Egg inducing drugs have been in use for more 30 years and have been taken by millions of women as part of IVF treatment to help them have children. Now a study of more than 15,000 women - 30 years after they gave birth - has suggested they are at least three times more likely to develop cancer of the womb. While the risk still remains low, the scientists who carried out the survey, believe it is worth further investigation and that those who undergo the treatment should be carefully monitored.
It is estimated that one in six couples have difficulty conceiving and around 34,000 women a year undergo fertility treatment in Britain. Ovulation-inducing drugs are prescribed to women who have trouble conceiving, are undergoing IVF, or who want to donate or sell their eggs.
Dr Ronit Calderon-Margalit at Hadassah-Hebrew University in Jerusalem and colleagues have studied the effects of these drugs by comparing cancer incidence in a group of 15,000 Israeli women 30 years after they gave birth. Of the 567 women who reported having been given ovulation-inducing fertility drugs, five developed uterine cancer – which is about three times the incidence in members of the group who had not been given these drugs. For the 362 women who took clomiphene, which tricks the body into making extra eggs by blocking oestrogen receptors, the risk was over four times that of women who did not take the drugs. Calderon-Margalit accepts that the numbers are small, but says they carry extra weight because they make "biological sense" as tamoxifen, a breast cancer treatment which, like clomiphene, reduces sensitivity to oestrogen, was known to increase the risk of womb cancer.
But Richard Kennedy, a consultant at the Centre for Reproductive Medicine at the University Hospital Coventry and a spokesman for the British Fertility Society, sought to reassure patients.
"There have been a high number of studies that have failed to find a conclusive link," he said.
"It is important to remain vigilant about these things but the broad message must be reassurance."
Jodie Moffat, health information officer at Cancer Research UK, said it is difficult to draw any firm conclusions from the results.
"This study didn't include a detailed history of fertility drug use, and the number of women who developed uterine cancer was very small," she said.
A spokesman for Sanofi-Aventis, which markets clomiphene, says: "This concern had already been by experts and so far no conclusion has been established."
An earlier study relating fertility drugs and a link to ovarian cancer found there was no link.
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