Metastatic Breast Cancer Prevalence in New South Wales, Australia, in 2016: A Health Record Linkage Study

To estimate the number of females living with metastatic breast cancer (MBC) in New South Wales (NSW), Australia, in 2016 using linked health records.

The primary study dataset (cohort 1) included females in the NSW Cancer Registry (NSWCR) with breast cancer diagnosed during 2001-2002 and 2006-2007 linked with administrative hospital records, medicine dispensing, radiation services, and death records. From this dataset we counted the number with a record of de novo MBC or recurrent MBC (following stage I-III cancer) alive at the end of each year (2001-2015). The second dataset (cohort 2) included females with breast cancer diagnosed 2003-2005 and 2008-2015 without linked records. We imputed MBC prevalence for cohort 2 by calculating MBC prevalence proportions at the end of each year in cohort 1 and applying these proportions to NSWCR incidence counts in cohort 2.

Cohort 1 comprised 16,521 females with breast cancer, of whom 4364 had MBC recorded (976 de novo; 3388 recurrent). A total of 1245 individuals with MBC recorded were alive on January 1, 2016 (270 de novo, 21.7%; 975 recurrent, 78.3%). When extrapolated to all females diagnosed with breast cancer in 2001-2015 in NSW, 5009 individuals were estimated to be living with MBC on January 1, 2016 (1609 de novo, 32.1%; 3400 recurrent, 67.9%).

This study estimates that a large number of individuals are living with MBC and demonstrates the importance of identifying individuals with recurrent MBC, in addition to de novo MBC, to inform funding and delivery of appropriate clinical and supportive care services.