Declining incidence of breast cancer after decreased use of hormone-replacement therapy: magnitude and time lags in different countries

Throughout the latter half of the 20th century, hormone-replacement therapy (HRT) use steadily increased in the Western world. In 2002, the early termination of the Women's Health Initiative trial due to an excess of adverse events attributable to HRT, led to a precipitous decline in its use. Breast cancer incidence began to decline soon thereafter in the USA and several other countries. However, the magnitude of the decline in breast cancer …