In a nutshell
This review looked at whether women who used fertility medications more often developed breast cancer later on. It found that women treated with ovarian stimulation had similar rates of breast cancer to other women.
Treatment for infertility has become common, both as people have children later, and as the condition is more commonly treated. Ovarian stimulation (OS) is an important aspect of treatment for infertility. OS uses hormonal medications to cause multiple oocytes (eggs) to mature in a single menstrual cycle. OS increases levels of the reproductive hormones estrogen to much higher than is found in a natural menstrual cycle. The effect of these high estrogen levels on the body can be similar to an additional 2 years of menstrual cycles.
Estrogen affects organs throughout the body, including the uterus, brain, and bones. In particular, estrogen affects breast tissue. Each month, breast tissue grows and matures in response to the hormones estrogen and progesterone. Over time, this normal tissue growth due to estrogen can contribute to breast cancer risk. While not all breast cancers are the same, many of them grow in response to these hormones. Women who have longer periods of time with high estrogen due to irregular cycles also may have a higher risk of breast cancer.
It is not clear whether the OS drugs for infertility treatment can increase breast cancer risk.
Methods & findings
This review included 20 studies evaluating OS and breast cancer risk. 19 studies used the OS medication clomiphene citrate (CC; Clomid). CC causes the body to release gonadotropin hormones which stimulate the ovaries. 14 studies investigated synthetic gonadotropin (Gonal-F). Gonadotropins are generally a stronger medication than CC. All of the studies compared women who were prescribed OS medications by their doctors to other women in the general population. Women in this analysis were followed for an average of 27.1 years.
Women who used CC later had similar rates of breast cancer as women in the general population. Their breast cancer rates were also similar to women with untreated infertility. Women who used gonadotropins also had similar breast cancer rates to the general population.
The bottom line
This review found that women treated with OS drugs did not have higher rates of breast cancer than other women.
The fine print
Not all the studies in this review accounted for factors that can affect breast cancer risk, such as body weight or family history of breast cancer.
Published By :
Fertility and Sterility
Jul 01, 2021