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Fertility Drugs Not Tied to Long Term Breast, Ovarian, and Uterine Cancer Risks

July 15, 2014
By Dr. Randall Loy

The results of a large and 30 year-long follow up study presented on June 30, 2014 at the Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) suggested that there is "little evidence" that the use of fertility medications used for stimulation of the ovaries increases the long-term risk of breast or other gynecological cancers. However, the prolonged usage of clomiphene citrate was associated with an increased risk of breast cancer in women who had used clomiphene for twelve or more cycles.

Dr. Louise Brinton of the US National Cancer Institute was the principal investigator of this study involving 12,193 women who were treated for infertility between 1965 and 1988 at five sites in the United States. Follow up lasted until 2010, with evaluation based upon an extensive questionnaire and records from US death and cancer registries. A total of 9,892 women were followed for their cancer outcomes. Most previous studies which had suggested a possible link between fertility drugs and breast, ovarian and uterine cancers were small studies with shorter follow up periods and without adequate controls. Because of the size and long-term nature of this particular study, it has greater statistical power than previous such studies.

Only 10% of this study population had been treated with gonadotropins [human menopausal gonadotropin (hMG) and/or purified follicle stimulating hormone (pFSH)] and most of these were in combination with clomiphene citrate. In the hMG and pFSH group there is no association with cancer risk except in those women who never conceived.

In short, the Brinton study does not support a strong relationship between the usage of fertility drugs (mainly clomiphene citrate) and breast or gynecological cancers. Although this study is reassuring, further studies, mainly involving the usage of gonadotropins and especially in the IVF setting are certainly warranted.

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