Using combined hormone replacement therapy (HRT) to relieve
symptoms of the menopause can double a woman’s normal risk of
developing breast cancer, according to a new study.

Estrogen-only HRT has already been shown to raise the odds of
breast cancer. New research by scientists at Britain’s Cancer
Research UK provides evidence that combined HRT — estrogen and
progestagen — is even more dangerous.

In the study of more than one million women in Britain aged 50-64
who filled in a detailed questionnaire and were followed up for
more than two years, combined HRT caused four times as many extra
breast cancers as estrogen-only HRT.

The results, reported in The Lancet medical journal, showed that
users of HRT also had a 22% higher risk of dying from breast
cancer compared to women who had never taken it.

The researchers reported that the risk goes up with the duration
of use and is apparent within 1-2 years. But once a woman stops
taking HRT, the risks quickly recede.

Source: Lancet, August 9, 2003, 362(9382)