Fertility Drugs and Cancer Risk
This is a very hot and controversial topic, so I want to begin by reminding us all how unclear any of this data is and how complicated are the questions. The basic issue is whether the use of fertility drugs increases a woman's risk of developing cancer--usually ovarian or breast. Over the years, I have known quite a few women with breast cancer who had previously undergone various fertility treatments. Some had been successful in achieving healthy pregnancies, and some had not.
Immediately, there are a number of confounding factors--starting with the risk of cancer increasing with age, numbers of women delaying pregnancy until later in life and, therefore, trying to have babies at the time that their cancer risk was beginning to rise anyway. None of the women whom I have known would have traded the realities of their beloved children for not having breast cancer. Hard to know what decisions might have been made at the time of beginning IVF, but clearly the cancer risks are still low and unclear. This particular study seems especially confusing as women who received IVF and did not conceive had a lower risk, while those who did and carried pregnancies for at least ten weeks had a higher risk.
Here is the beginning of an editorial from JNCI and then a link to read more:
Breast Cancer Risk After Use of Fertility Drugs: Stimulating New Controversy
Louise A. Brinton
Considerable controversy has surrounded the effects of fertility drug use on cancer risk, primarily as related to ovarian cancer. In this issue of the Journal, Fei et al. (1) presented unique data from a case-control study of sister pairs (one of whom had breast cancer) that allowed evaluation of associations between fertility drug use and young-onset (<50 years at diagnosis) breast cancer. Although a reduced risk associated with drug usage was noted overall, this association was not observed among women who conceived as a result of treatment and who subsequently carried their pregnancies for at least 10 weeks.
These results (1) are difficult to interpret in the context of pre- vious studies, given that findings have ranged from reduced risks to increased risks to the absence of any relationship (2). Several biological explanations are possible for these associations. On the one hand, reduced risks are possible given that clomiphene is a selective estrogen receptor modulator (SERM) with structural sim- ilarities to tamoxifen, a well-established chemopreventive agent for breast cancer. On the other hand, increased risks could reflect that fertility drugs induce ovulation and raise estrogen levels (3). For ovarian cancer, some studies have shown elevated risks primarily among patients who are unable to conceive and remain nullipa- rous (4-6). This has been interpreted as indicative of these patients having either resistant types of infertility linked with higher can- cer risks, genetic predispositions to both infertility and cancer, or higher drug exposures.
If you are interested in reading the research article by Fei et al, please go here.