More doubt cast on HRT ‘link to breast cancer’

The UK Million Women Study, funded by Cancer Research UK, reported in 2003 that using combined HRT doubles a woman’s risk of developing breast cancer.

An update last year found similar results after a longer follow-up, including a “rapid fall in risk after HRT is stopped”.

But the link has proved controversial, with several studies suggesting the finding has been blown out of proportion, while others have reinforced the link.

Experts writing in the Journal of Family Planning and Reproductive Health Care claim the Million Women Study does not establish HRT as a cause of breast cancer – although they did not rule out it may increase the risks.

Researchers from South Africa, Germany and the UK highlighted several design flaws they claim would have skewed the findings.

“Size alone does not guarantee that the findings are reliable. If the evidence was unreliable, the only effect of its massive size would have been to confer spurious statistical authority to doubtful findings,” they said, adding that the study evidence “was indeed unreliable”.

Prof Dame Valerie Beral, lead author on the Million Women Study, said the issues raised “are not new and have been refuted previously”.

“The authors omit to say that Million Women Study findings of an increased risk of breast cancer in users of HRT, especially of oestrogen-progestogen combinations, have been replicated in over 20 other studies,” she said.

“The totality of the worldwide evidence is now overwhelming. In line with the findings from these studies, the recent large decrease in HRT use has been followed in many countries by a nationwide decline in the incidence of breast cancer.”

Hazel Nunn, of Cancer Research UK, said women should not be unduly worried by the review.

“HRT can be an effective short-term treatment for menopausal symptoms – women taking it should try and use the lowest dose possible for as short a time as they need it,” she said.

“Studies suggest that in 2005 there were 1,400 fewer cases of breast cancer in the UK among women aged 50 to 59 than would have been if there had been no drop in HRT use.”