ABSTRACT
Fertility treatments using ovarian stimulation have been suspected to influence cancer risk, mainly through the supraphysiologic secretion of estrogen that is induced during this treatment. Although the association between ovarian stimulation and cancer risk has been extensively studied over the past 40 years, to date data are limited. Several factors have made it difficult to investigate the association, such as small numbers of cancer cases in the studies reported, a relatively short follow-up time, lack of detailed information about the stimulation drugs and protocols used, and the issue of potential confounding by the underlying causes of infertility.
The results of studies to date indicate that the currently used ovarian stimulation protocols for treatment of infertility are not associated with an overall increased risk of breast cancer or endometrial cancer. There are some indications that high doses and/or multiple cycles of clomiphene citrate treatment may be associated with a slightly higher risk of endometrial cancer; however, this treatment regimen has been discontinued in many countries, and it is not broadly used today. Infertile women treated with ovarian stimulation seem to have a higher risk of ovarian cancer and borderline ovarian tumors, although it remains unclear whether the observed risk is due to the fertility treatments per se or to other inherent characteristics of the women, such as the underlying infertility.
