Talking to your family and identifying cancer in your family tree can be a good indicator of your health risks. Download our Family Tree Worksheet here. Be sure to include yourself, children, parents, siblings, aunts, uncles, and grandparents.
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:
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.