Recent studies have shown falls in the incidence of breast cancer in Australia and the United Kingdom.1 2 This decline in hormone receptor positive tumours was found in post-menopausal women but not in pre-menopausal women, and has also been noted across much of Europe and the United States.1 3 Most of these reports have linked this declining diagnosis of breast cancer to a decrease in use of hormone replacement therapy (HRT) following publication of the women’s health initiative study. The oestrogen plus progestogen arm of this study was halted in May 2002 because of an excess risk of breast cancer.4

A subsequent US study that examined trends of breast cancer incidence and HRT use within a screened population likewise found a fall in the incidence of breast cancer corresponding to a decrease in the use of HRT.5 The rapid decrease in breast cancer incidence reported in these studies suggests that withdrawal of hormone therapy leads to a regression of preclinical cancers.6

In the first 2 years of the oestrogen plus progestogen versus placebo arm of the women’s health initiative study, fewer breast cancers were diagnosed in the women taking combined HRT than in those taking placebo. This finding is …