A UK expert says a 50 percent drop in HRT use in recent years had probably stopped up to 1,000 breast cancer cases a year.
The risks of HRT have been hotly debated since the Women's Health Initiative study linking combined estrogen and progestin with breast cancer.
Stanford researchers say their new findings should end the debate over the link.
However, some specialists insist that the fall in breast cancer rates may be due to other factors.
