Hormones can play an important role in how breast cancer develops and grows. The medicines used to treat women’s infertility problems affect hormone levels. So researchers have wondered if infertility treatments might increase breast cancer risk.
A study suggests that infertility treatments don’t appear to increase breast cancer risk.
The research was published in the April 2014 issue of Cancer Epidemiology, Biomarkers & Prevention. Read “Long-term Relationship of Ovulation-Stimulating Drugs to Breast Cancer Risk."
The researchers looked at the medical records of nearly 10,000 women who asked their doctors for fertility advice between 1965 and 1988 at five treatment centers in the United States. The women were followed until 2010. About half of the women were followed for more than 30 years and half were followed for fewer than 30 years.
The records showed that 749 of the women developed breast cancer.
The researchers also looked at what type of infertility treatments the women took:
- Clomid (chemical name: clomiphene), taken by 38.1% of the women
- a gonadotropin, such as Ovidrel or Pregnyl (chemical name: human chorionic gonadotropin), Bravelle or Repronex (chemical name: human menopausal gonadotropin), or Follistim or Gonal-F (chemical name: recombinant human follicle-stimulating hormone), taken by 9.6% of the women
Overall, there was no difference in breast cancer risk between women who took a gonadotropin and women who never took a gonadotropin, even when the researchers looked at smaller groups of women who had received more cycles or higher doses of the medicine.
Similarly, when the researchers compared all the women who took Clomid to women who didn’t take Clomid, there was no difference in breast cancer risk. Still, when the researchers looked at a very small group of women (36) who had received 12 or more cycles of Clomid, they found that they had a slightly higher risk of breast cancer compared to women who had never taken fertility medicines.
Current practice standards say that a woman should get only three to six cycles of Clomid at doses up to 100 mg, which is much lower than past standards. Because this study looked at women treated in 1965, some women in the study were prescribed doses of Clomid of up to 250 mg, often for many years.
Because a number of women in the study received high doses of fertility medicines, the researchers were encouraged by the very small increase in breast cancer risk they found in the small group of women exposed to the highest levels of the drugs.
Echoing the results of other studies, the researchers also found that women who didn’t get pregnant after taking a gonadotropin or Clomid had nearly twice the risk of breast cancer than women in the study who never took either type of medicine. While this result is troubling, the researchers believe that this higher risk is likely because infertility and not because of the fertility drugs. This may explain why some earlier studies have suggested a link between infertility treatments and breast cancer risk. Instead of the fertility treatments increasing risk, it seems that being infertile puts women at higher risk. More research is needed to better understand the relationship between infertility and breast cancer risk.
The results also emphasize the importance of regular monitoring and breast cancer screening for women who take fertility drugs.
If you’re considering fertility treatments or have used them in the past, this study is very reassuring. The researchers concluded that women and their doctors do not need to worry about hormonal infertility treatments increasing breast cancer risk.
If you’re having fertility issues, you may want to visit the RESOLVE website. RESOLVE is an organization that provides education and support to people with fertility problems and has local chapters throughout the United States. For more information, visit www.resolve.org.