What causes ovarian cancer?

We don’t know exactly what causes ovarian cancer, but we do know that a family history or genetic mutation can increase a woman’s ovarian cancer risk.

Gene mutations

About 15% of epithelial ovarian cancers are due to inheriting a faulty gene from either your mother’s or father’s side of the family. Ovarian cancer triggered by inheriting a faulty gene mutation is called ‘hereditary cancer’. BRCA1 or BRCA2 genes are responsible for most hereditary cases. BRCA 1 (BReast CAncer gene 1) and BRCA 2 (BReast CAncer gene 2) are named for their connection to breast cancer and can also be linked with other cancers, including cancer of the fallopian tube, peritoneum, pancreas, prostate, and breast cancer in men. 

DNA strandOvarian Cancer Australia reports women who inherit a faulty BRCA1 gene have approximately a 44% risk of developing ovarian cancer, while women who inherit a faulty BRCA2 gene have an approximately 18% risk; in the general population the risk is about 2%. 

If your parent carries the BRCA 1 or BRCA 2 mutation there is a 50% chance (or 1 in 2 chance) of you inheriting the mutation.

Although less common, some other genes that increase the risk of developing ovarian cancer include: 

  • Lynch syndrome is a cancer predisposition syndrome linked to faults in the genes MLH1, MSH2, MSH6 and PMS2. The most common cancer in these women is bowel cancer. Still, women with Lynch Syndrome have up to a 15% risk of developing ovarian cancer, although this depends on the specific faulty gene inherited.  
  • RAD51C and RAD51D faulty genes (uncommon and accounts for only 2% of cases).

In my practice we conduct genetic testing for all ovarian cancer patients with cell types other than mucinous tumours (mucinous tumours are not linked to inherited genes). To do that, we send a sample of the tumour tissue to a lab and request testing. The test result is only a screening test (it’s not confirmatory). If a screening test indicates an abnormality, we organise formal genetic testing, which then requires a blood test. We can refer you and your family to a genetic counsellor should your family members also wish to discuss testing options.

Family history

A family history of cancer means having one or more blood relatives who have been diagnosed with cancer. This could be a grandmother, mother, daughter or sister with ovarian cancer.

The type of cancer those family members had is important. For example, cervical cancer is not inherited, as many other tumour types are also not inherited. However, other tumour types can be inherited and in cancer families they are clustered. For example, families with multiple family members of breast, ovarian or pancreatic cancer should be recognised and tested for BRCA2. Family members with uterine, ovarian and bowel cancer should be tested for Lynch.

The more blood relatives who have had cancer, the more likely the cancer is due to an inherited faulty gene.

Other risk factors that increase the chance of developing ovarian cancer include:

  • Over 50 years. The average age of women diagnosed with ovarian cancer is 64 years.
  • Family history of certain cancer types
  • Being overweight or obese
  • Being of Ashkenazi Jewish descent due to a higher BRCA incidence
  • Early onset of periods (before 12 years)
  • Late menopause
  • Women who have not had a pregnancy
  • Women who have their first full-term pregnancy after the age of 35
  • Smoking, which may slightly increase mucinous ovarian cancer
  • Using oestrogen-only hormone replacement therapy
  • Endometriosis increases the risk of rare but aggressive types of ovarian cancer.

While the risk increases if you have one or more of these risk factors this does not mean you will develop ovarian cancer. If you are at higher risk, know the signs and symptoms and speak to your doctor if you are concerned.

For more information visit our Ovarian Cancer page.

If you are concerned about any of these risk factors and wish to discuss them with a Gynaecological Oncologist, please enquire about an appointment.

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