To the Editor: We question the conclusions drawn by Canfell and colleagues1 from their analysis of trends in hormone replacement therapy (HRT) prevalence and breast cancer incidence for Australian women aged 50 years or older. Their ecological analysis lacks individual-level information on HRT use and information on tumour oestrogen receptor (ER) status, and captures only 2 years following the decline in HRT prevalence. This is an inadequate design within which to judge issues of causality; it is at best an hypothesis-generating exercise.2
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- 1 Anti-Cancer Council of Victoria, Melbourne, VIC.
- 2 Barwon Health, Andrew Love Cancer Centre, Geelong, VIC.
Correspondence: graham.giles@cancervic.org.au
- 1. Canfell K, Banks E, Moa AM, Beral V. Decrease in breast cancer incidence following a rapid fall in use of hormone replacement therapy in Australia. Med J Aust 2008; 188: 641-644. <eMJA full text> <MJA full text>
- 2. Paul C. Hormone therapy and breast cancer incidence: did epidemiologists miss an effect on national trends [commentary]? Int J Epidemiol 2008; 37: 638-640.
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