Study: Does IVF increase a woman’s risk for breast cancer?

IN DEPTH REVIEW OF RESEARCH

Study background:

The hormones estrogen and progesterone are known to affect breast cancer risk. Because the process of in vitro fertilization (IVF) temporarily alters the levels of these hormones, healthcare providers and researchers have expressed concerns about the effect of IVF on breast cancer.

Although other studies have looked at the effect IVF may have on breast cancer risk, many of these past studies had a short follow-up time after IVF, or did not compare breast cancer rates in women who had IVF to women who did not use IVF but were also having difficulty conceiving.

Alexandra van den Belt-Dusebout and her colleagues from the Netherlands Cancer Institute and other institutions published work in the July 2016 Journal of the American Medical Association (JAMA) that assessed the long-term risk of breast cancer for women who had IVF.

Researchers of this study wanted to know:

Does a woman’s breast cancer risk increase after undergoing IVF?

Population(s) looked at in the study:

The 25,108 women in this study were part of the Omega study cohort of women who were being treated for difficulty conceiving in IVF clinics in the Netherlands between 1980 and 1995. The group included 19,158 women who had undergone IVF, whether or not it resulted in a successful pregnancy, and 5,950 women who underwent fertility treatments other than IVF, such as artificial insemination, tubal surgery, and other hormonal treatments. None of the women had cancer before their IVF treatment.  Women in the study were followed for about 21 years after their IVF treatment to see if they developed breast cancer.

Study findings: 

1. The number of women who developed breast cancer after IVF was not significantly different from the number of women who developed breast cancer, but not after having IVF. This suggests that IVF did not influence breast cancer risk:
   • 3% of women who underwent IVF developed breast cancer by age 55.
   • About 3% of women who did not undergo IVF (but had a different fertility treatment) developed breast cancer by age 55.
2. The number of women who developed breast cancer after IVF was not significantly different compared to the number of women who were expected to develop breast cancer in the general population.

Limitations:

This study is based of IVF treatment procedures used until 1995. Current IVF procedures differ slightly in the number and length of some cycles.

For most women in the study, the researchers did not know their age at menopause or menopausal status at the end of their follow up. The researchers stated that, “If IVF-treated women reach earlier menopause than women in the general population, breast cancer risk after IVF may have been underestimated.”

This study looked at women in the general population, and did not ask about the women’s family history of cancer or mutation status that might affect cancer risk, so we do not know if these results apply to carriers of BRCA or other mutations that increase breast cancer risk. However, these results are similar to a previous study done on breast cancer risk in BRCA mutation carriers who had IVF or took other fertility medications. But this study population was small, and the researchers emphasized the need to interpret their results with caution and to see if they could be confirmed with a larger study.

Conclusions:

The results of this study suggest that in vitro fertilization does not increase a woman’s risk of developing breast cancer.  However, because of the limitations of the study, more work needs to be done in a population that includes postmenopausal women, so that researchers can assess postmenopausal breast cancer risk in women who use current IVF procedures and confirm these findings. Women who are having trouble conceiving should talk to their healthcare provider to determine what options are best for them.

Posted 8/23/16

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