Women who undergo in vitro fertilisation may not have a raised risk of breast cancer, according to a new study.
There had been concerns about the risk of breast cancer because of the artificial hormones used in treatment, researchers say.
Oestrogens and progestogens made by the body, and taken as medication, have been shown to affect breast cancer risk, explain researchers from the Netherlands Cancer Institute in Amsterdam, in yesterday’s (19 July) Journal of the American Medical Association.
Dr Alexandra van den Belt-Dusebout and her team explain that, since in vitro fertilisation procedures temporarily cause decreased oestradiol and progesterone levels (during down-regulation of the natural cycle), and strongly elevated levels (during stimulation phase), it might influence breast cancer risk.
Because previous studies of this risk have been inconclusive, due to limited follow-up times, the team looked at historical information on 19,158 women who started in vitro fertilisation treatment between 1983 and 1995, and compared it with 5,950 women on other fertility treatments between 1980 and 1995.
Follow-up was about 54 years. During follow-up, 839 cases of invasive breast cancer and 109 cases of in situ breast cancer were diagnosed.
The researchers report: "Breast cancer risk in in vitro fertilisation-treated women was not significantly different from that in the general population and from the risk in the non-in vitro fertilisation group."
At age 55, the risk of breast cancer in the in vitro fertilisation group was 3.0%, and 2.9% in the non-in vitro fertilisation group. The risk did not increase with longer time since in vitro fertilisation treatment.
"These findings are consistent with absence of a significant increase in long-term risk of breast cancer among in vitro fertilisation-treated women," the authors conclude.
van den Belt-Dusebout, A. W. et al. Ovarian Stimulation for In Vitro Fertilization and Long-term Risk of Breast Cancer. JAMA 19 July 2016; doi:10.1001/jama.2016.9389 [abstract]
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