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Your risk of developing breast cancer

What are the risk factors for breast cancer?

There are many risk factors that contribute to an individual’s likelihood of developing breast cancer. Some are risks we can increase or reduce depending on our lifestyle choices, but there are some risks, like being a woman and getting older, that we have no control over.

In a small percentage of cases, family history is also a risk factor – your risk of developing breast cancer increases if a close relative is diagnosed with breast cancer, the number of your relatives diagnosed with breast cancer, and if your relatives are diagnosed at a young age.

Even though there are many factors that could increase the likelihood of developing breast cancer, it’s important to understand that your actual risk is fairly low. Assuming you live to age 85, your risk of getting breast cancer over your lifetime is 1 in 40, or about 2.5 per cent.

While most of us can do little to change the general (unmodifiable) risk factors for developing breast cancer, researchers estimate that close to 30 per cent of all breast cancers could be prevented if women live healthier lives – and there are some very important ways you can help reduce your chance of getting the disease.

Ways to reduce breast cancer risk

Reduce your alcohol intake: Research has shown a strong link between alcohol and the risk of developing breast cancer. To reduce your risk of breast cancer, try to limit your alcohol intake to no more than two standard drinks a day.

Maintain a healthy weight throughout your life: Women who put on a lot of weight in adulthood, particularly after menopause, may have a higher risk of breast cancer.

Be active: Studies have shown that regular exercise reduces the risk of breast cancer. The exact amount of physical activity needed to reduce your risk is not yet clear but studies show that moderate exercise, like a brisk walk, can be enough to reduce your cancer risk. And the more you do, the greater the benefits.

Have children early and breastfeed if you can: Although your choices about having children are made for a variety of reasons, not having children or having them later in life can increase your risk of developing breast cancer. And the reverse is true as well; having more children early in life and breastfeeding (12 months or more) provides long-lasting protection from breast cancer.

Eat well: A healthy diet, of at least five serves of vegetables and two serves of fruit a day, may help to reduce your risk of cancer. Research recommends sticking to low-fat dairy products and limiting how much red meat you eat to prevent increasing your risk of breast cancer.

Try not to stress: There is no conclusive evidence that stress causes the initial development of breast cancer, however, a recent study has found that chronic stress could be related to recurrence and spread of breast cancer in mice.

Avoid long-term use of hormone replacement therapy (HRT): Many women use HRT to alleviate the symptoms of menopause and/or osteoporosis, to boost female hormones estrogen, progesterone and levels that lower with age. However, there is evidence to suggest that using long-term use of HRT increases the risk of breast cancer and other health problems.

Don’t smoke: There have been a number of studies conducted to investigate the relationship between active cigarette smoking and breast cancer risk. A landmark study conducted in the USA in recent years demonstrated an association between active smoking and breast cancer risk, specifically for women who had started smoking at a very early age and before their first pregnancy.  Smoking should always be avoided to prevent a range of diseases and to maximise overall health and wellbeing.

Non-modifiable factors of risk

Being a woman: 99 per cent of breast cancer cases are women. A small minority of men can get breast cancer, but women are at a much higher risk.

Ageing: The older women get the higher their risk of developing breast cancer. In Australia, breast cancer can occur in younger women, but about three out of four breast cancer cases occur in women aged 50 years and older.

Early puberty: Reaching puberty early prolongs the amount of time you are exposed to the fluctuating levels of estrogen and other female hormones that are associated with the menstrual cycle. Starting menstruation before the age of 12 is associated with higher breast cancer risk.

Late menopause: Women who experience menopause later (at age 55 or after) have twice the risk of developing breast cancer of women who experience natural menopause at ages younger than 45.

Family history: Breast cancer is a common disease so having one relative diagnosed over the age of 40 is not unusual and would not normally suggest that other family members are at increased risk. However, you might have an increased risk of developing the disease if several blood relatives in your family have had breast cancer or ovarian cancer, or you have blood relatives who were diagnosed with breast cancer at a relatively young age (e.g. under 40).

BRCA1 and BRCA2: Women who carry a fault in the BRCA1 or BRCA2 genes have a high lifetime risk of breast cancer, estimated to be in the range of 30-60 per cent, and a lifetime ovarian cancer risk of about 20 per cent. Genetic testing is available for high risk women who are referred by their doctor.

Being tall: Studies have found that being 175cm or taller is associated with a slightly increased risk for breast cancer.

High breast density: Women with denser breast tissue are more likely to be diagnosed with breast cancer than women with less dense breasts. Breast density is measured by mammograms.

Ethnicity: Women from different ethnic backgrounds have varying rates of risk for breast cancer. Caucasian and Jewish women are among the highest, and Asian women among the lowest rates for breast cancer.

Previous breast cancer: Being previously diagnosed with a non-invasive breast condition such as ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS), is associated with an increased risk of developing invasive breast cancer.

How research is helping

Breast cancer researchers are working towards saving lives through more effective treatments and earlier detection, and many are also seeking ways to prevent tumours developing in the first place. Working out how to prevent breast cancer requires them to understand and the risks that make a woman susceptible to developing the disease so they can then counteract risk factors.

Mimicking pregnancy protection: Dr Kara Britt is studying the cellular and functional changes associated with childbearing to understand how the protective effect of having children works and if it can be replicated. Her research may suggest ways to prevent breast cancer in the future.

Dense breasts: Research to identify the reasons why women of the same age differ so much in breast density will lead to a better understanding of the causes of breast cancer and how to prevent it. Researchers are also looking at more effective ways to detect breast cancer in women with dense breasts.