In assessing the legal landscape within the U.S. regarding the contraceptive intrauterine device (IUD) Mirena, manufactured by Bayer AG, one of the most significant and newest areas of concern is allegations of an increased likelihood of cancer in breasts. This article, written from the U.S. product-liability law perspective explores the main concerns, developments since 2017 and the legal issues surrounding the issue, which is commonly known as”the “Mirena breast cancer lawsuit.”

Mirena & The Alleged Breast Cancer Risk

Mirena is an intrauterine device with a T-shape with the ability to release levonorgestrel, which is a hormonal hormone which is approved within the United States for both contraception as well as heavy menstrual bleeding. Certain legal claims suggest that the exposure of hormones through Mirena could increase risk of breast cancer, but the regulatory, scientific and legal pathways are a bit muddled.

In 2014, Finnish researchers published a study in Obstetrics & Gynecology indicating that women who used levonorgestrel-releasing IUDs (such as Mirena) to treat heavy menstrual bleeding might face a ~20% higher risk of breast cancer. In addition, recent studies (e.g. in Denmark) have shown a 40 percent higher risk of breast cancer in those who use levonorgestrel IUDs (not specific to Mirena) as compared to non-hormonal IUD users.

These facts support many of the legal arguments which claim that Bayer ought to have warned patients and doctors or changed the labelling of their products to indicate the risks.

Legal Claims & The 2017 Context

Though a majority of the major MDLs (multidistrict litigations) with regard to Mirena (for the uterine perforation and pseudotumor cerebri, device migration) were confined prior to 2017 and the breast cancer aspect was beginning to emerge.

• By 2017, Bayer had offered a ~US$12.2 million settlement for thousands of claims regarding migration/perforation injuries–but not for breast cancer claims.
• The claims for breast cancer weren’t in no way yet all consolidated or widely resolved until 2017. A large portion cases were in their very early stages.
• An important development was that in 2017, courts weighed in on the possibility of allowing claims to be allowed to proceed. While many of the device-migration/pseudotumor cerebri cases were being dismissed for lack of causation or statute-of-limitations, the breast-cancer claims faced similar legal headwinds. For instance an order from 2017 discussed Bayer’s “2017 signal assessment” of adverse incidents.

So, even though 2017 is frequently cited as a year that marks the beginning of the Mirena timeline of litigation, the breast cancer part of the litigation was developing and unresolved as of the time of this date.

The Legal Theories in Play

A typical “Mirena breast-cancer” claim, the legal theories comprise:

1. Inadequate warning or inadequate labeling Plaintiffs assert that Bayer had knew about the increased breast cancer risk, but failed to communicate it to prescribers as well as patients. For instance, the class action suit filed on the state of California (March 2022) states that Bayer failed to disclose the “significantly increased risk of breast cancer” for Mirena users.
2. Negligence and strict liability Plaintiffs can claim that their device is faulty constructed and that warnings provided were inadequate, leading to legal liability for product liability under the state law.
3. Fraud on the consumer or false representation Certain assertions frame the problem as fraudulent marketing (i.e. the claim that Bayer advertised Mirena as safe but did not provide adequate information about the risk of cancer).

As with other difficult medical device lawsuits, the main obstacle is finding the causality (that Mirena caused or significantly raised the likelihood of developing breast cancer for the particular patient) and establishing the company’s capability or knowledge to have notified.

Developments After 2017 and Current Status

Since 2017, the lawsuit has changed

• In the month of October 2023 the U.S. federal judge cleared the class-action suit that claimed Mirena has caused cancer of the breast. The judge allowed the case to move past the stage for dismissal and found that Bayer’s arguments about scientific causation as well as federal preemption raised issues regarding the future proceedings.
• But, as of 2024, some of these claims have been dismissed from the sides (e.g. the stipulation for dismissal on May 20, 2024) however the scientific research continues to advance.
• A large Danish group study (e.g. women between 15-49 who use levonorgestrel IUDs) discovered an 1.4-1.8x increase in breast cancer risk over 6.8 years when compared to non-hormonal IUD users. This is not Mirena-specific however it was pertinent to a legal arguments.
• Legal commentary notes that many lawyers are not accepting new Mirena breast cancer or migration/perforation cases, especially given the closure of MDLs and expiration of statutes of limitation in many states.

Key Legal Challenges

For plaintiffs involved in a Mirena breast cancer case, there are the following issues are particularly significant:

• General causality showing how Mirena (or that hormone called levonorgestrel which is injected via Mirena) can be responsible for creating breast cancer at the rate it is claimed. The courts conduct rigorous reviews of experts in accordance with Daubert/FRE 702 guidelines.
• Particular causation: For a specific plaintiff, it is necessary to prove that the device led to or affected her risk of breast cancer (vs. other risk factors).
• Statute of Limitations / repose Many claims can be denied if filed late in accordance with the law of the state. In contrast to claims involving device migration that are that were filed earlier the breast cancer lawsuit could be subject to different time-limits, based on the jurisdiction.
• Preemption or regulatory defense: Bayer may assert that federal FDA regulation and labelling are preempted by some state laws (though in the order of 2023 the court ruled against many preemption arguments in an early stage)
• Risk level While certain studies show an increased risk, the overall risk is still relatively low, posing concerns about damages and if warning could have influenced the decision to use. A study for instance discovered fourteen additional cancers of the breast for every 10000 women in five years in IUD users.

Implications and Advice for Potential Claimants

If a person (or an advisor to the legal profession) is considering a claim that claims Mirena has caused breast cancer, these specifics apply:

• The clock is ticking. Check your state’s time limit or the repose period.
• Keep all medical records, including the insertion and removal records and the date of diagnosis of Breast cancer (or precancerous conditions) and implant time, as well as any exposure information.
• Note other risk factors (family history, hormone therapies and lifestyle) as these could be challenged.
• The fact that a study has shown an increased risk of levonorgestrel IUDs, doesn’t necessarily mean Mirena was the cause of a plaintiff’s personal cancer. Each case must establish causality.
• Examine whether multiple jurisdictions might be applicable (state laws, federal class actions and federal class action. ).
• Legal counsel who has experience in product liability for medical devices is vital, given the regulatory, scientific and procedure-related complex nature of the case.

Conclusion

Although by 2017 many of the large-scale device migration/perforation litigations involving Mirena had advanced significantly, the breast cancer dimension remained emerging. As time has passed, more scientific reports and filings with the courts have helped bring this matter into greater focus. However, plaintiffs are faced with a number of legal hurdles, particularly causation, limits to timeframes, and risk levels. For women who took Mirena and then later suffered from breast cancer, lawsuits are an avenue to redress, but they also emphasize the heavy the burden of proof that is present in modern medical device litigation.