Decrease in breast cancer incidence following a rapid fall in use of hormone replacement therapy in Australia

Abstract

Objective: To determine if the recent rapid fall in use of hormone replacement therapy (HRT) in Australia has been followed by a reduction in breast cancer incidence among women aged 50 years or older, but not among younger women. Design and setting: Analysis of trends in annual prescribing of HRT, using Pharmaceutical Benefits Scheme data, and in annual age‐standardised breast cancer incidence rates in Australian women for the period 1996–2003. Results: In Australia, prescribing of HRT increased from 1996 to 2001, but dropped by 40% from 2001 to 2003. Age‐standardised breast cancer incidence rates in women aged ≥ 50 years also increased to 2001 but declined thereafter. The incidence rates in this age group were lower by 6.7% (95% CI, 3.9%–9.3%; P < 0.001) in 2003 compared with 2001, equivalent to 600 (95% CI, 350–830) fewer breast cancers (out of about 9000 incident breast cancers annually for women this age). There was no significant change in breast cancer incidence for women aged < 50 years. Conclusions: While other factors may have contributed to a recent reduction in breast cancer incidence among Australian women aged ≥ 50 years, the available evidence suggests that much of the decrease is due to the recent fall in use of HRT. This is consistent with other evidence that the HRT‐associated increase in risk of breast cancer is reversible after ceasing use of HRT.

Opposite trends in incidence of breast cancer in young and old female cohorts in Hungary and the impact of the Covid-19 pandemic: a nationwide study between 2011–2020

“…The association between the decline in use of HRT and a decrease in breast cancer incidence has been showed by several studies. In Australia, a substantial, 40% reduction in HRT prescriptions from 2001 to 2003 resulted in a significant, 6.7% decrease in the incidence of invasive breast cancer in women aged ≥50 years ( 18 ). Similarly, a study conducted in Canada found a 9.6% decline in breast cancer incidence rates from 2002 to 2004 among women aged 50–69 years, which coincided with a significant, 7.8% drop in the use of HRT ( 19 ).…”

Comparing cancer and cardiovascular disease trends in 20 middle- or high-income countries 2000–19: A pointer to national trajectories towards achieving Sustainable Development goal target 3.4

“…A study from Norway estimated 20% and 23% reductions in breast cancer mortality as a result of screening invitations and treatment improvements, respectively, among women aged over 50 years [43] – although the relative contributions of these factors must certainly vary by countries. The downward trends in incidence rates in a number of high-income countries, following a reduction in the use of post-menopausal hormonal therapy during the 2000 s [44] , [45] , [46] may have also had some knock-on effect on the probability of premature death. Lastly, it is worth noting that relative to the successes in prevention of the aforementioned cancers – which are amenable to one or more effective preventative or curative interventions – pancreatic cancer has become a leading cause of premature death by virtue of its consistently poor prognosis.…”