Advances in breast cancer treatment over recent decades have transformed outcomes for many patients. Earlier diagnosis, more effective systemic therapies, and improved supportive care have all contributed to longer survival. As a result, increasing numbers of people are now living for extended periods with metastatic breast cancer (MBC). However, despite this growing population, reliable estimates of how many people are living with MBC — and who they are — remain limited.
This new population-based study from New South Wales (NSW), Australia, sought to address this gap by quantifying the number of people living with MBC and describing their demographic and clinical characteristics using routinely collected health data.
CLINICAL SUMMARY
What was examined
A population-based retrospective cohort study estimating the number and characteristics of people living with metastatic breast cancer in New South Wales using linked routinely collected health data.
Key findings
- 6,692 people were living with metastatic breast cancer in NSW on 31 December 2020.
- Prevalence increased by approximately 75% between 2011 and 2020.
- Over half of patients were aged 65 years or older, and around one quarter lived in regional or remote areas.
- Oestrogen receptor-positive/HER2-negative disease was the most common subtype.
- Nearly one quarter of patients with recurrent disease developed metastases at least 10 years after initial breast cancer diagnosis.
Clinical implications
- Metastatic breast cancer represents a growing, long-term patient population requiring sustained oncology and supportive care services.
- Older age, geographic dispersion, and cultural diversity highlight the need for equitable access to specialist care.
- Long latency to metastatic progression in some patients supports ongoing survivorship awareness beyond traditional follow-up periods.
Researchers conducted a retrospective cohort study using linked administrative health datasets in NSW. These included cancer registry records, hospital admissions, pharmaceutical dispensing data, and death records. Together, these sources allowed identification of individuals with either de novo metastatic breast cancer or progression to metastatic disease following an earlier breast cancer diagnosis.
The analysis focused on estimating point prevalence — that is, how many people were living with MBC at a given time — with 31 December 2020 used as the primary reference date. Trends in prevalence over time were also examined from 2011 onwards. In addition, the study explored age, geographic location, country of birth, tumour subtype, pe, and time from initial diagnosis to metastatic progression.
How many people are living with metastatic breast cancer?
On 31 December 2020, an estimated 6,692 people were living with metastatic breast cancer in NSW. This represents a substantial population with advanced disease, underscoring that MBC is increasingly managed as a long-term condition rather than a short terminal phase.
Importantly, the number of people living with MBC increased markedly over the study period. Between 2011 and 2020, prevalence rose by approximately 75%. This growth reflects both population ageing and improved survival following metastatic diagnosis, likely driven by better systemic therapies and supportive care.
These findings challenge assumptions that metastatic breast cancer is rare and short-lived, and instead highlight its expanding footprint within cancer services.
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Demographic characteristics
The cohort was predominantly older, with more than half of the individuals aged 65 years or above. This reflects both the age distribution of breast cancer overall and the accumulation of long-term survivors with metastatic disease.
Geographic and cultural diversity were also notable. Around one quarter of people with MBC lived in regional or remote areas, while a similar proportion were born in non-English-speaking countries. These findings point to potential barriers in accessing specialist oncology services and supportive care, particularly for those facing distance, language, or cultural challenges.
Taken together, the data suggest that the population living with MBC is not only growing, but also heterogeneous, with implications for how care is delivered across different communities.
Tumour subtype and disease pathways
Among those with known tumour subtype, oestrogen receptor-positive/HER2-negative disease was the most common, accounting for approximately two-thirds of cases. This aligns with broader breast cancer epidemiology and reflects the subtype most often associated with prolonged disease control using endocrine and targeted therapies.
The study also distinguished between de novo metastatic disease and metastatic recurrence following earlier-stage breast cancer. While many individuals developed metastases within a few years of initial diagnosis, a substantial proportion experienced very late progression. Nearly one quarter of people with recurrent metastatic disease developed metastases ten or more years after their original breast cancer diagnosis.
This finding reinforces the long natural history of some breast cancers and the need for sustained survivorship awareness well beyond the traditional five-year follow-up window.
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Implications for health systems and care planning
The rapid growth in the number of people living with metastatic breast cancer has important implications for healthcare planning. MBC requires ongoing systemic therapy, imaging, symptom management, and psychosocial support, often over many years. As prevalence increases, so too will demand on oncology services, primary care,e and community-based supports.
Professor Tracey O’Brien AM, one of the authors of the study, commented, “Why this matters is simple. If people are not counted, they are too easily overlooked in planning, funding,g and service design. And in 2026, metastatic breast cancer is increasingly a long-term condition.”
The demographic profile observed in this study highlights particular areas of need. Older patients may require more complex care due to comorbidities and frailty. Those in regional and remote settings may face difficulties accessing specialist treatment and clinical trials. Cultural and linguistic diversity further emphasises the importance of tailored communication and supportive services.
From a policy perspective, the findings provide robust, population-level evidence to support investment in metastatic breast cancer services, including survivorship-oriented care models that recognise MBC as a chronic, life-limiting condition rather than a short terminal phase.
Strengths and limitations
A major strength of this study is the use of linked, whole-of-population data, reducing reliance on self-report or small clinical cohorts. This approach allows more accurate estimation of prevalence and provides insight into real-world patient characteristics.
However, reliance on administrative data also introduces limitations. Tumour subtype was not available for all individuals, and clinical details such as sites of metastases or lines of treatment could not be fully characterised. The study also focused on a single Australian state, so results may not be directly generalisable to other countries with different healthcare systems.
Despite these limitations, the study offers one of the most comprehensive population-based estimates of metastatic breast cancer prevalence to date.
Conclusion
This large population-based study demonstrates that the number of people living with metastatic breast cancer is substantial and rising rapidly. The cohort is older, geographically dispersed, and clinically diverse, with many individuals living for long periods after progression to metastatic disease.
These findings reinforce the need to recognise metastatic breast cancer as a growing public health issue and to plan services accordingly. Future work will be needed to better understand treatment patterns, quality of life, and long-term outcomes for this expanding population.
Paper: You, H., et al. Estimating the number of people living with metastatic breast cancer: a population-based retrospective cohort study using linked health data. The Lancet Regional Health – Western Pacific, Volume 67,
2026, 101786, ISSN 2666-6065, Access online.
Editor’s Recommendation: For readers interested in exploring this topic further, I recommend our podcast ‘Supportive Care Matters S2 E2: No Longer Invisible’ in which Professor Bogda Koczwara chats to Associate Professor Nic Hart and Dr Andrea Smith (one of the authors of the paper) about their work advocating for better supportive care for metastatic cancer patients worldwide.
