Mammograms made to suit

Since the start of Australia’s breast cancer screening program in 1991, breast cancer mortality has almost halved, dropping from 74 deaths per 100,000 people to 40 deaths per 100,000. The program currently invites women between 50 and 75 for a free mammogram every two years, but some researchers suggest screenings based on individual risk factors may make it even more successful.

A study by the University of Sydney, Curtin University and BreastScreen Western Australia has identified key age-related risk factors that could help inform “risk-stratified breast cancer screening”.

“The idea of risk-based, or risk-stratified, breast screening is for people who are at higher risk of developing breast cancer to have more frequent screenings or additional imaging, as opposed to everyone being invited every two years,” explains Dr Naomi Noguchi, a researcher at Sydney University’s Faculty of Medicine and Health, and first author on a paper describing the study, published in the Medical Journal of Australia.

Factors that place people at higher risk of breast cancer can include certain genetic mutations, family history, hormone replacement therapy and some physiological markers such as breast density. With risk-stratified screening, people with one or more of these risk factors would be invited to get mammograms more frequently.

“Or they may have additional imaging modalities,” says Noguchi. “In addition to mammograms, they might have an ultrasound, or an MRI.

“The opposite end of the risk spectrum would be people who don’t have any known risk factors. Risk-stratified screening might include seeing these people less often than the current two-year intervals.”

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Aside from being more convenient, fewer screenings for low-risk people could decrease the anxiety caused by false positives from mammograms, without necessarily decreasing the benefit of breast cancer screening. There might also be a lower number of medical interventions for people with breast cancers that wouldn’t have become symptomatic in their lifetimes.

“People who wouldn’t have died from breast cancer, they still receive chemotherapy, [or] surgery, when it might not have caused any problems,” says Noguchi.

“[This] is especially the case for older women.”

Noguchi and colleagues used data from Western Australia’s BreastScreen program, examining mammography screening episodes from 2007 to 2017. In total, they examined over a million screens from 323,082 women. They looked at demographic information, risk factors, recall rates and cancer incidence in this dataset.

“We quantified – meaning that we worked out the numbers – of additional cancers that are related to each risk factor,” says Noguchi.

“It’s important to have local data, and also new data, because a lot of the modelling studies are based on data from 10, 20 years ago in other countries.”

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The researchers found a range of patterns in the data, with different risk factors having different-sized impacts, and age increasing variation further. Some risk factors increased cancer detection at screening, while others increased cancer detection between screening.

Noguchi says that while the study doesn’t advocate for or against risk-stratified breast cancer screening, it will be useful for informing future research on the topic – for instance, designing trials to find the health impacts of more or less intensive screening programs based on risk.