New Zealand and Australia have some of the highest rates of breast cancer diagnoses in the world at around 1 in every 1,000 females, according to a new study of 185 countries.
Our rates of death from breast cancer, however, were at the lower end of the scale, and reducing by 2.1% per year – well on our way to meeting the World Health Organization Global Breast Cancer Initiative goal of 2.5% a year.
The SMC asked local experts to comment.
Professor Jason Gurney, Epidemiologist, University of Otago, comments:
“Female breast cancer is the most common cancer diagnosed in Aotearoa New Zealand. Kiwi women around the motu are diagnosed with this cancer every day, whether through our well-run national screening programme – which tends to find cancers that haven’t caused symptoms yet – or through women presenting to clinical services with symptoms like a suspicious lump. Because of factors including screening, breast cancer tends to be detected at a point when it can be successfully treated, and survival for this cancer is high relative to other cancers. This contrasts with cancers like lung cancer, which tend to be diagnosed at a more advanced stage.
“The International Agency for Research on Cancer (IARC)-led study shows that our breast cancer incidence rate has marginally increased over time. This increase could be due to actual increases in the burden of breast cancer, and/or increases in the identification of early breast cancers (e.g. through screening). Crucially, our mortality rate has reduced over time, which is likely because we are diagnosing more cancers early, and have better treatment options for those with later-stage disease.
“Finally, it must be emphasised that there are strong disparities in breast cancer incidence, survival and mortality for Māori and Pacific women relative to NZ European women, and these disparities are invisible within this IARC study.”
Conflict of interest statement: Director of a Health Research Council Programme Grant; Senior Epidemiologist at Te Aho o Te Kahu – Cancer Control Agency until December 2024.
Dr Annette Lasham, Senior Research Fellow, Molecular Medicine and Pathology, University of Auckland, comments:
“A newly released global study has confirmed New Zealand’s position as having one of the highest breast cancer (BC) incidence rates worldwide. While this statistic is concerning, there’s also encouraging news: mortality rates in New Zealand are showing a positive trend, indicating improved outcomes for those diagnosed.
“While we can’t change certain risk factors like age, family history, or dense breast tissue, we can focus on reducing our risk by modifying lifestyle factors. Maintaining a healthy bodyweight, reducing alcohol consumption, and engaging in regular exercise are crucial steps. Additionally, a recent British Medical Journal publication highlighted the association between ultra-processed foods – those with ingredients not typically found in home kitchens – and increased breast cancer risk, underscoring the importance of a diet that minimises our intake of ultra-processed foods.”
“The good news regarding mortality rates is consistent with findings from the “30,000 Voices” report, a comprehensive analysis of breast cancer in New Zealand from 2003 to 2020, that my colleagues and I conducted with the Breast Cancer Foundation NZ in 2022. This report revealed significant improvements in survival, particularly for those with later-stage diagnoses, including Māori and Pacific women. However, disparities persist, with European and especially Asian women experiencing better outcomes.
“Early detection remains paramount. Specifically, the detection of early-stage breast cancer, which is far more treatable, is crucial. Our Breast Cancer Cure-funded study shows that 75% of breast cancers detected through screening are stage 1, highlighting its effectiveness in finding cancer early. However, the same study reveals that only 60% of breast cancers in women aged 45-69, who are eligible for free mammographic screening, are detected through screening. The remaining 40% are diagnosed with symptoms, often by their GPs. This means a significant proportion of women are being diagnosed with more advanced, later-stage disease, which requires more aggressive treatment and is associated with poorer outcomes compared to early-stage detection. Therefore, we must improve screening uptake, potentially by adapting our predominantly Western screening system to better serve the diverse communities within New Zealand.
“The decreasing mortality rates are a testament to the dedication and expertise of New Zealand’s clinicians. The ‘30,000 Voices’ report demonstrated that once women are diagnosed, they receive high-quality care, adhering to Australian and New Zealand reporting standards. However, access to newer, potentially life-saving drugs available in other Western countries remains a challenge, and addressing this could further improve outcomes.”
“Moving forward, continued investment in research is essential. We need to focus on strategies to increase screening participation, understand the potential unique factors contributing to New Zealand’s high incidence rates, and strive for equitable access to the latest treatments. By addressing these challenges, we can work towards a future with better breast cancer outcomes for all New Zealanders.”
No conflicts of interest.
Our colleagues at the Australian Science Media Centre have also gathered expert comments.
Professor Nehmat Houssami, Professor of Public Health and NBCF Chair in Breast Cancer Prevention, University of Sydney, comments:
Note: Professor Houssami is a co-author of the paper.
“By analysing breast cancer incidence and deaths data from 185 countries, the study shows the worldwide substantial burden of breast cancer (most or 2nd most common female cancer and the leading cause of cancer deaths in females in the majority of nations).
“However, this burden is not spread equally across countries and regions, there are large variations in incidence rates and more concerning are the disparities in breast cancer mortality. Countries that are less affluent and have less developed health systems (measured using the HDI in the study) have much worse breast cancer outcomes (higher mortality) than the more developed/affluent countries. So a woman who develops breast cancer in a low-middle income country has a higher likelihood of dying from her cancer than her counterpart in a high-income country.
“These disparities in breast cancer deaths are not new but have become more evident (in the current analysis) and are predicted to further widen in the future (projected to 2050) flagging an urgent need for governments, especially in low-middle income countries, to invest in providing access to breast cancer diagnosis and treatment services.
“The study also shows that Australia has achieved sustained reductions in breast cancer death rates over the past decade; however in 2022, Australia (and New Zealand) had the highest incidence rates of breast cancer globally — there are various reasons for this related to the population structure (e.g., ageing) and risk factor profile (breast cancer risk factors that women may be less aware of include alcohol consumption, low physical activity, and post-menopausal obesity) so we need to improve support for women to reduce these potentially modifiable risk factors.”
Conflict of interest statement: Nehmat has declared no conflicts of interest. Nehmat declares receiving grant funding (for research) from the NHMRC & the NBCF; and is currently a member of the Expert Advisory Group for the BreastScreen Australia National Policy Review.