More evidence for HRT link to ovarian cancer
A large Danish study has found more evidence that women who take - or have ever taken - hormone replacement therapy (HRT) are more likely to develop ovarian cancer than those who have never used it.
Previous studies, including Cancer Research UK's Million Women Study, have suggested a link between HRT use and ovarian cancer. This research, published in the Journal of the American Medical Association, provides further evidence for this association.
Researchers at Copenhagen University found that the link remains, regardless of the duration of HRT use, the type of HRT taken, the amount of oestrogen received or the way in which it is given.
However, their study also confirms that the elevated risk of ovarian cancer starts to decline after a person has stopped taking HRT.
The researchers studied data on all Danish women between the ages of 50 and 79 from 1995 to 2005, including information on prescriptions handed out for HRT and on the incidence of ovarian cancer.
A total of 909,946 women were included in the analysis, none of whom had been diagnosed with hormone-sensitive cancer or had undergone an operation to remove both of their ovaries.
Nine per cent of the women were using HRT at the end of the study period, 46 per cent of whom had been using it for more than seven years.
Twenty-two per cent of participants had previously used HRT, while 63 per cent had not used the therapy at all.
The women taking HRT were found to be 38 per cent more likely to develop ovarian cancer compared with those who had never used it.
The researchers noted that the risk of ovarian cancer among people who had taken HRT for an extended period of time was not significantly higher than among those who had only been taking it for a short time.
They calculated that for every 8,300 women who take HRT each year, there is likely to be one extra case of ovarian cancer.
"If this association is causal, use of hormones has resulted in roughly 140 extra cases of ovarian cancer in Denmark over the mean follow-up of eight years, i.e., five per cent of the ovarian cancers in this study," they wrote.
The study authors suggested that women should take this slightly increased risk of ovarian cancer into account when deciding whether or not to use HRT.
Nell Barrie, science information officer at Cancer Research UK, commented: "This large study adds to the evidence that HRT slightly increases the risk of ovarian cancer. In common with other studies in this area, it also shows that when a woman stops taking HRT, her risk of ovarian cancer goes back to normal after a few years.
"Any woman who is worried about HRT and ovarian cancer should speak to her GP who can discuss the risks and benefits in her individual situation."