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

In reply: In saying that our work on the effect of hormone replacement therapy (HRT) on the development of breast cancer is “at best an hypothesis-generating exercise”, Giles and colleagues ignore both the preceding literature and the fact that our analysis of Australian data explicitly tested the hypothesis raised by an analysis of United States data. Both the US and Australian analyses showed falling breast cancer incidence from 2001 in women aged ≥ 50 years, but not in younger women, following large reductions in HRT use.1,2