unusual cases of a specific cancer type (for example, breast cancer in a man)
- The presence of birth defects, such as certain noncancerous (benign) skin growths or skeletal abnormalities, that are known to be associated with inherited cancer syndromes
- Being a member of a racial/ethnic group known to have an increased risk of having a hereditary cancer and having one or more of the above features, as well
Why I tested —to offer my sister peace of mind
Juli J.’s mom was diagnosed with breast cancer when she was 55. She underwent a left-side mastectomy and was deemed cancer-free, until she developed cancer in her right breast 15 years later. Juli’s aunt also had breast cancer, diagnosed in her 30s. Five years after her mother’s second reoccurrence, Juli decided to get tested for the breast cancer gene mutation BRCA1 and BRCA2. Neither of her sisters wanted to test. “I don’t have kids,” Juli explains. “I did it more for my sister and niece. I thought if I was negative, it may offer them some peace of mind.” Juli was negative.
In Part 2 of this series, we consider the decision-making process for getting a genetic test to assess cancer risk and how to assess results.
If you are facing a cancer diagnosis, exceptional treatment is available in Carson City, South Lake Tahoe, Fallon or Gardnerville, through Sierra Nevada Cancer Center. Same week or sooner appointments are available by calling 775-883-3336.
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