Risk factors we can't change

The two biggest risks for breast cancer can’t be changed: being born female and getting older.

Gender

Breast cancer is the most common cancer affecting women in Aotearoa New Zealand. Breast cancer can happen to men – around 26 men are diagnosed in New Zealand every year. But women are at a much higher risk. 1 in 10 women will be diagnosed with breast cancer in their lifetime.

Breast cancer can also affect transgender and non-binary people.

Ageing

Your risk of breast cancer increases as you get older. Most breast cancers are diagnosed in people over 50, but breast cancer can happen at any age.

As you get older, it's important to know the normal look and feel of your breasts, and continue having mammograms, either free through BreastScreen Aotearoa if you’re eligible, or privately. Find out where you can get a mammogram here.

Your risk may be higher if you’ve previously had:

• A breast cancer diagnosis
• Ductal carcinoma in situ (DCIS), where abnormal cells are found inside the milk ducts
• Lobular carcinoma in situ (LCIS), where abnormal cells are found in the breast lobules
• Noncancerous conditions called atypical ductal or lobular hyperplasia, where more abnormal-looking cells than usual are found in the ducts or lobules.

Most breast cancers are not inherited. Around 5-10% are caused by a genetic change inherited from a parent.

If you're worried about your own family history, the checklist below can help you understand when it's worth talking to your doctor. You can also watch our webinar, Genetic Risk of Breast Cancer.

You may have a higher risk of developing breast cancer if:

• Your parent, sibling or child has had breast and/or ovarian cancer (especially if under 50 years old)
• You have multiple close relatives affected by breast cancer (male or female) or ovarian cancer
• You have relatives who were diagnosed with breast cancer before menopause
• One of your relatives has had both breast and ovarian cancer
• You have relatives diagnosed with bilateral breast cancer (breast cancer in both breasts)
• You are of Ashkenazi (Eastern European) Jewish ancestry.

If you’re concerned about breast cancer in your family, talk to a GP or healthcare provider. They can help assess your risk and may refer you for genetic counselling or testing.

Do you have breast cancer in your family? Find out about your own risk

Some factors that affect how long breast tissue is exposed to hormones are linked with a small increase in breast cancer. These include:

• Starting periods at a younger age (under 12)
• Reaching menopause at an older age (over 55)
• Having few or no pregnancies
• Limited breastfeeding or no breastfeeding
• Having your first child at a later age (after 30).

Breast tissue is made up of fibroglandular tissue (glandular tissue and fibrous connective tissue that supports the breast) and fatty tissue. Dense breasts have more fibroglandular tissue, while non-dense breasts have more fatty tissue. 

Dense breasts can put you at higher risk of breast cancer. Dense breasts can also make breast cancer harder to see on a mammogram because both dense tissue and cancers appear white.

You can’t tell whether you have dense breasts by looking at or touching them. Breast density can only be assessed on a mammogram. 

Breast density is influenced by genetics, age, weight, hormone treatments, ethnicity and physical activity. Dense breasts are more common in younger women, which is why mammograms aren’t routinely used for breast screening in young women under 40. 

It's important to regularly touch and look for breast changes, but especially if you have dense breasts.

If you’ve been told you have dense breasts, talk to a GP or breast specialist about what this means for you and whether you need a personalised screening plan.

In Aotearoa New Zealand, breast cancer affects population groups differently. Wāhine Māori have a higher rate of breast cancer than non-Māori and are more likely to die from it. 

Ethnicity itself does not cause breast cancer. Differences in risk and survival rates are caused by a range of reasons, including genetics, wider causes of health issues, and differences in access to timely screening, diagnosis and treatment.

People who have had chest radiation treatment as children or young adults – for example, as a treatment for lymphoma – may have an increased risk of developing breast cancer. 

If this applies to you, talk to a GP or specialist about when you should start breast screening and which type of screening is right for you.

Being taller slightly increases breast cancer risk, although the reasons are not fully understood.

This is not something you can take action on. Breast cancer risk is affected by many factors, and height alone doesn’t say enough about an individual’s overall risk.