What are the Risk Factors?

Certain risk factors may increase a woman’s chance of developing breast cancer, but it does not always mean it will happen. There are many cases where women have no apparent risk factors and still develop breast cancer. This is why regular screening and being proactive about your health can help detect breast cancer early when it is most treatable. Common risk factors include: 

Personal Factors

add_circle_outline remove_circle_outline
  • Age: Statistically, the risk of breast cancer increases as a woman ages and is typically diagnosed in women 50 years and older. However, we now see about 5% of diagnoses in women under 30 years.
  • Gender: Both women and men are at risk of developing breast cancer, but 1 in 7 Australian women will develop breast cancer in their lives and are 100 times more likely to develop the disease than men.
  • Breast density: Dense breast tissue makes it difficult to detect breast lumps and may lead to a missed diagnosis, increasing the risk for more advanced stages of breast cancer. Dense breasts may also be associated with a slightly increased risk of breast cancer despite the difficulty in the identification of cancers.
  • Personal history of breast cancer: Women with breast cancer in one breast are at a slightly increased risk of developing cancer in the other breast.

Family History Factors

add_circle_outline remove_circle_outline
  • Genetics: A family history of breast cancer, especially in a mother, sister, or daughter (first-degree relatives) increases the risk of developing the disease, which increases even further if a relative is diagnosed before the age of 50 years. Male breast cancers or a first-degree relative with bilateral (both sides) breast cancer also increases the genetic risk of breast cancer.
  • Gene mutations: These changes in the DNA sequence happen during cell division when cells make copies of themselves, leading to illness or other genetic disorders. Not all women with these gene mutations need a bilateral mastectomy (double breast removal). A discussion with the clinical geneticist and the specialist may involve recommendations around annual surveillance with MRI, or risk reducing surgery for breasts and/or ovaries. Commonly known genetic mutations that increase breast cancer risk include:
    • BRCA1 and BRCA2 genes - are the most widely known and discussed mutations and are seen more frequently in certain ethnic populations such as Ashkenazi Jewish. Those with a BRCA gene mutation have a 45%-85% chance of developing breast cancer and 10%-46% of ovarian cancer.

    • PALB2 (Partner and Localiser of BRCA2) - the third most common gene mutation after BRCA1 & BRCA2. Approximately 35% of women with a PALB2 mutation will develop breast cancer before the age of 70 years.

    • TP53 (P53) - this mutation causes Li-Fraumeni syndrome, which increases the chance of breast cancer by 54% by the age of 70 years.

    • PTEN (Phosphatase and TENsin homolog) - this mutation may cause Cowden syndrome, which can increase the chance of breast cancer by 25% to 50%.

    • CHEK2 (Checkpoint Kinase 2) - this gene mutation doubles the risk of breast cancer in women and makes it 10 times more likely for it to occur in males.

    • CDH1 (CaDHerin 1) - those with this mutation have a 39% lifetime risk of developing invasive lobular breast cancer.

    • STK11 (Serine/Threonine Kinase 11) - this mutation causes Peutz-Jeghers syndrome and carries a 32% risk of developing breast cancer by age 60.
  • Other genetic mutations include:
    • ATM
    • BARD1
    • BRIP1
    • NBN
    • NF1
    • MSH2
    • PIK3CD
    • DSPP
    • CTCF

Along with many more that are continuously being discovered and studied. There are many gene mutations that are still unknown. A strong family history of breast/ovarian cancer without a known gene mutation still increases the risk of breast cancer in women. These women are at high risk and require regular high-risk surveillance imaging and observation.

It’s important to note that not everyone with gene mutations will develop breast cancer, but it may be beneficial to test for genetic links if there is a known family history to help reduce risk and take preventive measures.

*More information about gene mutations and genetic testing is available here.

Hormonal factors

add_circle_outline remove_circle_outline

Women who have started menstruating before age 12, started menopause after 55 years of age or never gave birth are thought to be at a slightly increased risk of developing breast cancer.

Lifestyle factors

add_circle_outline remove_circle_outline

Regular alcohol consumption, lack of physical activity, poor diet, smoking, and being overweight or obese have all been linked to an increased risk of developing breast cancer.

Medical history & medications

add_circle_outline remove_circle_outline

Previous breast cancers or atypical disease, Hodgkin’s disease, previous radiation to the chest, long-term use of combined oral contraceptives and long-term use of menopausal hormone therapy have all been linked to a slightly increased risk of breast cancer.

*More information about breast cancer risks can be found here.