Menopausal women who take hormone replacement therapy (HRT) boost the risk of ovarian cancer by 40 percent, even if they take the treatment only for a few years, a study said Friday.
The probe marks the widest-ever analysis of the risk of ovarian cancer from HRT, a treatment whose use declined when its safety was questioned a dozen years ago.
Researchers publishing in The Lancet carried out an overview of 52 published studies, covering nearly 21,500 women in North America, Europe and Australia who had been diagnosed with ovarian cancer.
The disease has been dubbed a "silent killer," as it is often spotted too late.
"For women who take HRT for five years from around age 50, there will be about one extra ovarian cancer for every 1,000 users, and one extra ovarian cancer death for every 1,700 users," said Richard Peto, a University of Oxford professor who co-authored the study.
HRT uses the female hormones oestrogen or progestogen, sometimes combined, to ease menopausal symptoms such as hot flushes, vaginal dryness and lack of sex drive.
The increased risk was the same in both types of treatment.
It was also seen in the two most common types of cancer -- known as serious and endometrial ovarian cancers -- but not in the rarest kinds, mucinous and clear-cell cancers.
The risk fell back over time after women stopped taking HRT.