What is breast cancer?

Breast cancer in Aotearoa New Zealand

Every year more than 3,000 women and a small number of men are diagnosed with breast cancer. Breast cancer mostly affects women over 50 years (70%) and a higher proportion of Māori women get breast cancer (130 per 100,000 in 2017) compared to non-Māori (90 per 100,000).

You are more likely to survive breast cancer if it is found early. Research from 2014 shows that 88% of New Zealanders diagnosed with early or locally advanced breast cancer will live longer than five years.

New Zealand’s breast screening programme

New Zealand has a free breast screening programme available to all New Zealand women aged 45 to 69. Mammograms can save lives by finding breast cancer early before it spreads. For more information about breast cancer screening, and the possible benefits and harms of having regular mammograms, you may like to visit the BreastScreen Aotearoa website www.timetoscreen.nz/breast-screening.

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What causes breast cancer?

There is no clear reason why you might get breast cancer but some factors contribute to getting it. They include:

• increasing age

• a past diagnosis of breast cancer or DCIS (ductal carcinoma in-situ)

• atypical hyperplasia (increased number of abnormal cells) can be seen in a breast biopsy

• increased breast density

• a strong family history of breast cancer

• inheriting a faulty or altered gene that is linked to an increased chance of developing breast cancer (BRCA1 and BRCA2)

• lifestyle factors such as being overweight after menopause, physical inactivity, drinking alcohol and smoking

• use of hormone replacement therapy during menopause.

Having children before you are 30 and breastfeeding can both slightly reduce your risk of developing breast cancer.

Breast cancer in families

If you have any concerns about breast cancer risk for yourself or your family/whānau members, speak to your GP. It is thought that only about 5% of breast cancers occur in people carrying inherited faulty genes, the two most common of which are BRCA1 and BRCA2.


Most people who develop breast cancer have no family history of the disease.