Dr Makrakis and Dr Giannaris reviewed the current literature regarding any possible harmful association between fertility drugs and cancer.
Until 2008, the relation between fertility drugs and breast cancer has been investigated in 12 large, reliable studies. In nine out of those studies there has been no proof of any statistically significant association between fertility drug intake and risk of breast cancer; in one of them an increase of risk was observed in the generally subfertile population regardless the intake of drugs; in one of them there was only a temporary increase in cancer occurrence (for the first year of drug intake) which was attributed to the development of pre-existing tumors; in only one of those studies (which was of a relatively low statistical validity) an increase in cancer occurrence was observed, and that was only in women using drugs for more than six ovarian stimulation cycles. It should be noted that the abovementioned conclusions regard ‘fresh’ ovarian stimulation cycles and not cryopreserved embryo-thawing transfer cycles. Subsequently, the results drawn until now are rather reassuring about the safety against future cancer development in women having undergone IVF efforts.
The relation between fertility drugs and endometrial cancer has been investigated in six large studies; none of these studies have revealed any significant correlation between administration of gonadotropin injections and increased risk of developing this type of cancer. Finally, the results drawn from a great number of reliable studies on the investigation of correlation between fertility drugs and risk of ovarian cancer appear to be equally reassuring.
Since 2008, there are only two published studies on the topic. A study published in the British Journal of Cancer in 2009 included a British cohort of 7355 women with ovulatory disorders; 43% of them were prescribed ovarian-stimulation drugs; there were no significant differences in the risk of cancers of the breast, corpus uteri, ovary, or of any other site, between women who had been prescribed ovarian-stimulation drugs and those who had not. Further analyses by type of drug and dose revealed a dose–response gradient in the risk of cancer of the corpus uteri only for women given X2250 mg of clomiphene (when a single tablet contains 50mg and for a cycle stimulation we usually give 300-600mg). In a similar trend for clomiphene (association of >6 cycles of clomiphene with endometrial cancer) concluded as well the second recent study of a large cohort of 54,362 Danish women diagnosed with infertility; in that study the ever use of any fertility drug was not associated with uterine cancer risk.