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Hereditary Breast & Ovarian Cancer: What you need to know

What is hereditary breast and ovarian cancer?

10-15% of ovarian cancer and 5-10% of breast cancer are hereditary.

To kick off October as Breast Cancer Awareness Month, we’re going to dive into a lesser-discussed topic that bridges the gap between ovarian and breast cancer: hereditary breast and ovarian cancer (HBOC). Many people have a general sense that people with family history of cancer have a higher cancer risk, but do you know why that is?

The answer lies in genetic mutations — changes to the sequence or content of genes in our DNA. We know that a number of genes, including BRCA1 and BRCA2, can have mutations associated with a higher risk for breast and ovarian cancer. While BRCA1 and BRCA2 are the most well-known breast and ovarian cancer susceptibility genes, they are not the only ones.

These genetic mutations can be passed down from one generation to the next, increasing the risk of cancer within a family as well as increasing one’s personal risk of breast, ovarian or other cancers. We know that BRCA1 carriers have a 44% chance of developing ovarian cancer, compared to 1.3% of the general population. BRCA2 carriers have a 17% chance of developing ovarian cancer, compared to 1.3% of the general population. And BRCA mutation carriers have a 50-85% chance of developing breast cancer, compared to 11% of the general population.

So what does this mean for you?

How do I know if I carry a genetic mutation associated with breast and ovarian cancer?

0.2% to 0.3% of the general population carries a BRCA mutation.

A genetic test can indicate whether or not you carry a known genetic mutation associated with breast or ovarian cancer. Most genetic testing companies now look at the sequence of all DNA bases for BRCA1, BRCA2, and many other genes with mutations associated with breast and ovarian cancer.

Should I consider genetic testing?

Consider the below criteria to determine whether you have a higher likelihood of HBOC and talk to your trusted health care provider to see if genetic counseling is right for you. All indicators have to do with family medical history, so you’ll need to talk with your family to learn your family health history if you haven’t already.

To simplify the process, you can download our handy family history worksheet.

In your family research, take special note of the following:

  1. General history of breast/ovarian cancer, especially if cases are between generationally close relatives, and/or if breast cancer was diagnosed before age 50.
  2. Family member with a young diagnosis of breast cancer. A diagnosis before age 35 is telling of a possible genetic mutation.
  3. Both breast and ovarian cancers in a single family member. The two may be genetically linked and can point towards a genetic predisposition.
  4. Ashkenazi Jewish heritage. 1 in 40 people in the Ashkenazic Jewish population carry a BRCA mutation.
  5. Family member with primary cancer in each breast, especially before age 50.
  6. Family history of male breast cancer. It’s rare, but it happens! Men with a BRCA2 mutation have a 6% chance of developing breast cancer, as opposed to less than 1% in men without the gene mutation.
  7. Family member with identified BRCA1 or BRCA2 mutation.
  8. Family member with pancreatic cancer.
  9. Family member with prostate cancer before age 55 or two or more family members with prostate cancer

What you need to know about genetic counseling

Think genetic counseling might be right for you? Here’s what to expect when scheduling an appointment with a genetic counselor:

  • You’ll review a comprehensive analysis of your family’s medical history.
  • You and your genetic counselor will assess your risk for breast, ovarian and other cancers.
  • Your genetic counselor will provide education on the potential benefits, harms, limitations, and outcomes of genetic testing and sharing the results with family
  • If you move forward with a genetic test, your genetic counselor can help interpret the results and discuss management of screening or risk-reduction options with breast, ovarian, and other cancer specialists

If you’re ready to start looking or want to learn more, you can find a genetic counselor at https://www.nsgc.org.

Knowledge is power – and we can be powerful together

Your greatest asset in the fight against breast/ovarian cancer is knowledge – of both the scientific facts and your own biology. This includes being educated on HBOC and the intrinsic link between breast and ovarian cancer. If caught and treated early, ovarian cancer patients’ 5-year survival rate is 92%. However, only 20% of cases are actually diagnosed this early. We need to change this. Please share this article with friends and family members. Keep up with us on social media for helpful tips, inclusive events, and up-to-date facts.

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Higher Risk in the Ashkenazi Jewish Population

In the general population, around 1 in 400 people carry a BRCA1 or BRCA2 mutation. People of Ashkenazi Jewish ancestry have a 1 in 40 chance of carrying a BRCA mutation, making them 10 times as likely to carry a BRCA mutation as someone in the general population. Whether you’re a man or a woman, if you have a BRCA mutation then there is a 50% chance of passing the mutation on to your children, whether they are boys or girls. It’s important to note that these mutations significantly increase risk, but are not a guarantee a person will get cancer.

Why is the Ashkenazi Jewish population at higher risk?

