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 fertility treatments might increase breast cancer risk.
A large Dutch study strongly suggests that in vitro fertilization (IVF), a type of fertility treatment, doesn’t appear to increase breast cancer risk, even years after the fertility treatment.
The research was published in the July 19, 2016 issue of The Journal of the American Medical Association. Read the abstract of “Ovarian Stimulation for In Vitro Fertilization and Long-term Risk of Breast Cancer.”
One type of fertility treatment involves harvesting mature eggs from a woman’s ovaries. Without fertility drugs, only one or two eggs at most per cycle will be harvested. With fertility drugs, as many as 8 to 10 mature eggs can be released and harvested. To minimize any risk, most fertility doctors develop a customized egg-stimulating regimen for each woman. In IVF, harvested eggs are fertilized in a test tube with sperm from a woman’s partner or a donor. The fertilized eggs grow briefly into tiny embryos which are then implanted in a woman’s uterus.
In the study, the researchers followed more than 25,000 Dutch women who had fertility treatment from 1980 to 1995. The women were followed for about 21 years, which is a very long follow-up time.
- 19,158 women had IVF treatment
- 5,950 women had other fertility treatments that involved less exposure to hormones
The women were about 33 years old when they started fertility treatments and had about 3.6 IVF cycles.
During the follow-up period:
- 839 cases of invasive breast cancer were diagnosed
- 109 cases of DCIS (ductal carcinoma in situ, which is non-invasive disease) were diagnosed
The incidence of breast cancer at age 55 was:
- 3.0% for the women who had IVF
- 2.9% for women who had other fertility treatments
After taking into account a number of factors that are linked to a higher risk of cancer, including:
- each woman’s age when she gave birth to her first child
- a woman’s overall number of children
- number of IVF treatments
the researchers found that women who had IVF treatments had no higher risk of breast cancer than women who had less intensive fertility treatments and had about the same risk of breast cancer as the average women.
"Earlier studies [on IVF] that reported no increase of breast cancer based their conclusions on shorter follow-up and smaller numbers of breast cancers, whereas some studies reported increased risks in subgroups of IVF-treated women," said lead author Alexandria W. van den Belt-Dusebout, Ph.D., of the Netherlands Cancer Institute, in an interview. "Because of the conflicting results in the literature and methodological limitations of earlier studies, even in reviews and a meta-analysis, a large study with long follow-up was needed."
The study also found that having seven or more IVF cycles was linked to a lower risk of breast cancer, compared to having one or two cycles.
"That’s reassuring, because you would think if you did IVF 10 times, your risk would be higher," said Owen K. Davis, M.D., president of the American Society for Reproductive Medicine, in an interview in The New York Times.
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 IVF 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.