Key takeaways
- The FDA acknowledges a potential breast cancer risk for Mirena IUS users, advising those with current, past, or suspected breast cancer to avoid hormonal contraception like Mirena due to hormone sensitivity in some breast cancers.
- Studies on LNG-releasing IUS and breast cancer risk are inconsistent. Some suggest no increased risk, while others, indicate a possible increase, especially in older users, necessitating careful benefit-risk assessment by healthcare providers.
- Recent studies show a slightly increased risk of breast cancer associated with LNG-releasing IUS use, but also a lower risk of endometrial and ovarian cancers. Ultimately, the decision to use Mirena IUS should involve discussing health concerns with a doctor to determine the best option.
The most recent label information from the Food and Drug Administration (FDA) acknowledges a potential breast cancer risk for people who use the Mirena intrauterine system (IUS), stating that people who:
“currently have or have had breast cancer, or have a suspicion of breast cancer, should not use hormonal contraception, including Mirena, because some breast cancers are hormone-sensitive.”
The label references reports of spontaneous breast cancer in some people who use Mirena IUS. However, the label also suggests that more research is necessary, stating:
“Observational studies of the risk of breast cancer with use of a LNG-releasing IUS do not provide conclusive evidence of increased risk.”
Key terms explained
- LNG: LNG stands for levonorgestrel. Levonorgestrel is a synthetic form of the hormone progesterone.
- IUS: IUS stands for intrauterine system. This is a small, plastic, T-shaped device that a doctor inserts into the womb, where it releases LNG.
Mirena is a LNG-releasing IUS. People may take it for contraceptive or medical purposes. It thickens mucus in the cervix, which prevents sperm from reaching the eggs that the ovaries release.
It also makes the uterine lining thinner, and may partially suppress ovulation for some people, which may help them manage heavy menstrual bleeding and other hormone-related health problems.
Some research links synthetic progesterone to an increased risk of breast cancer. Research into Mirena and other LNG-releasing IUS devices and breast cancer risk is ongoing.
A 2023 systematic review suggests that LNG-releasing IUS is not a risk factor for breast cancer. However, the researchers emphasize the need for more research, highlighting inconsistencies in current studies.
In contrast, a
The researchers state that other factors may also be responsible for this risk, but recommend that healthcare professionals weigh the potential benefits and risks carefully when prescribing this contraceptive for long term use.
A 2024 Swedish study examined the association between LNG-releasing IUS and certain breast and gynecologic cancers in 514,719 women.
The researchers associated LNG-releasing IUS use with a 13% higher risk of breast cancer, but a lower risk of endometrial and ovarian cancers.
The use of binary terms such as “male” and “female” or “men” and “women” in this article reflects the language of the sources we’ve used. Unless otherwise noted, it’s unclear whether the research we reference included participants with expansive gender identities.
A 2024 Danish study associated LNG-releasing IUS use with a 14% greater risk of breast cancer in females ages 15 to 49 years. The risk did not increase with a longer duration of use.
Ultimately, more studies are necessary to fully understand the effects of synthetic progesterone when prescribing a Mirena IUS. For some people, the benefits of Mirena IUS may outweigh the potential risks.
A doctor may consider nonhormonal birth control or other medication for someone with other breast cancer risk factors.
Birth control is a personal choice. When choosing, people can discuss health concerns with their doctor to determine their best option.