Breast density reporting in Aotearoa New Zealand: policy imperatives and research priorities

Breast density reporting within community-based breast screening has drawn significant attention in the scholarly literature. The practice of reporting to women about their breast density has been recognised as encompassing both potential benefits and harms. Despite these recognised complexities, many breast screening authorities—for instance, those in the United States of America (USA),¹ Canada² and Australia³—have adopted policies to notify women of their breast density status within community-based screening settings. Additionally, the European Society of Breast Imaging has issued recommendations encouraging member countries to inform women about breast density during breast screening.⁴ A recent technical review of breast density in cancer screening by Health New Zealand – Te Whatu Ora has outlined the country’s current position on breast density reporting within cancer screening, highlighting the practical challenges faced domestically.⁵ This comprehensive report manifested that the evidence needs at a system level relate to workforce capacity, supplemental imaging access and infrastructure readiness. This view highlights persisting implementation gaps that emphasise the absence of timeliness, governance accountability, communication strategies and policy progression.

Breast density refers to the proportion of fibroglandular and connective tissue that appears as white and bright area of breasts on a mammogram, in contrast to the darker appearance of fatty tissue.⁶ It matters principally for two reasons. Firstly, it is a strong independent risk factor for breast cancer and, subsequently, high breast density can mask a tumour on a mammogram, thereby reducing the modality’s diagnostic sensitivity. Breast density is routinely classified in four categories, as outlined in the fifth edition of Breast Imaging Reporting and Data System (BI-RADS) for mammography proposed by the American College of Radiologists.⁷ Among them, BI-RADS a/b (entirely fatty/scattered areas of fibroglandular tissue) are grossly classified as low density and BI-RADS c/d (heterogenously dense/extremely dense) are labelled as high density. Despite mammography’s widespread use as a primary breast cancer screening tool globally, it is concerning that its sensitivity is inversely proportionate with increasing breast density. For example, the sensitivity of mammography declines from approximately 84% in heterogeneously dense breasts (BI-RADS c) to about 64% in extremely dense breasts (BI-RADS d).¹

Breast density reporting policy in Aotearoa New Zealand

Current policy of BreastScreen Aotearoa (BSA) is to not notify women about their breast density within the community-based screening programme.⁸ Established in 1998, BSA initially targeted women aged 50–64 years for biennial screening, subsequently expanding the eligible age range from 45–69 years in 2004.⁹ The screening age is being progressively extended from 69 to 74 years across New Zealand since October 2025.¹⁰ Additionally, BSA depends on double-reading by two independent radiologists, rather than employing artificial intelligence (AI) based mammography tools for reporting.⁵ While this approach provides the benefit of expert human judgement, it may also introduce subjectivity into assessments both within and between observers,^11,12 including the evaluation of breast density. These may limit standardisation achievable with automated systems. Recent evidence from a large-scale longitudinal cohort demonstrates that AI systems generate markedly more consistent BI-RADS breast density assessments than radiologists, with high accuracy and inter-observer variation.^13,14 Additionally, it is evident that AI combined with radiologists is capable of reducing workload by 38% and ensuring a productivity gain.¹⁵ A recent Harvard University study has confirmed AI tools’ superiority in determining interval breast cancer, claiming that AI tools successfully identified approximately one-third of interval breast cancers that were initially missed during routine screening by expert human judgement.¹⁶ Interval breast cancers are diagnosed between screening rounds after a negative screening, which shows biological aggressiveness at the time of detection.¹⁷ These cancers are classified based on mammography and ultrasonography findings into several categories: 1) true interval cancers, which show no signs on prior screening mammograms, 2) occult carcinomas, with no suspicious findings on both screening and diagnostic mammograms (often detected by supplementary imaging like ultrasound), 3) minimal signs, which present subtle changes retrospectively, visible but not initially recognised, 4) false-negatives due to reporting errors, where cancers were overlooked during screening, and 5) false-negatives due to technical errors, involving inadequate imaging quality or positioning during screening.¹⁸ BSA is progressing a study involving AI as a second reader together with AI research to better understand how AI tools may be integrated into mammographic reporting.

To minimise the incidence of interval breast cancers by developing awareness among women, breast density reporting has been introduced into community-based screening in several countries. Consequently, supplemental imaging is advised to the women with highly dense breasts in a plethora of community-based screening settings. Evidence indicates that supplemental screening for women with dense breast tissue—for instance, contrast-enhanced mammography, ultrasonography and magnetic resonance imaging—have already shown increased cancer detection rates, earlier detection of cancer and decreased rate of interval cancer.⁵ The current position of the Royal Australia and New Zealand College of Radiologists is to support the notification of breast density in all mammographic assessments.¹⁹ However, introducing breast density notification and subsequent arrangement of supplemental imaging for women with high breast density in New Zealand would likely impose significant additional demands on the screening infrastructure, with potential implications for resource allocation, workforce capacity and overall system sustainability.^8,9 Considering different challenges relating to consumers and resource management, BSA is still not routinely incorporating breast density reporting into community-based screening, although they recommend the referral of women with high breast density and co-existing strong family history of breast cancer or pathogenic variants for additional medical support outside their programme.²⁰ Indeed, a transition timeline or framework for breast density reporting has not been specified by BSA. However, witholding breast density information from women limits their autonomy and right to shared decision making about their breast health. Moreover, this policy also undermines trust and equitable care.⁶ In contrast, women paying for their private mammogram might receive this information.²¹ Therefore, the dichotomy between BSA’s omission and the private sector’s selective action may contribute to inequity unless a national, co-ordinated approach to breast density reporting and follow-up is implemented.

