Hormone treatment increases breast cancer risk, study shows
Long term use of combined hormone replacement therapy (HRT) doubles the risk of breast cancer, according to a major epidemiological study. It showed for the first time the higher risk with combined oestrogen and progestogen treatment.
From 1996 to 2001 the million women study recruited 1 084 110 women in the United Kingdom aged 50-64 years. When they were invited to attend for routine mammography the women were asked to complete a questionnaire that included questions about their use of HRT. They were then followed up for mortality and incidence of cancer.
The results of the study, published in the Lancet (2003;362:419-27), showed that current users of all types of HRT, including oestrogen only, combined oestrogen and progestogen, and tibolone (synthetic hormone treatment), had a higher risk of breast cancer than women who had never used HRT. The risk of breast cancer increased with longer use of HRT, but the