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IVF drugs may reduce breast cancer risk if fertility treatment unsuccessful

23 July 2012
Appeared in BioNews 666

Women who undergo fertility treatment but do not become pregnant have a reduced risk of developing breast cancer before the age of 50, according to scientists.

The research, conducted at the National Institutes of Health in the USA, found the risk was slightly reduced in women treated with ovulation-stimulating fertility drugs. Women who went on to have a pregnancy lasting for ten weeks or longer, however, had a significantly higher risk compared to those for whom treatment was unsuccessful. This increased risk was comparable to that of women who have never received fertility treatment, suggesting that pregnancy reverses the protection provided by the fertility drugs.

'I don't see the results as any cause for alarm. But everyone needs to manage their risk and be careful', lead researcher Dr Clarice Weinberg, from the National Institute of Environmental Health Sciences, said.

Dr Marcelle Cedars, a reproductive endocrinologist from the University of California who was not involved in the study, added: 'Even in the group at an increased risk after their pregnancy, their risk was not higher than the general public. If you use fertility drugs, you're not increasing your risk'.

The researchers followed 1,400 women who had been diagnosed with breast cancer before the age of 50, along with 1,600 of their sisters who had never had breast cancer. Of these women, 288 reported using ovulation-stimulating fertility drugs, with 141 going on to conceive a pregnancy lasting for ten or more weeks. Those who received treatment but did not become pregnant had a significantly reduced risk of young-onset breast cancer compared to those who did go on to conceive.

Ovulation-stimulating drugs increase the production of oestrogen - a hormone that has previously been linked to breast cancer. Oestrogen levels gradually return to normal in women who do not become pregnant, but remain high in those who do and may affect breast tissue remodelling during pregnancy.

Dr Louise Brinton, chief of hormonal reproductive epidemiology at the National Cancer Institute, believes that the choice of fertility drug - most of the women in the study were treated with clomiphene, which belongs to the same family as the chemotherapy drug tamoxifen - explains the reduction in breast cancer risk.

The research is published in the Journal of the National Cancer Institute.

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7 April 2014 - by Dr Lux Fatimathas 
Fertility drugs used to stimulate ovulation did not increase the chances of breast cancer for most women in a long-term study of around 10,000 women in the USA...
5 August 2013 - by Rivka Marks-Maran 
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25 February 2013 - by Dr Lucy Freem 
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10 September 2012 - by Daryl Ramai 
Women carrying mutations in their BRCA genes may be more susceptible to breast cancer if exposed to diagnostic chest X-rays before the age of 30, say scientists...
30 April 2012 - by Dr Daniel Grimes 
French researchers have reported an association between drugs given to mothers undergoing fertility treatment and an increased risk of leukaemia in their children...
31 October 2011 - by Sarah Pritchard 
Women who undergo IVF treatment have an increased risk of developing borderline, non-fatal ovarian tumours according to a clinical study from the Netherlands...
6 December 2010 - by Rosemary Paxman 
A new study has shown that IVF may not be linked to an increased risk of certain cancers among female patients. A team of Swedish researchers concluded that although cancer or cancer treatment may increase the need for IVF, the risks of cancer post-IVF treatment were low...
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