Warning over timing of HRT

Starting hormone therapy at around the time of menopause is linked to a greater risk of breast cancer compared to starting after a longer gap.

Researchers have found that women who started hormone replacement therapy (HRT) five years or more after menopause had little or no increased risk, regardless of the type of treatment used, how long they used it, and whether they were overweight.

Many studies have found that breast cancer incidence increases in users of HRT, in particular among women who use a combination of hormones as opposed to oestrogen alone.

But few have looked at the timing of therapy as a risk factor.

Valerie Beral, from Oxford University and colleagues, writing in the Journal of the National Cancer Institute, said they found women starting hormone therapy at the time of menopause were at greater risk of breast cancer than those starting it later.

"A new finding of this study, which has been little investigated previously, is that the interval between menopause and starting hormonal therapy has a substantial effect on breast cancer risk," they said.

Two previous studies have suggested this association but only in certain groups of women.

"In this large study, we found greater risks of breast cancer if hormonal therapy use began either before or soon after menopause than after a longer gap," the researchers added.