What causes ovarian cancer?

We don’t know the causes of most ovarian cancer. Research into the causes of ovarian cancer is continuing in Australia and overseas.

We do know that there are some factors that may increase a woman’s risk of developing ovarian cancer and that there are some protective factors that may reduce a woman's risk.

It is important to know that many women who develop ovarian cancer do not have any known risk factors — while many women who do have risk factors never develop ovarian cancer.

Known risk factors include:

• Age is the main risk factor for ovarian cancer.

The risk increases with age, and women aged over 50 are more likely to develop ovarian cancer. However, ovarian cancer can affect women of all ages.

Because you can't do anything about your age, it is especially important for all women to be aware of ovarian cancer symptoms. Listen to your body and don't be tempted to put worrying symptoms down to menopause, age, stress or a busy life. Have any symptoms that are new, persistent or not quite right for you checked out by your doctor. If you are not comfortable with your doctor's diagnosis, or you are still concerned about unexplained persistent symptoms, you should seek a second opinion.

• Genetics and family history are responsible for around 10% of ovarian cancers. Click here to learn more about genetic risks and genetic testing.
Other factors that may increase your risk include:

• Being a white (Caucasian) woman living in a westernised country with a high standard of living.
• Being of Ashkenazi Jewish descent.
• Having no or few full-term pregnancies.
• Never taking oral contraceptives.
• Smoking cigarettes.
• Eating a high fat diet, or being overweight or obese.
• Multiple exposures to fertility drugs (studies are not conclusive).
• Using oestrogen-only hormone replacement therapy (HRT) for 10 or more years (studies are not conclusive).
• Genital contact with talcum or asbestos, which are sometimes used in talcum powders, douches and condoms (this is highly controversial and not proven).

If you have any of these known or possible risk factors for ovarian cancer, talk to your doctor about what they may mean for you. If you and your doctor are concerned about your increased risk of ovarian cancer, you can ask to be referred to a gynaecological oncologist who can advise about ways of reducing the risk of developing ovarian cancer or suggest a surveillance program, which aims to look for early signs of the cancer.
Protective factors

There are some factors that may help to reduce your risk of ovarian cancer:
• Having children.
• Taking oral contraceptives.
• Removal of your uterus.
• Removal of your ovaries.
• Having your fallopian tubes tied.

These factors may be protective because they give the ovaries a ‘rest’ from ovulation.
About 10% of 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 are eager to find out if the cancer may be hereditary.

What are genes?
Genes are small pieces of DNA, the material that acts as a master blue print for all the cells in your body. Your genes determine such things as what colour hair and eyes you have and how tall you are. Your genes also provide the ‘recipe’ for building all the chemical substances in your body and keep it running smoothly. Sometimes there is an error in one of your genes that means the gene cannot do its job properly. This is called a genetic ‘fault’ or ‘defect’. In some cases, these faults can lead to disease.

BRCA1 and BRCA2 genes
Inheriting a faulty BRCA1 or BRCA2 gene is involved in most cases of hereditary ovarian cancer.

The BRCA1 and BRCA2 genes both make a chemical substance that helps your body prevent cancer. Most men and women have two normal copies of the BRCA1 and BRCA2 gene. Some women have a genetic fault in one copy of their BRCA1 or BRCA2 genes and so they don't produce a normal amount of this cancer-fighting substance. These women are at higher risk of developing breast or ovarian cancer (and some other cancers).

Women who inherit a faulty BRCA1 gene have approximately a 40% lifetime risk of developing ovarian cancer, while women who inherit a faulty BRCA2 gene have approximately a 10-15% risk of developing ovarian cancer.

You inherit one copy of each of your genes from your mother and a second copy of each of your genes from your father. If one of your parents has a faulty BRCA1 or BRCA2 gene, there is a 50% chance that you may inherit their faulty copy and a 50% chance you may inherit their normal copy. If you inherit a faulty copy, then each of your children has a 50% chance of inheriting it from you. Both men and women can pass on the BRCA gene even though men don't have ovaries.

Other genetic links to ovarian cancer
Another known genetic link to ovarian cancer is inheriting a syndrome called HNPCC, which is short for hereditary nonpolyposis colorectal cancer syndrome. In HNPCC, inherited faulty genes increase the risk of colorectal, ovarian, endometrial, renal tract and other gastrointestinal cancers. Women with HNPCC have about a 12% lifetime risk of developing ovarian cancer.

There are also other rare genetic links to ovarian cancer, and ongoing research may uncover genetic links that are not currently known.