Infertility has long been recognized as a risk factor for various cancers, including breast and gynecologic cancers. More recently, concern has been raised regarding effects of drugs used to treat infertility, particularly since these drugs stimulate ovulation and raise endogenous estrogen levels. Investigators in DCEG assembled a retrospective cohort study in collaboration with four large reproductive endocrinology practices where women have been evaluated and/or treated for infertility. The study included 12,193 women seen at these practices prior to 1989.
Detailed information was abstracted from medical records, and located patients were administered questionnaires to obtain updated information (through 1998) regarding disease risk factors and health status. Linkages were also performed with eight cancer registries and the National Death Index.
Results regarding effects of ovulation-stimulating drugs on ovarian and breast cancer were largely reassuring, although there were slight but non-significant increases in risk among the women followed for the longest periods of time. Nearly two-fold increases in risk of uterine cancers were seen among women treated for long periods of time with clomiphene, of interest given that this is a selective estrogen receptor modulator with chemical properties similar to tamoxifen, another drug extensively linked with this cancer. In the previous follow-up, the cohort was relatively young. Investigators have therefore recently initiated another round of follow-up, which will provide another 10 years of follow-up and considerably greater power to evaluate effects not only for the cancers previously evaluated but also for other cancers that might be affected by hormonal exposures (e.g., melanoma and thyroid cancers).
For more information, contact Louise Brinton.