Genetics and ovarian cancer
Finding out you have ovarian cancer can come as a huge shock. You may feel a range of intense emotions and have lots of questions. Many people wonder what caused their cancer. They also worry it may be a hereditary cancer that other family members may get. You may also be a family member of someone diagnosed with ovarian cancer, concerned about your own risk of developing a cancer yourself. The information below discusses genetic testing and hereditary ovarian cancer.
What are genes?
Genes carry “chemical instructions” that tell our body’s cells what to do. They control our growth, what we look like and how our body works. Humans have about 25,000 pairs of genes in every cell. One copy of each pair of genes is inherited from each of our parents.
What are gene variants?
Most cancers are caused by genetic changes because of damage to our DNA that happen in a single cell. These are called “somatic” variants and do not run in families. Sometimes changes happen in genes that can stop the gene from working properly. This is known as a ‘mutation’ or ‘pathogenic gene variant’ and in some cases can cause disease.
Ovarian cancer in the family
Most people diagnosed with ovarian cancer do not have a family history of ovarian cancer. However, some people’s family history of ovarian cancer can increase their risk of developing the disease. Some people may have a family history just by chance, or it may be due to a gene variant running in the family that increases the risk of developing cancer. The family history on your father’s side is just as important as the history on your mother’s side. 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 who have had cancer
AND you have a strong family history, meaning two or more close relatives on the same side of the family (father’s or mother’s relatives) who have, or had cancer, diagnosed before they were 50
OR you have a family member who has had genetic testing confirming they have a gene variant that causes cancer
OR you have Ashkenazi Jewish ancestors (who have a higher incidence of BRCA mutations than the general population)
OR your own cancer was diagnosed at a young age, or you have had more than one type of cancer
Inheriting an ovarian cancer gene
Ovarian cancer that is caused by an inherited gene variant is called ‘hereditary cancer’. If you inherit a gene variant that causes hereditary cancer, it means you are at greater risk of developing the types of cancer linked to that gene. The type of cancer that develops is specific to the gene involved—such as breast cancer in a person who has inherited a BRCA1 gene variant. People who carry a gene variant usually inherit it from one of their parents and have a 50% chance of passing it on to each of their children. Having a personal or family history of ovarian, breast, colon or endometrial/uterine 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 gene variant without having a family history of these cancers.
Variants in the BRCA1 or BRCA2 gene are responsible for most cases of hereditary ovarian cancer (up to 20% of ALL ovarian cancers). 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
The BRCA1 and BRCA2 genes normally help to prevent cancer, but when someone inherits a variant that stops either gene from working, they are less protected against cancer. Anyone with ovaries has about a 2% risk of developing ovarian cancer. However, people who inherit a faulty
BRCA1 gene have an increased risk to 40% of developing ovarian cancer in their lifetime.
BRCA2 gene have an increased risk to 18% of developing ovarian cancer in their lifetime.
Many people 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:
Not everyone who carries a gene variant will develop cancer. Other family members may have inherited a gene variant that increases their risk but have not had cancer.
There may be few females in a family, making it difficult to see a pattern of family history
There may be little information known about someone’s family history of cancer or family genetics
Other gene variants
Less common genes that can also increase the risk of developing ovarian cancer include
BRIP1 which causes about a 6% chance of developing ovarian cancer
RAD51C and RAD51D which causes about a 10% chance of developing ovarian cancer, as well as an increased risk of breast cancer
PALB2 which causes about a 5% chance of developing ovarian cancer, as well as an increased risk of breast and pancreatic cancer
Mismatch repair genes MLH1, MSH2, MSH6 and PMS2 cause Lynch Syndrome (also known as hereditary nonpolyposis cancer syndrome HNPCC). Variants in these genes cause up to 15% risk of developing ovarian cancer (depending on the gene), and an increased risk of bowel, uterine and other cancer.
Ongoing research may uncover new genetic links to ovarian cancer that we don’t know about yet.
Tumour (Somatic) genetic testing
Cancer usually develops because of genetic changes in cells which cause abnormal growth. These usually happen after someone is born. They are called somatic variants and occur only in the tumour cells as the cancer develops. Sometimes people will be offered genetic testing for somatic variants in the tissue of their tumour. Finding a somatic mutation may help to target treatment options. Tumour genetic testing can also reveal inherited gene variants.
HRD testing has only recently been funded in Australia. Homologous Recombination Deficiency (HRD) is a characteristic of some cancer cells that makes it harder for them to fix or repair damaged DNA. This mean that these cancer cells can die when treated with PARP inhibitor medicines.
Doctors originally thought that only pathogenic variants (also called mutations) in BRCA genes caused HRD in cancer cells. However, research has now shown that HRD can result from alterations in other genes as well and that up to half of high grade serous ovarian cancers have HRD. If you are eligible for HRD testing, tumour tissue is collected for this test. To find out more about the recent expansion of eligibility on the PBS to include HRD please visit here.
