Know your hereditary risk for developing ovarian cancer

Genetic counsellor, Monica Araujo, helps us understand the hereditary risk and factors for developing ovarian cancer.

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What is ovarian cancer?

The ovaries are a pair of female organs that produce hormones and eggs for sexual reproduction. In ovarian cancer, certain cells in the ovary become abnormal and multiply uncontrollably to form a tumour. Unlike normal cells, cancer cells make new cells that aren’t needed by the body and don’t die when they should.

Cancer cells can also grow into other tissues. Over time, a tumour can grow large and invade tissues outside the ovary, such as the fallopian tubes. Cancer cells can also spread to other parts of the body; this process is called metastasis.

Most ovarian cancers start in the layer of tissue surrounding the ovaries, called the epithelium; this is called epithelial ovarian cancer. High-grade serous carcinoma and high-grade endometrioid carcinoma are the two most common types of epithelial ovarian cancer.

Surgery is the recommended first-line treatment whenever possible. This usually involves the removal of both ovaries, both fallopian tubes and the uterus.

Hereditary and somatic cancers

The majority (85-90%) of cancers are considered sporadic and occur for unknown reasons but approximately 10-15% of cancers are inherited (genetic). There are many different cancer syndromes which increases your risk of developing certain cancers. These cancer syndromes are caused by faults (mutations) in genes.

Genes are instructions that tell the body how to perform specific functions. If there is a mutation in one of these genes, the function of that gene may be impaired. There are several genes that have been found to be associated with an increased risk for developing ovarian cancer.

These include the BRCA1 and BRCA2 genes which account for 65-85% of cases. Families with a history of Lynch syndrome and Li-Fraumeni syndrome may also be at risk for developing ovarian cancer and other cancers.

Many of the genes associated with an increased risk of developing ovarian cancer are also associated with an increased risk of developing other types of cancer, such as breast and colon. The type of cancer and associated-risk depends on the gene involved.

Studies have shown that approximately 20% of cases of ovarian cancer occur because of faults in a gene that is known to increase an individual’s risk for ovarian cancer. Genetic faults that are known to be associated with an increased risk are inherited in an autosomal dominant manner. This means that a carrier of a mutation has one functional gene and one faulty gene. The faulty gene can be passed on to their offspring. Children of a mutation carrier have a 50% chance of inheriting their parent’s mutation and a 50% chance of not inheriting it. Mutation carriers have a high risk (but not 100% risk) of developing cancer in their lifetime. 

The difference between somatic and germline mutations

Germline mutations are the genetic faults that an individual is born with. These are mutations that have been inherited and passed down in a family over many generations. Germline mutations are often identified through genetic testing done on blood or saliva (non-tumour cells).

Somatic mutations are genetic faults that occur in the genetic information of the tumour cells only. All tumours have genetic mutations that occur as the tumour develops. Identifying a somatic mutation in tumour cells (usually from biopsy) doesn’t mean that a cancer is hereditary. Somatic mutations can’t be inherited.

In some cases, somatic mutations are able to provide information about the tumour and guide treatment and management. Somatic mutations may also be used to determine whether you are eligible for certain clinical trials.

Genetic testing for ovarian cancer

Genetic testing is recommended for everyone who is diagnosed with ovarian cancer, regardless of their age at diagnosis. Referral to a genetic counsellor is recommended for anyone wanting to pursue genetic testing for hereditary cancer syndromes.

Genetic counsellors are healthcare professionals who have specialised education in both genetics and counselling. We provide risk assessment, education and support to individuals and families affected by, or at risk of, genetic conditions. We interpret genetic testing results and communicate them in an understandable manner and provide psychosocial counselling and serve as patient advocates.

Earlier referral to a genetic counsellor can be beneficial because treatment and management options can be better-informed if a hereditary cancer syndrome is diagnosed.

The outcome of genetic testing may also have important implications for biological relatives. At-risk relatives are then able to access genetic counselling and testing and, if necessary, put appropriate screening and management practices in place to manage their risk going forward.

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