“The most recent label information from the U.S. Food and Drug Administration (FDA) acknowledges a potential breast cancer risk for women who use the Mirena IUD, stating:
“Women who currently have or have had breast cancer, or suspect breast cancer, should not use hormonal contraception because some breast cancers are hormone-sensitive.”
However, the label goes on to note that research studies on the increased risk are not definite, advising the following:
“Observational studies of the risk of breast cancer with use of a LNG-releasing IUS do not provide conclusive evidence of increased risk.” “
Research suggesting a link
“A 2014 observational study in Obstetrics & Gynecology looked at women aged 30–49 years from Finland who used the Mirena IUD to control heavy menstrual bleeding.
The findings showed that Mirena decreased the risk of endometrial, ovarian, pancreatic, and lung cancers. However, the study reported a higher incidence of breast cancer than the researchers expected.
The journal Acta Oncologica published a large study in 2015 that also found a connection between the increased risk of breast cancer and Mirena use.
A 2016 systematic reviewTrusted Source in Breast Cancer Research and Treatment did not associate progestin-only birth control with a higher incidence of breast cancer. However, the researchers noted that small sample size limited most of the studies, and there was a need for scientists to do further research.
More studies are necessary to help medical professionals better understand the effects of synthetic progesterone on women when they are prescribing a Mirena IUD.
Post Reproductive Health published a more recent reviewTrusted Source in 2017. It stated that the risk of breast cancer that hormonal contraception induced is relatively low and that the benefits of contraceptives may outweigh the risks. However, again, the review said the limited evidence should not imply safety.”