The Link Between Fertility Drugs and Ovarian Cancer

No one knows what causes ovarian cancer. One theory is that the release of an egg each month—a process known as ovulation—results in damage to the ovarian surface. Over time, according to this theory, the ongoing damage can lead to ovarian cancer. If this is true, it would explain why birth control pills protect against ovarian cancer. Birth control pills prevent monthly ovulation. The theory might also explain how ART could lead to cancer. ART may increase the number of ovulations per cycle.

Newer theories backed by research suggest that multiple ovulations don’t cause ovarian cancer. Still, things that increase how often a woman ovulates—for example, never having babies or not breast feeding—also increase the risk of ovarian cancer. Things that decrease the number of ovulations—for instance, having many children, breast feeding, or using birth control pills—reduce the risk. So it is possible that ART could increase the risk.

A lot of studies have focused on the connection between fertility drugs and ovarian cancer. Some do suggest that fertility drugs might increase a woman’s risk. But these studies aren’t always easy to understand. Here’s why:

  1. Many of the studies include large numbers of women who received many different types of ART medications. And some older studies included medications that are no longer used. As a result, it’s hard to tell which medication might be causing the higher risk. It’s also possible that all ART medications increase risk. But there’s no way to tell.
  2. The studies include reports of more than one type of cancer. Some reported cancers are invasive epithelial ovarian cancer. This is the most common ovarian cancer. It’s also the most lethal. A lot of the cancers, though, are borderline ovarian cancer. These are common even in infertile women who do not receive ART. Also, these tumors commonly are not lethal. They do not usually require chemotherapy for cure.
  3. Many infertile women have a condition called endometriosis. This means there is menstruating tissue outside the uterus. Sometimes, this can turn into cancer. So we don’t know whether the endometriosis is turning into cancer or the ART is causing cancer.
  4. Having babies is called parity. Not having babies is nulliparity. Parity lowers the risk of ovarian cancer. Nulliparity increases the risk. In some studies, women who had ART and then got pregnant did not have an increased risk. Women who had ART but could not get pregnant did. It may be that the “infertile” ovary is at risk with or without ART. By the same token, a woman who gets pregnant with ART may not be at increased risk. This might be true especially if she has more than one pregnancy.
  5. A lot of the studies do not follow women much past the age of 50. But ovarian cancer usually starts in the 50s or 60s. So it is possible that the risk after ART is higher than we think. We might not know because we haven’t followed the women long enough.
  6. Women who have a family history of breast or ovarian cancer are at higher risk for these cancers. This is especially true if they carry a gene called BRCA. However, this genetic information is not available for the women included in the studies.

Based on available data, experts believe that fertility drugs are probably safe in terms of developing ovarian cancer. There is a theoretical risk. But it is impossible to know how high that risk is. It is also possible that if ART is successful and a woman has a baby, she will lower her risk. Another possibility is that infertility and nulliparity are risks for ovarian cancer. We just don’t know. Each woman should discuss her risk with her doctor before having ART.

Researchers do not believe that a family or personal history of ovarian or breast cancer should keep a woman from using fertility drugs. But a woman with such a history might want to consider genetic counseling. She might also consider enrolling in a screening program.