Researchers at the University of Oxford showed that for every 1,000 women taking the drugs for five years from the age of 50 there is an extra case of ovarian cancer.
Sir Richard Peto, lead researcher for the study, said existing claim of no risk associated with short courses of HRT “simply isn’t true.”
A leading cancer charity mentioned this was a “modest increase on a relatively uncommon cancer.” Many medication charities who analyzed the research said the findings were robust, but added that the risk dropped after HRT stopped.
The drugs are used to reduce the intensity of the symptoms associated with menopause, which in some cases can be so severe they interfere with daily life activities. In the U.K. women follow the hormone replacement therapy between two and five years.
Even though the drugs reduce the risk of osteoporosis and bowel cancers, doctors have reported an increased risk of breast cancer, which has been well documented.
On the ovarian cancer front however, there has been a heated debate, especially for those who take the drug for less than five years.
The study was published in Lancet.
In the study, researchers looked at data from 52 separate studies including 21,500 women with ovarian cancer, and identified there is a link.
“It’s a risk, about a million women in this country have HRT and 1,000 will get ovarian cancer from it,” said Prof Sir Richard Peto.
There is an extra death from ovarian cancer for every 1,700 women who follow the HRT, but the risk would be reduced for those taking it for a shorter time.
“If it were me and I had really bad symptoms, I’d worry more about those than any possible risk. But [these findings] should edge towards less use rather than more use,” Sir Richard said.
Commenting on the findings, Prof Montserrat Garcia-Closas, from the Institute of Cancer Research in London, told the BBC: “There’s been a question for a long time about how solid the evidence was and this paper shows really very convincingly that there is an association.”