Germline (hereditary) genetic testing
Germline genetic testing is when a blood or saliva sample is tested for gene variants that run in families. If a person inherits a gene variant from one of their parents, they will have that variant in all the cells in their body. Finding a pathogenic (disease-causing) gene variant means that other people in the family (blood relatives) should also have testing. This can help clarify their risk of ovarian and other cancers as well as options to reduce their risk.
What does genetic testing involve?
Your doctor may organise testing themselves or refer you to a Family Cancer Clinic. If you learn that you have an inherited gene variant that has caused your ovarian cancer you should be referred to a Family Cancer Clinic who can discuss the results with you in greater detail. They should review your family history, and discuss:
the specific tests available to you
the accuracy of these tests (i.e. what they will and won’t tell you)
the pros and cons of genetic testing
what a positive or a negative test result may mean for your treatment
what a positive or a negative test result may mean for your family
how genetic test results can affect you emotionally and psychologically
the risk of passing on the gene variant if you have children
If a gene variant is identified, the genetic counsellor may suggest offering genetic testing to other family members. If other family members have inherited the same gene variant, and are at an increased risk of ovarian cancer, they may be referred to a gynaecological oncologist who can advise on ways to reduce their risk. If a hereditary gene variant is not found, it means their risk of developing ovarian and other cancers is likely to be the same as the general population.
However, if your test doesn’t find a hereditary gene variant responsible for your cancer, your family members don’t need to have a genetic test. If you have a strong family history of cancer, even if you don’t carry a gene variant, your close relatives may still need advice about reducing their risk.
Is there a cost associated with genetic testing?
Family cancer centres are often managed through the public hospital system so there is no direct cost to you. There are also several private genetic services in Australia which are likely to cause out-of-pocket expenses, as not all tests are covered by Medicare. You can find a list of public and private services at www.hgsa.org.au.
Medicare funds some genetic testing for people with breast or ovarian cancer who have a high probability of having a gene variant. The test is also funded for relevant family members but testing for other faulty genes may not be covered by Medicare. Genetic tests ordered online are not covered by Medicare, and not all are reliable. It is important to have a healthcare provider involved in any genetic testing to help you understand the implications of the test and ensuing results.
Reducing your risk
Although there is no effective screening test for ovarian cancer, there are options to reduce your risk. There may be several options to consider, including:
regular screening for other cancers
A specialist doctor or clinic can discuss the best approach with you based on your general health, your family history, and your test results. They can also refer you to the most appropriate specialists for cancer screening and/or risk-reducing surgery. You can learn more about risk reducing surgery by reading Considering surgery to reduce your risk of ovarian cancer (thewomens.org.au)
Some people are concerned about the impact that genetic test results may have on their current or future insurance policies. In Australia, health insurance is not based on a risk assessment of your health and therefore genetic testing should not affect public or private health insurance policies. New information should not affect any current policies you have. Having a personal and/or family history of cancer can affect other types of insurance, regardless of whether you have had genetic testing or not. For up-to-date information about other types of insurance and genetic testing please see Life insurance products and genetic testing in Australia (genetics.edu.au). You may also like to speak with an insurance broker for individual advice.
Impact on ovarian cancer treatment
Genetic test results can impact upon treatment options for people diagnosed with ovarian cancer. It may make someone eligible to participate in certain clinical trials, and for those people who have an identified genetic mutation such as BRCA or HRD, they may be offered PARP (poly ADPribose polymerase) inhibitor drugs for maintenance treatment to help prevent a recurrence.
PARP is a protein in our body that helps damaged cells repair themselves. Cancer cells with altered BRCA genes depend on PARP to keep their DNA repair mechanisms working. PARP inhibitors stop PARP from working, meaning the cancer cells cannot mend themselves. Some PARP inhibitors have been approved for use in Australia in specific circumstances for people with ovarian cancer linked to BRCA1 and BRCA2 gene variants. Speak with your oncology team about the latest clinical trials and treatments to determine whether you are eligible for PARP inhibitors.
If you have been diagnosed with ovarian cancer and have not been offered genetic testing, you should discuss this with your specialist.
Webinar: Genetics and Ovarian Cancer
This webinar provides information about genetics and ovarian cancer including the importance of genetic testing and the difference between germline and somatic testing. Clinical implications of genetic testing are discussed, both in terms of treatment and the implications for personal and family cancer risks.
Cancer Council Australia has a section on hereditary cancers with useful resources and links Cancer information and support | Cancer Council
For more information on specific gene variants, visit https://www.eviq.org.au/
To speak with an ovarian cancer nurse for more information on genetics and ovarian cancer, phone our helpline on 1300 660 334 (Monday-Friday during business hours AET) or email email@example.com