Risk Factors For Breast Cancer – Protective Factors of Cancer

A risk factor is anything that increases the possibility of getting a disease

Different cancers have different risk factors. For example, we know that exposing skin to strong sunlight is a risk factor for developing skin cancer and that smoking is a risk factor for cancers of the lung, mouth, larynx, bladder, kidney, and several other organs.

Risk Factors For Breast Cancer

What are your risks?

Research has shown that there are some things that can increase your chance of getting breast cancer.  Some are preventable and some are out of our control.  However we are all different and risk factors will not affect us all in the same way. Even so, it’s important to understand what your risk factors are so that you can manage them where possible or be vigilant in screening if necessary.

Protective factors

Being a woman

Being a woman is the single biggest risk factor for developing breast cancer.  In 2020, it is estimated that 19,807 women will be diagnosed as will 170 men.  Women have a 1 in 7 chance of getting breast cancer before the age of 80 while for men it’s 1 in 670.


As with many other diseases, your risk of getting breast cancer increases as you get older.  Approximately 75% of breast cancers are diagnosed in women 50 years or older.  Breast cancer can occur in younger women but the incidence in women in the 20s and 30s accounts for less than 5 percent of cases.

Family History

Most women who develop breast cancer do not have a strong family history. This usually only accounts for 5-10% of cases.  However, having one or more first or second-degree relatives on the same side of the family with breast cancer can increase your risk.

Faulty genes

There are a number of genes associated with an increased risk of breast cancer, the best known of these are the BRCA1 and BRCA2 genes.  When normal these genes help to prevent cancer, so women who inherit an abnormal gene have an increased risk of cancer, particularly breast, ovarian and fallopian tube cancer.  Abnormalities in these genes occur in about 1 in 400 Australian women.

There are also other, even less common, inherited gene abnormalities that increase the risk of developing breast cancer.  If you have a strong family history of breast cancer you might consider discussing it with your GP.

Being overweight or obese

Overweight or obese women have a higher risk of being diagnosed with breast cancer, especially after menopause.  Being overweight can also increase the risk of recurrence in women who have had the disease.

It’s thought the reason for this is that the body’s main source of oestrogen after menopause, when the ovaries stop producing it, is fat cells.  Having more fat tissue means more estrogen in the body, and estrogen can make hormone-receptor-positive breast cancers develop and grow.

Drinking alcohol

Research consistently shows that drinking alcohol increases a woman’s risk of developing breast cancer.  Alcohol can increase levels of oestrogen and other hormones which, in turn, can increase your risk.  It may also increase your risk by damaging DNA in cells.


Smoking is a major cause of heart disease, lung cancer and many other cancers.  Whilst the link between smoking and breast cancer is unclear, toxins from cigarettes have been found in breast cells.

Smoking can also increase complications from breast cancer treatments, including:

  • Damage to the lungs from radiation therapy.
  • Difficulty healing wounds after surgery and breast reconstruction.
  • Higher risk of blood clots when taking hormone therapy and medicines.
Pregnancy history

Women who haven’t had a full-term pregnancy or have their first child after the age of 30 have a higher risk of breast cancer compared to those who gave birth before the age of 30.  Your first full-term pregnancy makes the breast cells fully mature and grow in a more regular way and this helps protect against breast cancer.

Breastfeeding history

Breastfeeding can lower breast cancer risk, especially if a woman breastfeeds for longer than one year.  When the breast are making milk 24/7 it limits the breast cells’ ability to misbehave.  Also when breastfeeding most women have fewer menstrual cycles resulting in lower oestrogen levels.

Menstrual History

Women who started menstruating younger than 12 have a higher risk of breast cancer later in life.  The same is true for women who go through menopause when they’re older than 55.  The longer a woman menstruates, the higher her lifetime exposure to the hormones oestrogen and progesterone which are associated with a higher risk of breast cancer later in life.

Having dense breasts

Breasts are made up of fatty tissue, fibrous tissue and glandular tissue.  Someone is said to have dense breasts when their mammogram shows they have more glandular and fibrous tissue and less fatty tissue.  You can’t tell whether or not you have dense tissue by feeling the breasts.  Dense breast can only be seen on a mammogram. Women with very dense breasts have a greater chance of developing breast cancer than women with less dense breasts.

Radiation to chest or face before age 30

If you had radiation to the chest to treat another cancer (not breast cancer), such as Hodgkin’s disease or non-Hodgkin’s lymphoma, you may have an increased risk of breast cancer.  If you had radiation to the face as an adolescent to treat acne (something that is no longer done), you may have an increased risk of breast cancer.

Using the oral contraceptive pill

A number of studies have suggested there is a slight increase in the risk of breast cancer for women taking the oral contraceptive pill and for up to 10 years after stopping it.  For younger women, the risk is small but for older women and those with other strong risk factors ( like faulty genes) the risk may be greater.

Using HRT (Hormone Replacement Therapy)

Studies have shown that women using combined HRT for five years or more have a higher risk of being diagnosed with breast cancer.  This risk reduces over time once you stop.

Some risk factors are preventable but some are out of your control.  What is important is that if you have a lot of risk factors for breast cancer you monitor your breast and report any changes to your GP.  All women over the age of 40 are eligible for free breast screening mammograms with BreastScreen WA every two years.

If you would like to understand your level of risk you can use iPrevent (an online breast cancer risk assessment tool).  If you would like to read more about breast cancer risk factors visit Cancer Australia’s webpage on breast cancer risk factors.

Protective Factors


Active women have reduced breast cancer risk compared with inactive women.  National guidelines recommend at least 30 minutes of at least moderate intensity exercise most days of the week.  Moderate exercise should make you puff.


Breast feeding for longer is associated with lower breast cancer risk.

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