Hormone replacement therapy significantly increases the risks of women suffering the two most common forms of ovarian cancer if it is taken by over-50s for up to five years, according to a major global study published today.
In the analysis of more than 50 studies from North America, Europe and Australia, published in the Lancet, women who use HRT for just a few years are about 40 per cent more likely to develop ovarian cancer than women who have never undergone HRT.
Current WHO, US and European safety guidelines do not specifically warn about the dangers of ovarian cancer from HRT treatments, which are used by six million people in the UK and US.
In Ireland, the Irish Medicines Board has said the benefits of HRT outweigh the risks for menopausal women, but “minimum effective dose should be used for the shortest duration”. However, the risks are “unfavourable” as a first-line treatment for osteoporosis, it says.
The study carried out by the Collaborative Group on Epidemiological Studies of Ovarian Cancer was organised by the University of Oxford and involved more than 100 researchers who analysed 52 studies.
The risks of contracting either of the two most common forms of ovarian cancers, serous or endometrioid, “significantly increased in women who had been recent ex-users and would at the time of diagnosis have still have been within five years of last use”, the research reports.
Decreased
The risks decreased after women had stopped taking it, though the women concerned were still “at significantly increased risk” for up to a decade later, according to the
Lancet
-published research.
The cancer risks were roughly similar whether women used oestrogen-only or oestrogen-progestogen preparations, though there is insufficient evidence to say that the risks are higher or lower depending on whether it is taken orally or by other means.
Previous reviews by the WHO were “completed before results from most large studies were published, so merely concluded that there was insufficient evidence about any ovarian cancer risk”.
Meanwhile, government-run studies have argued HRT treatments starting before the age of 60 “should cause no material harm”, though most of them were “too small to assess reliably any risks associated with use for only a few years”.
However, president of the International Menopause Society Prof Rod Baber of the University of Sydney said the risk for women taking HRT was “very, very low in absolute terms”.
The latest analysis is “heavily influenced” by two studies which had taken into account the risks facing women who had taken oral contraceptives, while HRT treatments today, he said, were less powerful.
“My advice to women using HRT would be that this study at worst suggests a very small increase in risk with use of HRT, that this is no reason for them to stop taking their HRT, that the benefits of HRT in their own case should be weighted against this,” he said.
