HRT therapy can double breast cancer risk

Certain kinds of hormone replacement therapy (HRT) can double a woman's risk of breast cancer, according to major research study of more than a million women.

Researchers found that post-menopausal women using combination HRT were twice as likely to develop breast cancer as non-users. The risk also increased among users of tibolone and among users of oestrogen-only HRT. However, these effects were shown to wear off within a few years of ceasing use.

Scientists at the Cancer Research UK Epidemiology Unit in Oxford analysed data from over one million women between the ages of 50 and 64 as part of the ‘Million Women’ study, funded by Cancer Research UK, the NHS Breast Screening Programme and the Medical Research Council.

The findings of the study indicate that HRT may be responsible for around 20,000 additional cases of breast cancer over the last 10 years.

The study also found that current HRT users have a 22% increased risk of death from breast cancer compared with women who have never used HRT. Although the result was of borderline statistical significance and it is too early to estimate the number of extra deaths associated with HRT use.

Lead author Professor Valerie Beral, Director of the Cancer Research UK Epidemiology Unit, said: "We estimate that over the past decade use of HRT by UK women aged 50-64 has resulted in an extra 20,000 breast cancers, oestrogen-progestagen therapy accounting for 15,000 of these.

“Comparing the risks is by no means simple, and women may well want to discuss options with their doctor."

Julietta Patnick, Director of the NHS Cancer Screening Programmes, thanking the 66 Breast Screening Units and the million women who took part in this study said that she hoped that the results would “help provide women with the information they need to make an informed choice about use of HRT."

Dr John Toy, Medical Director of Cancer Research UK said that the study, the largest ever conducted, would allow accurate assessment of the size of the effects of women on HRT.

He said: "It would be sensible for a woman to take HRT for only as long as it is necessary to deal with her medical problems as advised by her doctor. A woman wanting to take HRT for a long time would be extremely wise first to consider carefully the findings of this large study and other relevant research."

(SP)