Time and geographical variations in utilization of endocrine therapy for breast cancer in Australia

Background: Endocrine therapies, aromatase inhibitors and tamoxifen, are commonly used as an adjuvant treatment in women with breast cancer.

Aims: This study examined the trends in use of endocrine therapies in Australia between 1996 and 2008, including a comparison between Australian states.

Methods: Prescription and expenditure data for tamoxifen and aromatase inhibitors (1996-2008) were obtained from the Drug Utilisation Sub-Committee. We converted prescription data to defined daily doses (DDD)/1000 population/day, the international unit of drug utilization. Utilization data in each state/territory (2003-2008) were adjusted for female population and age-standardized incidence rates of breast cancer.

Results: Total utilization of endocrine therapies increased by 30% from 1.66 to 2.14 DDD/1000/day between 1996 and 2008. Over this period, there was a shift in use from tamoxifen to aromatase inhibitors which became the highest used products in 2008. Anastrozole was the most used aromatase inhibitor and its use increased markedly after being listed on Australia's national Pharmaceutical Benefits Scheme (PBS) for early breast cancer in 2005 (average increase of 0.14 DDD/1000/day per annum between 2005 and 2008). PBS expenditure for endocrine therapies increased by 265% from $16 million to $58 million between 1996 and 2008. Utilization of endocrine therapies was overall comparable between regions except that it was substantially lower in the Northern Territory.

Conclusions: Use of aromatase inhibitors has overtaken use of tamoxifen in 2008. Further real-world effectiveness data are required to evaluate whether large associated increases in expenditures partly because of the higher costs of aromatase inhibitors are actually justified.