Sarah Boseley, health editor
April 19, 2007
Hormone replacement therapy may have caused the deaths of more than 1,000 women in the UK from ovarian cancer since 1991, scientists reveal today.
HRT has been used by millions of women to alleviate the symptoms of menopause or - in some cases - because they hope it will help them remain youthful and active for longer.
But today's authoritative study by Professor Valerie Beral and colleagues from Oxford University reveals that those who take HRT for five years or more are risking death from a particularly lethal form of cancer. The research, published online by the Lancet medical journal today, will not be the last straw for HRT, but it may well reduce the numbers willing to take the risk of hormone treatment.
It is the first firm calculation of deaths related to HRT, but Prof Beral and her colleagues have already shown that women who take the therapy are at increased risk of breast cancer and womb cancer. The risks of breast cancer are the highest, accounting for a probable 20,000 cases over a decade.
The article says the ovarian cancer risks should not be taken in isolation. "In total ovarian, endometrial and breast cancer account for 39% of all cancers registered in women in the UK. The total incidence of these three cancers in the study population is 63% higher in current users of HRT than in never users," it says.
HRT leads to "a material increase" in these common cancers, the authors conclude. When women stop taking it, however, their risk returns to normal.
Asked whether the results of the study should lead to HRT being taken off the market, Prof Beral said that was up to the regulatory bodies, not her.
"The regulatory bodies have said for five years if you want to take HRT, take it for as short a time as possible and in as low a dose as possible," she said. "The trouble is that there are some people who say they couldn't survive without it.
"My personal view is that it would be quite hard to do that [ban HRT] but I think this is just more evidence that it is not a good idea to take HRT for very long because the risks do go up with duration, as with breast cancer."
Early findings about health risks attached to HRT were hugely controversial, but Prof Beral thinks the problems have now been generally accepted.
"People like to say there is a debate about HRT. I think that's not true," she said. "Some people like to make out that it is uncertain what is going on, but I don't think there has been a debate for a long time. GPs are increasingly aware and so are women. The important thing is that women know these figures are right and not exaggerated."
The Million Women Study recruited 1.3m women around the age of 50 between 1996 and 2001. They completed a questionnaire about their lifestyle, their social and demographic background and their use of HRT. Three years later they were sent a second one, which 64% filled in. Every participant is followed up for death, emigration or cancer registration.
The study is the largest of its kind in the world, with one in four women in the UK of the target age participating, and it shows that one woman in 2,500 will get ovarian cancer while a long-term user of HRT and one in every 3,300 will die from it.
For all its drawbacks, HRT is very effective in promoting stronger bones in elderly women with osteoporosis who are at risk of fractures if they fall. "My personal view is that the sensible thing is to take HRT when you are 80," said Prof Beral. "My mother is 90 and has had a lot of fractures. I was very happy to say to my mother take HRT at 90." What mattered at that point was her quality of life. "If she has breast cancer when she is 95 - so what?"
Prof John Toy, medical director of Cancer Research UK, which funded the work, said: "Women should think very carefully about whether to take HRT. And women who choose to take HRT should do so for clear medical need and for the shortest possible time."
In a commentary in the Lancet, Dr Steven Narod of the Women's College Research Institute at the University of Toronto said that use of HRT had declined dramatically in the UK and elsewhere since concerns were initially raised and it was thought this had led to a decline in breast cancer rates in the USA.
"With these new data on ovarian cancer, we expect the use of HRT to fall further. We hope that the number of women dying of ovarian cancer will decline as well," he said.