Up to 20% of epithelial ovarian cancers are thought to be the result of inheriting a faulty gene from either your mother’s or father’s side of the family.
Many women who have ovarian cancer or who have a relative with ovarian cancer want to find out if the cancer may be hereditary.
What are genes?
Genes are made up of DNA. They act as ‘chemical instructions’ that tell our body’s cells what to do. Genes determine things such as what colour hair and eyes we have and how tall we are. Genes also provide the recipe for building all the chemical substances in our bodies and allow the cells to function normally. Humans have between 20,000 to 25,000 pairs of genes in every cell of their bodies. One copy of each pair of genes is inherited from each of our parents. Sometimes changes can occur in genes that may stop the gene from working as it should. These changes are often called a ‘faulty gene’ or ‘mutation’. In some cases, these faulty genes can lead to disease.
Ovarian cancer in the family:
Most women diagnosed with ovarian cancer do not have a history of ovarian cancer in their family. However, some women’s family history of ovarian cancer can increase their risk of developing the disease. You may have a family history by chance or because you have inherited a faulty gene that increases your risk of developing cancer. You are considered to have a strong family history of cancer if you have two or more close relatives on the same side of the family (father’s or mother’s relatives) who have or had cancer and one of the following applies:
- The family members have all had ovarian cancer or different cancers (e.g. bowel or breast) that can be caused by the same faulty gene. The cancers were diagnosed when the relatives were younger than age 50;
- You have a family member who has had genetic testing confirming they have a faulty gene;
- You have Ashkenazi Jewish ancestry (who have a higher incidence of BRCA mutations than the general population); or
- Your own cancer was diagnosed at an early age, or you have had more than one type of cancer.
Inheriting an ovarian cancer gene:
Ovarian cancer caused by inheriting a faulty gene is called ‘hereditary cancer’. Having a personal or family history of ovarian, breast, colon or endometrial cancer may mean you have inherited an increased risk of developing ovarian cancer.
Generally, the more relatives from the same side of the family who have had these related cancers, the greater your risk of having a hereditary cancer. However, it is still possible to inherit a faulty gene without having a family history of these cancers.
Inheriting a faulty BRCA1 or BRCA2 gene accounts for most cases of hereditary ovarian cancer. These genes are named for their connection to breast cancer (BReast CAncer genes 1 and 2) but can also be associated with other cancers, including cancer of the fallopian tube, peritoneum, prostate, pancreas and breast cancer in men.
The BRCA1 and BRCA2 genes normally help to prevent cancer, but when a woman inherits a faulty version of either gene, she is less protected against cancer. Women who inherit a faulty BRCA1 gene have about a 44% risk of developing ovarian cancer, while women who inherit a faulty BRCA2 gene have approximately a 18% risk of developing ovarian cancer up to the age of 80. This compares to less than 2% risk for women in the general population.
Many women who have a faulty BRCA1 or BRCA2 gene do not have a known family history of ovarian or breast cancer. This can happen for many reasons including:
- Other family members may have inherited a faulty gene but not have developed ovarian or breast cancer;
- There may be few females in a family, making it difficult to see a pattern of family history; and/or
- There may be little know about the family history (eg. a women is adopted)
Although rare, inheriting faulty genes other than BRCA1 and BRCA2 can also increase your risk of developing ovarian cancer. Some of the other genes known to increase the risk of developing ovarian cancer include:
- Lynch syndrome (also known as hereditary nonpolyposis colorectal cancer syndrome (HNPCC)) is a bowel cancer predisposition syndrome linked to faults in the genes MLH1, MSH2, MSH6 and PMS2. Women who inherit a faulty copy of one of these genes have up to a 15% risk of developing ovarian cancer, however, the risk varies depending on the specific faulty gene inherited.
- RAD51C and RAD51D faulty genes (very rare).
There are also other rare genetic links to ovarian cancer, and ongoing research may uncover genetic links not currently known. Inheriting one of these gene faults increases a person’s risk of developing ovarian cancer but doesn’t mean that they will develop ovarian cancer.
Guide to genetic testing and hereditary ovarian cancer
Learn more by downloading our Ovarian Cancer Australia Genetic Testing Booklet