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Decrease in breast cancer incidence following a rapid fall in use of hormone replacement therapy in Australia.
Karen Canfell1, Emily Banks, Aye M Moa
1Cancer Epidemiology Research Unit, The Cancer Council NSW, Sydney, NSW, Australia. karenc@nswcc.org.au
The Medical Journal of Australia
|June 3, 2008
Summary
The decline in hormone replacement therapy (HRT) use in Australian women aged 50 and over correlated with a significant drop in breast cancer incidence. This suggests the reduction in HRT is linked to fewer breast cancer cases in this age group.
Area of Science:
- Oncology
- Epidemiology
- Public Health
Background:
- Hormone replacement therapy (HRT) use has seen significant fluctuations.
- Concerns exist regarding the association between HRT and breast cancer risk.
- Understanding the impact of HRT cessation on breast cancer incidence is crucial.
Purpose of the Study:
- To investigate the relationship between the decrease in HRT use and breast cancer incidence in Australian women.
- To determine if this association differs between women aged 50 years or older and younger women.
Main Methods:
- Analysis of Australian Pharmaceutical Benefits Scheme data for HRT prescribing trends (1996-2003).
- Examination of age-standardized breast cancer incidence rates in Australian women during the same period.
- Statistical comparison of incidence rates before and after the decline in HRT use.
Main Results:
- HRT prescribing in Australia decreased by 40% between 2001 and 2003.
- Breast cancer incidence in women aged 50 years and older declined by 6.7% from 2001 to 2003.
- No significant change in breast cancer incidence was observed in women younger than 50 years.
Conclusions:
- The observed reduction in breast cancer incidence among older Australian women is likely linked to the decrease in HRT use.
- This finding supports the reversibility of HRT-associated breast cancer risk after cessation.
- While other factors may contribute, the fall in HRT is a significant suggested cause for the decline.
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