BreastScreen Australia

In Australia, population‑based breast cancer screening is available through BreastScreen Australia. First established in 1991, BreastScreen Australia is a joint program of the Australian and state and territory governments. It aims to reduce morbidity and mortality from breast cancer using screening mammograms to detect unsuspected breast cancers in women who have no symptoms and therefore would not otherwise know they had the disease. Detection of breast cancers at an early stage allows access to diagnostic and treatment services early, so that women can benefit most from available treatments.

Women in the target age group 50–74 are offered 2‑yearly screening mammograms through BreastScreen Australia, with women aged 40–49 and 75 and over also eligible to attend.

Transgender women, transgender men, non-binary, and gender diverse people who have breast tissue suitable for breast cancer screening can seek advice from state and territory BreastScreen services as to whether screening for breast cancer may benefit them.

Lower morbidity from breast cancer is achieved by detecting cancers when they are small, as small breast cancers tend to be associated with increased treatment options (NBOCC 2009). Research shows that 59% of breast cancers detected by BreastScreen Australia are small, compared with just 28% of breast cancers detected outside BreastScreen Australia (AIHW 2018). Further, treatment of breast cancers detected by BreastScreen Australia is more likely to involve breast‑conserving surgery (74%, compared with 56% outside the program) (NBOCC 2009), which is associated with decreased morbidity.

Mortality reduction from breast cancer screening is also due to the detection of breast cancers when they are small, as it has been shown that finding breast cancers when they are small leads to improved survival (AIHW & NBCC 2007).

An Australian Institute of Health and Welfare (AIHW) data linkage study demonstrated the benefits of breast screening. It found that breast cancers detected through BreastScreen Australia had a 54% to 63% lower risk of causing death than breast cancers diagnosed in women who had never screened through BreastScreen Australia (AIHW 2018).

In 2009, in a comprehensive evaluation of BreastScreen Australia, it was estimated that breast cancer mortality had been reduced by 21–28% as a result of breast cancer screening (BreastScreen Australia EAC 2009). Further, analysis of data from the Swedish Two‑Country Trial and England’s breast cancer screening program estimated that, respectively, 8.8 and 5.7 breast cancer deaths per 1,000 women screened were prevented by screening (Duffy et al. 2010).

In 2015, the International Agency for Research on Cancer conducted a full review of available high‑quality observational studies to ensure that the evidence compiled in 2002 – which showed a reduction in mortality as a result of screening mammography (IARC 2002) – was still relevant today. The study determined that women aged 50–69 who attended breast cancer screening using screening mammography had about a 40% reduction in the risk of death from breast cancer, with a substantial reduction in the risk of death also observed in women aged 70–74 (Lauby‑Secretan et al. 2015). These mortality benefits align with the women targeted by BreastScreen Australia (those aged 50‍–‍74).

While mammographic screening reduces breast cancer deaths by detecting cancers earlier, some breast cancers detected through screening might not otherwise have been diagnosed during a woman’s lifetime. This is referred to as ‘overdiagnosis’. However, it is not currently possible to predict at diagnosis to which cancers ‘overdiagnosis’ would apply (see Box BreastScreen Australia 1 for more information about ‘overdiagnosis’ and Cancer Australia’s position statement on this).

Box BreastScreen Australia 1: ‘Overdiagnosis’ of breast cancer by BreastScreen Australia

The following points are from Cancer Australia’s position statement on ‘overdiagnosis’:

  • A majority of breast cancers found through screening would be progressive and would become symptomatic within a woman’s lifetime if left untreated.
  • It is likely that some screen-detected breast cancers (ductal carcinoma in situ or invasive breast cancer) might never have progressed to become symptomatic in a woman’s lifetime. Detection of these cancers is sometimes referred to as ‘overdiagnosis’.
  • It is not possible to precisely predict at diagnosis, to which cancers overdiagnosis would apply.

Research is needed, including molecular and genomic research, to find means of identifying cancers that would be of minimal risk of progression and therefore could be managed more conservatively.

For further information, see the position statement endorsed by the Australian Health Ministers’ Advisory Council Standing Committee on Screening, Cancer Council Australia, and the Royal Australian and New Zealand College of Radiologists, and supported by the Cancer Australia Advisory Council: Overdiagnosis from mammographic screening (Cancer Australia 2014).

 

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