Starting hormone therapy at around the time of menopause is associated with a greater risk of breast cancer compared to starting after a longer gap, says a new study.
In this large, prospectively followed cohort of women, those who started hormone therapy five years or more after menopause had little or no increased risk, regardless of the type of hormone therapy used, how long they used it, and whether they were overweight or obese.
To investigate this question, Valerie Beral, FRS, of Oxford University and colleagues, used data from the Million Women Study (MWS) in the UK. The researchers estimated the adjusted relative risks of breast cancer in hormone therapy users and past users compared to non-users in 1.13 million women in the study. They also compared women on different types of hormone therapy.
The study has been published in The Journal of the National Cancer Institute.