Aim
To estimate number of women living with mBC in NSW.
Methods
The linked-record dataset comprised two cohorts of females in the NSW Cancer Registry (NSWCR) diagnosed with breast cancer in 2001-2002 and 2006-2007 linked to administrative hospital records, medicine dispensings, radiation services and death records up to 2016. Women with mBC were identified from diagnosis or treatment records for metastasis. The number of women living with de novo or recurrent mBC was used as mBC point prevalence on 1 January 2016. We calculated prevalent proportions of mBC at the end of each calendar year and applied these to NSWCR counts of new breast cancers to impute mBC prevalence for cohorts without linked records (2003-2005; 2008-2015).
Results
The primary study cohorts comprised 16,521 women with breast cancer, of which 4364 incident mBC cases were identified (976 de novo mBC; 3388 recurrent mBC). Women with recurrent mBC were identified from NSWCR episode records (2435, 71.9%), with an additional 602 (17.8%) identified from hospital records and 351 (10.4%) from radiation services or dispensed medicines. At 1 January 2016 1240 women with mBC from the 2001-2002 and 2006-2007 cohorts were estimated to be alive (272 de novo, 21.9%; 968 recurrent, 78.1%).
When extrapolated to all those diagnosed with BC in 2001-2015 in NSW, 5009 women were estimated to be living with mBC on 1 January 2016 comprising 1609 (32.1%) de novo mBC and 3400 (67.9%) recurrent mBC. Results were similar when imputation was stratified by age and extent of disease. For context, NSW recorded 290 new de novo mBC and 5372 new non-metastatic breast cancers in 2015.
Conclusion
This study suggests there is a large number of people living with mBC and highlights the importance of identifying those with recurrent metastatic disease. Given people with mBC require lifelong treatment, these estimates can inform funding and delivery of appropriate clinical and supportive care services.