Over 90% of the BRCA mutations found in the Jewish community are one of three “founder mutations”. A founder mutation is a specific gene mutation in a population that was founded by a small group of ancestors that were geographically or culturally isolated. Because the population was isolated, the rate of founder mutations in descendants is much higher than it would be if the population were larger and co-mingling with more genetically diverse populations. A large expansion in the population caused the current high frequency of the mutations in the Ashkenazi Jewish population. If you are of Ashkenazi Jewish ancestry, the chance of carrying a BRCA gene mutation compared to the general population is increased tenfold. BRCA mutations can be passed down from either your mother’s or father’s side, and may be associated with any of the following cancers:
  • Breast cancer
  • Ovarian cancer, fallopian tube, peritoneal cancer
  • Male breast cancer
  • Prostate cancer
  • Pancreatic cancer
  • Colon Cancer

Ready to take action? Knowledge is power. Take this short quiz to be proactive about your health.

Genes 101

Our bodies are made of many tiny building blocks called cells. Our cells contain a copy of our genome – all of the DNA genetic code we inherited from our parents. Our genome is organized into 46 chromosomes, 23 inherited from mom and 23 from dad. Each chromosome has hundreds or thousands of genes. Each gene has the instructions to make a protein that may control the structure or function of cells, can determine many things including how tall we are or the color of our eyes. Genes also contain instructions for many things inside of us that we cannot see, such as how our bones are formed or how our heart works. Each gene is made up of molecules called nucleic acids (A, T, C, and G). The specific sequence of the nucleic acids holds the instructions that control all the components and their functions in cells.

If the DNA sequence is changed, like a spelling mistake, the instructions may not make sense. The technical term for this change is “mutation,” meaning there is a change to the usual genetic code that may change the instructions stored in the gene. A mutation in a gene that repairs DNA damage or controls cell growth can increase the risk of developing cancer.

Sporadic vs Hereditary Cancers:

Ovarian and breast cancer can be either sporadic or hereditary. Sporadic cancers make up the vast majority (85-90%) of ovarian and breast cancers and are not associated with family history of either cancer or inherited cancer-associated mutations. Sporadic cancers arise from genetic mutations acquired in some cells of the body by events part of normal metabolism and environmental factors. This type of cancer can happen to anyone. Most acquired gene mutations are not shared among relatives or passed on to children.

Hereditary (also known as inherited, or familial) cancers are those that occur due to genetic mutations that are inherited from mom or dad. Other blood relatives may also share these same gene mutations. Parents give one copy of each gene to their children. If a parent has a genetic mutation in a gene, each of their children have a 50% chance of inheriting that mutation. Therefore, even in families with hereditary cancer, not all family members inherit the mutation that is causing cancer, and their risk of cancer is similar to the average person in the general population. Individuals who are suspected to have a family history with high incidence of ovarian, breast, and other cancers may be offered genetic testing to try to find the specific genetic mutation that may put them at risk. Importantly, individuals who do not have a known genetic mutation but have high incidence of ovarian, breast, or other cancers in their families are still considered at higher risk for developing those cancers.

Hereditary cancers often occur at an earlier age than the sporadic form of the same cancer, so experts often recommend starting cancer screening at a younger age for individuals at high risk for hereditary cancer. Hereditary cancers can also be more aggressive than the sporadic form of the same cancer. Individuals who have inherited a gene mutation may be at a higher risk for more than one type of cancer.

BRCA 1 and BRCA 2: Most Common hereditary breast and ovarian cancer

The genes that are most commonly involved in hereditary breast and ovarian cancer (HBOC) are BRCA1 and BRCA2. These genes are named for their link to breast (BR) cancer (CA), but they are also linked to ovarian cancer risk as well as other cancers. Both women and men can inherit mutations in these HBOC genes. BRCA1 and BRCA2 are tumor suppressor genes that have a usual role in our body of providing instructions on repairing DNA damage and preventing cancer. When a family has an inherited mutation in BRCA1 or BRCA2, this leads to an increase in cancer risk. Not every man or woman who has inherited a mutation in the BRCA1 or BRCA2 gene will develop cancer, but people who have a mutation do have a significanlty increased chance of developing cancer, particularly cancer of the breasts or ovaries.

While breast and ovarian cancers are the most common cancers diagnosed in people with BRCA1 and BRCA2 mutations, the risk of some other cancers is also increased. Men with BRCA1 and BRCA2 mutations have a higher risk of early-onset prostate cancer than men without mutations in either gene. Other cancers seen at increased rates, particularly in individuals with BRCA2 mutations, include pancreatic cancer and melanoma. Researchers are continuing to find new genes that are involved in hereditary breast and/or ovarian cancer so it is important to follow up with a genetic counselor on a regular basis if hereditary breast and ovarian cancer is likely in your family.

Talk to your family about your health history and take the Assess Your Risk quiz here

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