Breast density reporting challenges and implementation gaps

BSA continues to face critical questions regarding the appropriate approaches to breast density notification and management.⁵ New Zealand’s existing guidance and decision making concerning breast density notification is substantially depending upon the research literature based in Australia, the United Kingdom and the USA. However, the population demographics for New Zealand differ significantly from those countries as a sizeable proportion of the women in the target age group represent Māori and Pacific women who have differing traits to Europeans and Asians. This distinct ethnic composition underscores a clear need for local research that captures the real-world perspectives, understanding and informational needs of New Zealand women regarding breast density measurement and reporting. Generating robust evidence tailored to the New Zealand context will be essential for informing equitable, culturally responsive breast screening policy and practice in the future. To mitigate these gaps and challenges, comprehensive studies in relation to current understanding of women from different cultural backgrounds are recommended as it is not clear what New Zealand women know about this risk factor.

To understand breast density, women exhibit diverse preferences for sourcing information.²² A recent study indicated that healthcare providers (71%), online resources (14%), friends and family including colleagues (14%), print media (8%), patient advocacy groups (6%), electronic media (3%) and social media (2%) are the principal sources of breast density information for women.²³ However, understandability and readability of available online resources are of critical concern. Moreover, misconceptions might arise due to improper comprehension of breast density. This diversity of understanding is already observed among different racial/ethnic backgrounds and literacy levels.²⁴ Therefore, information available to women may at times lack clarity or consistency, potentially affecting comprehension. Indeed, there is a paucity of research about comprehensive assessment of the accuracy, understandability and readability of the currently available New Zealand online resources specific to breast density. A recent Australian study confirmed that average grade reading level across 42 websites displaying breast density information was 12.4.²⁵ Regrettably, the readability of BSA and Breast Cancer Foundation New Zealand websites were grade levels 14.9 and 13.1 respectively, which are way above the recommended grade level 8. Additionally, existing online resources in New Zealand are barely successful in explicit display of common misconceptions and key facts statistics. Considering these circumstances, there is a pressing requirement to evaluate existing breast density information resources in New Zealand.

There is a concern that reporting breast density to women during screening might escalate their anxiety. In this context, the latest Australian study revealed that there are no significant differences of heightened anxiety between the groups of women with high and low density. This research utilised the highly reliable and validated psychological tool titled the State-Trait Anxiety Inventory.²⁶ Moreover, it was also evident in this study that women exhibited escalated anxiety even after knowing that they belong to a low breast density group. This was the first study that showed that low density status could also escalate the anxiety if there is lack of perfect understanding about breast density. Therefore, further research is required to understand New Zealand women’s responses to receiving density information. Although the technical review recognised this need, an implementation timeframe has not been established and operational responsibility has not been defined. Moreover, it remains necessary to assess women’s current opinions regarding the absence of breast density notification, as well as the psychological, informational and behavioural impact of disclosing such information. This approach will provide critical data to guide policymakers in aligning notification strategies with the needs and preferences of New Zealand’s diverse and distinct population.

Additionally, communication of complex information like breast density is always challenging. It is important to know what could be the best way to report breast density. BreastScreen Western Australia generates a letter to women with high density (category c and d) incorporating the information about the masking effect, sends educational material and advises them to consult their general practitioners (GPs) for the next steps.⁶ On the contrary, all participants in BreastScreen South Australia irrespective of density status (category a to d) receive density information with mammogram findings, and a fact sheet explaining its impact.²⁷ Similar courses of action are also taken by BreastScreen Victoria and New South Wales.²⁶ However, only BreastScreen Western Australia and BreastScreen South Australia directly notify the GPs of their clients about breast density. To notify both the clients and their GPs is good practice and ensures a duty of care. A USA study confirmed that breast density notification letters are usually written at reading levels higer than recommended for the greater population.²⁸ Moreover, the actual understandability of the content is not standard, with scores ranging from 11% to 33% based on formal assessment reflecting poor clarity and comprehension.²⁸ This indicates that a substantial proportion of participants are not fully informed about the implications of their breast density status, highlighting gaps in communication and information delivery. Therefore, an important recommendation is to structure the letters with the best readability and understandability using simplified language and keeping the content at grade 7 and 8 readability. In this way, equitable communication can be ensured by designing the materials to make them understandable for women with wide spectrum of literacy status. Additionally, the content of the letter may be designed considering the women’s cultural and ethnic backgrounds—for instance, Māori and Pacific cultural content can be incorporated to make it more familiar and interesting for them. Therefore, a pilot study can be planned following the footsteps of BreastScreen South Australia, where they reported breast density to their consumers in three centers. Thereafter, they announced the breast density reporting policy for all women, which is based on their study outcome.²⁹

 The clinical management and consultation of women with high breast density by GPs remains an area of ongoing development and uncertainty. However, recent research from the University of Adelaide provides important insights into how breast surgeons address these issues in practice.³⁰ To begin in New Zealand there is a need to assess GPs’ current understanding of breast density and how best to manage this cohort.

Conclusion

Breast density notification is increasingly embedded within international breast screening policy due to dual relevance for breast cancer risk and reduced mammographic sensitivity. While Health New Zealand – Te Whatu Ora’s technical review outlines evidence requirements and identifies areas for further evaluation, a persistant implementation gap remains. There is no defined timeline, assigned governance leadership for implementation or policy pathway to progress density notification. Addressing implementation barriers is crucial to ensure that New Zealand women are not left without transparency regarding their breast density status. A co-ordinated, ethically grounded and equity-focussed approach is important to advance policy deliberation and align New Zealand with contemporary global breast screening practice.