Millions of women in the United States have sought treatment for fertility-related problems over the past 35 years. Because many of these treatments –including fertility drugs and in vitro fertilization (IVF) – use hormones to stimulate ovulation, researchers have explored whether such therapies might increase the risk of breast or ovarian cancer.
The vast majority of studies published to date have found no connection between fertility treatments and a higher risk of these cancers. A few smaller studies have come to the opposite conclusion, but the methods used in some of these studies have been called into question by some researchers.
It isn’t surprising that hormone use in fertility treatments doesn’t appear to increase the chances of developing breast or ovarian cancer. Birth-control pills, which contain hormones, have been found to reduce the risk of ovarian cancer. Some studies have found that long-term use of birth-control pills can produce a slight rise in the risk of breast cancer, but that risk generally drops when women stop taking the pills.
Exploring whether there is a connection between fertility treatment and cancer risk is a formidable scientific challenge. The ideal study would look at how long and in what doses women take fertility drugs, and whether those who took the highest doses for the longest period had the greatest rise in cancer occurrence. But that kind of data has not been consistently collected.
Another challenge is that some of the same factors that prompt women to seek fertility treatment may also increase their risk of cancer. For example, women who have their first child later in life have an increased risk of breast cancer. But women who are late in their child-bearing years are also the most likely to seek fertility treatments such as IVF. If a woman who went through IVF later develops breast cancer, was it related to the fertility treatment or to the later age at which she had her first child, or to some other factor?
The take-home message for women considering infertility treatments is that, while it’s natural to be concerned about the effect of hormone treatments, the weight of scientific evidence is that that such treatments are unlikely to lead to breast or ovarian cancer. Women and their partners experiencing infertility should feel comfortable seeking fertility assistance.
Wendy Chen, MD, is a breast cancer specialist in Dana-Farber Cancer Institute’s Susan F. Smith Center for Women’s Cancers. She studies the factors that raise women’s risk of breast cancer how treatments can be better tailored to their needs.