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Study Connects Breast Cancer Risk to Mirena IUD

Mirena Breast Cancer Study – 20 Percent Increased Risk

Bayer’s Mirena intrauterine device (IUD), a popular form of birth control for women due to its convenience, has been associated with a higher risk of breast cancer. The recent study specifically examined women who used Mirena, Skyla, and similar IUDs that release a synthetic progestin known as levonorgestrel to treat heavy periods.

The Mirena IUD is a small, plastic, T-shaped device that is placed in the uterus by a gynecologist or other healthcare provider. It releases levonorgestrel to prevent unwanted pregnancies for up to five years. Mirena works by reducing the possibility that sperm will reach and fertilize an egg, by partially suppressing ovulation, and by thinning the uterine lining to prevent implantation of a fertilized egg.

Risk increased by 20 percent

The study examining the link between Mirena and breast cancer was published in the Obstetrics & Gynecology medical journal. The researchers from Finland examined information from over 93,000 women between the ages of 30 and 49 who used IUDs that release levonorgestrel. The data extended from 1994 to 2007. All of the study participants specifically chose those types of IUDs to treat menorrhagia, or heavy and prolonged menstrual bleeding.

Out of all the study participants, the researchers noted 2,781 cancer diagnoses. When considering data from the general population, the researchers anticipated that there would be approximately 1,292 breast cancer cases among the study participants. However, there were 1,542 cases, indicating a 20 percent increased risk of breast cancer among users of IUDs such as Mirena.

Some of the study participants were diagnosed with other types of cancer. However, the levonorgestrel-releasing IUDs were found to have a lower risk of certain forms of cancer. For example, there were only half of the expected cases of endometrial adenocarcinoma and pancreatic cancer. Diagnostic rates of lung cancer declined by 32 percent and the researchers found only 60 percent of the expected number of cases of ovarian cancer.

“Using the levonorgestrel-releasing intrauterine system for treatment of menorrhagia during reproductive years was associated with a lower incidence of endometrial, ovarian, pancreatic, and lung cancers than expected,” said the researchers.

The researchers further implied that additional studies would be helpful to take into consideration other potential risk factors for cancer, such as genetics and lifestyle choices.

Doctors advise greater patient education

Although rates of certain types of cancers may decline with this form of birth control, the 20 percent increase in breast cancer rates with Mirena is troubling patient advocates. In a recent interview, the director of Comprehensive Women’s Health in Silver Spring, Maryland urged healthcare providers to increase patient education initiatives regarding the serious risks of IUDs such as Mirena.

“We need to educate our patients, because many of these therapies may work, but some could have serious side effects. Women need to be told. Then it’s up to the patient, along with a doctor’s guidance, to make the decision,” said Dr. Angela Marshall.

In addition to the heightened risk of breast cancer, Bayer, the manufacturer of Mirena, has come under fire for other serious health concerns. Reported Mirena IUD side effects include spontaneous migration and perforation of the uterus.

Thousands of Mirena injury lawsuits have already been filed against Bayer by women who have claim to have suffered these and other complications.

  1. Obstetrics & Gynecology, Cancer Risk in Women Using the Levonorgestrel-Releasing Intrauterine System in Finland,

  2. CNN Health, IUD may carry higher risk for breast cancer in certain women,