Breast cancer is the most common cancer in women and the second most common cause of cancer deaths in women in Australia. In 2022, it was estimated that 20,640 new cases of breast cancer would be diagnosed in Australia (20,428 in women, 212 in men). The risk of being diagnosed with breast cancer by the age of 85 years is currently estimated as 1 in 8 (or 13%) for women and 1 in 668 (or 0.15%) for men.¹

An assessment should be undertaken to understand a patient’s individual degree of risk (see Table 1) in order to provide evidence-based guidance for preventive activities. Breast cancer risk is not normally distributed: most women have a low (<4%) lifetime risk.²

Table 1. Risk of breast cancer³

There are multiple risk factors for breast cancer (genetic, hormonal, lifestyle and environmental).³ However, BreastScreen, Australia’s national breast cancer screening program, focuses on age, inviting all Australian women aged between 50 and 74 years for biennial mammographic screening. Women are able to self-refer for biennial mammographic screening in BreastScreen from the age of 40 years.

Clinicians have an important role in identifying people with a strong family history of breast cancer, as well as other cancers, associated with high-risk genetic variants (eg in BRCA1 and BRCA2) and offering referral to a familial cancer service. The Genetics chapter provides further information on family history and the use of the family history questionnaire.

Screening

For asymptomatic, average-risk women, BreastScreen Australia recommends screening mammograms every two years for women aged 50–74 years and actively recalls women in this age bracket.² However women at average risk may choose to commence mammography through BreastScreen from the age of 40 years.

For women at moderate risk, annual mammograms from age 40 years may be recommended. Annual mammograms are not recommended for women with a single relative diagnosed at age >50 years, because there is no clear evidence of benefit.¹⁰

Ongoing surveillance strategies for women at high risk of breast cancer may include imaging with MRI.

A Medicare rebate is available for MRI scans for asymptomatic patients aged <60 years at high risk of breast cancer.¹¹

Reviews of evidence from randomised controlled trials of mammography estimate rates of overdiagnosis of breast cancer of between 11% and 19%.¹² More recent modelling data from the US estimate that biennial screening from ages 40 to 74 years would result in 14 overdiagnosed cases of breast cancer per 1000 women screened over the lifetime of screening (estimated range 4–37 overdiagnosed cases).¹³ Screening mammography in women aged 40–49 years reduces the risk of dying of breast cancer, but the number of deaths averted is much smaller than in older women, and the number of false-positive tests and unnecessary biopsies is larger.¹³

There is controversy on how to screen women with dense breasts. The current evidence is insufficient to assess the balance of benefits and harms of supplemental screening for breast cancer using breast ultrasound or MRI in women identified to have dense breasts on an otherwise negative screening mammogram.⁴

Thermography is associated with high false-positive and false-negative rates and is not recommended as a screening modality. Polygenic risk scores to determine breast cancer risk may have a role in the future, but are not currently recommended in general practice.

A single nucleotide polymorphism (SNP)-based breast cancer risk assessment test should only be undertaken after an in‐depth discussion led by a clinical professional familiar with the implications of genetic risk assessment and testing, including the potential insurance implications. Genetic testing should be offered only with pre- and post-test counselling to discuss the limitations, potential benefits and possible consequences.¹⁴

Estimated risks for factors for which there is sufficiently strong evidence of an association with risk of breast cancer (ie factors for which the body of evidence was classified as either ‘Convincing’ or ‘Probable’, are summarised in table 5.2 of the 2018 Cancer Australia publication Risk factors for breast cancer: A review of the evidence.¹⁵

For specific recommendations for Aboriginal and Torres Strait Islander people, please refer to the Prevention and early detection of breast cancer chapter in the National guide to a preventive health assessment for Aboriginal and Torres Strait Islander people.

For women at potentially high risk or carrying a mutation, offer referral to a familial cancer clinic for risk assessment, possible genetic testing and a risk reduction management plan.

Individualised surveillance and risk reduction plan, including consideration of associated risks for other cancers (eg ovarian), may include:

• regular clinical breast examination and annual breast imaging with mammography, MRI or ultrasound
• chemoprevention with selective oestrogen receptor modulators (SERMs; eg tamoxifen or raloxifene) or aromatase inhibitors (eg exemestane and anastrozole)¹⁶
• mastectomy and/or salpingo-oophorectomy.

iPrevent is a validated tool to help in the assessment of breast cancer risk.