Fertility Status and Cancer
Elevated estradiol levels associated with ovulation-stimulating drugs used to treat infertility and ovarian punctures involved with in vitro fertilization (IVF) have led to concerns regarding long-term cancer effects. Assessed risks, however, have been contradictory. This may reflect small sample sizes and short follow-up times, as well as an inability of many studies to adjust for appropriate potential confounders, such as causes of infertility and parity. While early studies of ovulation-stimulating drugs suggested large increases in large ovarian cancer risk, more recent studies have not confirmed this. However, several investigations have noted risk elevations associated with drug use or IVF among women who remain nulliparous, possibly due to resistant infertility. Studies also suggest increases in borderline ovarian tumors, although the effects of surveillance bias are unclear. Investigations have not shown large increases in breast cancer risk, although a few studies suggest possible increases in select subgroups, including nulliparous women or those with high drug dosages in the distant past. A few studies have evaluated risks of other cancers (endometrium, colorectum, thyroid, and melanoma), without definitive results. Since women exposed to fertility treatments are just beginning to enter typical cancer age ranges, further well-designed investigations are needed to fully delineate long-term effects.