Having breast or ovarian cancer in your family can be scary. Learn more about how genes and heredity affect your cancer risk.
It’s common for women to worry about breast cancer. Your anxiety may be even greater if other women in your family have had it.
From 5 percent to 10 percent of breast cancer cases are linked to inherited factors. Some of these women have changes (mutations) in genes known as BRCA-1 or BRCA-2. (BRCA stands for BReast CAncer.) These mutations are more likely to be present in families with many cases of breast and/or ovarian cancer, male family members with breast cancer or breast cancer that occurs at a young age.
This information can help you understand more about genes and how a family history of breast or ovarian cancer may affect your risk.
What are genes?
Genes are the basic unit of inheritance. Each gene contains a different piece of information that tells your cells how to work and grow. Genes determine particular traits, such as hair color, eye color and blood type.
Each person has over 30,000 genes, and most of them are exactly the same from one person to the next. But everyone has some mutations in their genes. Some of these mutations occur within an individual’s lifetime. Others are inherited from one or both parents. Some of these hereditary mutations are related to racial or ethnic background.
How are genes involved with cancer?
Two main types of genes are known to play a role in cancer risk: oncogenes and tumor suppressor genes.
- Oncogenes are a mutated form of normal genes called proto-oncogenes. Proto-oncogenes work like a switch that turns on and off to control cell division. When they mutate into oncogenes, they are turned on all the time. This allows cells to grow out of control, which can lead to cancer.
- Tumor suppressor genes are normal genes that slow cell growth, repair cell damage or cause cells to die if they can’t be repaired. When they are mutated, tumor suppressor genes are turned off. They no longer act as a brake on cell growth so abnormal cells can grow and become cancer.
What are the BRCA genes?
BRCA genes are tumor suppressors that control the growth of breast cells and prevent tumor growth. Mutated BRCA genes allow breast cancer to grow. The BRCA-1 and -2 genes were the first and second genes found to be linked with hereditary breast cancer. They are not the only genes related to hereditary breast cancer, but they seem to be the most common.
BRCA mutations are known to raise cancer risk, but they are rare. More than 90 percent of women who get breast cancer do not have such a mutation.
It’s important to remember that a single gene mutation does not cause a breast tumor to grow. Any kind of cancer involves a complex interaction of inherited and environmental factors. That’s why many women who have BRCA mutations do not get cancer.
How much do BRCA genes increase the risk of cancer?
The risk of getting breast cancer is much higher than normal for women with BRCA mutations.
- An average woman in the U.S. has about a 12 percent chance of getting breast cancer if she lives to the age of 90.
- A woman with a BRCA mutation has about a 60 percent chance of getting breast cancer by age 70.
BRCA mutations also raise the risk of ovarian cancer.
- An average woman’s lifetime risk of getting ovarian cancer is about 1.4 percent.
- A woman with a BRCA mutation has a 15 to 40 percent chance of getting ovarian cancer in her lifetime.
Male breast cancer is rare. Less than 1 percent of all breast cancer cases occur in men. However, men with BRCA mutations have almost a 7 percent chance of getting breast cancer. They may be at increased risk for pancreatic and prostate cancers, too.
I’m worried about my risk for inherited cancer. What can I do?
The first step is to discuss your family history with your doctor. Your doctor may advise that you see a genetic counselor to understand your risk. A genetic test for BRCA mutations may be suggested if you have a strong family history of breast cancer. Only about 2 percent of women fit this category.
In general, a strong family history of breast cancer means having:
- Three or more family members on the same side of the family with breast or ovarian cancer
- Two or more close family members with diagnosis of ovarian cancer or breast cancer at a young age
- One close relative with breast cancer diagnosed at or before age 50 and one with ovarian cancer on the same side of the family
- A close male relative with breast cancer
- Ashkenazi (Eastern European) Jewish ancestry, with a family history of breast or ovarian cancer
Whether or not you have BRCA testing, your doctor can help you understand ways to manage your risk. These may include getting regular breast exams and imaging tests, such as mammograms and MRIs. Women at very high risk may have other options, such as taking a medicine to reduce the risk of getting breast cancer or having their breasts or ovaries removed.