The First Step

Learning about breast and ovarian cancer and the risk factors associated with these cancers is crucial to being able to take control of your health.

What is cancer?

The human body is made up of billions of cells, which frequently renew themselves. Cell renewal is normal and is the process of growing new cells to replace old ones that get destroyed once the new cells are made. Cell renewal happens for a variety of reasons. Cancer begins when cells in the body stop renewing or growing at the normal rate and start to grow in an uncontrolled way.

We all have genes to help our cells keep the rate of cell renewal and growth at the normal rate. However sometimes these genes can stop working properly and sometimes it disrupts the process that keeps cell growth in check. Once cells begin to grow out of control, this is the first step in the process of a cancer developing. The factors that cause these genes to stop working are largely unknown but in most cases is not due to factors we inherit from our parents.

Cancer is not a single disease with a single type of treatment. There are more than 200 different kinds of cancer, each with its own name and treatment.

How common is breast and ovarian cancer?

The first thing to know is that most women do not develop breast or ovarian cancer. The lifetime risk of breast cancer for most women in Australia is less than 1 in 8 (12.5%). Ovarian cancer is rarer. For most women, their lifetime risk is less than 1 in 80 (1.2 %). Breast cancer is very rare in men (lifetime risk is about 1 in 1000).

Breast and ovarian cancer risk factors

Breast and ovarian cancer risks are affected by many factors such as personal health history, lifestyle factors and family history.

Personal health history

Personal health history includes a past history of cancer in yourself as well as some types of benign (non-cancerous) conditions. It is best to speak with your doctor about whether any factors in your past health affect your risk of cancer. For example, if you have had breast cancer already, this affects your future risk of a new breast cancer. Some types of benign changes in the breast (but not most cysts) can increase your risk of breast cancer risk –it depends on the detail of what has been found.

Having dense breast tissue

Women who have dense breasts on mammogram have a 1.2 to 2 times greater risk of breast cancer than women with average breast density.1
Breast density may be greater in women who are younger, pre-menopausal, who use certain drugs such as menopausal hormone therapy, during pregnancy and as a result of genetics.1
Whether or not someone has dense breasts depends on the type of tissue present. Breasts are made up of three types of tissue – fatty, fibrous and glandular tissue.1 A person with dense breasts (on a mammogram) has less fatty tissue and more glandular and fibrous tissue.1
Unfortunately, traditional mammograms may be less accurate in women with dense breasts.1

Lifestyle factors

Lifestyle factors mean non-hereditary factors. Some lifestyle factors affect the risk for breast or ovarian cancer but others affect the risk of other cancer types. The good news is you can change some of these to reduce your cancer risks. This includes your diet, how much alcohol you have, smoking and exercise (

Some medications such as the oral contraceptive pill and hormone replacement therapy affect breast and ovarian cancer risks but this varies with the age you are, the type of medication and the length of time they are taken. See Cancer Australia for further information.

Family History

Most women who develop breast or ovarian cancer do not have a family history of either cancer. Their cancers are mainly thought to be due to ‘chance events’ (random changes that happen in a breast or an ovarian cell).

For most women who have a family history of breast or ovarian cancer, there is usually only one person with a breast or ovarian cancer. This type of family history does not automatically put the other family members at a high risk for cancer as those cancers are most likely caused by ‘chance events’.

Some cancers are due to changes (mutations) in combinations of unknown genes, which are still being understood by researchers. Some cancers might be due to a mutation in a hereditary gene where genetic testing is now possible. About 5% to 15% of all cancers are due to a hereditary gene mutation. About 1 in 20 (5%) of women with breast cancer and about 1 in 7 (15%) of women with ovarian cancer, have an inherited mutation in a known high risk cancer gene.

The most common hereditary breast and ovarian genes are BRCA1 and BRCA2. Everyone has these genes but in some families there can be a mutation (fault) in one copy of either of these genes. Women with a BRCA mutation have a higher risk for breast cancer and ovarian cancer – than the general population and thus there are different ways to manage the risks involved.

Looking at a family history is a good starting point to assess why a history of breast and/ovarian cancer might have occurred, if genetic testing might be helpful and what this means for an individual woman’s risk of breast or ovarian cancer.

So if you have a family history of cancer we would encourage you to complete our Know Your Risk tool to help you start a conversation with your doctor.

Reference: 1. American Cancer Society. Available at: Accessed June 2017.

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